My bench power supplies all have built-in current limiters but sometimes it's necessary to limit the current delivered from the mains itself. I often receive items like old valve guitar amps that repeatedly blow fuses for example and a current limiter will help diagnose issues as well as keep me safe. You can't easily buy stuff like this anymore so I decide to make my own DIY test equipment current limiter.
There are some pieces of equipment which might have been readily available a few decades ago but today, they're simply not as common as they used to be. Indeed, this is something I've been meaning to build for a while, now.
In line with the look and feel of the guitar amps that my current limiter will be driving, I gave this bit of DIY test equipment, a slightly 'retro' touch.
Functionally, it's quite simple and works on an established principle of using an incandescent light bulb (or two) to limit the current into an attached load, like an amp. With no short-circuit in the load, the light bulb (or light bulbs) won't come on.
This current limiter has two 40W light bulbs allowing me to select two current ratings; about 165mA or about 330mA. Of course UK mains voltage is 240V. If larger currents are required, all I need to do is drop in higher power-rated light bulbs.
When testing 115V / 120V equipment, the current ratings would naturally be doubled.
The current limiter also has a bypass switch which allows me to conveniently bypass the limiter function without the necessity to unplug anything. A vintage style neon indicator reminds me when the unit is bypassed.
Using the limiter set to 'low', it would appear that the Randall shown below, clearly has a fault. As you can see, the amp is still on standby. Following a brief visual inspection which showed nothing obviously amiss with most of the amp, the power side did look as if it had sustained some fluid spillage in the past. There was corrosion and it just didn't look good.
My DIY mains current limiter in action and showing up a fault on this Randall amp.
My DIY test equipment current limiter isn't the only piece of gear that I've made for use in my lab. Amongst other things, one of my oldest items is a 2-channe,l heavy-duty 8Ω dummy load. As we all know, valve amps need to be connected to a suitable load, when powered up. Not doing so, risks damage and possibly destruction of the output transformer so when working with valves, a dummy load is absolutely essential.
Built when all my heavy test gear was rack-mounted, one of my oldest pieces of DIY test equipment, is my 2 x 8 Ohm dummy load, now with switchable isolated outputs.
Built before a time when speaker simulators and 'power soaks' came to be, my 2 x 8Ω load has lasted me well for several decades and continues to be used on a very regular basis.
It's a bit special. As you can see. it's rack-mounted. This was to save space at the time as all my heavy test equipment was in a 16U rack. As I'd often be out on the road, the rack solution was also very practical, if not bloody heavy!
My ol' faithful dummy load has recently been updated with a 600Ω : 600Ω audio transformer on the backend of each channel. Via the front-panel switches, I have the option to either have two conventional dummy loads or a pair of fully isolated loads which are perfect for the new generation of D-class amps with so-called 'balanced' speaker outputs which are isolated from mains earth. This keeps my oscilloscope very happy! 😎
The potentiometer simply provides a little control over the signal level going into my 'scope. As well as being perfectly suitable for attaching to 2-channel amps like the Marshall 9100 or 9200, it's easy to wire the two loads in series for 16Ω or parallel for 4Ω.
Just before Christmas, a customer brought me a loft-find Simmons SDS9. It was in pretty good cosmetic condition but didn't boot properly. With the start of the New Year, this Simmons SDS9 repair became my first of 2025.
Having been told that this was a 'loft-find', I figured that the battery should be the first thing I should check out. Yep, it was totally dead and the usual white stuff had started accumulating around it.
The customer got lucky though and there wasn't too much damage. Once I'd cleaned the area around the battery and replaced the original Ni-Cd device with a lithium CR2032, I reinitialised the unit as I powered up for the first time.
Okay, good news... it booted. We'll see how much of this SDS9 works but first a few words on that battery change...
I normally replace a Ni-Cd with a 3.6V lithium battery when doing the Ni-Cd / lithium conversion thing. On this occasion, I didn't. The reason I went for a more conventional solution on this Simmons SDS9 repair, is that since the main-board is secured to the top-case, components up, there's not enough room to squeeze in a CR123 or ½AA battery holder and battery. Neither did I want to mount the battery to the bottom case as it would have to be unplugged for maintenance, thus forcing the SDS9 to lose all of its pre-sets or kits as they used to known. Makes sense, I guess... drums, kits...
You can't just replace the original battery with a different type. Some modification to the circuit is required.
IMPORTANT - You CANNOTjust replace the Ni-Cd with a lithium battery. Remember that the Ni-Cd is charged when the unit is powered on. If you don't modify the circuit, the same will happen with the lithium battery and that's something you really don't want to do!
With battery surgery complete, I then discovered that all the switches had issues and were either sticking, double triggering or not triggering at all. To be able to access various functions, that was the second thing that needed sorting out.
After removing the switches from the board, they can be easily dismantled and the metal spring contact and terminal contacts can be cleaned. Yep, they were certainly grubby!
The SDS9 didn't use encoders for data entry. Instead, analogue voltages were derived via potentiometers so while I was at it, I cleaned them too.
I dismantled and cleaned the switches but as you can see, the integral buttons remains a little tarnished from age.
After reassembly, the switches worked perfectly and the integral buttons looked just a little newer. Other issues with this SDS9 soon became apparent, however:
The boot time was much longer than it should be (I actually noticed that before) and once in a while, it would freeze kind of mid-boot.
There was more than the usual amount of hum on the audio outputs.
The low-tom wasn’t triggering from the pad input but was working fine via button-tap and MIDI and the low-tom sound was playing in demo mode.
The rim and intermittently, the high, mid and low toms were self-triggering, like machine gun style. The frequency (tempo, if you like), of the self-triggering would reduce over several minutes and eventually it would die down to nothing.
Intermittently, triggering the snare / rim would also trigger the low-tom albeit with a low velocity. Triggering the low-tom didn't trigger either the snare or the rim, however. This thing was one-way and would also settle down after several minutes.
The customer told me that he reckoned this SDS9 had been in his loft for at least fifteen years, if not nearer twenty. With cold and damp winters and humid summers over here in the UK, I was surprised that the case hadn't at least, started to rust. I wasn't surprised that there were problems with the electronics, though.
So, I decided to replace all the electrolytic capacitors on the power supply. Actually, while I was at it and since there weren't too many electrolytics on the main-board, I changed them, too. If looked after and regularly used, the recap might not have been necessary but remember that this was a loft-find.
New capacitors on the power supply helped reduce hum on the audio outputs.
Now that the unit was booting as it should, I started to look at the other problems.
The self-triggering gave me the impression that capacitors were charging / discharging and so I checked out the schematics for some caps which I thought could be responsible.
Do consider this, however...
The term 'IC' stands for 'integrated circuit' and we can assume (as if we didn't know already), that most chips (ICs) comprise various components, including capacitors. So, while checking out the discrete capacitors, one shouldn't dismiss ICs.
Indeed, there are lots of (ceramic) 1nF capacitors all over the place and so I changed them, like all of them, not just those associated with the self-triggering channels.
On the pad trigger inputs, there's a simple RC pull-down network attached to the inverting input of the first op-amp. Virtually all SDS9s I've seen however, have the resistor and capacitor on the mid-tom pad trigger input, wired the opposite way around to those on all the other channels. Instead of being 'RC' it's 'CR' if you know what I mean. I can't remember why this was done but space is tight here, if you want to wire them 'correctly' so perhaps the reason was that simple... space. Anyway, when I get a SDS9 in, I always put this right.
After swapping out a couple of TL084s (yes, they can and do indeed go screwy as well) , I replaced IC19, the 4051 multiplexer that passes triggers from the 8031 processor to the channel trigger inputs.
By now it was time to reattach the main-PCB to the power supply and jack-board and fire up this thing.
The SDS9 was now booting as expected and consistently. The excessive hum on the outputs was gone. The self-triggering on the rim had gone too but the toms were still giving me a headache and I still had that weird snare / rim to low-tom crosstalk. 😒
I replaced all of the 1nF capacitors associated with the pad trigger inputs as well as several apparently duff TL084s with TL074s
There was one more component that often causes problems but which I was hopeful, I didn't have to change and that's the 4067 (IC50). Like the 4051, this infamous multiplexer is also a common source of issues in all kinds of gear from the same era as the Simmons SDS9. The reason I didn't want to change it was simply because unlike the 4051, it's quite difficult to procure now-a-days.
Scoping the trigger lines going into the 4067, I noticed that triggering either the snare or rim, also produced a pulse on Pin 4 (the low-tom channel) of the 4067. This confirmed a crosstalk issue between the snare / rim and the low-tom. Oh dear! There wasn't anything weird going on between the TL084 trigger outputs and the 4067 inputs. The connections were good so this suggested that there was indeed a problem with the multiplexer itself and I really didn't want that to be the case. 😡
After having checked for short-circuits, I tested all the other channel inputs into the 4067 and everything was clean.
As well as multiplexing the channel triggers, the 4067 also multiplexes the voltages off the potentiometers. If you have a SDS9 with potentiometers that are starting to act a bit weird, there's a good chance that the 4067 will be the root of the problem.
A common source of issues in many systems from the eighties, the 4067 'traffic cop' multiplexer.
So back to the Simmons SDS9 repair...
Wow! That's more like it! Swapping out the 4067 resolved the self-triggering issues and the snare / rim to low-tom crosstalk.
Now that I had a 'silent' SDS9, I looked at the duff pad trigger input on the low-tom. That was down to a broken trace between one of those 1nF capacitors and the associated TL084.
With a normal boot period, no self-triggering, all pad inputs working and no channel crosstalk, all seemed good but this Simmons SDS9 repair wasn't quite over just yet...
There was a really weird thing going on with this Simmons SDS9 repair. The high and mid toms didn't sound right. It seemed like there was noise missing from the high-tom and the pitch of the mid-tom was higher than I thought it should be.
I went into program mode and levelled the toms so that they all sounded identical. This wasn't a simple case of pushing over the pots to one extreme, though. Indeed the tone pitch of the mid-tom had to be tweaked so as to be the same as the high and low toms. The filter pitch of the high-tom also had to be tweaked so as to be similar to the mid and low toms. In fact, the lack of 'noise' on the high-tom was actually down to the high-tom filter not opening all the way. To be honest, I did have a hunch about that.
Each of the SDS9 tom signals passes through a CEM 3394 and it was common practice to socket these ICs. This was good because I was able to swap them around and quickly eliminate them as the cause of the high and mid tom issues. I was now able to focus my efforts further upstream.
The fact that the CEM3394s were socketed, made it easy to eliminate them from the cause of the problems with the tom channels.
Each CEM3394s is fed from a pair of LM13600 dual operational transconductance amplifiers (OTA). This makes conventional fault diagnostics a bit challenging as you can't monitor currents on an oscilloscope. The required technique involves a lengthy process of elimination, until such point that you're nearer 100% sure that the respective OTA is faulty. So, that's exactly what I did but... I wasn't convinced.
I sent a WhatsApp message to my friend and Simmons Vintage Technical Network colleague, Michael Buchner, telling him about my Simmons SDS9 repair and how it's almost 100% working now, except for these two annoying issues. He got straight back to me asking if by chance, the firmware was version 6.0. "Yes, it was." I confirmed. He immediately recommended that I downgrade to version 3.0. Seriously? I didn't understand how a firmware bug could manifest itself by producing such an obvious couple of symptoms.
Surprisingly, downgrading the firmware fixed the last two issues I was having with the toms. THANK YOU, Michael Buckner for the heads-up!
Well, believe it or not, downgrading the firmware fixed the weird tom issues. The bad filter response on the high-tom and tuning error on the mid-tom were suddenly gone! Perhaps there was a calibration error in version 6.0 firmware. Who know, who cares! Michael's recommendation worked!!
I was at Simmons during the SDS9 period but I must confess to not having any recollection of this issue.
WOW!! Thanks, Michael.
So let's see what got fixed with this Simmons SDS9 repair:
Battery leakage cleaned up and SDS9 converted to lithium battery back-up.
Bad switches and potentiometers cleaned.
Slow boot up fixed.
Excessive hum fixed.
Rim and toms self-triggering fixed.
Low-tom pad trigger input not working fixed.
Snare / rim to low tom crosstalk fixed.
Bad calibration of filter pitch on high-tom fixed
Bad calibration of tone pitch on mid-tom fixed.
Sad customer is now a happy customer! 😎
To be honest, I really quite enjoyed working on this one.
Despite having been used extensively by many named artists, the Simmons SDS9 never acquired the same legendary status as other Simmons systems like the SDSV and SDS7. It's a shame because it's actually very good.
I guess Simmons decided to continue with the SDS7 idea of mixing digital samples with analogue synthesis but being a bit choosy how they did that, thus making the SDS9 more affordable.
The kick is generated in software. At the other extreme of technology of the time, the toms are classic (Simmons) analogue generated. Well, that's not quite true. They're digitally generated but pass through analogue filters which changes the sound and feel considerably. The snare and rims are sample-based making the SDS9's sound sources, as diverse as they could possibly be in 1985.
The end result was really very good and as I said, the SDS9 is quite an underrated e-kit. The sounds are classically 'Simmons' with punch, analogue 'fatness' and yet retaining clarity and definition.
Simmons SDS9 repair - almost like new now.[/captionSDS9 die-hards will notice that this example has blue knob caps on the volume controls as well as on the parameter controls. To the best of my knowledge, everything is original so how those knobs ended up not being grey like the pad input sensitivity controls (and like other SDS9s), I don't know.
A LITTLE SIMMONS SDS9 STORY
Back in the summer of 1987, I took a week's break with a whole bunch of friends, to the Isle of Wight. Halfway through our week, we all drove up to Hammersmith as having been involved with Def Leppard, I didn't just have tickets but I also had backstage passes. As soon as the show ended, we made our way backstage. Rick Allen clocked me, pulled me aside and asked if it sounded okay out front.
"Hang on a second. Rick Allen, the drummer from Def Leppard is asking me if it sounded okay?" WTF?!?!?!?
How do you answer a question like that from Rick Allen? The man who had been through so much but who was determined to carry on and carry on he did!
Anyway, Rick was using a SDS9 and WOW! What a show. I'll never forget it.
I've been trying to get permission to use this image but as yet, no one's got back to me. Could I kindly ask for someone from deflepparduk.com contact me?
ON A VERY PERSONAL NOTE...
For me, Def Leppard was not just another rock band. My connection with the band went way back, prior to my time at Simmons. In fact, I was a Phil Collen fan when he was in Girl and for a while in like 1981 (or '82), I had Pete Willis' famous white Hamer guitar as, while a student, a mate of mine lived in a flat above the Def Leppard crew.
The guitar went up for sale for only 350 GBP. I was a student so I just didn't have that kind of money. The other guitarist in the band did however and Neil bought that amazing guitar.
Neil had multiple sclerosis and sadly passed away many, many years ago. As for Pete Willis' Hamer, who knows what happened to that! 😢
As the eighties progressed, I have to admit that Def Leppard was very influential in the development of my own musical and production styles, my guitar sound and playing technique and even my song writing.
Today I look at the pictures, watch the videos and play those records and a sense of that ol' wide-eyed magic washes over me, as it did back in the day, forcing a nostalgic tear to run down my cheek.
Today, a simple Simmons SDS9 repair can seriously take me back and if I ever get around to writing an autobiography, Def Leppard would have to feature in it.
UPDATE - 5th March 2025
When the customer came to collect, we got talking and I mentioned how Simmons made available a ZIF socket set for the SDS9, the idea being that swapping out EPROMs would be quick and simple. It comprised three ZIF sockets and a plastic EPROM compartment cover which replaced the original factory cover. The replacement cover was raised so as to fit comfortably over the EPROMs.
Well, Simon thought it was an awesome idea. Only problem was that the kits are now considerably more rare than a nice condition SDS9.
Simmons SDS9 with ZIF sockets making EPROM swap-out quick and simple.
Anyway, I thought I'd help him out as best as I could and fitted some rather smart ZIF sockets.
UPDATE - 30th March 2025
These two Simmons SDS9s are now fully functional and in really nice cosmetic condition.
Late last night I put the finishing touches on the second SDS9 I had in this year and which I briefly mentioned earlier in this post.
The customer asked for a full service including the following:
Replace all electrolytic capacitors.
Supply ROM A EPROM.
Bass drum trigger input not working.
Not exactly an extensive list and after a thorough examination, I advised the customer that the electrolytic capacitors didn't actually need replacing and that I couldn't find anything wrong with the bass drum trigger input.
Adrian had also given me a SDS1000 which he said (also) had a non-functioning bass drum trigger input. I wonder if things got a bit confused. What I did discover on the SDS9 however, was that the rim trigger input wasn't working and that the rim channel wasn't producing any sound.
I quickly sussed out that the non-functional rim trigger input was down to a wrong value capacitor. It took me a little longer to sort out the rim sound.
A little known fact about the SDS9 is that the rim technically has two voicings which can be output simultaneously and from different physical outputs.
the 'processed' rim is mixed with the snare and is output via the tip pole on the SDS9 snare audio output.
the unprocessed rim is available on the ring pole of the snare audio output.
So what do I mean by processed and unprocessed?
Well, the processed rim passes through the CEM3372 with the snare but the unprocessed rim is basically the raw sample, directly off the EPROMs.
Anyway, there was raw rim being output so the problem was either with the CEM3372, the TL084 that supplies the CV or both. Yep, you guessed it, both! 😕
I managed to convince Simon, the customer of the first SDS9, that I should correct the colour layout of his unit's knob caps. The knob caps on the second SDS9 were seriously faded, like the grey caps were brown and the blue caps were almost green. Hence, both units got a mild cosmetic make-over.
Working on vintage synthesisers means that a lot of the time, I have to create a 'test' patch and with so many instruments that come into the lab, it often gets quite challenging. So a few days I ago, I made the decision to buy something that would simplify my life; the Kiwitechnics Patch Editor.
This little box is as rare as well, something that's really rare and I was very lucky to find a pristine example on ebay UK. It was expensive but of course it was... because it's a rare (I just said that), it's mega cool and this one was like new (I just said that too). So I snapped it up.
At the moment, I have a Roland MKS-70 in, as well as a Roland MKS-80 and two Cheetah MS6s. To date, I've used PC editors to create test patches but what's available for the MS6 isn't great and the one that is, isn't compatible with Windows 11. 🙁 On top of that, I don't always want to switch on my PC, just to program a synthesiser module. Well now I don't have to. I can just plug in my new Kiwitechnics Patch Editor. Oh this is so cool.
Just some of the synth modules I get in on a regular basis. The Kiwitechnics Patch Editor is going to make programming these so much easier.
Made from steel with illuminated controls and a large display (for old gits like me), the design, attention to detail and shear build quality of the Patch Editor, is incredibly professional. It feels like it's going to last a lifetime.
Controls that are active for the selected profile, illuminate with a menu option to turn down brightness. The rear panel has the usual complement of MIDI and power sockets, the latter taking 500mA at 9V - 12V DC, with centre pin negative on a 5.5mm x 2.5mm low-voltage barrel connector.
You'll also notice the 'EXT IN' jack socket which is a nice touch, allowing a foot controller for example, to be connected.
Murray at Kiwitechnics told me that Unfortunately, the Patch Editor was eventually discontinued because it just wasn't economically viable. It's something I can relate to as I'm constantly struggling to keep the prices of the stuff I make, as low as possible.
Having said that, the Patch Editor is still very much supported. In fact, a CPU upgrade is available for older units providing the same power and profile storage capacity as those with newer serial numbers. Since mine is S/N 1045 (an early version), I've decided to buy the new Patch Editor Plus.
The Patch Editor originally retailed for 450 USD, exc. shipping. I bought mine for 525 GBP. Today's exchange rate makes that about 655 USD. It was second-hand but it's an amazing little box and in my humble opinion, worth every penny. Hey, don't forget... you're getting half-a-dozen programmers in one! I just wish there was a way to get Kiwitechnics to continue production of the Patch Editor and keep this ultra cool product out there. The vintage synthesiser world needs the Kiwitechnics Patch Editor!!!
Last year, a customer brought me an ARP 2600 that had just been serviced with the exception of the power supply. The customer said that the synth would sometimes freeze and be unresponsive so I gave him a choice; I could either service the original power supply or design something a little more up-to-date. We both decided to take advantage of the situation and my Sirius replacement power supply for the classic ARP 2600 was the result.
To be honest, I took on way too many design projects in 2024 . So much so, that my repair work seriously slipped and I found myself constantly apologising to my good customers and thanking them for their patience. I figured I'd done enough design work for a while and vowed that 2025 would be different. Time to take things easy.
Well, almost...
Sirius is one of two projects from last year that kind of overspilt into the New Year, the other being Nebula-X, my balanced outputs jack-board for the Roland JX-10.
Anyway, life is great so enough moaning...
The original ARP 2600 power supply, including the transformer but excluding the fuse (no idea why they did it like that but , hey), is attached to a metal plate which is screwed to the inside of the wooden 2600 case. This keeps things very tidy, focused and easy to work on. That being said, the power supply is at the rear of the instrument and can be a bit awkward to get to. The construction of the 2600 is such that you have to kind of reach over the synthesiser front-panel, to get to the back of the instrument.
The power supply in the classic ARP 2600 is very neatly mounted although it seems strange that the fuse is separate.
With only +/-15V lines, on the face of it, the original power supply couldn't be more simple. I measured the static current consumption to be about 170mA per rail so that wasn't at all a big deal, especially when I had 25W converters in mind for this project.
Static current consumption of the ARP 2600 seems quite modest.
In the previous paragraph I used the phrase "on the face of it". That's because things are potentially a little more involved. The original PSU has a pair of potentiometers which allow for adjustment of the supply lines. The electronics will run fine with a reasonable margin of error but annoyingly, many synthesisers of this era, including the 2600, took reference directly from the power lines. The 'reference' voltage is used for things like the VCOs and hence, scaling of the keyboard. Wanting to use a modern, modular switched-mode design like my other power supplies, it wouldn't be easy to emulate this feature.
I was able to include independent voltage references on both my Aurora PSU for the Roland MKS-80 and my Supernova PSU for the Roland Juno-106 for example, as the original power supplies for these instruments didn't take references directly from the supply lines.
The 10V reference on Aurora emanates from a 5V reference source (Q1) with a tolerance of 0.1%. Amplified by a factor of 2, the output is also fully adjustable.
It's quite possible to use sufficiently accurate devices so as not to need adjustment and so I looked at how I could do that. The Vigortronix AC/DC converters I intended to use and which I'm very familiar with, have a specified accuracy of 2%. That's pretty good. I measured the voltages of several 15V AC/DC converters that I had in stock. Coupled with my experience of my other power supplies, all of which are sent out with a test certificate, I could see that the tolerance was no worse than 1.6% with the vast majority of devices falling within a tolerance of 0.75%. This was really quite encouraging.
Okay, let me provide a little perspective...
There's no denying that accuracy and tolerances of electronic components and systems has jumped leaps and bounds since the ARP 2600 appeared on the scene in the early seventies. In fact, we should question the accuracy of the equipment that was used to calibrate the supplies at the factory in the first place. With this in mind, I decided to continue with my Sirius replacement power supply for the classic ARP 2600 prototype but I also decided to hand-pick the converters, choosing those which had an accuracy of no less than 1.0%. That would give a worst case scenario of 14.85V or 15.15V. It would be interesting to see what would happen.
After a couple of weeks of testing, it was a great relief to note that things seemed to work just fine. My ears, my oscilloscope and my precision tuner, didn't reveal anything strange. With a view to offer Sirius to the wider ARP 2600 community however, I thought I could do better and so the executive decision was made to use converters with an accuracy of 0.7%. Yes, I know... it won't make any difference in the real world but I'll be able to sleep better! 😴
Sirius has precision filters, voltage supply active indicators and convenient test points.
Weighing just 215g my Sirius replacement power supply for the classic ARP 2600 is less than a third of the weight of the factory power supply (727g). This meant that Sirius could easily be secured using the original mounting plate. Indeed, although the Sirius PCB is attached to the plate using M3.5 fixing hardware, I didn't see a problem using the original screws to secure the plate to the inside of the 2600 case. Not having to supply a custom mounting solution would help keep the cost down.
"M3.5 fixing hardware?" I hear you ask! Glad you spotted that. So I've just explained that I wanted to use the original mounting plate, right? Well, the plate had been drilled to accept countersunk screws of some old UNC or UNF standard and so I had no option other than to choose my fixing hardware to be as close to the original as possible. Adequate to support Sirius, M3 screws and hex spacers would have been too small and I wouldn't have been able to use the original mounting plate.
Removing the original power supply was straight-forward and simple. Securing Sirius to the the original mounting plate and then fixing that into the position of the old power supply was also straight-forward and simple. I was however, concerned about soldering the connections from the mains input, synthesiser and the keyboard port, to Sirius. It would mean leaning over the synthesiser and I wanted to reduce the risk of an accident for others who might be looking to install Sirius themselves. I therefore chose to use screw terminals for all connections.
Screw terminals means that hooking up Sirius to your ARP 2600 requires minimal soldering.
With over-voltage, over-current and even reverse polarity protection built-in, advanced noise filtering on the back-end and nearer 95% efficiency as opposed to perhaps 15% efficiency of the original PSU, Sirius will also allow your ARP 2600 to be powered from virtually any domestic power supply, like 100V to 240V. That means that there's no need to change transformer taps, should you suddenly find yourself on the other side of the planet, alone with your favourite synthesiser! 🙂
The two power supplies couldn't look more different!
In contrast to the image above, below is a picture of Sirius fully installed and I can't help feeling that it looks like its always been there! 😂
By the way, those aren't the original power input cables. I took the opportunity to change them to something a little more 'standard'.
Sirius installed and working just fine.
You may also notice the addition of an extra earth wire which is strapped to the voltage lines going back in the direction of the synthesiser. This is important. Unlike a linear power supply, 0V on the output of a SMPS, is not always connected to earth through the power supply itself. For the filters on Sirius to work properly, the return path for the each supply has to be direct. Earthing 0V through the PSU will break this path and the filters will be ineffective. Instead, 0V is earthed through the 'load' (the synthesiser) and the additional earth wire shown, is connected to the metal chassis (front-panel) of the 2600. Of course, this maintains safety as well as providing the required return path integrity. Earthing in this way also ensures that the effect of any parasitic capacitances on the outputs of the AC/DC converters are completely removed.
I made sure that after several hours of operation, the ARP 2600 still worked fine. As for Sirius, it didn't even get warm!
Of course, once I'd established that Sirius was working, a complete recalibration was required. Don't forget, voltage references are taken straight off the PSU.
I'd only just got back from spending New Year's Eve in the Bavarian Alps two days ago and officially, I'm not back to work 'till Monday but I simply couldn't wait to tell my customer the good news. In fact, he asked if he could come over the next day. Of course, that wasn't a problem as Ryan had been very patient and appreciated all the precautions I took with his beloved ARP 2600.
So the next day, Ryan turned up. We went into the lab and he couldn't wait to switch on his baby. The first thing he noticed was that there was no hum! Oh yeah, I kinda forgot to mention that. 🤣
It took Ryan a few minutes to remember how it all worked but then after dialling in an initial sound, Ryan commented that he wouldn't have been able to do that before, as the instrument would become unresponsive and kind of freeze soon after power-on. The only option was to restart.
I was so excited to hand over Ryan's ARP 2600, now working just fine oh and with no hum!
APOLOGIES BUT I NEED TO MAKE IT QUITE CLEAR...
It should be no surprise that in recent years, various clones have been made of the iconic ARP 2600. Please be warned however, that my Sirius replacement power supply for the classic ARP 2600 was designed for the original, now vintage, ARP 2600 from the 1970s. I don't imagine the Korg ARP 2600 FS or the Korg ARP 2600M to bear any resemblance to the original instrument. As for the Behringer 2600 type of thing, forget it. So... DON'T even think about fitting Sirius to any of these machines!
Yes, the original power supply can be fixed and in fact, it's not at all difficult to service but Sirius changes things big time offering reliability, stability, longevity and... NO HUM.
Sirius is available to purchase here:
All I need to do now, is compile the installation manual. 😕
In the meantime, here's some interesting reading regarding the legendary ARP 2600:
After years of searching and trying so many devices, I finally found the actual device that Marshall used to switch power on and off on the Marshall JMP-1 and here it is; the power switch for the Marshall JMP-1.
This is NOT an equivalent component. It's the actual switch! Check it out in the image below as it's pictured next to a faulty switch which I recently pulled from a JMP-1.
This switch is NOT an equivalent. It's the same!
A WORD OF WARNING
The power switch is secured to the inner front chassis with a small bracket. This must be removed and fitted to the new switch as it's NOT supplied with this bracket.
DO NOT DISCARD THIS BRACKET FROM YOUR OLD SWITCH!
Obviously made by Marshall at the factory, this is bracket is effectively a bespoke part so DO NOT THROW AWAY YOUR FAULTY SWITCH until you remove the mounting bracket.
Below shows the bracket (or collar) mounted to the switch. Once the switch has been slipped into the bracket, you just need to carefully bend four posts over the top of the switch.
The switch easily slips in the mounting bracket and is secured by four small posts that need to be bent over the top of the switch.
My friend and graphics designer, Tony Burlinson and I have been meaning to dive into the world of 3D printing for years. This year (2024), the opportunity presented itself, for me to take that dive and Tony was keen to join in. Little did I know that it would be the start of my Creality nightmare!
During 2024, I’d taken on a lot of design projects. Amongst them, was AMEP, my advanced memory expansion pack for the Simmons SDS7. It was a mega-cool product and I wanted to do it justice with some cool packaging. Indeed, AMEP was my fist product to have its own box.
To keep AMEP secure, I knocked up a design for a piece of foam but I was shocked when I received quotes from various manufacturers. At 5.88 GBP per piece in batches of 120, I figured I could print these from plastic, myself! So that was the ‘opportunity’ to dive into 3D printing.
After some research, I bought a Creality K1. The price was very reasonable and Tony and I thought that it would be a good starting point for our us newbies, with potential to grow to perhaps a semi-professional level.
Tony already had a lot of experience with 3D CAD but had never made anything physical. With Tony’s artistic flare and my engineering background, a dynamic team was born. We only had six attempts at the AMEP insert before we got it spot on. Not bad for our first 3D print.
You get a ‘free’ 200g spool of white hyper-PGA with the K1 but once that was used up with practice / protype prints, it was time to change to a 1kg spool of black hyper-PGA.
So here was the first pain; feeding the new filament through both feeders (rear and pre hot-end) wasn’t easy. A couple of YouTube videos later, we found a solution which involved taking a lot of stuff apart. Neither Tony or I were keen to do that so we persevered and in the end, we got the bugger through.
The second issue involved the filament clamp on the hot-end. In the ‘locked’ position, it didn’t seem well, locked. Our next print failed because in fact, the filament lock wasn’t indeed locked. It took a while to sort this out but we weren’t at all 100% sure about our efforts to correct this issue.
Eventually, we managed to print a couple of AMEP inserts in black PLA.
Pictured are the only two successful AMEP inserts that I managed to print on the Creality K1.
Nine prints in, that includes the five prototypes, things went wrong, like BIG time. I’d already had a bad experience leaving the printer unattended. After having bought Creality’s own filament, I was shocked one afternoon, when the print kind of ended up jamming and not completing a print, only to discover that the filament spool had snagged… on itself.
Number 9 however, was the big disaster, my Creality nightmare! It was 2:00 in the morning. I thought that I'd ironed out all the issues and that perhaps things might now be okay (for a pile of shit, that is). I figured I’d print one more insert, go home for an hour, come back and another AMEP would be good to go. When I came back to the lab, I expected to find a perfectly printed AMEP insert. Instead, the K1’s plate was empty. At first, I thought it was another filament snagging problem but as I walked up to the printer, I could see the massive, alien looking, collection of hardened plastic, around the entire hot-end assembly.
This is what I saw when I went to pull my ninth print attempt on my brand new Creality K1.
So it was 3:30 in the morning and I shot an email over to Creality. Well, they wanted to know everything, like serial number, proof of purchase, what my favourite colour was, blah, blah, blah. Once I’d passed their security (?) they apologised for the inconvenience and proceeded to ask for pictures, which I’d already sent them, incidentally. They then sent me instructions on how to repair my printer! Now my Creality nightmare was really beginning.
“Hang on a minute. I’ve only just bought this. It’s done nine (well, seven actually) prints. It’s not even three weeks old and I was on holiday for a week of that.”
Creality insisted that I try to fix things myself and recommended that I use a heat gun (or hair dryer) to remove the plastic around the hot-end. This is what what resulted.
Here's the contents of one of the emails I received from Creality:
Dear customer,
The hotend kit is currently overflowing. So currently you can't get into the filament when you replace the new hotend kit. Please follow the steps below to see if there are other problems besides the hotend kit.
The hotend kit is overflowing, and it can be solved by replacing the hotend kit. You can follow this tutorial to disassemble and clean it, and then see if there are other parts damaged besides the hotend kit, and you can take photos together.
If you can't heat it, do you have a hair dryer or a heat gun at home? You can use these two to heat and clean the filament.
At this stage, I need to make the point that after several email exchanges, with me talking about wanting a replacement printer and Creaility not reading any of that and simply telling me how to repair the printer, I kind of gave up. Or did I?
I needed to get these AMEP inserts done. I was desperate for my customers so I bought another printer, the massive CR-30 3D print mill. Creality didn’t have this in stock but I did find one at the uk-creality-official-store on ebay. That’s ‘UK’ in the ebay name by the way and yet the goods were located in California. Hmm…
I also bought something called a CR-30 extended bracket which is like a roller thing, specifically for that printer.
My Creality nightmare continued as the next day, I received an email from the seller informing me that in the last CR-30 extended bracket they had, items were found to be missing so would I accept a credit.
“No problem” I replied. “Please just put it on back-order.”
The reply to my request said something like they had no idea when they would have stock. A refund seemed the only option.
I then ended up buying a CR-30 extended bracket directly from Creality’s website. The deal cost me an additional 17 GBP as I’d lost the benefit of the Black Friday deal on ebay. Grr…
A couple of days later, the CR-30 turned up but by then I’d decided to try to wake myself up from my Creality nightmare. The rare customer service email responses I received, blatantly reflected Creality’s inability or unwillingness to read the important bits in my emails. Bits like “I want a replacement printer”, etc. I’d decided that ‘resistance is futile’ so here I am, summarising my Creality nightmare for all to read and advising that no one considers buying one of this company’s products… EVER!!!! Hey, Creality is NOT going to honour anything, right? Remember that line, ‘cos in my experience, it’s true.
With no confidence that anything would be done about this, I then boxed up the K1 in readiness to take it down the dump. Creality UK or whatever, can eat shit, for all I care.
Regrettably and very disappointingly, PayPal was unable to assist with my purchases from the Creality website. I then went to return the CR-30. The relevant ebay page displayed the notice ‘This seller does not accept returns for this item’. Well, why should I be surprised? After a little digging, I sought some comfort in the fact that the sale was backed by ebay’s money back guarantee.
It's unbelievable that an 'official' store has this notice on its ebay listings.
After a stinking ebay message and a ton of negative feedback, I did get a response from the seller and an offer was made to send me a returns label.
Not there yet... Of course the returns label had insufficient funds on it so when I took it to the post office, the package was rejected as it was considerably more than the 2kg specified on the returns label. Oh what a surprise! At this stage, I tried to contact ebay for help. Hmm... That's not as easy as it used to be so I messaged Creality offering one more opportunity to sort this all out.
I eventually received a valid return label and took the unopened CR-30 to the post depot.
Yeah, I know lesson or lessons learnt and all that.
“What about that CR-30 extended bracket thing?” I hear you ask. Remember, I bought that directly from what I thought was the Creality store and not ebay. Well, several days later I received a return label to a UK address which was the same as the return address for the CR-30 that I'd bought off ebay. On this occasion however, I had to pay for the return carriage myself. Yes, that's right. It cost me 15.86 GBP to return an item that cost me 119 GBP.
There’s something else to note. I’ve mentioned uk-creality-official-store. There’s also crealityofficial.co.uk. I bought the CR-30 extended bracket from store.creality.com/uk. Support emails apparently go to store.uk@creality.com but some go to CS@creality.com. The truth is, that you don’t know where the hell you are and who the hell you’re dealing with!
My experience suggested to me that Creality UK (or whatever), operates in a way which ignores retail / trading law and legislation of various territories around the world and which simply prioritises the Creality way over the right way. Globalisation makes it extremely difficult for organisations such as Trading Standards here in the UK, to control how companies operate when selling products to for example, the UK market.
Okay, some may consider my stance as slightly prejudice. THIS IS NOT THE CASE. Indeed, here are a couple of examples of far eastern brands which I think are just awesome:
I’m a qualified and fully insured drone pilot and my drone arsenal predominantly comprises DJI drones and we all know where they come from. Both Tony and I use Huion pen monitors which are just awesome. Another example, one perhaps more people can relate to, is that of computers. You can’t buy a computer without the insides being made in the far east! So NO, I’m not prejudice.
Here's me in July 2022 after having just qualified as a drone pilot. I'm holding one of my favourite DJI drones.
I would urge good companies from the same country (like China, oops!) to put pressure on companies such as Creality, as the latter is giving the good guys a bad name.
Creality is a company that doesn’t give you all the facts in the first place. Its marketing strongly suggests that it’s based in your country and Creality seems to have its own customer support standard which it prioritises over standards which are taken for granted in other parts of the world where consumer protection exists.
In these situations, one needs to be pragmatic and objective. I can’t help feeling that the consumers’ expectations are unrealistically high, when it comes to this market. The Internet is flooded with videos of 3D printers making all sorts of cool things and manufacturers’ specifications on some devices boast astonishing figures of accuracy and resolution, for example. Truth be known however, real commercial 3D printers cost a lot more than a few hundred quid like, you can easily add a zero on the end of the price tag. On the other hand, the manufacturers themselves are generating the stuff we see online and paying influencers to promote their products doesn’t exactly help.
In fact, I can imagine companies like Creality having teams of people working on online marketing, trimming SEOs on various websites and platforms, offering insane deals to influencers and hammering social media. In contrast, their customer support teams appear to be very thin and working to poor guidelines.
With the above in mind, I like to think that while I was very excited at getting into 3D printing, my expectations were reasonably realistic, especially for the entry-level printer I'd just bought. One thing's for sure though, I didn't expect a complete head assembly meltdown!
Anyway, Plasma Music fans and friends will be relieved to hear that I persevered with the whole 3D printer thing. Bambu Lab came to the rescue and woke me up from my Creality nightmare. I ordered a X1 Carbon and yeah, it cost a lot more than the Creality K1 but both the printer and the company have a very different feel about them. It’s called ‘professional’, Mr. Creality. 😊
As I await a pedestal to arrive for the lab, my Bambu Lab X1 Carbon remains in the kitchen!
Okay, so this page is loaded with tags and the SEO has been optimised which means that there's a reasonable chance of potential or existing Creality customers stumbling across it. I feel obliged therefore, to make it clear that this post is based on my experience and I simply felt obliged to tell people about just that; my Creality nightmare. There will be those who will disagree with me. There will be those who perhaps feel that Creality is the best 3D printer brand out there. On the other hand, if I'd come across a page like this, while checking out Creailty and the K1, I might not have wasted a lot of time and money!
I'm sorry but having a deal with a shipping company and a warehouse doesn't make you 'UK' or whatever. You need local service and respect either the consumer law of the territory that you wish to operate in or 'distance selling' law.
UPDATE - 23rd December 2024
A couple of days before Christmas 2024, I confirmed with Creality customer support, that all the spare parts sent to me had been received. Creality is however, continuing not to acknowledge the image that I sent them showing the completely destroyed head assembly. Indeed, the tone of the emails suggests that they're quite puzzled as to why I'm not able to repair the printer. Here's the latest email from Creality:
Dear customer,
So you have received all the accessories, right?
Are you not sure which accessories to replace? You can let us know and we will try our best to guide you.
Not sure which bit of "Can you please just arrange to have the printer returned for a refund" they don't understand.
UPDATE - 27th January 2025
Just gone midnight, I received an email from Creality advising that a refund is in progress.
My Creality K1 cost me 369 GBP. I also bought a nozzle kit and a camera for an additional 27 GBP so I'm expecting 396 GBP back. I paid via PayPal and nothing has shown up in my account yet but to be fair, it's been less than twenty-four hours.
UPDATE - 12th February 2025
No refund. No collection. NOTHING. All I'm getting is videos on how to change the hot-end. Well, not quite. The first link was to some stuff about a completely different item. When I eventually got the right link, the first minute was taken up with adverts.
"Hey, Creality.... You don't put adverts on bloody support videos!"
So I'm now drawing the line. When I get some time, I'm taking this pile of shit down the local dump.
Oh, one more thing... my Bambu Lab X1 Carbon is still going strong! 🙂
It's been a long wait but the AMEP packaging is now sorted and so I'm delighted to announce that AMEP is finally good to go!
Printed upside-down on to a textured plate, gives the AMEP inserts a rather attractive, kind of leatherette finish.
During 2024, I developed several peripherals for the Simmons SDS7, one of which was AMEP, Advanced Memory Expansion Pack.
With a lot of help from my dear friend Guy Wilkinson, a radically new approach compared to previous memory back-up solutions for the Simmons SDS7, AMEP went from concept to pre-production prototype, in just three months. After being hugely disappointed by quotes for foam packaging, I decided to make my own, all be it in plastic. That process took a disproportionately long period, almost two months, as it turned out. The problem was mainly down to the fact that I'd chosen the wrong 3D printer, or rather the wrong 3D printer brand.
My experience of the Creality K1 3D printer and perhaps more so of Creality the company, left a very bitter taste in my mouth. In fact, Creality has got to have the worst after sales service I've ever encountered but that's not the subject of this post. Indeed, I ended up detailing my Creality nightmare, here.
After some research on the company as well as the printers, I ended up buying a Bambu Lab X1 Carbon (or X1C) which is in a totally different league to the Creality stuff I had before.
As I await a pedestal to arrive for the lab, my Bambu Lab X1C remains in the kitchen!
The new printer is just amazing. Many thanks to Tony Burlinson, my graphics guy and friend for his support and his 3D CAD knowledge and experience.
Printing in progress!
The X1C is in a totally different league to the Creality K1. Yes, it's more expensive but this is a classic example of 'you get what you pay for'. After an hour of assembly and set-up, the X1C has delivered several flawless prints. More importantly, I have a feeling (although I might be totally wrong), that Bambu Lab will have my back, if anything goes wrong.
Bambu Lab wasn't just a random choice. As mentioned earlier, I did a bit research and was convinced by posts like these:
SO WHY DID I GO TO ALL THIS TROUBLE?
Unlike interfaces on machines that came much later, the data lines on the SDS7's expansion port are fully exposed and more importantly, completely unprotected. So, to help protect your SDS7 from the possibility of electrostatic discharge (ESD) damage and to offer SDS7 lovers something a little more reliable for a change, AMEP's packaging is made from conductive PLA, thereby reducing the risk of electrostatic accumulation.
Of course, I didn't buy a 3D printer just to make some packaging for AMEP. Tony and I have meaning to dive into this stuff for a long time. AMEP just gave us the perfect excuse to do it now!
The Bambu Studio software looks pretty much like other stuff we've tried but it feels very smooth and slick and has rather cool features that made Tony and me decide to stick with it.
I'm sorry to say that I'm back from my holiday 2024! I had such a great time with family members and old friends, I could easily have stayed for a lot longer.
My eldest daughter Katana, had a few days annual leave left so she kindly booked a short break for my wife Julie and me, in Malta.
I absolutely love what I do but even a workaholic like me, needs a break every once in a while. I've always had a special connection with Malta but I've never actually been so the opportunity to visit the island was something I was busting to take advantage of.
Katana, Julie and I stayed in an AX Odycy hotel located quite close to Valletta, Malta's capital city. The weather was fantastic. For us Brits, a gorgeous 21°C compared to 0°C in the UK was fabulous but many locals were wearing heavy winter clothes.
It was only three days but I was so excited, not just to get away but to meet my friend Josie Catania of TRX Electronics.
Josie and I pre-arranged to meet up for lunch one day. Josie is one of the nicest people I know and his wife Maithese is equally charming. Three hours went by without us even noticing and Katana, Julie and I were sorry to say goodbye.
It all started a few years ago when I tracked down Graham Sopp, the man who designed the transformer for the Marshall JMP-1 MIDI valve pre-amp, with a view to develop a better version of this device. My journey took me to Malta and indeed, TRX Electronics, the same factory that made the original TXMA-00014.
Since then, I've been supplying upgraded replacement transformers for this classic pre-amp and have had the pleasure of dealing with the lovely Josie Catania.
And here it is... my PML TX-01 transformer for the Marshall JMP-1
As I said, a lovely few days but now that I'm back from my holiday 2024, I'm equally excited to get stuck into my work. 🙂
I'm continually receiving requests to install various upgrades into all the instruments featured on my website but in the past few months, I've had to turn my lab into a Roland MKS-70 full upgrade production line, just for this machine!
I'd planned to take August off, this year. No, not for a fancy holiday or even a romantic get-away to somewhere exotic and beautiful with my wife (sorry, Julie). The truth is that I had taken on a lot of R & D projects and I really wanted to get them finished. I was finding it difficult to focus on other things in my life. I couldn't even just relax.
As it turned out, I was quite ill in August as I succumbed to a chest infection. In fact, I ended up in hospital. 🙁 As such, I decided to slow down and August got stretched out to mid-September. My customers were amazing and allowed me to peacefully recover. I felt quite guilty though and so decided to leave my online store, open.
Well, however nice and understanding people are, they can't wait forever and as soon as I felt good to go, I cracked on with a small backlog of customer repairs and upgrades that had built up.
I also finished off my projects, making the executive decision to leave my Nebula-X balanced outputs jack-board for the Roland JX-10 'till Christmas. Hey, the prototype is all built but I still need to fully test it and document the results.
I've managed to build my Nebula-X prototype but I won't have time to test it for another few weeks.
Winter 2023 was a crazy MKS-70 period, one which I never thought would have been repeated. Oh how naïve! Almost a year later and I've had to set up my Roland MKS-70 full upgrade production line again.
I've had a couple of MKS-80s in too. Both had faults which I've had to fix and the owners have also requested Aurora to be to installed.
It looks like things are going to get busy in the studio too. Booked up until February next year, I wasn't really looking to take on anymore recording or production work. A few days ago however, a friend of a friend approached me, asking if I'd consider producing several of his latest songs.
Hmm... I think I might need to get a plan together...
UPDATE - 28th October 2024
Here on the bench, is the last in this run of MKS-70 full upgrades. All the way from beautiful Finland, Nebula was fitted over the weekend and now I only have the front panel switches to change, the GU280 VFD to install and the encoder to swap out. Testing will take a few days so I guess this will be on it's way home by the end of the week. 🙂
Over forty years and a couple of clones later, I'm delighted to announce the all new AMEP Advanced Memory Expansion Pack for the Simmons SDS7.
It can take days, weeks or even months to program a bunch of patches into your Simmons SDS7. After all your hard work, there's only ever been one way to back it all up and that's with a memory cassette via the expansion port. Well, not anymore! 🙂
The original Simmons memory cassette is exceedingly rare, more so than the SDS7 itself and finding one that hasn't been eaten by the batteries is virtually impossible. Unfortunately, the same can be said for the clones that have appeared over the years.
Also using 6116 SRAM chips, the original MEP was very large and just like the memory-board in the SDS7, it had built-in NiCad batteries that required the memory cassette to be regularly plugged into a powered up SDS7, so that the batteries could be recharged.
The original Simmons memory cassette was large, used a NiCad battery that required regular charging and was annoyingly unreliable.
Being a large device, connecting it to the SDS7 via the rear DIN 41612 socket that wasn't really designed to take that kind of thing, caused its own problems. A lot of people kept a box of matches with their memory cassette. Perhaps you can work out why.
Over the years, clones have been developed but strangely, they're all copies of the original Simmons memory cassette. Hence the term 'clone', I guess. Despite huge changes in technology since 1983 however, this means that all the issues associated with the original Simmons memory cassette, have also been copied.
This year, while developing a couple of peripherals for the Simmons SDS7 which were intended to enhance performance and reliability and hopefully extend life span, I realised a need for a 'better' external data storage solution, especially since two of the peripherals I've developed, involve disconnecting the SDS7's memory back-up battery. Of course doing so, will mean losing all the data.
A good starting point for something like this was to define objectives so here's a sneak peak at the design brief I gave myself:
Small and compact design
More memory than the original MEP
Retain the 'Data' Protect' function
Remove dependency associated with rechargeable batteries
Battery should last for ten years minimum
Include a mechanism so that when the battery is changed, data is retained for a minimum of ten minutes
The new device must be affordable.
So all that was great but how was I going to achieve it?
The first thing was to get a concept together and then take a look at the Simmons SDS7 to see if something radical could actually work.
Well, I couldn't do all that by myself, not in any realistic timeframe, anyway. Fortunately, I've got a friend. In fact, I think I can safely say, that Guy Wilkinson is my best friend! 🙂
Guy and I got to know each other back in 2020, through the work he's done on the Roland Super-JX and my first product Aurora, a modular switched-mode power supply for the Roland MKS-80.
In June 2024, Guy and I took a day out and went to the 'Synthesised' exhibition at the National Computer Centre in Cambridge. We arrived early so went for a coffee and it was then that I mentioned my idea of AMEP Advanced Memory Expansion pack for the Simmons SDS7. Guy was surprisingly excited and quite keen to help.
Me and Guy at a coffee shop somewhere in Cambridge, UK.
As has already been pointed out, the original Simmons memory cassette was very large, exerting undue torque on the SDS7's DIN 41612 expansion port. Hence, the box of matches which people would put underneath the cassette! So, not wanting to copy (clone) the original device and using newer, more compact technology instead, my idea was to make AMEP such that the body would sit perpendicularly to deck and parallel to the back panel of the SDS7. Instead of sticking out from the SDS7, it would run up the back of the SDS7. To keep costs down, Guy and I also explored the potential for a 'caseless' design.
To achieve this, AMEP began as a sandwiched, 2-board idea which both Guy and I were really happy with and which allowed us some versatility with regards layout.
Oh and there's one more thing...
When hooked up to the SDS7, the original memory cassette obstructed access to the SDS7's sequencer input 1 jack socket. SERIOUSLY?!?!? It should be straight-forward enough to design AMEP so it doesn't do the same!
When engaged, the original Simmons memory cassette compromised access to sequencer port 1. AMEP does not!
Within a very short period, Guy had knocked up the concept and contacted me to come over and rip apart my test SDS7. I was developing my Dark Matter modular switched-mode power supply for the SDS7 at the time, as well as Pleiades, my lithium battery converter and Tubbutec uniPulse adapter, so I was a bit apprehensive. On the other hand, this had to be done and I really wanted all three products to go out at roughly the same time.
I had some other plans for the new storage device and so we checked out a lot stuff on the SDS7 than we actually needed to. Unfortunately, the 'keep these free for future expansion' lines as referenced on the original SDS7 schematics, didn't go anywhere and my idea of including MIDI for example, went straight out of the window. 🙁
8th September 2024 and we had our first prototype. Guy came over and plugged it in. I performed a bank dump. I removed AMEP, switched off my test SDS7, pulled the battery and then we tried to reload from the AMEP. Well, we were delighted. AMEP seemed to work. We tried this several times, checking the memory protect function and writing / reading from all four banks on the AMEP.
The first AMEP prototype worked straight-away. Well, after I'd remembered how to save to an external device! You also get a glimpse of my Dark Matter prototype in this picture and if you know what you're looking for, you can even catch a bit of Pleiades.
Yes, AMEP prototype 01 looked a bit 'Heath Robinson' but Guy and I didn't know for sure if SDS7 would even talk with our new gadget so knocking up something to see if SDS7 would recognise a friend, was a necessary first step. Anyway, the test results were very encouraging. In fact, we were positively thrilled and so we continued.
The next couple of weeks were busy. Guy poured a considerable number of hours into finalising a pre-production prototype while I focused on further testing, graphics, enclosure and packaging.
You'll notice the very small LR44 type battery on Prototype 01 in the image above. Well, one criteria missing off the original list was that AMEP should use a standard and readily available battery and so the design had to be changed to accommodate a much larger CR2032. An appropriate battery holder has to make battery changing easy but should also be as discrete as possible.
I continued to test AMEP on my studio SDS7, my test SDS7 and a customer unit (thanks, Peter). Initially, AMEP didn't work on the customer's machine and I quickly discovered a problem with the 40-way IDC ribbon cable between the PSU board and the back plane. You need to remember that these cables are forty years old! One new IDC cable later and everything was fine. Hey, I'm not even sure if Simmons tested the SDS7 expansion port during the production process.
After forty years, every SDS7 could benefit from new IDC cables.
One problem that Guy and I have is that we use different electronic design software. This makes exchanging files very difficult and with something as involved as a new data storage device for a forty year old synthesiser, we had to come up with workarounds, which was a headache in itself.
By 24th September 2024, we were ready to submit an order for the first batch of PCBs.
1st October 2024 and AMEP first production PCBs turned up.
Friday 4th October 2024, Guy came over and we made three AMEPs. It was an exciting and fun-packed afternoon. We even had Duran Duran playing in the background. Hey, all three AMEPs worked perfectly! 😮
4th October 2024 and Guy and I are making the first AMEPs. By the way... THANK YOU Ed Rose for the awesome SDSV T-shirt! I can't believe you made this, Dude!!!
WRITE VERIFICATION
There's no mention in the Simmons SDS7 manual about any routine to verify that data has correctly been written to an external data storage device. Guy and I discovered however, that if AMEP's memory protection switch is ON and one attempts to write data to an AMEP memory location that already has that data, then the SDS7 display will flash up 'AC' meaning that everything's fine. We couldn't see any reason why SDS7 would respond differently, with an original Simmons memory cassette as this feature doesn't have anything to do with AMEP. We're definitely not claiming any credit for that one but it's a cool hidden feature.
The left image shows what is displayed on SDS7 when a write command fails. The right image shows what SDS7 displays when a write command is either successful OR with the AMEP memory protect switch ON and attempting to write data to an AMEP location that already has that data (verification).
I couldn't wait to tell my Simmons Vintage Technical Network colleagues the good news. With confidence high, Michael Buckner asked a question which was going to come sooner or later; "Would AMEP Advanced Memory Expansion pack for the Simmons SDS7 also work on the SDS6?"
Well, I couldn't see why it wouldn't but having confirmation would be a big deal so I decided to send Michael Buchner and Ed Rose, AMEP samples and await their response.
At last! Decades after its release, there's now a cost-effective and reliable way to save your valuable SDS7 and indeed, your SDS6 data to an external device.
AMEP is handmade in Hemel Hempstead, Hertfordshire, United Kingdom, only a few miles from St. Albans where Simmons used to be based and where I used to work.
And finally...
I really wanted to do AMEP justice so AMEP is supplied in it's own bespoke tin which has a transparent lid section.
I designed an insert, originally to be made from ESD foam but the quotes I received for this small item were insanely prohibitive. In fact, I figured that I could buy a 3D printer and make something better, myself.
Well, my graphics guy Tony and I have been meaning to get into 3D printing for a long time and we thought this would be a good excuse to make a start. Hence, the insert is 3D printed by me.
Plagued by whole load of things that gave the Simmons SDS7 the unfortunate reputation of being quite unreliable, albeit that virtually all the issues can now be resolved, I wanted SDS7 lovers to have something that they could depend on for a change. That's one reason why the AMEP packaging took a bit longer to sort out than I'd have liked. While AMEP is pretty robust and not particularly vulnerable to electrostatic discharge (ESD) damage, the same can't be said for your SDS7.
Unlike machines that came later, the data lines on the expansion port on the back of the SDS7, are completely exposed and unprotected. THIS IS A BIG DEAL. Whether you have AMEP or not, please do take appropriate precautions when handling your SDS7.
Anyway, I digress slightly. AMEP packaging is made with a conductive PLA, thus reducing the risk of ESD damage, not to AMEP but to your SDS7. 🙂
Bambu Studio is a nice bit of software.
Tony observed that everything about AMEP except the tin, is made by Plasma Music Limited! How cool is that?
If you're keen to keep all your Simmons SDS7 data safe, you can buy AMEP here:
And finally, AMEP advanced memory expansion pack for the Simmons SDS7 would have taken much longer to develop and perhaps might not have happened at all, if it wasn't for the help, support and encouragement I received from my Simmons Vintage Technical Network friends and colleagues. THANK YOU Ed Rose, aka The Simmons Guy, Michael Buchner and Patrice Jacquot.
In particular, special thanks go to my dear friend Guy Wilkinson of Super Synth Projects who poured in hours and hours of work into this one. Guy, THANK YOU for doing so much to get AMEP finished and working. What you did is just brilliant! 🙂
UPDATE - 16th October 2024
Wow! I've already received the big question pertaining to the weird SDS7 Bank Anomaly. Whilst this hasn't got anything to do with AMEP, it's an important question and so I thought I would add my answer to this post.
According to the original owner’s manual, the SDS7 has two banks: HI and LO. The HI bank includes patches 40 to 79 and the LO bank includes patches 01 to 39.
Well, it doesn’t take a rocket scientist to notice that the HI bank has forty patches and the LO bank has thirty-nine patches! 🤔
THE SDS7 BANKS ARE NOT THE SAME SIZE 😡
So how the hell does this work? A good question and I don’t have a working original Simmons memory cassette to test that.
In theory, backing up the HI bank and then writing it to the LO bank will mean that you’ll lose a patch. Going the other way, backing up the LO bank and writing it to the HI bank will mean that you’ll have one patch unaffected (patch 40).
So here’s how it works:
Backing up the HI bank (patches 40 – 79) and writing to LO will result in patch 40 being lost. Patch 41 is written to patch 01 instead and patch 79 is written to patch 39.
Backing up the LO bank (patches 01 – 39) and writing to HI will result in patch 40 not being written to. Patch 01 is written to patch 41 instead and patch 39 is written to patch 79.
Yeah, I know. WTH?!?!?!?
Whilst AMEP is an incredibly cool piece of kit, it’s not ‘intelligent’. AMEP doesn’t have an on-board processor to negotiate the SDS7 bank anomaly. If it did, AMEP would have been prohibitively expensive and physically, much larger. ☹
BUT…. There’s a workaround:
!!! DON’T USE PATCH 40 !!!
Of course, if you save the LO bank and write it to the LO bank and if you save the HI bank and write it to the HI bank, everything will be fine. If however, you want to swap banks, then you'll have to use the workaround. I'd imagine it's the same if you have an original Simmons memory cassette.
UPDATE - 1st November 2024 - AMEP IS NOW ARM'D
Manufacturing tolerances have changed considerably over the past forty years and while AMEP will click in nicely into a brand new female DIN 41612 connector, that's not always the case with the same connector on the back of the SDS7. After four decades, things can feel a little loose.
To cater for a loose fit, AMEP now has an Anti Rock Mechanism (ARM) which securely keeps it in place. Not rocket science, just some PCB spacers added to AMEP's connector end but which work just great.
AMEP now features an Anti Rock Mechanism.
Unlike the original Simmons memory cassette, AMEP is small and light but the new ARM makes things feel even more solid and will hopefully reduce wear of the SDS7 expansion slot, over coming decades.
AMEP's ARM keeps it securely in place and prevents rocking when engaged with the DIN 41612 connector in the back of the SDS7.
The new anti rock mechanism allows AMEP to 'snap' into place. Yes, a simple idea but very worth implementing.
UPDATE - 26th January 2025
Compiling installation manuals and in the case of AMEP, a user guide can often take longer than the technical development of the respective product. Wanting my stuff to be available to the wider vintage music gear community, ideally, I'd like all of my manuals translated into several languages. Realistically that's not going to happen but when someone volunteers to translate at least one manual into one language, I simply have to jump at the chance.
That's exactly what happened while I was having a casual on-line conversation with my Simmons Vintage Technical Network buddy, Michael Buchner, who just said "Would you like a German version of the user guide?".
One of the guys who kept me motivated during my recent flurry of Simmons related projects, Michael did a great job and delivered a Bedienungsanleitung, within only a few days of our conversation.
Michael, THANK YOU so much for this! 😎
The AMEP user guide is made available after purchase but there's also a QR code on the packaging which will take you to a combined English / German file.
