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June 12, 2020Guitar cab connection can sometimes be a bit of a mystery but is critically important if for example, you’re using valve amps. That’s amps which have a valve power amp. If you have an amp that has a valve pre-amp section and a semi-conductor (transistor) power amp section, then it’s not a big deal. WHY IS IT SO IMPORTANT TO CORRECTLY MATCH UP CABS WITH AMPS? The valves in your power amp don’t connect to your cabs directly. Instead, they go via a transformer. The job of the transformer is to match up the output impedance of the valves to the input impedance of your cabs. Impedance is like resistance. It’s even measured in Ohms (Ω). Unlike resistance however, impedance is different at different frequencies and so varies depending on the frequency at which it is measured. To keep life simple, the impedance of a system is specified as an optimum, meaning that although the impedance changes as the frequency changes, the specified impedance is a particular quantity plus or minus so much. The impedance of for example, an 8 Ohm (or 8Ω) cab is roughly 8 Ohms across the used audio spectrum, plus or minus a bit. BIG DEAL. SO WHAT HAPPENS IF I GET IT WRONG? If there is an impedance mismatch between a valve amp and its load (the cab that it’s connected to), the transformer in the amp is put under stress. This stress will burn out the transformer, your amp set-up stops working and you’re definitely in for a very expensive repair. If the connection between your amp and your cab is broken and becomes what’s known as ‘open circuit’, then the same thing will happen. Effectively, your amp’s output has been set to drive a specific impedance. With nothing attached, your amp is trying to drive an infinite impedance; BANG!!!!! I’VE GOT LOADS OF CABS. HOW DO I KNOW WHAT IMPEDANCE TO SET MY AMP TO? Like anything, it’s actually quite simple if you remember a few basics. For starters, it might be worth noting the following: Speaker cabs come in combinations of one, two or four speakers. Virtually all individual speakers in all cabs are 16Ω. The impedance of the cab itself, is a combination of the 16Ω speakers that are inside it. I’ll show you how to work that out in a minute. Once you know the impedance of individual cabs, there’s a simple way to work out the impedance of all the cabs connected to your amp. The last point is the most important; there are exceptions! While most manufacturers follow the rules and apply them to most of their amps, that’s not always the case. The Roland JC-120 is a classic example and I’ll show what I mean a little later. So, let’s have a look at cabs. The simplest cab is the humble single speaker cabinet like a 1 x 12”, for example. With a single 16Ω speaker, the impedance is (you guessed it) 16Ω. A dual speaker cab will comprise two speakers of the same impedance (usually 16Ω). These will be connected in parallel. When resistors and impedances are connected in parallel, the combined resistance or impedance is worked out as follows: 'Z' is the engineering notation for impedance, so Zt is the total cab impedance and Z1 and Z2 are the impedances of the two speakers respectively. Of course since the impedance of the individual speakers is the same, the formula becomes quite simple, like this: So to work out Zt (the overall impedance of our 2-speaker cab): So you might have noticed that two speakers of equal impedance, connected in parallel, have a combined impedance of half of the impedance of one speaker... you have noticed right! If you’re still with me, let’s throw in some numbers. Let’s start by remembering that our speakers are 16Ω each: And of course, 8Ω is the correct answer! The impedance of a 2 x 12” cab comprising two 16Ω speakers is 8Ω. That’s because they’re connected in parallel. The combined impedance of series connected speakers (one after the other) is much simpler; you just add ‘em up. So if for example, our two speakers in the cab above were connected in series, then the combined impedance would be 16 + 16 = 32Ω. This doesn’t actually happen, well not to my knowledge. Cabs with four speakers combine series and parallel wiring to achieve a combined impedance of 16Ω. Modern cabs have two speakers in series which makes 32Ω. Another two speakers in series which makes another 32Ω. The two pairs are then connected in parallel. You can of course do this the other way around; parallel / series, achieving the same combined impedance. In fact most vintage speakers are wired like this so two speakers are wired in parallel to make 8Ω. The other two speakers are also wired in parallel to make another 8Ω. Then the two pairs are wired in series to make (8Ω + 8Ω) 16Ω. If you're not used to all that arithmetic, it can kind of look a little intimidating. On the hand, if you go over it couple of times, it will hopefully start to make sense. So, cabs can be treated in the same way as individual speakers although cabs are usually connected in parallel inside your amp... err... with one exception (that I know of) and that the Roland JC-120. Firstly, although it's a combo the speakers aren't powered by one amplifier. There are two independent amps, one driving each of the speakers. Secondly and more relevant to this post, when you plug in additional speakers, they're actually connected in series with the internal speakers. Remember that the JC-120 is a transistor amp so impedance matching isn't an issue. What it does mean however, is that the load on each amp, will increase when you plug in more speakers, thereby reducing the power output of the whole amp. Remember that we worked out that 4 x 12 cabs are normally rated at 16Ω? Now consider using two 4 x 12 cabs to make a full stack. Plugging them both into a single amp where they are connected in parallel inside the amp, will make the overall speaker load, 8Ω, just like our very first 2 x 12 example. 2 x 12 cabs work in the same way. Each 2 x 12 cab is 8Ω. Connect two of them to a single amp and the combined overall impedance will be 4Ω so you need to set you impedance switch on the back of your amp, to 4Ω. As with most things in life and as I've said a couple of times in this post, there are exceptions. As I say, the nice thing about standards is that there's so many to choose from! 🙂 Now then, pictured below is the back of a Marshall TSL122 100 Watt 2 x 12 combo. So is this confusing or what? For starters, the speakers in this thing are different. Marshall decided to combine a Celestion Vintage with a Celestion Hertitage. Yeah, I know people do that but I'm not a fan, to be honest. Anyway, the point is that each speaker is 8Ω. On top of that (and the second point), is that they're wired in series to create 16Ω. Well that kind of makes everything I've just said, seem like a complete and utter waste of time. On this particular amp, the on-board speakers are plugged into the (default) 16Ω speaker output, the markings of which are obscured in the picture, by the lead. Plugging into this socket, disengages the other sockets. If you want to use external cabs, you need to unplug the lead going to the on-board speakers, plug into one or both of the other sockets and if your cab impedance is 4Ω or 8Ω, you'll then need to select your impedance appropriately. If you've got a 16Ω cab, you have to unplug the lead going to the built-in speakers and plug your cab into the 16Ω output. That's really confusing and personally, I can't see a way to use the on-board speakers and an extension cab! I'm not a fan of the TSL series but this kind of thing really makes me back off! Then there's the Roland JC-120 which I've mentioned a couple of times, earlier. Not a valve amp so impedance isn't at all a big deal but... it's rather interesting that anything plugged into the speaker jacks around the back, is put in series with the on-board speakers. You have to remember that this thing came out in 1979, so what was Roland thinking? On the other hand, who'd want to mess with the sound that comes out of a bog-standard Roland JC-120? It's gorgeous! So the bottom line is that you need to always check. Read anything that's written on the back of your amp and on the back of your speaker cab. Make sure that you read the manual and if you do get stuck, then you can always just call me! Oh and one more thing; ALWAYS USE GOOD QUALITY SPEAKER CABLE!!!!!!!...

USB MIDI KEYBOARD TO MIDI HARDWARE HOW TO

May 15, 2020One subject that comes up time and time again is "how to connect a USB MIDI keyboard to MIDI hardware". I've therefore decided to put up this post... It's not exactly difficult but at the same time, you can't take it for granted that the MIDI keyboard you've got your eye on, actually has well... MIDI ports. Just about every controller seems to be designed to plug straight into your computer and hence, only has a single USB port. Manufacturers tend to offer their controllers in versions with those little 5-pin DIN sockets but they're usually upgraded versions with for example, seventy-six keys instead of the sixty-one keys that you wanted and perhaps more to the point, the version that'll fit on your desk or that's within your budget. In a market that has been increasingly dominated by computers, some might concede that it's hardly surprising that MIDI ports are omitted from modern (MIDI) controllers. On the other hand, for those of us that have a collection of hardware sound modules, synthesisers and drum machines, MIDI controllers without MIDI ports is kinda useless! Fortunately there's a potentially very simply and cost-effective work-around; introducing the MIDI USB host! So a MIDI USB host is basically a small box running embedded firmware that recognises any class-compliant USB MIDI controller. That middle bit (class-compliant) is really important. A MIDI USB host is designed to be switched on and left. There's no monitor, QWERTY keyboard or mouse attached and there's no way to access the 'operating system'. It stands to reason therefore, that connecting anything to it, should be immediately recognisable and that means that anything connected to it MUST be class-compliant. Well, fortunately most USB MIDI keyboards are just that but it's always worth checking. Several manufacturers make MIDI USB hosts but perhaps two of the most well known are those made by Kenton Electronics and MIDITech. Be expected to pay about 85 GBP for the former and 66 GBP for the latter. For the DIYers amongst us, I've chosen to include the USB Host Controller Board V2.4 in the image above. Available from https://www.hobbytronics.co.uk/ for a modest 16.20 GBP (at the time of writing), this kit is available in a variety of 'pre-blown' versions, with appropriate firmware put on to the 24FJ64GB002 microcontroller before it's sent out. One version makes this little board into a great USB MIDI host. You'll need to connect 5-pin DIN sockets, provide power and box it up yourself but for anyone who feels a little adventurous, this can be a very cost-effective solution. One point worth noting, is that these boxes require power and both examples mentioned above are equipped with USB power ports that are secondary to the USB port that's used to accept the connection from your USB MIDI keyboard. MONSTER MIDI INTERFACE A company called iConnectivity makes a series of MIDI interfaces that are superbly designed and particularly suited for the modern audio production environment. The MioXL for example, has ten (yes TEN) USB MIDI ports as well as a bunch of conventional 5-pin DIN MIDI ports and... it also supports RTP-MIDI via a RJ-45 connection. Fully configurable via software hosted on your computer, the MioXL also has an elegant OLED display providing an array of status information. Available for under 350 GBP, this is a seriously powerful interface that's designed to connect to just about anything that can carry MIDI. LATENCY Anyone working with digital audio will be familiar with something called 'latency'. Loosely defined as the time between a signal entering a digital system and leaving the same digital system, latency is basically the time taken to digitally process a signal. If that means simple analogue to digital or digital to analogue conversion, then even that process takes a finite period. This is not the case with analogue electronics although there does exist an almost analogous parameter called 'propagation delay' but let's not confuse things just yet, eh? When working with computers specifically, latency can be quite substantial as there's a lot going on in these boxes that we've all grown used to. Having said that, clock speeds and more efficient processing both in software as well as hardware, has reduced latency over the years and in most situations, it's not a real concern anymore. On top of that, manufacturers of audio interfaces introduced 'direct monitoring' a long time ago which was and still is a great work-around to the issue of latency. So going back to our USB MIDI host, it should be noted that by design, the smaller boxes are very simple and are designed to do one thing and one thing only. Hence, while latency technically still exists, simply by the nature of the beast, it is negligible. I use a Kenton Electronics MIDI USB host myself and I can assure you that if latency was an issue, I simply wouldn't bother....

ROLAND SUPER-JX UPGRADES

May 12, 2020Following on from my post covering the installation of a replacement power supply into a Roland MKS-70, I decided to do another post on a whole bunch of cool Roland Super-JX Upgrades which I discovered during lock-down 2020. Apologies if some stuff is kinda repeated. Back in April 2020, I got a Roland MKS-70 in for repair. It was powering up but wasn’t booting. While replacing original components that were over thirty years old on the power supply, another MKS-70 came in with err… power issues. This all happened during lock-down so progress on the repairs was kinda slow. I did however, have lots of time to see what I could find on-line. I very quickly came across supersynthprojects.com and over a period of days, got to know Guy Wilkinson, a vintage synth enthusiast with a very relevant background. Guy has developed a switched-mode power supply for the JX-10 and MKS-70. Guy also supplies a variety of displays, one of which particularly caught my attention, the Super-JX OLED upgrade display. As many Super-JX owners will know, the original vacuum fluorescent display (or VFD) as well as the FIP coil that drives it, is just about impossible to get hold of now. VFDs and FIP coils fail, so any potential replacement is well worth checking out, especially if it's going to be OLED cool. I've always wondered why some people use the adjective "sexy" to describe tech'. Guy's Super-JX OLED looks stunning and now I know. I just can't stop looking at it! 😛 As I continued my research into the world of Roland Super-JX upgrades, I came across vecoven.com and the Vecoven PWM upgrade; a kit which provides the Super-JX sounds with pulse-width modulation. WHAT!?!?!?! Fred Vecoven sells the PWM upgrade as a self-assembly kit comprising two small PCBs (one for each voice board), lose components, three EPROMs and two replacement 80C320 processors (again one for each voice board). An option to buy populated PCBs is also available. Neither the self-assembly kit or the pre-assembled PCBs kit are however, supplied with cabling or connectors, presumably because there are several potential mounting options. Guy's website has detailed installation instructions for Fred's PWM kit, both for the JX-10 and MKS-70. Below is a pair of Vecoven PWM upgrade PCBs which I have made up myself. The keen and eagle-eyed will have noticed that the ICs aren't soldered directly to the PCB and that instead, I've chosen to use turned-pin sockets; always a good idea! Fred Vecoven has also rewritten the Super-JX firmware and has developed a flash upgrade module which, apart from increasing the memory to the equivalent of thirty-two Roland M64C cartridges (yes, that's right... 32 x M64Cs), allows firmware updates via MIDI. Fred's firmware also gives you some control over how Guy's displays work. Hey, is that teamwork or what? Well it just so happens that I also have a Roland MKS-70 (yeah, I know... you're really surprised, right?) and all this stuff just sounded soooo exciting. Within a few days, I ended up with a switched-mode power supply PCB and an OLED kit from Guy and a PWM kit and a Super-JX flash module from Fred. My wife wasn't happy. And I thought lock-down was going to be oh soooo boring! I had to buy all the components for the P0004 power supply but conveniently, Guy has a very detailed bill of materials (BoM) on his website. This made components purchase very easy. The OLED module came fully assembled and Guy e-mailed me instructions on how to install it. As previously mentioned, Fred's PWM kit doesn't include connectors and cables so I also had to buy some bits to get this going. Getting to know Guy and Fred was a privilege. In fact, I eventually struck up a deal with Guy and I am now offering ready-built versions of his P0004 switched-mode power supply board, as well as an installation service for this fantastic upgrade and his Super-JX replacement displays. Click here for my prices. If you're fitting the switched-mode power supply module yourself and your MKS-70 or JX-10 has a 2-pin IEC mains input socket, then you must replace it with a 3-pin IEC mains input socket. The replacement switched-mode power supply MUST be connected to earth as must the chassis of your Super-JX. The 3-pin IEC mains socket kit comprises the following: 1 x IEC 3-pin chassis socket. 3 x pre-cut heat-shrink strips. 1 x insulating boot for IEC socket. 1 x M3 earth tag. It is paramount that if fitted, a 2-pin IEC mains socket be replaced with a 3-pin IEC mains socket and that the chassis and the P0004 are connected to earth.Installing these Roland Super-JX upgrades into my own MKS-70, was hard work but I had a lot of fun doing it and... I got to know a couple of seriously intelligent dudes. My humble contribution to the awesome work that Guy and Fred have done, is a simple bracket which makes mounting the PWM boards into a MKS-70 a little easier. IMPORTANT: Since the bracket secures to the transformer mounting studs, it can only be fitted if Guy's P0004 switched-mode power supply is also installed. The IDC connectors I've used, don't have the tidy fold-over clamp (retainer). That's because those ones are too high and this neat little mounting solution won't work as the whole assembly will simply be too high to fit in the MKS-70's 2U case. I wasn't going to offer this bracket as an item as it didn't seem worth it but I've been persuaded to get some made up and so I’m selling them with fixing hardware (screws, washers, spacers), as a kit for 22 GBP. If you fancy one, you can either buy now from here or just message me. Note that the bracket isn't necessary when fitting the PWM kit into a JX-10. Inspired by Guy's switched-mode power supply, I've proposed a couple of joint projects so watch this space! !!! WORDS OF CAUTION !!! These machines are over thirty years old. As such, nuts and screws have seriously bedded in. You may find some glue around the nuts and even some signs of corrosion. If you're upgrading one of these machines yourself, please take care when undoing nuts and screws. The studs which secure the massive heat-sink plate of the original power supply and also the transformer for example, can become lose. When trying to remove the nuts on the inside of the chassis, they'll just spin around and they won't undo. If this happens, you'll need a pair of mole-grips to carefully hold the studs from underneath the case while gently loosening the nuts with a box spanner on the inside of the case. Mole grips can be a little aggressive so you might want to think about protecting the case with some thick tape. Put the tape around the lug of each stud and also put some tape on the tips of the jaws of the mole-grips. I found thick masking tape best for the case and lugs and cloth (or gaffer) tape is good on the mole-grips. When re-assembling, I would recommend replacing the nuts and soaking them in a lubricant like WD-40 prior to fitting. !!! NOT FOR THE FAINT HEARTED !!! The second point I should make is that with the exception of the Vecoven Flash module, all other upgrades mentioned here, require some considerable experience of soldering, desoldering, working with surface-mount devices and respecting electrical safety and electrostatic sensitivity. You should also be prepared to drill into existing PCBs and / or original chassis metal work. !!! Remember, if you get it wrong, you might permanently damage your synth !!! Today, my MKS-70 still looks pretty much as it did when my good friend Rob donated it to me, several months ago. Under the bonnet however, it’s quite a different beast. The sound is still lush and beautiful but... As a result of installing Guy’s P0004 switched-mode power supply, not only has reliability and longevity been increased but this machine can be plugged straight into just about any mains supply on the planet. The sounds can now benefit from pulse-width modulation thanks to the Vecoven PWM upgrade. The Vecoven Super-JX flash module has increased the memory to a ridiculous amount; more patch changes and less SysEx transfers! Firmware updates can now be performed over MIDI. Guy's Super-JX OLED display looks quite simply, beautiful. To the experienced Super-JX user, it might be the only indication that something is err... different. The Super-JX OLED will live much longer than the original VFD and FIP coil which can only give peace-of-mind. LIVE FOREVER BATTERY MOD This is something I do which isn't unique to the Roland MKS-70 and which can be fitted into almost any synthesiser or effects processor. It's NOT literally a 'Live Forever' battery mod as nothing obviously lives forever. The chances are however, that it'll out live you! The damage caused by battery leakage can be irreversible. It's not just a case of losing all those tones and patches that you err... forgot to back up. Battery leakage can seriously damage the PCB on which the battery is mounted; usually the CPU board in most machines. I mount a high-capacity lithium battery off any PCB giving you the following three main benefits: Will last a lot longer than the standard CR2032 which is found in most synthesisers and effects processors. Mounted off-PCB so in the remote event that it does leak, sensitive electronics inside your equipment is protected. Positioned such that battery voltage can be easily checked by only removing the top of your machine. If you missed it earlier, all my prices can be found here. SUPER-JX EDITORS, CONTROLLERS, PROGRAMMERS Anyone with a Super-JX will be aware of the Roland PG-800, a programmer / editor, specifically for the JX-10 and MKS-70. Today, PG-800s are hard to find, relatively expensive and quite honestly, you'd be lucky to find one in really good condition. I'm not talking cosmetically but electronically and it's worth bearing in mind, that parts are becoming ever scarcer. Thankfully, a company called RetroAktiv makes a small collection of hardware programmer / editors for several popular vintage synthesisers... including our beloved Super-JX. I don't have one of these myself but I've heard only good things about the RetroAktiv MPG-70. On top of that... damn, it looks good! At 875 USD, the RetroAktiv MPG-70 costs a couple of hundred USD more than an original Roland PG-800. The thing is, even if you forget about the fact that this box is going to be considerably more reliable than thirty-something year old electronics, you're getting a lot more for your money and (I'm going to say it again) it just looks awesome. If you're still not convinced, then RetroAktiv also makes a smaller Super-JX editor called the MPG-8, which retails for just 349 USD. One of the many features of both of these controllers, is full compatibility with the Vecoven PWM upgrade and firmwares. For some time now, I've been using a plug-in called Ctrlr. It’s basically an open-source environment for Windows, OS X and Linux, which allows users to develop programmers and editors for just about anything. Many users share their ‘panels’ on the Ctrlr website and I was so surprised to find a panel specifically for the Vecoven V.4 firmware upgraded Roland Super-JX. This doesn't really fall into the category of Roland Super-JX upgrades as such but I think it still deserves a mention. Available for Windows and OS X, 32 or 64-bit and in plug-in or stand-alone format, you really need to check this out. Oh and it's free! 😀 The RetroAktiv programmers will work with Super-JXs running standard (factory) firmware although some sliders and knobs won't do anything as there's no PWM to modify, for example. The Ctrlr panel above will ONLY work with Vecoven version 4 firmware. While I've seen Ctrlr panels that'll work with Vecoven version 3 firmware, I haven't come across anything that'll work with bog standard Roland firmware. It's been most reassuring to discover that I'm not alone, that there's a whole community out there that share my appreciation and even passion, for this underrated monster of a synthesiser. I'm so grateful to people like Guy, Fred and the RetroAktiv crew, who after more than thirty years from it's launch, have embraced the potential of the Roland Super-JX, developing upgrades that ensure this magnificent machine lives on. I'd love to contribute what I can so please don't hesitate to contact me if you'd like more information on any of the Roland Super-JX upgrades mentioned here. I'd love to hear from fellow fans of this awesome synth. 😎 In the meantime, here's a few links that you might want to check out: http://super-jx.com/ - Sites like this, truley keep the legend alive! http://www.vintagesynth.com/roland/jx10.php - An excellent reference site. https://www.facebook.com/groups/SuperJX/ - You just knew that there had to be a Facebook group, right? https://www.facebook.com/groups/1837407526336417/ - ...or two!!! UPDATE: 11th July 2020 Wow! Since I put up this post, things have got a little busy....

LCD BACKLIGHT REPLACEMENT

May 10, 2020A relatively common problem on older equipment, is the failure of the LCD backlight (or EL-panel). Often accompanied with a very high-frequency whine emanating from the LCD area of the gear in question, it's time to consider LCD backlight replacement. Here's a Roland GC-8 editor / controller for the massive Roland R-880 reverb (circa 1988). Without the controller, the R-880 which really is an awesome machine, is kind of useless as there's little out there to program it via MIDI. Luckily and thanks to a company called backlight4you, LCD backlight replacement is now worth looking into to. A variety of EL-panels that are suitable for a whole bunch of older gear, is available at the company's website which is also full of other useful and related information. Their backlights are reasonably priced and arrive from Germany pretty quickly and in very stiff cardboard packaging. After fitting the replacement EL-panel, I powered up the unit to check. Wow! It looks great and on this occasion I got lucky and that bloody annoying whine has gone! IMPORTANT: As a backlight ages, its electrical characteristics change, These changes put a strain on a small component called an inverter which converts dc within the unit to high-frequency ac which is required to drive the EL-panel. As this components deteriorates, it starts to whine. In many cases, replacing the backlight will fix that problem but... not always. : ( If after swapping out your backlight, your unit is still whining, then backlight4you may still be able to help. Take a closer look at their website and you'll find a section on inverters. Designed to run from common voltages and power many of the EL panels that are sold on the website, these replacements are very reasonably priced. Replacement inverters might not be pin-for-pin compatible, especially with very old equipment but with a little ingenuity, you might be able squeeze a one in somewhere. Due to the low cost of replacement inverters, I would personally recommend swapping out the inverter when fitting a new EL-panel. Need help with a hard-to-read LCD? Drop me a line....

ROLAND MKS-70 POWER SUPPLY REPLACEMENT

May 2, 2020Never thought I’d make a new friend over lock-down but I have recently struck up a relationship with Guy Wilkinson of supersynthprojects.com. While working on a very broken Roland MKS-70 that I have in for repair, I came up with the idea to design a MKS-70 power supply replacement but figured that after all these years, perhaps someone has already thought of this. After a few minutes of searching on-line, I stumbled across https://supersynthprojects.com. The work that Guy has done, is truly amazing. His power supply design is quite simply, elegant and I’m so impressed with his methodical record keeping. As it turns out, Guy seems to be a bit of an expert on several vintage machines. Anyway, having a Roland MKS-70 myself, one thing led to another and I’m currently in the process of building one of Guy’s P0004 switched-mode power supplies and installing his Super-JX OLED display module into my own MKS-70. It’s a bit difficult doing this during lock-down but I’ll keep you posted of progress. Guy sells the P0004 switched-mode power supply bare PCB and the pre-assembled Super-JX OLED display directly but you'll need some competence to populate the former and fit either, into a JX-10 or MKS-70. If you're cool enough to admit that all of that sounds a bit too much for you, then please don't hesitate to contact me to discuss getting either (or both) fitted into your machine. Click here for prices. If you're fitting the switched-mode power supply module yourself and your MKS-70 or JX-10 has a 2-pin IEC mains input socket, then you must replace it with a 3-pin IEC mains input socket. The replacement switched-mode power supply MUST be connected to earth as must the chassis of your Super-JX. The 3-pin IEC earth bonding kit comprises the following: 1 x IEC 3-pin chassis socket. 3 x pre-cut heat-shrink strips. 1 x insulating boot for IEC socket. 1 x M3 earth tag. It is paramount that if fitted, a 2-pin IEC mains socket be replaced with a 3-pin IEC mains socket and that the chassis and the P0004 are connected to earth.UPDATE - 10th MAY 2020 Last night I installed the assembled switched-mode power supply into my own Roland MKS-70. I'd already tested it outside the machine but I was still nervous. Hey, the MKS-70 fired up straight-away. The power supply worked just fine and quite honestly, if you're having issues with the power supply in your Roland MKS-70 or JX-10, then getting one of these is a no-brainer! UPDATE - 12th MAY 2020 Took a while and was a bit tricky but the display got done and works absolutely brilliantly (pardon the pun). In fact it looks positively beautiful. The Super-JX OLED module 'learns' the system's firmware so before I switched on the unit to test, I thought I'd drop in the Vecoven Super-JX flash module. Pressed the power button and everything powered up just great. UPDATE - 19th MAY 2020 Several days ago, I posted here that I'd keep you updated of progress on this project. I also suggested that I'd probably end up making a new post. Guess what? So, click here for more on Roland Super-JX Upgrades. ...

ROLAND MKS-70 REPAIR

March 19, 2020Recently, this gorgeous vintage Roland MKS-70 synth module came in for repair. The MKS-70 is basically the rack version of the Roland JX-10 keyboard synthesiser, which itself is essentially two JX-8Ps. Also known as the Super-JX, the JX-10 and the MKS-70 are famous even today for their rich, analogue tone and pristine sound quality. At this point I need to make something clear; the Super-JX is not actually 100% analogue unlike for example, one of it's well known predecessors, the MKS-80. The oscillators are in-fact, digital. So when I refer to 'analogue' tone, I'm referring to just that, the tone. Check out more details and some sounds here and here. Anyway, the customer said that it wasn't powering up properly with just a flash briefly appearing on the display and then nothing. Well, let's see if we can get this ol' girl singing again.. Apart from being a giant classic, the MKS-70 like the MKS-80, has hinged circuit boards which means that it opens up quite nicely. Having said that, if you need to get at the 'CPU' board (the service notes refer to this as the Assigner board, for some reason), you really do need to disconnect and remove the lower analogue voice board. Checking voltages before anything else, I realised very quickly that I had a major problem. The voltages on the power supply were all about 25% more than what they should be. Eek! Hope no serious damage has been done. I'll keep you posted on this fix but please bear in mind that I'm respecting the COVID-19 lock-down so it may be a while before I'm back. UPDATE - 2nd April 2020 The power supply is a really clever and well thought out design for the time but I don't think the Roland R & D team had any idea that their machines would still be making music over thirty years after their conception. There's a small voltage monitor chip on the power supply which when fails, sends the +/-15 V rails to like 22 V. Unfortunately the +5 V rail for the digital stuff has a dependency on the +15 V rail so if that freaks out, then so does the +5 V rail. I decided to change all the major components on the PSU including transistors, capacitors, bridge rectifiers and of course that frigin' voltage controller IC. Okay, so now power is good. UPDATE - 14th April 2020 Well my worst fears an' all that... The voice-boards turned out to be fine but the CPU or assigner-board was seriously not happy. The code was trying to run but not getting anywhere. This was going to be a hard fix....

PLASMA MUSIC SALE 2020

March 18, 2020Last year, I started to downsize my recording facility and so a lot of stuff is now up for grabs in my Plasma Music Sale 2020. It's not just studio gear but drums, cymbals, guitar and keyboard stuff, video cameras, computer equipment and live performance gear like complete PA systems, mixing desks, powered monitors, multi-track recorders, amps, radio mics and so much more. Some of it's old and some of it is relatively new but either way, it's all been lovingly looked after while I've had it and most of the stuff is in pristine condition and it all works perfectly. Please do check it all out my Plasma Music Sale 2020 here before it all goes on eBay! If you need more information about a specific item or just not sure about something, then please don't hesitate to contact me. NOTE: I haven't bothered with an on-line shop. Seems a bit over-the-top. To date, buyers have been quite happy either paying via PayPal, bank transfer or cash on collection....

OK GOOGLE SWITCH ON MY COMPUTER

March 1, 2020NO MESSING AROUND WITH LOADS OF APPS NO CUT AND PASTE COMMANDS JUST SET THIS UP AS A DEVICE IN GOOGLE HOME OR AMAZON ALEX Occasionally I build a batch of things which I put up here for sale. It's not worth me puting up an on-line shop just yet, so if you want anything, just contact me. Anyway, recently I built a bunch of smart momentary switches which will allow you to turn on your computer from your Google Assistant or Amazon Alexa. Just say "OK Google, switch on my computer" or "Alexa, switch on my computer" and it just happens! This item is basically a kit comprising some parts which need to be attached to the header on the motherboard inside your computer. Hence, this kit is ONLY suitable for computers which have an accessible motherboard and a standard motherboard header. UNFORTUNATELY THIS KIT IS NOT SUITABLE FOR LAPTOPS, TABLET PCs, STICK PCs AND MACs. Since parts need to be attached to your computer's motherboard, a basic proficiency of working with computer hardware is required. If you're not confident to open up your computer and move a couple of bits around, then either find someone who is or think again about buying this. Included is a small ABS box which contains the electronics and which has an integral USB lead for power, a USB power supply, a standard PCI back-plate (this should fit most ATX sized cases) and a connection cable which connects the box to your computer via standard 3.5mm jack plugs. Oh and a link to download full instructions (in UK English only, I’m afraid), are also included. I can't exactly call this box an OK Google switch on my computer box! Instead, I'm just calling it 'SMS' which stands for Smart Momentary Switch. OK GOOGLE, OPEN MY GARAGE DOOR Yes, that's right! I make a version of this gadget which can be used to open and close your electric garage door via your Smart Home (Google Home Assistant or Amazon Alexa). So how much does it cost? £59 including postage to UK mainland. That's a bit more than I'd like but I hand make these myself in small batches. Click here to buy....

BEHRINGER DEQ2496 REPAIR

February 26, 2020On the bench today is a Behringer DEQ2496 repair. This is the third generation of 'Ultra-Curve' from the well-known German manufacturer. The DEQ8020 and DEQ8024 were both 2U units but in 2005, Behringer released the super high-specification 1U DEQ2496. These extremely high-quality and versatile processors do a lot more than graphic equalisation. Amongst the machine's function is a real time spectrum analyser. You can purchase a Behringer ECM8000 calibration microphone and quickly and easily set up the graphic to 'compensate' for room acoustics, for example. There's also a mired of other functions such as parametric eq, dynamic eq, dynamic processing and time delay, to name but a few. With digital inputs and outputs (S/P DIF on TOSLINK and AES / EBU), the analogue side of the DEQ2496 is balanced and boasts a fantastic dynamic range with its 24-bit / 96 kHz conversion. Finding popularity amongst hi-fi enthusiasts and audiofiles, the latest and current Ultra-Curve is of course also very popular with PA hire companies, recording studios and even in musicians' instrument rigs. So, unreliable power supply, then? No, definitely not! The date code on the one that's on the bench today is July 2006. That makes in almost fourteen years old and quite honestly, it's done bloody well, in my humble opinion. The repair to the power supply takes just over an hour. The parts cost about twenty quid and in no time, the machine's going to last another fourteen years, at least. 🙂 So, if you're in need of a Behringer DEQ2496 repair, don't hesitate to give me a call. Check out the Behringer DEQ2496 Ultra-Curve here....

UNBALANCED TO BALANCED CONVERTER

February 17, 2020Many musicians, engineers and producers appreciate why signals should be kept as 'hot' as possible. High signal levels can reduce your noise floor and of course a lot of professional, studio equipment is designed to run at +4dBu (about 1.25 volts). What many might not appreciate is the virtue of also running balanced signal lines. Running an analogue audio signal over a balanced line severely increases immunity to noise. I won't go into the physics of just why that is yet, although I'll no doubt end up adding to this post at some time in the future. Unfortunately there's a lot of older gear out there including stuff we all love dearly, which has unbalanced +4dBu outputs. The Marshall JMP-1 that was featured in a recent post, is a prime example. The Roland RSP-550, an excellent nineties multi-effects processor, is another example. So, the traditional way to convert an unbalanced signal to a balanced signal is to run it into a D.I. box. We're all familiar with those little boxes that cover many a studio and stage floor, right? They work just great but while they balance the signal, they also knock down the level of the signal to a few millivolts which means that you have no option other than to run the other end into a mic. pre-amp, either as a separate unit or built into a desk. That's not always convenient and it seems stupid attenuating a signal, only to amplify it again, anyway! Have you noticed another downside to trying to use a D.I. box to solve this problem, yet? Earlier I gave the example of the Roland RSP-550. It's an effects unit. It has +4dBu inputs! So you ain't easily gonna be able to send signal from your desk to it via a D.I. box! The inputs on the RSP-550 are looking for either -20dBV or +4dBu. The microphone level output from a D.I. box just won't be enough to drive the unit. On top of that, the D.I. box output is balanced. The inputs on the RSP-550 are unbalanced. That's actually two downsides. 🙁 To convert an unbalanced signal to a balanced signal and maintain the level of the original signal was a problem I decided to solve once and for all, many years ago. I developed the transformer coupled interface (TCI). It's not rocket science (as they say) but boy, do these things come in handy. The TCI is a non-powered device (like a passive D.I. box) which basically comprises a single transformer on each channel. I designed the transformer myself as not only did I want the best linearity I could get over the entire audio spectrum but I also wanted minimum phase distortion, especially down the bottom end, something that cheaper transformers tend to generate. Anyway, I managed to get a bunch of these things made here in the UK and the TCI was born. Similar to a passive D.I. box, one hidden benefit to using the TCI, is that it offers something called 'galvanic' isolation which means that the signal path between your source and destination equipment is 'broken'. With the ability to easily lift the earth on the output (balanced side) of the TCI, these things are just great for getting rid of ground loop problems! IMPEDANCE All equipment has what’s called an input impedance and an output impedance. Impedance, like resistance and is measured in Ohms but differs in that it's frequency dependant. The impedance varies depending on the frequencies in the signal. Taking a guitar signal as an example, the input impedance of an amp let's say, will be different at 500Hz than it will at 5kHz. Having said that, due to the nature of things, a common resistor is often used on for example, the output of an electronic circuit to provide the output impedance of a device. Most guitarists will be quite aware that everything to do with guitar electronics is high impedance and that the first thing you plug your guitar into should have a very high input impedance. This reduces the ‘loading’ on the guitar pick-ups and allows for a good frequency response further on down the chain. Unbalanced outputs like those found on a lot of consumer electronics such as hi-fi gear, have a high impedance, perhaps in the order of thousands of Ohms. Balanced outputs in contrast, are always low impedance; just a couple of hundred Ohms. Again, I won't go into the physics suffice to say that this is why amongst other things, low impedance outputs allow for long cable runs. There are exception; unbalanced outputs on a lot of ‘studio’ gear can be low impedance. This makes life a lot easier! The TCI has a low input impedance and while it will technically work on something with a high output impedance, you might notice some high-end roll-off. Basically, you’ll need to check the output impedance of your gear before considering a solution like the transformer coupled interface. That’s why D.I. boxes are so popular. D.I. boxes have a high input impedance which means you can plug in just about anything. Like my transformer coupled interface, passive D.I. boxes also have a transformer to convert the input to a balanced line. The turns ratio of the transformer however, is such that while presenting a high impedance at the input and low impedance at the output, the signal voltage is greatly attenuated. Hence, the output of D.I boxes is mic. level....

MARSHALL JMP-1 SERVICE

February 13, 2020Here’s a Marshall JMP-1 MIDI valve pre-amp that I’ve just serviced. I’ve changed the valves and power supply capacitors, cleaned up the metal work and implemented my ‘Live-for-Ever’ battery mod’. The battery is bang in the middle of the board so you really don't want this to leak. The serial number indicates that it was built in early 1992 which not only makes it twenty-eight years old but one of the first JMP-1s off the Marshall production line. An early MIDI valve pre-amp, the Marshall JMP-1 has always been a really under rated bit of kit, despite the fact that named artists such as Billy Gibbons (ZZ Top), Phil Collen (Def Leppard), Iron Maiden, Megadeth and many more, still use them even today. In production for well over ten years, also says something about this little gem. The JMP-1 is not a modeler like modern stuff; it’s the real thing, just with MIDI. Run into a valve power amp (or two), it just sounds amazing and the quality of the speaker emulated outputs is definitely good enough to go straight into the board or your DAW. With most of the distortion being generated in the semi-conductor domain (some of which is highlighted in the image below), many purists might shy away from this beast. On the other hand, classic Marshalls such as the legendary Silver Jubilee series and the monstrous JCM900 Dual Reverb, also use semiconductors to produce some of their distortion tones. And then there's the clean channel of the JMP-1 which is based on the classic Fender design... with a few tweaks, of course. Anyway, at the end of the day, it's the sound that counts and as I've said, these things have still got it, even today. RATTLE A' HUM If there's one annoying characteristic of an ageing Marshall JMP-1, then it's got to be the humming transformer. Anyone in the know, might think it strange that this box which resides in a 1U rack enclosure doesn't have a toroidal transformer. The thing is, the JMP-1 transformer chucks out several voltages including those required for the two valves and it's quite challenging to build all that into a toroidal design. So after a few years, the laminates inside the conventional transformer can become lose and start oscillating. The mechanical vibration can be annoying but does not appear on the audio signal. If you're heavily in love with your humming JMP-1 and want to do something about it, then give me shout! Marshall JMP-1s now go for between £400 and £700 (yes, £700). If you can pick one up nearer £400, then I personally think you've got yourself a bargin and a seriously good bit of gear. If you want to find out more about the JMP-1, then there's loads of resources on-line and of course the Marshyall JMP-1 forum on Facebook: https://www.facebook.com/MarshallJmp1/ If you have a JMP-1 and it's in need of a little TLC, then don't hesitate to contact me. MARSHALL JMP-1 FACTORY RESET WARNING: Implementing this procedure will permanently delete all user-made changes to any patches. Switch off JMP-1 via the power button on the far right. Hold down the OD1 button and the CLEAN 1 button. While holding down these buttons, switch on the JMP-1. Wait a few seconds while the display flashes and then release the OD1 and CLEAN 1 buttons. ...

AUDIO TRIGGERED MAINS SWITCH

February 11, 2020Over the past couple of weeks, I’ve been designing a gadget to switch on a power amp when an audio signal is detected and to wait a few minutes to switch off the power amp when no signal is present on the input. The audio signal comes straight from the sub bass output of an A/V amp and is therefore about -10dBV (approximately 310 mV) unbalanced. So apart from auto switch-on / switch-off, the circuit also amplifies the input signal to +4dBu (about 1.25 V) balanced so as to properly drive the power amp. After testing a prototype for several months, this evening I ordered the PCB (the design of which is pictured above) for the final version. SO WHAT'S THIS ACTUALLY USED FOR? Well, the power amp in question, drives a sub-bass system on a home cinema. It's a big, professional amp and definitely wouldn't come with auto power-on / power-off which of course, the main (consumer) A/V amp does have and which 99.9% of consumer sub-bass units have built-in. The idea is that when the home cinema system is switched on, the power amp comes on when it detects a signal. When the system is switched off, the power amp switches off a few minutes later... PERFECT! CREDITS I don't see the point of reinventing the wheel, especially if someone has already designed something really good that works. Hence, the switching circuitry of this gadget is based on a design by Rod Elliot of Elliot Sound Products (see project 38). Rod puts up some fantastic, in-depth explanation into how the circuit works and how it can be tweaked to your specific requirements. UPDATE - 18th February 2020 This morning, my PCBs arrived. I couldn't wait and quickly got down to populating one of them ready to test later in the afternoon. Well, I'm pleased to report that all worked well. With a 1kHz sine wave, the sensitivity of the circuit is about 4.5mV and the delay to switch-off time is about ten minutes. Unfortunately, the case I'll be using for this, is currently out of stock 'till 17th March, so it looks like this is going to sit on the shelf for a few weeks 🙁 UPDATE - 18th March 2020 Today I went over to RS Components in Watford to collect the enclosure that I'd planned to use for this project and the dimensions of which were part of the design of the PCB. Well, I couldn't believe what I was told; the boxes remain on back-order 'till, wait for it... 31st July. Seriously?!?!? I checked last night and there was no change in status. What the hell are you playing at?...

ROLAND VK-7 – POWER SUPPLY REBUILD

December 4, 2019This Roland VK-7 belongs to my mate, Alex Richards. The transformer is mounted upside-down on the inside of the top chassis. Guess what? It fell off! The machine was plugged in at the time so the accident caused considerable damage. To avoid this happening again, I mounted this heavy little component to the bottom (steel) chassis and laid new connections to the power supply board. Twenty years old, has taken quite a few knocks, it plays and sounds great....

NEKTAR IMPACT – BEST TECH SUPPORT EVER

December 4, 2019Customers’ units come first so when my own stuff needs repairing, it kind of gets put to the back of the que, especially if it’s not a critical system. Anyway, a few weeks ago, the attack slider on my Nektar Impact LX61+ MIDI keyboard started playing up. I tried to do a quick fix but the potentiometer was definitely duff. I fired up a support ticket and received the most amazing response from Nektar. The company basically just sent me a whole new PCB! All I really wanted was the slider pot’. Cost-effective, versatile and easy to program, the Nektar Imact range of MIDI controllers seem perfect for any project studio set-up. Now that I’ve experienced the company’s support first-had, I really can’t recommend them enough. Mine’s a 61-note which means it’s only got USB out. With a USB switch though, I can run it into my DAW or to a USB MIDI host which allows me to drive my MIDI synths....

MARSHALL MONDAYS

October 7, 2019Of course I don't just do Marshall repairs on Mondays but what a great way to start the week; a gorgeous 4502 JCM900 50W Dual Channel Reverb on the bench. There's nothing too wrong with this amp. It just came in for a re-valve and a tune-up (bias check) after the customer complained that it sounded a bit dull and lifeless. In my humble opinion, the JCM900 Dual Channel Reverb was the last 'proper' Marshall. Personally I'm a 100W head freak but the 50W heads and combos do sound sweeter. Put a 50W through a 4 x 12 and you get a whole lotta' beef underneath that sweetness. HEAR AND FEEL THE DIFFERENCE I ALWAYS USE PREMIUM MATCHED VALVES AND I ALWAYS RE-BIAS CONTACT ME I get a lot of people ask me about impedance matching valve amps and speaker cabs so sometime over the next couple of weeks, I'll be posting some bumf on how it all works and best practices. Stay tuned!...

COOL STUFF – THE YAMAHA GPI

October 5, 2019Virtually all high-end Yamaha mixing desks such as the DM series, PM5D, LS9 and CL / QL series to name but a few, are equipped with the Yamaha General Purpose Interface or GPI. The picture above shows the GPI buttons under the 'User Defined Keys' section on a Yamaha DM2000. It's a great idea and can be so incredibly useful in so many situations. Unfortunately, very few people know what GPI is all about and Yamaha only offer limited implementation options. Often used to interface a desk with video equipment, the Yamaha GPI standard can also be used to switch on and switch off other equipment such as amplifiers, computers and outboard gear which might be located some distance from the mixing desk. For recording and live applications, this facility could be so incredibly useful. To take advantage of the Yamaha general purpose interface, I build a distribution box and various gadgets which will allow the GPI on your Yamaha mixing desk, to do just that. Pictured below is a 3-channel mains power switcher in a solid steel case, capable of switching three loads totalling 10 amps. This particular interface switches three power amps located in another room in a recording studio. Also pictured, is the breakout box which splits the GPI from the desk to eight individual lines. Channels 7 and 8 of this particular switch for example, are used to switch on two computers, also directly from the desk. If you have a Yamaha mixing desk equipped with GPI and want to remotely switch gear on and off from it, then don't hesitate to get in touch....

RME FIREFACE 800 REPAIR

October 4, 2019On the bench today; a RME Fireface 800 with a faulty power supply. Many will know that I'm a mega-big RME fan. Stylish, reliable, oozing sonic excellence in abundance and very easy to use, RME interfaces like the Fireface 800 are sonically very transparent. When it comes to drivers and firmware, RME is constantly on the ball and software issues with their products simply don't exist. A bold statement I know but in my experience, it's true! Anyway, every six or seven years the power supplies on these systems pack up. Delivering a reliable but significant output, they do get hot and despite the use of high-temperature tolerant components, time takes its toll. Symptoms range from flashing lights on the front panel, to the unit not powering up at all. IMPORTANT!!! If you do get the flashing lights but the unit appears to work okay, please, please, please don't wait until it totally dies, to get it fixed. If you do, you'll probably need a completely new power supply... if you're lucky. If you're unlucky, you'r Fireface 800 might need major surgery. 🙁 So, if you're in need of a RME Fireface 800 repair, then I'll be more than happy to help you out. It's well worth it. These interfaces are just great. I charge a standard £85.00. You can pay here or just contact me if you want to chat. Click here for more information on RME interfaces. In the meantime, here's the spec': Input AD: 8 x 1/4" TRS, 4 x XLR Mic, 4 x 1/4" TRS Line, all servo-balanced. 1 x 1/4" TS unbalanced Output DA: 8 x 1/4" TRS, servo-balanced, DC-coupled signal path. 1 x 1/4" TRS unbalanced Input Digital: 2 x ADAT optical or SPDIF optical, SPDIF coaxial (AES/EBU compatible) Output Digital: 2 x ADAT optical or SPDIF optical, SPDIF coaxial (AES/EBU compatible) MIDI: 1 x MIDI I/O via 5-pin DIN jacks, for 16 channels low jitter hi-speed MIDI Dynamic range AD: 109 dB RMS unweighted, 112 dBA THD AD: < -110 dB (< 0.00032 %) THD+N AD: < -104 dB (< 0.00063 %) Crosstalk AD: > 110 dB Dynamic range DA: 116 dB RMS unweighted, 119 dBA (unmuted) THD DA: < -103 dB (< 0.0007 %) THD+N DA: < -100 dB (< 0.001 %) Crosstalk DA: > 110 dB Input/Output level for 0 dBFS @ Hi Gain: +19 dBu Input/Output level for 0 dBFS @ +4 dBu: +13 dBu Input/Output level for 0 dBFS @ -10 dBV: +2 dBV Sample rate internally: 32, 44.1, 48, 64, 88.2 kHz, 96 kHz, 128, 176.4, 192 kHz Sample rate externally: 28 kHz - 200 kHz Frequency response AD/DA: -0.1 dB: 5 Hz - 21.5 kHz (sf 48 kHz) Frequency response AD/DA: -0.5 dB: < 5 Hz - 43.5 kHz (sf 96 kHz) Frequency response AD/DA: -1 dB: < 5 Hz - 70 kHz (sf 192 kHz) ...