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Being able to convey feel to the sound after the keys are played, can transform a performance into something quite unique and almost magical. Indeed, Roland was definitely on to something when aftertouch began appearing on itโ€™s synthesisers in the mid-eighties. Today, many classic synthesisers have aftertouch strips that either donโ€™t work or are a shadow of what they used to be. Almost forty years later, my modern FSR-based replacement aftertouch sensor for the Roland D-50, has considerably more dynamic range and is infinitely more reliable than the second-generation transducers that Roland originally used in the D-50 and transcends the instrument into another dimension.

AT-D-50 FSR replacement aftertouch sensor for the Roland D-50
AT-D-50 FSR replacement aftertouch sensor for the Roland D-50.

Following on from my AT-JX-8P, AT-JX-10 and AT-AJ-2 projects and as promised, development of my AT-D-50 replacement aftertouch sensor for the Roland D-50 begins today! I'm so excited. ๐Ÿ˜€

Being basically refined versions of the type of carbon-track sensors that Roland originally used but delivering a lot more dynamic range as well as other benefits, FSRs are perfect for this kind of application. In fact, modern aftertouch sensors and even some drum pads use FSRs. The principle is the same but the resistive polymer material is of a modern composition and the manufacturing process makes FSRs considerably more robust and reliable than previous pressure sensors.

How FSRs work
Cross-section of a force sensitive resistor (FSR) illustrating how they work.

So, last night I picked up the instrument that's going to be the first to have my AT-D-50 replacement aftertouch sensor for the Roland D-50 installed. It's in lovely condition and really does deserve something special.

Donor for AT-D-50 replacement aftertouch sensor for the Roland D-50
Here's the guinea pig for my AT-D-50. An almost pristine example of this classic synth.

Before I opened up this D-50, I thought I'd reacquaint myself with the aftertouch buffer / amp circuit. Wow, a little more involved than pervious synthesisers and Roland started using SMD passives. That's gonna be fun!

Of course, another interesting issue is that if I remember correctly, the D-50 was the first Roland Synthesiser to have everything, including the keyboard chassis, secured to the inside of the top-case. Unscrew the bottom case and you're in and there's nothing bolted to it.

Roland D-50 with new upside-down assembly
Roland D-50 with the new 'upside-down' assembly. Inย  I guess in comparison to building half the synth on a piece of wood and then connected to it the other half which was built into metal / plastic, this approach saved a lot of manufacturing time in 1987.

This aspect of the project presented some challenges which made me consider that the AT-D-50 might be my first FSR-based replacement aftertouch system that would be supplied in kit form. Here's why...

Just about every keyboard that features aftertouch and that I've worked on, has a small notch cut into the keyboard side of each end-cheek, just underneath the key-line, which allows for a margin of error in the length of the sensor. I take full advantage of this notch as however hard I try, I cannot cater for extremes of assembly / construction tolerances in a machine that's almost forty years old.

While the D-50 and similarly constructed synthesisers, also have this notch, it's quite small and things can be tight.

Aftertouch sensor notch in D-50 case left
Note the notch cut into the inside of the left-hand end-cheek. There's one on the other side, too. They allow any excess aftertouch sensor to be neatly slipped out of the way. My sensors are a little wider than the original so I have to engineer things very precisely as I can't use this and I definitely don't expect customers to make this larger!

The idea of having to provide one of my aftertouch systems only in kit form didn't appeal to me at all. Many of my customers have a good degree of competence with electronics but the issues here were really mechanical. I didn't want to exert unnecessary pressure on those who already have a potentially challenging installation job ahead of them and so I had no option other that to persevere and find solutions to the problems.

Well, it took me a couple of weeks but I got there in the end. Once word of my replacement aftertouch sensor for the Roland D-50 got out, amazingly I had another D-50 come in which allowed me to confirm my measurements and installation procedure.

Similar to my other FSR-based aftertouch sensors, my AT-D-50 replacement aftertouch sensor for the Roland D-50 comprises two force sensitive resistors. The terminals of each sensor are passively connected on a little FSR Aftertouch Interface (FAI) PCB which is supplied with the AT-D-50.

FAI D-50 FSR aftertouch interface PCB
FSR Aftertouch Interface (FAI) PCB combines the outputs of each FSR and provides a simple way to select one of two sensitivity ranges.

The output from the FSR combination is quite different to the original carbon-track based system that Roland used in the eighties. FAI compensates for that difference but also offers something else.

FAI provides the facility to select one of two sensitivity ranges. Yes, that's right! What a cool little feature. ๐Ÿ™‚ On top of that, the aftertouch control next to the volume control on the top of the D-50 still works as it did before.

With the aftertouch fader on the D-50 set to about 80%, a MIDI velocity of about 90 and an average pressure, responses were recorded into Cubase with FAI in Norm and Hi modes. As you can see, a MIDI aftertouch value of 127 is reached in both modes. It's just that you get there quicker in hi mode.

Don't forget that you still have control over how aftertouch interacts with each sound within the patch settings.

FAI D-50 MIDI response in norm and hi modes
FAI D-50 MIDI response in norm and hi modes

The 'upside-down' construction (as I call it) of the D-50, means that it's simply not practical to mount FAI to the bottom-case. With so little room on the inside of the top-case, FAI's four self-adhesive feet safely secure it to the inside of the D-50's left side-cheek. I've tried to make things as ergonomic as possible but of course the bottom-case has to be removed to access FAI. Positioning FAI on the inside left side-cheek however, does offer an excellent degree of access to FAI once you're in so switching aftertouch sensitivity ranges in the future, won't be too difficult.

FAI for the D-50 required a redesign of previous versions. Being side-mounted, I decided to use straight (vertical) Molex connectors, for example. It just makes life easier.

Also, up until FAI D-50, the facility to switch between two aftertouch sensitivity ranges was done by changing the value of the feedback resistor in the aftertouch buffer op-amp circuit. In FAI D-50 however, I decided to do the same job by switching the value of the series resistor between the FSRs and the op-amp.

Remember I mentioned earlier that the D-50 has a lot of passive SMDs? Well one big bonus of adjusting aftertouch gain by varying the series resistor to the buffer op-amp, is that no components on the bender-board need to be replaced. In fact, the bender-board doesn't even need to be removed. All you need to do is solder a two wires to the bender-board.

Roland D-50 bender-board
The bender-board in the D-50 is packed with SMDs. FAI D-50 uniquely delivers the option of switchable aftertouch sensitivity ranges, without you having to touch them!

You've developed an FSR-based aftertouch sensor for one synth (in fact, three) and you think it would be easy to knock up an FSR-based aftertouch sensor for another. Hmmm... not quite. Each synthesiser has it's own challenges and I'm so glad I persevered with this project. I'm delighted that AT-D-50 not just works brilliantly but is now a system which can be installed by anyone with a little patience and technical competence.

With an abundance of sensitivity and very high dynamic range, my replacement aftertouch sensor for the Roland D-50 truly gives this classic synthesiser, a whole new lease of life. It's like suddenly having velocity sensitivity! ๐Ÿ˜€ The added expression is just magical.

Modern FSRs are very reliable and it's not uncommon to see specifications quoting figures such as 'more than 10,000,000 actuations'. Being sealed units, FSRs are vulnerable to contaminants and oxidation problems like the old carbon-track sensors. It's no surprise then, that modern instruments that feature aftertouch, use FSRs. As previously mentioned, FSRs have a much greater dynamic range than their carbon-track counterparts which makes them ideal for modern drum pads.

I sometimes get asked to provide audio samples but I've backed off from doing that. Aftertouch isn't a sound, it's the result of a feel. You don't 'hear' aftertouch. You hear the effect of aftertouch. So posting an audio file with no reference to how the synthesiser was played, just seems a bit pointless to me. What I can tell you, is that the feedback I've had from users who have installed my FSR systems is humbling and inspiring. For a couple of hundred bucks, it's really worth a shot.

Roland D-50


The AT-D-50 is sent out complete and in one straight piece. Although it weighs very little, the external double-sided carboard box is just under 1.2m long. Using normal courier methods worked out to be horrendously expensive and so I engaged the services of a shipping agent.

Packaging the ATD-50 starts with sandwiching it in between two pieces of hardboard. The wires are then neatly folded and secured to the hardboard with masking tape.

FSR Aftertouch sensor sandwiched between hardboard strips
It's important that the sensor is kept straight so I sandwich it in between two pieces of hardboard.

To keep any moisture off the sensor during transport, the package is then put into a long polythene bag.

FSR Aftertouch sensor packed in polythene
A polythene bag is then used to reduce the potential ingress of moisture and damp during its travels. FAI and any other bits are put into an electrostatic bag and then into a small bubble-wrap bag.

The protected sensor is then packed into a double-sided cardboard box and wrapped in black pallet-wrap which gives the package a little security and added protection against damp and moisture.

FSR aftertouch sensor packed for shipping
Final external packaging is pretty robust!

AT-D-50 is now available to purchase here: