Deckard’s Dream: An 8-Voice Polyphonic Analog Synthesizer.

  • Inspired by the Yamaha CS-80
  • 8- Analog voice cards, each with:
    • 2 VCOs (CEM3340)
    • 8 VCAs (Cool Audio V2164)
    • 2 VCFs
    • LFO
  • Digitally controlled autotune
  • 4 Envelope Generators
  • Midi in & Through.
  • USB Type B
  • Polyphonic Aftertouch and MPE.
  • 127 Factory patches, and two 127 slots for custom patches
  • 1/4 Audio out
  • 1/4 Audio in for the LFO

“If you have to ask what a Yamaha CS-80 is, you need to listen to recordings by Vangelis or listen to the soundtrack from the movie Blade Runner”.

A couple years ago Roman Fillipov (of Sputnik Modular) has this dream of building a decent polyphonic synth that could replicate the sound of a Yamaha CS-80. With the help of Scott Ryder, his new company Black Corporation released their new synthesizer as both a prebuilt or as a DIY “Kit”. I use the term kit here with a broad view. It is really just a set of 12 printed circuit boards, Schematics and a Bill of Materials. When I obtained the DIY version, there were no instructions.

This synth will most likely be, the most arduous machine you will ever tackle. It is huge, with well over a 1000 components and 7,000 solder joints. Some of which are going to be 0508 sized SMT capacitors. Fortunately, all of the DACS and the MCU, which are also SMT packages, come pre-soldered to the PCBs for you. This makes it easier, but you also have to take extra care when building this thing that you don’t blow these components up. Having said that, this synth, in my opinion, is one of the best sounding and most dynamic analog polyphonic synthesizers available.

Supplied motherboard

I was fortunate to be one of the first to build this synth after a small group of enthusiastic builders setup a Facebook page specifically for this project. We all joined the group long before the PCBs even arrived, and went through several BOM changes (even caught a couple of errors). Another DIYer also developed a steel case and front panel which can be purchased here:

Instructions for building this kit, where actually developed within the Facebook group by the members, and additional errors were caught and documented as people progressed through the early builds. Anyone who would obtain the PCBs now, could be able to build directly from the instructions found on this Facebook group. Roman has stated that “even a beginner, or someone who has never built a synthesizer” could build this project.

There actually was someone, (who had never built a synthesizer), who did successfully complete this project, but he relied on past experience and had decent knowledge of electronics. He also had assistance from the experienced builders who had completed their builds. I personally have serious doubts that many beginners will complete this kit successfully. I would not recommend this project for anyone as a first or even second DIY synth project. Unfortunately statistics are not kept, but I would venture to state that 25% of the people who take on this project, won’t get this properly working or it will sit uncompleted. Reversing a IC here or there, bridging a capacitor or other component has the potential to destroy the MCU or the DACS. One of the other issues is that many of the experienced builders, move onto other projects and the stop monitoring the forums and groups. So, as time progresses, it becomes increasingly harder it is to find help. I also think that some folks just don’t ask for help for fear of looking inept. If you want to take on this project, please consider these stats (derived from surveying builders on the Facebook group):

  • Total cost to build (PCBs, components, case): About $2700 USD
  • Total time to build (experienced builder): 65 to 80 hours
  • Testing, inspection and cleaning: 10 hours
  • Planning and component purchasing: 20 hours.

If you have a large stock of components like I do, the costs will be less. I keep thousands of resistors, capacitors, diodes, transistors, etc in my cabinet. I spent a few hours finding substitutes from the BOM with what I had in stock.  I also had the tools for soldering surface mount components and programming firmware for microprocessors. Of course, you can always buy a pre-built unit as well. The price is $3750 USD. An they are not exactly the same as the DIY. The prebuilt units are all SMT, not through hole, and do not use the Cool Audio V2164 chips on the voice cards. But apparently, they sound the same. You can order the PCBs or a pre-built directly from Black Corporation HERE.

Planning this project

There really is not perfect place to start this project, you could build the 8 voice cards first or build the power supply first or even build the hardware or motherboard first. I chose to build the input/output board first (Required for power connections), then the power supply, then I built all 8 voice cards, then the motherboard and finally the hardware board.

If the board had SMT capacitors, I always soldered those first. Generally I did 10 to 15 at a time in a process of apply flux to the pads, tin one of them, place and heat one end of the capacitor, then solder the other end. Then check that lot for straightness, flatness and clean joints. Then test for a short. I cannot emphasize this enough: It is absolutely imperative, that you test for any shorts across power rails whenever you build a section of a PCB, and then again before you apply power to the completed board.

For the voice cards, I setup a small assembly line, doing all 8 cards simultaneously: First resistors, then diodes, then IC Sockets, then through hole capacitors. Because many of the capacitors came from the same manufacturer, and where the same C0G type, they where all blue. To help me identify and distinguish between the different values, I painted a dot using brightly coloured nail polish on top of each one: Each value gets a different colour.

Completed voice card

Once the voice cards were completed, I moved onto the motherboard and then the hardware board. Care must be considered when working on the motherboard at all times, this board has many DACS and and MCU pre-populated and they can easily be damaged by  solder, scratching, or dropping. Build the same way, SMT caps first, then resistors, diodes, IC Sockets, capacitors.  I still can’t say this enough: It is absolutely imperative, that you test for any shorts across power rails whenever you build a section of a PCB, and then again before you apply power to the completed board. Check all of the edge connectors for any shorts and ensure all power rails are connected.

Populated motherboard

Finally, move to the hardware board. The difficulty with this board is that the sliding potentiometers can easily be damaged if too much heat is applied. I advise testing these for operation before you solder them. They do not have to be that accurate between pots (resistance value). These are all read by the ADCs on the processor and converted into a numerical quantity to be used for setting up patches, etc. You want them to be smooth and have a clean range. Just a digression here. I said this is an analog synthesizer, and many might question the use of DACs, ADCs and a processor. The entire audio signal path, from VCO through VCA, VCF and output audio is entirely analog. Control voltage (CV) however, is digitized and stored as a large numerical structure, so patches can be easily saved and recalled. Basically, the ADCs on the processor read the voltage from the sliders, convert that to a numerical value (digitally) and then supply that back through the DACS to provide control voltage for the VCOs, VCAs, VCFs, LFOs, Enveloped, etc. The VCOs use the famous CEM3340 analog chip used way back in the 1970s and 1980s. The Curtis family decided to start making them again as the commercial world of synths is having a resurgence in remaking many of the older synthesizers. The V2164 is a Cool Audio remake of the older Curtis SSM2164. The IP and patents no longer apply to many of these, so they can be made literally by anyone who thinks they can make money doing so. Behringer Audio actually bought Cool Audio, in order to keep a supply of the circuits for their plans in building clones of many older synth models.

Anyway,,, digression over…..Do not solder the lug pins, just the 3 pins for the pot. Soldering the lug pins adds way too much heat, and does not really assist. The 3 pins are enough to hold this in place and maintain durability.

Completed hardware board

Before you connect everything together!

Test the power board and i/o board first (do not connect anything else). Ensure you are getting the proper power reading at each rail.

Power test 1

Then, test the power assembly with the motherboard/hardware board (do not plug in any voice cards)

Power Test 2

At this point, you can load the firmware, then add one voice card and ensure things are working properly. Then add another voice card, and test each card as they are added. Cards can go in any slot, so if you have an issue after adding it, you can swap it out with a known working card to determine if the issue is with the card or the motherboard. Example: hearing the same behaviour in a voice after swapping with a known good card would mean the issue is with the motherboard. There are hundreds of resistors and capacitors, I don’t know of any builder that did not have at least one wrong component.

Just what the heck is MPE?

MPE stands for Multidimensional Polyphonic Expression. We talked previously about polyphonic synthesizers, where by pushing  2 keys produces 2 independent voices (one for each pitch). This allows you to form chords on a synthesizer. MPE takes this further, it allows you to provide 3 axis of control independently. For a really good video, watch this.

The original CS80 came with a ribbon controller that allowed for slides within the music. The artist could slide from one pitch to another. MPE makes this much more flexible and enables non-traditional keyboards  or controllers to be used, in order to create even more musical effects. One such midi controller is Roger Linn’s LinnStrument. This synth is truly amazing, especially when you are using it’s fullest potential with an MPE enabled controller.

Testing the MPE functions.

What I find the best feature of this synth, is the combination of a fully analog audio path, and the advantage of digital control. The worst thing about playing analog synths, was their inability to save and recall patches, or the did not play with MIDI or USB well. Another builder on the Facebook page is also developing a PC (or MAC) application to provide designing, and pushing patches to the DDRM from your PC. This just increase the fun!!

More images below…..