Project PRO2021 - A Pro-One keyboard synth

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devinw1
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Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Mon Nov 05, 2018 1:44 pm

All build documentation:
https://github.com/devinw1/PRO2021/tree/master


PRE-ORDER FOR FULL KITS NOW AVAILABLE THROUGH SYNTHCUBE!:
https://synthcube.com/cart/weston-pro20 ... er-deposit


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Some sound samples of the PRO2021:
https://soundcloud.com/saywaht/pro2021-samples-2

Video comparison:


Some pics of what you build!:
Image

Image

Image

Image

All build documentation:
https://github.com/devinw1/PRO2021/tree/master

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UPDATES/STATUS
09/?/18 – Work starts on project
11/05/18 – Project thread kicked off
11/07 /18 – Prototype PCBs delivered/stuffed
11/12/18 – Board “A” prototype spin-up working
11/14/18 – Board “B” spin-up working but VCOA and VCOB locking together when close in pitch
11/26/18 – Board “B” complete re-route for signal on top, power on bottom with ground isolation + plug in modular VCO boards designed and ordered.
12/14/18 – Prototype fully calibrated and functional with new “B” PCB and VCO boards. Sound samples provided on SoundCloud.
12/15/18 – Pitch and mod functionality tested. Adjusting R117 and R118 on “B” PCB from 8.2k to 15k and adding optional inline 1M pot for adjustable pitch range. Without trimmer = ~1 octave range. With pot = ~1 half step-1 octave.
12/16/18 – 5 pieces each of prototype sheet metal enclosure top and bottom ordered.
12/16/18 – SLS 3D printed enclosure support bracket and Pitch/Mod wheels ordered.
12/17/18 – Final (hopefully) power supply PCBs ordered
01/05/19 - Kit interest list started
01/08/19 - Alpha prototype unit rough assembly complete.
01/09/19 - Start design of production pitch/bend assembly.
01/14/19 - Production pitch/bend assy design complete.
01/17/19 - Waiting on prototye pitch/mod assy manufacturing. Compiling kit pricing.
02/01/19 - Kit Pricing
02/03/19 - Shipping Estimates
02/03/19 - Open for deposits, first round of kits!
03/30/19 - Shipping first round of kits
04/02/19 - Most first round kits shipped

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ORIGINAL THREAD STARTS HERE
As I have probably mentioned in a couple other threads, I had intended to build a Pro-One clone of sorts - not a rack or module, but a whole standalone monosynth. Well, I've actually been working very hard on this for the past few months, and thought I'd start a thread to document my progress. My end goal is to possibly offer these in DIY kit form if people are interested, though it seems many more people are interested in modular than keyboards here. I, myself play in bands that play out and modular is not so ideal for that, hence my interest in standalong keyboards! Plus, I just think they look f**king cool! Before anyone asks, yes I know that Beringer already re-popped the Pro-One and it's probably like $200, but it's again a rack, and also I really don't like Beringer stuff (personal opinion only!). Oh, and I like to build my own stuff right here in the good ol USA. The whole process allows me to build my engineering skills (I am a ME by trade and graaaaadually learning EE stuff by working with synths) and have some fun along the way!

My plan from the beginning was to make a fully functioning Pro-One, with the following modifications:
1) MIDI on board
2) Utilize the MTI "Turbo CPU" and a Fatar keybed
3) Use re-popped CEM chips or Alfa clones for all the CEM stuff (of course)
4) Better pots all around and actually use some Audio taper pots where applicable (the original uses linear pots for EVERY pot)!
5) Separate high quality power supply instead of power supply on board
6) Simple enclosure with max of 2 custom sheet metal parts.

When I started with the PCBs, I decided it would be easier for me (and due to limitations of my PCB house having <=500mm length of PCB) to make the PCB in 2 pieces: 1 for most of the CPU and modulation and LFO stuff from sheet 1 of the schematic, and 2 for the rest. The 2 will link signals via 2 ground shielded ribbon cables as a "bus" much like how the original Arp Odyssey did.

So, my current status in all this is such:
-Power supply board designed and built. Just tested this weekend
-PCBs "A" and "B" drawn up, routed, and ordered. I should receive the PCBs today actually
-All electrical components have been purchased for the first prototype.
-Mechanical design is probably ~70% done (Render shown below). The keyboard is built with 2 anodized and laser etch sheet metal panels, attached with some PEMs, and tied together by the 2 Teak Wood CNC machined end cheeks and by 2 internal 3D printed support brackets.

PCB "A":
Image

PCB "B":
Image

Rendering:
Image

I will report back with status updates. Tomorrow I will begin stuffing the main PCBs!
Last edited by devinw1 on Tue Oct 22, 2019 10:56 am, edited 40 times in total.

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Post by nologin » Mon Nov 05, 2018 2:12 pm

Nice and ambitious project

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Post by ashleym » Mon Nov 05, 2018 2:52 pm

Great project. A stand alone mono synth was the gateway drug for me. Mono is good.

Obviously too late but did you think of 2 types of sync? a 3 way slider for sync would cover that. Slip this down to the mode section and you have room to add a slider for a triangle wave on Osc 1. (edit) LED for the LFO and up its top speed. Something builders could do themselves if this turns into a project.
Last edited by ashleym on Mon Nov 05, 2018 3:22 pm, edited 1 time in total.

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Post by djs » Mon Nov 05, 2018 3:18 pm

this is really cool.. will it also have cv/gate in/out? or just midi?
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Post by csaban » Mon Nov 05, 2018 3:48 pm

:woah:

Would it work with other keybeds?

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Post by Dan Lavin » Mon Nov 05, 2018 4:26 pm

ashleym wrote:Great project. A stand alone mono synth was the gateway drug for me. Mono is good.

Obviously too late but did you think of 2 types of sync? a 3 way slider for sync would cover that. Slip this down to the mode section and you have room to add a slider for a triangle wave on Osc 1. (edit) LED for the LFO and up its top speed. Something builders could do themselves if this turns into a project.
As an owner of the original Pro-1, that was my only regret on the SCI design: soft sync only. I'm a big hard sync fan and really wished it had it.

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by groove » Mon Nov 05, 2018 4:46 pm

I'm interested in building something like this - curious what the all-in would come out to.

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Post by devinw1 » Mon Nov 05, 2018 4:50 pm

ashleym wrote:Great project. A stand alone mono synth was the gateway drug for me. Mono is good.

Obviously too late but did you think of 2 types of sync? a 3 way slider for sync would cover that. Slip this down to the mode section and you have room to add a slider for a triangle wave on Osc 1. (edit) LED for the LFO and up its top speed. Something builders could do themselves if this turns into a project.
Thanks! Unfortunately I did not realize people wanted the hard sync on this! Like I said the proto boards are hitting my house today, but I think that will be easy to add later on a revision!

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Post by devinw1 » Mon Nov 05, 2018 4:53 pm

djs wrote:this is really cool.. will it also have cv/gate in/out? or just midi?
Yes! It will have all the jacks of the original including the Audio In, as will as MIDI in out and thru.

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Re: Project PRO2021 - A Pro-One keyboard synth

Post by devinw1 » Mon Nov 05, 2018 4:58 pm

groove wrote:I'm interested in building something like this - curious what the all-in would come out to.
Sweet! Once I get the drawings done for the sheet metal, I've got some work to find an affordable source, but I have a lot of connections in that industry, so I'm feeling pretty confident. For this proto build, some of the more expensive pieces are the one-off purchases of theTurbo CPU ($120) and the Fatar keybed ($100).

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Post by devinw1 » Mon Nov 05, 2018 5:03 pm

csaban wrote::woah:

Would it work with other keybeds?
So I've built this to give the original CPU (or the TUrbo CPU in this case) the 3 octave switch/diode matrix that it expects. It so happens that the Fatar 37 key OEM unit has this configuration. As long as the other keybed was laid out with the Make/Break switches the same, it would work.

The other way would be to just operate strictly off MIDI, but you would lose the built in Sequencer ability (that's why I chose to use the fatar direct to the CPU). The sequencer is pretty neato.

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Post by steffensen » Tue Nov 06, 2018 1:15 am

:sb: :party: :yay:
Following this with great interest!

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Post by csaban » Tue Nov 06, 2018 6:58 am

devinw1 wrote:
csaban wrote::woah:

Would it work with other keybeds?
So I've built this to give the original CPU (or the TUrbo CPU in this case) the 3 octave switch/diode matrix that it expects. It so happens that the Fatar 37 key OEM unit has this configuration. As long as the other keybed was laid out with the Make/Break switches the same, it would work.

The other way would be to just operate strictly off MIDI, but you would lose the built in Sequencer ability (that's why I chose to use the fatar direct to the CPU). The sequencer is pretty neato.
That's great, then it should be possible to use any other switch/diode matrix keybed. I'm not sure how accessible a 37 key Fatar keybed is, but it should be quite easy to re-use a broken midi controller.
Would there be extra pins available on the CPU for additional keys? (Assuming the code is not closed source an can be modified to accommodate an extra row/column)

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Post by devinw1 » Tue Nov 06, 2018 11:06 am

csaban wrote:
devinw1 wrote:
csaban wrote::woah:

Would it work with other keybeds?
So I've built this to give the original CPU (or the TUrbo CPU in this case) the 3 octave switch/diode matrix that it expects. It so happens that the Fatar 37 key OEM unit has this configuration. As long as the other keybed was laid out with the Make/Break switches the same, it would work.

The other way would be to just operate strictly off MIDI, but you would lose the built in Sequencer ability (that's why I chose to use the fatar direct to the CPU). The sequencer is pretty neato.
That's great, then it should be possible to use any other switch/diode matrix keybed. I'm not sure how accessible a 37 key Fatar keybed is, but it should be quite easy to re-use a broken midi controller.
Would there be extra pins available on the CPU for additional keys? (Assuming the code is not closed source an can be modified to accommodate an extra row/column)
Indeed it is not so easy to procure the 37 key OEM Fatar, but it is certainly possible. I have a feeling if people wanted to do a group buy and someone just got on the phone with Fatar and asked for a quote for 10 for example, they would sell them.

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Post by devinw1 » Tue Nov 06, 2018 11:08 am

Boards are here! Stuffing begins tonight:

Image

I did a quick check and looks like everything is OK, except I screwed the footprint of the 6 3PDT switches up and the pins are off set from the center by 30 mils. DOH! At least the nominal position is right. I can make it work still though and have fixed my Kicad file so the next batch if there should be one will be correct :).

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Post by minisystem » Tue Nov 06, 2018 1:23 pm

Amazing. Love these super ambitious projects! :nana:
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Post by Altitude909 » Tue Nov 06, 2018 1:29 pm

hm. interested.

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Post by 4floorsofwhores » Tue Nov 06, 2018 3:11 pm

oh wow
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Post by Eric the Red » Tue Nov 06, 2018 3:32 pm

I am definitely interested, this sounds awesome.
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Post by kragg » Tue Nov 06, 2018 3:41 pm

Wow :woah: :zombie: :banana:
Very ambitious (and exciting !) project !
I am looking forward to see how it evolves, I love the Pro-One to bits.

Out of curiosity :

- Will it feature the very same sequencer (2 patterns, 40 notes each) ? I like this sequencer a lot for quick and dirty sketches, basslines, complex arpeggios, etc.
Could we imagine to be able to export/re-import the sequences somewhere, in some way (using Midi, maybe) ?

- Will the LFO and sequencer sync to audio in trigger (this feature is a-ma-zing tok play everything in sync with other gear) ?

- Will the filter feature the same "uncompensated high resonance volume loss" ? It could be a feature, for the sake of a 1:1 clone, but it is also something i don't like a lot with that filter... So a switch allowing for "classic" and "compensated" would be great (a bit like Korg did for the Odissey reissue).

- Did you consider proposing a desktop module also ? I have read that you prefer keyboards, but for something buying a single unit for a kit, a keybed is quite expensive, and it also involves a bigger case (which is also expensive). So, to have it more portable and affordable, i would rather buy a desktop version than a keyboard version, if possible...

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Post by devinw1 » Tue Nov 06, 2018 4:25 pm

kragg wrote:Wow :woah: :zombie: :banana:
Very ambitious (and exciting !) project !
I am looking forward to see how it evolves, I love the Pro-One to bits.

Out of curiosity :

- Will it feature the very same sequencer (2 patterns, 40 notes each) ? I like this sequencer a lot for quick and dirty sketches, basslines, complex arpeggios, etc.
Could we imagine to be able to export/re-import the sequences somewhere, in some way (using Midi, maybe) ?

- Will the LFO and sequencer sync to audio in trigger (this feature is a-ma-zing tok play everything in sync with other gear) ?

- Will the filter feature the same "uncompensated high resonance volume loss" ? It could be a feature, for the sake of a 1:1 clone, but it is also something i don't like a lot with that filter... So a switch allowing for "classic" and "compensated" would be great (a bit like Korg did for the Odissey reissue).

- Did you consider proposing a desktop module also ? I have read that you prefer keyboards, but for something buying a single unit for a kit, a keybed is quite expensive, and it also involves a bigger case (which is also expensive). So, to have it more portable and affordable, i would rather buy a desktop version than a keyboard version, if possible...
Thanks! To answer your questions:

1) For this, I am using the Music Technologies Group "Turbo CPU", so yes it behaves exactly the same as the original 8021 CPU used on the Pro-One, including the sequencer.

2) Yes. The Pro-One rectifies the audio in signal to a threshold adjusted in the Mixer section and syncs the sequence.

3) I'm using the AS3320 clone of the CE3320, so I assume they behave quite the same! I haven't used this chip yet before though. This will be a first.

4) Absolutely will consider this. The hard thing will be to figure out the sequencer. Option 1 is to keep the CPU and just waste the keyboard wiring and the DAC involved in this circuit (since you'de obviously be just be using MIDI and/or CV in this config). Option 2 would be to make a new , simpler CPU module to retain only the sequencer portion. THis is beyond my skillset right now, but perhaps other DIYers will want to tackle this!

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Post by djs » Tue Nov 06, 2018 4:39 pm

There's a part of me that says "stack two of these together like a prophet 10"... I don't know why, but it sort of sounds like a good idea.
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Post by ashleym » Tue Nov 06, 2018 5:09 pm

djs wrote:There's a part of me that says "stack two of these together like a prophet 10"... I don't know why, but it sort of sounds like a good idea.
Surely a Prophet-Two?

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Post by tobb » Wed Nov 07, 2018 10:16 am

devinw1 wrote: 3) I'm using the AS3320 clone of the CE3320, so I assume they behave quite the same! I haven't used this chip yet before though. This will be a first.
The resonance of the AS version has a different behavior.

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Post by devinw1 » Wed Nov 07, 2018 12:22 pm

tobb wrote:
devinw1 wrote: 3) I'm using the AS3320 clone of the CE3320, so I assume they behave quite the same! I haven't used this chip yet before though. This will be a first.
The resonance of the AS version has a different behavior.
Good to know! I'm sure it will still sound pretty good though!

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