Project PRO2021 - A Pro-One keyboard synth

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Kevin Mitchell
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Post by Kevin Mitchell » Mon Sep 23, 2019 9:19 am

grantb5 wrote:Out of curiosity, has anyone looked at the Yamaha/Korg AT boards that are plentiful on eBay and Reverb?
This one?
Image

Looks super simple. Idk the specs for the zener but I'll likely put this on breadboard to play with.

-KM

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Post by grantb5 » Mon Sep 23, 2019 10:02 am

Yes, there are tons of those on eBay and quite a few variations as well. I think electronically they are all pretty much the same, just changes for size and connectors. I think Yamaha and Korg and maybe others licensed that circuit (in a similar way to SCI licensing Emu's keyboard scanner all those years). It's probably in some Service Notes too I would imagine.

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Kevin Mitchell
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Post by Kevin Mitchell » Mon Sep 23, 2019 11:21 am

Here's a quick n' dirty schematic of the Yamaha/Korg AT board.
Image

-KM

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Post by grantb5 » Mon Sep 23, 2019 12:58 pm


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Post by Altitude909 » Mon Sep 23, 2019 6:09 pm

worth mentioning: fatar strip is 4 pin, the two outside ones are the resistor

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Post by devinw1 » Tue Oct 22, 2019 10:51 am


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Kevin Mitchell
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Post by Kevin Mitchell » Tue Oct 22, 2019 11:36 am

:party:
Nobody put in an order until I reserve mine next week :razz:
I'm happy to see things moving along. It'll make for an awesome winter this year.

Thank you, Devin and the folks at synthcube for all your efforts.

-KM

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Post by LED-man » Tue Oct 22, 2019 12:06 pm

PCB, case, wheels as single Option please.
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Post by Check Mate » Tue Oct 22, 2019 12:07 pm

Haha Synthcube are you serious? Almost 2000$ with VAT and shipping to Europe?
That's 900€ more expensive than it cost in the first run!

I had loved a PCB and case/wheels only option by Weston themselves...I guess I pass then!
Last edited by Check Mate on Tue Oct 22, 2019 12:41 pm, edited 2 times in total.

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Post by devinw1 » Tue Oct 22, 2019 12:40 pm

Check mate, I will let SC chime in but maybe they will be able to offer a thinned down bundle to help EU customers.

As an aside, yes VAT is fixed problem we have to deal with for international and understand those frustrations, but that aside, I think SC's price is fair considering the first round of Beta builders got my chassis kit for $600 and then had to buy a Keybed, CPU, and all the other parts to stuff the board, putting them at around $1100 to finish the whole thing, and they got a great deal. By great deal, I mean I made virtually nothing on those 15 kits. The sheet metal chassis is expensive to produce and both parts are much more complicated than flat panel work for rack mount stuff. Also consider an original Pro-One sells for $1600+ (looking at Reverb) and will immediately need to have the keybed replaced if you want it to play anything as nice as PRO2021, will not have MIDI, and will be built mostly of plastic (including the crappy benders and mod wheel). Just some things to consider :).

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Post by JanneI » Tue Oct 22, 2019 2:09 pm

Yes, 2000usd for us EU people is a lot for Pro-one when you can get the same sound from Behringer way cheaper (it's not the same product, but it probably sounds very much the same).

Synthcube should consider offering the "chassis kit" to the people living in the EU since that's really all that is needed. This way you could save around 200usd.

If I'd live in US I'd jump in with the full kit and willingly pay the extra 100-200usd for the convenience of not needing to source anything. So don't get me wrong, nothing against Synthcube!

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Post by Kevin Mitchell » Tue Oct 22, 2019 2:10 pm

It's understandable that Devin had great pricing trying to break even. I wouldn't fuss about SC trying to turn a profit - as we had a fair warning.

I've done the shopping. I can vouch that the pricing for the entire kit isn't too far off from what the beta run had cost folks. Factoring in the convenience fee for not having to shop for parts I'd say the pricing is within reason. Plus ITS A HIGH QUALITY MONO SYNTH. It'll perform and last better than the original as explained.

My 2¢ at least

-KM

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Post by tobb » Tue Oct 22, 2019 4:58 pm

devinw1 wrote:Also consider an original Pro-One sells for $1600+ (looking at Reverb) and will immediately need to have the keybed replaced if you want it to play anything as nice as PRO2021, will not have MIDI, and will be built mostly of plastic (including the crappy benders and mod wheel). Just some things to consider :).
but..its a pro-one,i mean the real one ;)

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Post by gslug » Tue Oct 22, 2019 5:46 pm

Kevin Mitchell wrote::party:
Nobody put in an order until I reserve mine next week :razz:
Too late. I couldn't wait! :hihi:
One day I'll get an avatar!

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Post by devinw1 » Tue Oct 22, 2019 11:14 pm

tobb wrote:
devinw1 wrote:Also consider an original Pro-One sells for $1600+ (looking at Reverb) and will immediately need to have the keybed replaced if you want it to play anything as nice as PRO2021, will not have MIDI, and will be built mostly of plastic (including the crappy benders and mod wheel). Just some things to consider :).
but..its a pro-one,i mean the real one ;)
Haha yep I can't argue with that I reckon. :guinness:

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Post by synthcube » Wed Oct 23, 2019 8:19 am

We appreciate all the feedback--

Folks in Europe, we do have plans to offer the 'partial kit' -- we would like to get through this first run of 'full' kits, and will be working with Devin on additional supplies after that...

As in all our pre-order big kits, if the final price goes up a bit, you are protected from that increase, but if it goes down a bit, we'll refund you the difference.

Having seen the Michigan Synthworks example of this synth at Knobcon, we can say with certainty that builders will not be disappointed. This is like 'heirloom' quality stuff-- and its DIY.

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Post by JanneI » Wed Oct 23, 2019 9:41 am

synthcube wrote:Having seen the Michigan Synthworks example of this synth at Knobcon, we can say with certainty that builders will not be disappointed. This is like 'heirloom' quality stuff-- and its DIY.
Yes! Easily the best DIY mono analog synth with keyboard. Quality 10/10 !

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Post by devinw1 » Wed Oct 23, 2019 4:32 pm

Since I've got a minute or 2 before I order boards for the SC kits, I figure I might as well put the hooks in place for a basic AT mod. I'm thinking 2 4 pin .10" pin headers on the back of PCB-A to supply an AT piggy back board:

The first connector will supply: +15, G, G, -15

The 2nd will come from the summing node of U101D (pin 12) through an added 100K resistor that I'll put on PCB-A. I'll put the ressistor very close to the pin so you can just leave it off if not using an AT mod and it won't cause any problems.

That leaves 3 more pins if anyone has any other ideas I could map them to?

I want to keep this simple as I need to order PCBs in the next week or so and of course don't want to fudge with with the board much at all since making new problems for future builders is the kind of stuff that will keep my up at night lol. :deadbanana:

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Post by Altitude909 » Mon Oct 28, 2019 9:41 am


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Post by devinw1 » Mon Oct 28, 2019 10:19 am

Nice!

OK, so I pulled the trigger on the boards for the new kits. The new PCB-B (Rev AE) boards will have footprints for 2 4 pin (.10") pin receptacles spaced exactly 2" (sorry the original PRO2021 is done all in English) and an additional resistor (R1199) which can be placed and is directly connected to the summing node of U101D.

This should allow easy integration of Altitude's board via a couple of cables or a home-brew piggyback board which would only need the AT strip connected to it. There is room for the board to be a bout 2.25" x 1" which I believe should be plenty of room.

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Post by Kevin Mitchell » Wed Oct 30, 2019 7:42 am

I only need the chassis kit and keybed. Do I have to wait for the "‘ala carte’ parts page"?

-KM

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Post by JanneI » Thu Oct 31, 2019 4:36 am

I almost forgot this AT board thing :-) Here's the proto that I'll order now (10pcs) and if all is good, I can send the rest to whoever wants one. The mounting holes should match with the mainboard, thanks to Devin who provided me the correct dimension. 2-3 weeks and I can share the PCB gerbers here.

Image

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Post by Kevin Mitchell » Thu Oct 31, 2019 9:45 am

I have a question for Devin. I'm redoing my AT board to accommodate the spacing and connections provided.
Do you have an image you can share for the pins? I'm unsure of the orientation as well as the pin spot going to R1199. Also - have you tied the other 3 pins to any connections?

Here's the top side of my blank template with the 4 pin connectors.
Image

Hope you can clear this up.
-KM

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Post by devinw1 » Thu Oct 31, 2019 10:48 am

Kevin, I'll send you a screenshot from Kicad tonight of where the pins for the new board are. I think you'll have to make the board narrower/offset the pins to make sure it doesn't hang out past the A board and into the chassis though.


And to clear it up for anyone else, Janne's board will hang onto the unused mounting hole and corner mounting hole on PCB-A via standoffs on the Beta kits (PCB-A Rev AD). The new kits will have Rev AE PCB-As and the 4 pin headers so those boards can just hold on by the friction of the pins.

Thanks for all the work on this, guys! :tu: :tu:

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Post by devinw1 » Thu Oct 31, 2019 10:54 am

Actually, here is a shot of the gerbers. That is how the PCB sits in the synth if you are looking from the front. Top header is pin1 (square pad) going to the summing resistor for U101. Bottom header is pin1 +15V pin2,3 ground pin4 -15V. :sb:
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