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 Forum index » DIY Hardware and Software
New Doepfer single board DIY Synth
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Dan Lavin



Joined: Nov 09, 2006
Posts: 620
Location: Spring Lake, Mi, USA
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PostPosted: Wed Jan 27, 2010 7:01 pm    Post subject: New Doepfer single board DIY Synth
Subject description: Not bad for 100 euros
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I know a lot of folks here don't care for Doepfer, but they do have a number of products for us DIYers. If you wander over to their site and hit the NAMM 2010 news pdf link, you'll catch a quick overview of this 6 chip, single voice analog synth.

VCO, VCF, VCA, ASDR, LFO, inverter, lag processor, buffer for 100 euros is pretty reasonable. I'm guessing the ADSR and LFO might be PIC-based. The thing I like is that the pcb is pretty tiny, so making a polysynth in a reasonable amount of space is not out of the question.

It's available this Spring...which in Doefper-speak means by the end of 2010 Wink

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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Thu Jan 28, 2010 1:42 am    Post subject: Reply with quote  Mark this post and the followings unread

I personally have nothing against Doepfer (except for the prices!), but why not consider Motohiko Takeda's One Board Farm synth.

http://www.aleph.co.jp/~takeda/radio/OneBoardFarm.html

Out of interest I built one, the VCF is only 12db (korg clone), but as a basis for a simple poly it's not bad.

VCO, VCF, VCA, ADSR & LFO with delay, on a board 113 x 80mm

Andy.


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Mark Space-Ratio



Joined: Dec 06, 2009
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PostPosted: Thu Jan 28, 2010 6:26 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
... I built one.


Did you use the 2SK30 in the VCO section?

Mark
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kkissinger



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PostPosted: Thu Jan 28, 2010 7:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Mark Space-Ratio wrote:
AndyR1960 wrote:
... I built one.


Did you use the 2SK30 in the VCO section?

Mark


Does it track at 1v/octave?

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AndyR1960



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PostPosted: Thu Jan 28, 2010 7:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Mark Space-Ratio wrote:


Did you use the 2SK30 in the VCO section?


No, unfortunately I couldn't find the 2SK30, so I just used a 2N5459 (and a pair of 2SC1815's to replace the 2SC1583 Dual transistor), work's well enough though.

kkissinger - Yes, 1v/Oct, with ramp and square (PWM) outputs Very Happy
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Mark Space-Ratio



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PostPosted: Thu Jan 28, 2010 8:07 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:

No, unfortunately


They were used in the 303 and they are uncommon here in the UK. The BF245C is another option.

Mark
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llumen



Joined: Jan 07, 2010
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PostPosted: Tue May 25, 2010 8:05 am    Post subject: Reply with quote  Mark this post and the followings unread

anyone already had a go at that new DIY board of doepfer?
What is the impression, could it be a good start to a larger hybrid modular system with doepfer/etc and diy modules, and how should it than be build, all patched out?
I had a look at the DIY manual from doepfer and it's a lot of 'normally this is connected to...' which is in fact not so straight forward when building this as a novice

best

pieter
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glitched



Joined: Mar 25, 2006
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PostPosted: Fri Sep 10, 2010 10:15 am    Post subject: Reply with quote  Mark this post and the followings unread

Has anyone taken the plunge on one of these Doepfer DIY boards yet? I'm thinking of getting two of them, for a cost-effective mini-modular system.

Well, I was thinking about it before I took into account the cost of pots, the power supply, knobs, the case...etc. It can get pretty expensive.

Thoughts?
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v-un-v
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PostPosted: Fri Sep 10, 2010 11:52 am    Post subject: Re: New Doepfer single board DIY Synth
Subject description: Not bad for 100 euros
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Dan Lavin wrote:

VCO, VCF, VCA, ASDR, LFO, inverter, lag processor, buffer for 100 euros is pretty reasonable. I'm guessing the ADSR and LFO might be PIC-based. The thing I like is that the pcb is pretty tiny, so making a polysynth in a reasonable amount of space is not out of the question.



Wow, it is tiny! Shocked

Posted Image, might have been reduced in size. Click Image to view fullscreen.

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bod



Joined: Apr 28, 2009
Posts: 148
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PostPosted: Mon Sep 13, 2010 3:19 am    Post subject: Reply with quote  Mark this post and the followings unread

I bought one of these just to check it out as I have never really used doepfer modules.
I have yet to wire it all up, but to be honest that’s all there is to it, wiring. I would have preferred a complete diy version, but then I gather from their website they have had problems with this sort of thing in the past.
I decided to go for a wee standalone midi controlled synth, so the only inputs and outputs for CV are gate, 1v/oct and hard sync. I have midi control over 1v/oct, VCA amplitude, vcf cut off and pitch bend. Some people might not think this was the best route to go with this, but its what I wanted, something small and portable that I can take to gigs and studios that’s midi controlled, either from keyboard or computer sequencer. The whole thing will be mounted in a 7" flight case.

It’s a bizarre wee thing the synth. From what I can see there are no OTA's in use unless its hidden under the tempco pcb which hides 2 ic's mounted back to back with a small oven on the pcb that sits atop of it (I think, but cant be sure. it’s the extra pcb in the photo).

Other than that we have 1 Tl074, 3 tl084 and a 555 timer. The 555 is obviously for the ADSR, and the vca must be a transistor vca like the ms20. unless the tempco option hides an OTA, then I have no idea how they are building the vcf!! The lfo is your standard integrator/comparator.

I've added a sub octave generator based on the ramp output, through a comparator to generate a 50/50 square wave which is then pumped through a diode and a cmos flip flop.

Its not been cheap to be honest, but then synth diy never is. Even an mfos mini synth adds up when you think about everything involved.

So far I recon the finish thing will be about £300-350, but then I went all out and had a big front panel engraved, a flight case, +/-12v psu and a midi2cv module as well. You could easily build a modular synth out of it for well less than £175.

I received the front panel a few days ago so I'm just populating that at the moment before I start wiring, but have found I didn’t have enough 1m pots so its on hold until they arrive.

If nothing else its been fun just to concentrate on the design of the finished unit for once and not the soldering of the pcb and testing it all (but having said that I would kind of preferred it!).

once its finish i'll post some links to my website with a build report and sound samples.
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furio



Joined: Dec 25, 2009
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PostPosted: Tue Sep 14, 2010 2:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
I personally have nothing against Doepfer (except for the prices!), but why not consider Motohiko Takeda's One Board Farm synth.

http://www.aleph.co.jp/~takeda/radio/OneBoardFarm.html

Out of interest I built one, the VCF is only 12db (korg clone), but as a basis for a simple poly it's not bad.

VCO, VCF, VCA, ADSR & LFO with delay, on a board 113 x 80mm

Andy.


wow this board looks nice! I wanna try it because I have almost all components, but my biggest problem is finding the tempcos and the U3 on the vco LM431.

which diodes do you use instead of the 1S1588?
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PickNick



Joined: Oct 16, 2009
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PostPosted: Sun Oct 31, 2010 8:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

you can use 1n4148 or 1n914 instead of the 1S1588.
if u need LM431, i can send to you from Bp.
it cost 0.30cent in the local store///PM.
i have to buy some because something is wrong on my panel.
few minutes ago i did the first test, but the LM431 is goneee...pfff
maybe some shorts...?

there is any necessary modification on the board Andy?

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furio



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PostPosted: Mon Nov 01, 2010 3:03 am    Post subject: Reply with quote  Mark this post and the followings unread

PickNick wrote:
you can use 1n4148 or 1n914 instead of the 1S1588.
if u need LM431, i can send to you from Bp.
it cost 0.30cent in the local store///PM.
i have to buy some because something is wrong on my panel.
few minutes ago i did the first test, but the LM431 is goneee...pfff
maybe some shorts...?

there is any necessary modification on the board Andy?


Thank you PickNick.
I have just found and ordered from Reichelt some TL431.
Is that not the same?
Be it that I have ordered the false item then i will need to order it from you!

Product page http://www.reichelt.de/?;ACTION=3;LA=444;GROUP=A21D;GROUPID=2920;ARTICLE=39793;START=0;SORT=artnr;OFFSET=16;SID=28qC-TtKwQARwAAB8G@Z4ae63a6e14426c270ac5a785688a12a05

Datasheet http://www.reichelt.de/?;ACTION=7;LA=28;OPEN=0;INDEX=0;FILENAME=A200%252FTL431.pdf;SID=28qC-TtKwQARwAAB8G@Z4ae63a6e14426c270ac5a785688a12a05
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AndyR1960



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PostPosted: Mon Nov 01, 2010 9:38 am    Post subject: Reply with quote  Mark this post and the followings unread

furio wrote:

I have just found and ordered from Reichelt some TL431.
Is that not the same?


Sorry for not replying earlier, been very busy moving house.

The TL431 is exactly what I used, and also 1N4148's for the diodes, with no problems. Unfortunately I've now run out of Tempco's (both 1K & 2K) so all future projects are on hold until I find some at a fair price.
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PickNick



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PostPosted: Tue Nov 02, 2010 3:19 am    Post subject: Reply with quote  Mark this post and the followings unread

looks the same.

oops...i forgot to refresh the topic:)

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vladosh



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PostPosted: Mon Dec 13, 2010 12:57 am    Post subject: about the Doepfer
Subject description: dazed and confused
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Hi I got one of these boards and still haven't wired it . i understand the wiring most of it but a few things are not clear to me ,can anyone who already has made this board please help me out a bit i just wonder the manual voltage of the vca should it be 12 v or 5 v the vcf i understand it should be 12 v .. the sustain and the decay share the wiper the midle of both pots other connections are mentioned in the manual as i know or the forum ... thanks a lot
greetings
Vladko
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bod



Joined: Apr 28, 2009
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PostPosted: Mon Dec 13, 2010 1:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

I used 12v for the adsr pots, but the gate takes a minimum 5v to trigger it.

I also had to use 500k pots instead of 1m as I wanted a specific shaft length which I could only get from futurlec, but it still works fine.

I did switch something for the vcf filter frequency pot though. I'll need to check, but from memory it may have been a 12v/gnd instead of +/-12v. I went for a pre patched approach instead of lots of jacks like a modular synth.
I'll try and find my notes but they are buried under a room full of stuff packed into half of a smaller room while I paint the studio.....

I'd post a picture of it so far but this sodding ipad doesn't let you post pictures from the library!!!
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bod



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PostPosted: Mon Dec 13, 2010 1:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wow, every sentence started with an "I".... Confused
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vladosh



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PostPosted: Mon Dec 13, 2010 11:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Bod for the reply .. i got more confused now .. i thought adsr pots are not wired to any voltage just they got their conections on the board and that's it ..did you wired it somehow to be vc adsr Smile just trying to understand .. ?? about the vcf freq it does says it's + 12 v and ground i was gonna wire it that way just the vca init gain pot i'm not sure how should i wire it it says somewhere in the manual that the vca has range from 0 to 5 volts so i'm not sure guess is + 5 v ?? i'm a newbie so much ..well that's about it ,my knowledge in electronics is worst than my job Smile .. ok then
greetings

many sentences i wrote begin with i too no problem
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bod



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PostPosted: Tue Dec 14, 2010 2:15 am    Post subject: Reply with quote  Mark this post and the followings unread

oops, ignore me, you are completely correct! all the ADSR pots connect to each other or the board not directly to the power supply. that'll teach to spraff nonsense without reading my notes whilst in the pub.... but i was thinking about the initial VCA CV, which i used a +/-v for.

the gate is +5v to trigger it, the ADSR input is connected to the VCA via a pot to gnd, as is the lfo input, but i added a bigger resistor to the LFO sum input to give it a better range by increasing the resistor from the suggested 220K to 470k as the output of the LFO is a lot hotter than the ADSR.

i'm pretty sure there are others on here who have built this synth, i recognise some of the names and front panels from the doepfer site from some of the threads on here as well.
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vladosh



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PostPosted: Tue Dec 14, 2010 3:20 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks anyway .. it happens mistakes sometimes .. but i try to understand why - 5 v / + 5 v on the inti gain it would work for cv ofset as i've seen on other circuits but here i'm not sure .. but it's ok thanks for the help anyway .. all good
greetings
Vladko
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vladosh



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PostPosted: Tue Dec 14, 2010 3:43 am    Post subject: Reply with quote  Mark this post and the followings unread

it took me a while my electricity is a bit slow .. but thank you i think i understand that about the lfo input .. thanks
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the19thbear



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PostPosted: Wed Jan 19, 2011 3:09 am    Post subject: Reply with quote  Mark this post and the followings unread

so... how does it sound!Smile
how does overdriving the filter input sound?
and the filter itself?

some soundclips would be great! Very Happy
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vladosh



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PostPosted: Wed Jan 19, 2011 12:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi .. I'm still having some ground issues so i wouldn't record it it sounds all nice to me .. added two more lfo's .. and anyway haven't got a descent soundcard ..so maybe somebody else here ..
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Inventor
Stream Operator


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PostPosted: Wed Jan 19, 2011 7:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

I am happy to learn of these simplified mini-synths. One product I'd like to create if i get time is a miniature modular synth. No panels or jacks, just little 1"x2" circuit boards each doing some modular function. Hookup by 22 ga solid wire, perhaps you have read the details of this in the eChucK forum?

Les

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