Yves' archive, "Synthesizer schematics" by Thierry Rochebois

[alanwilder81]

hello everyone,

has anybody attempted to build the "keyboard interface CV-GATE-TRIGGER" circuit?
it looks really nice and low components count.
It is in Yves's archive, on the last article on the page bottom, called "synthesizer schematics" by Thierry Rochebois

http://yusynth.net/index_en.php?&arg=1

any comment or help would be appreciated

[yusynth]

Hi

No I haven't built it, but it was a student project that was successfully completed and the schematics published by Thierry were all tested therefore I guess you may be pretty confident in these. I see no flaw in them.

[alanwilder81]

good morning Mr. Yves,
greetings from Italy.
I'd like to show you my greatest appreciation for your amazing works and your efforts in sharing accurate schematics and knowledge with all of us.
That enabled me to build some of your modules,in particular the Steiner filter and the saw core VCO that proved excellent.

i am now building the "simple VCA" and the "classic ADSR", in order to make a very simple architecture synth.
I can now confidently build the keyboard circuit as soon as i get the missing components, and i will let you know about the developements.

Again, thanks for your time, and i hope i can get some of your advices when getting the modules together.

[alanwilder81]

hi Yves,

I built the VCA module, listed on "my old synths" circuit collection, from US1.
here's the link

http://yusynth.net/gear/US1/images/VCA-US1.gif

can i use it as a simple VCA for my mono synth project? How do i go about setting the trimmers properly?

I'd like to know how it compares to the more advanced "simple VCA", which i can't build, as i haven't got a dual trace scope

thanks in advance !

[gdavis]

[alanwilder81]

hey gdavis,
thanks for replying

it's the first time i've really ventured on building a VCA,so please don mind some noob questions !

can you shed some light on the basic VCA knobs and parameters ? am bit confuse as to what each knob does what. You know.


As far as what i can grasp, a VCA input can be both for AC and DC,respectively for processing audio stuff and CV signals. Right?
Now,i am only interested in running my humble VCO through the VCA to get a volume envelope.
Then, is the DC offset knob irrelevant to do my job?
Else,i keep seeing the BIAS knobs. What are they? And the gain knob?
When i built the US1 VCA i noticed that the volume stayed always ON, there was no way to silence it.
Is that how it's supposed to work?

excuse my many questions.trouble is ,despite much researching they have remained unanswered for most part.
thanks in advance !!

[gdavis]

[alanwilder81]

hello gdavis,

many thanks for your incredibly articulate response. I'll take a deeper look later.That sheds a light on the VCA working principles great stuff.

I have played VST synths forever. I've learned the crap out subtractive synthesis right on those fake sounding emulation
As bad,as cold, as sterile VST's might sound, they gave me the opportunity to get a solid gasp of the audio path,at least.

Also ,i recently had the chance to play some real analog baby, and i was hooked. I decided it was time to go DIY all the way because it's the real sound that i am after.

So i am humbly trying to get grasp with basic VCO-VCF-VCA architecture mono synths.Very rewarding experience !

[alanwilder81]

to gdavis,
should you need me to provide you with the schematics ive been working on,just dont hesitate to ask . I'll keep you posted with the next VCA developments. Again, thanks for the great infos and willingness !

[alanwilder81]

hey Gdavis,
there's some great news
i finally unraveled the VCA mistery,after making the US1 VCA and another one from EFM website by fonitronik.

The knobs are starting to make sense now, i manage to modulate the VCA by using the US1 AR generator.
Plus, i found a nice VCA ,very similar to Yusynth one,just a semplified version of the "simple VCA" that is in turn carbon copy of the US1 vca i built.
here's the schematics. It works,for whoever would be interested in it

http://kassu2000.blogspot.it/2015/10/vca.html

[Cfish]

The simplest example of this type of VCA I have ever found is the early PAIA VCA schematics. Sorry I looked for a few and couldn't find a link to it, but I know it's on line.

Glad to hear your making progress alanwilder81

[alanwilder81]

hello folks,

i am about to build the following keyboard CV GATE TRIGGER circuit that calls for a CD 4066 for the sample and hold section.
I recently got a bunch of CD 4016 ,i'd like to know if i can use it in place of the CD 4066 the circuit specifies. thanks folks !

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[yusynth]

Yes you can

[Cfish]

Hi alanwildr81

I have had this in my list of circuits to try since you posted it.

Would love to hear how it turns out for you. Looks like it should work great.

Wish I had seen the schematic a couple of years ago, however if I had, I might not have learned what I learned trying to build one I could understand.

[alanwilder81]

thanks very much Yves !

another question.
on the far left of the schematics,I see three outputs from the keyboard circuit called, from top to bottom, "noir", "blanc" ,"gris" .
They are connected to the circuit by the means of "dotted lines". Are those lines to be considered as regular cables and connections?
is there any particular reason for them not to be drawn as the rest of the circuit connectionss?
thanks !

[alanwilder81]

to Cfish

I am glad you found inspiration from that schematic.i am just about to breadboard it.

[yusynth]

[indigoid]

so I built myself a US-1 VCA also. My system is Eurorack, so +/-12V. I used TL072 and 2n3904 since that's what I had at hand, and as people often say 2n3904s are usually quite well matched for Vbe if they're from the same strip of paper tape, I didn't bother matching them.

When feeding it relatively-fast-but-not-audio-rate signals the top half [only] of the output wave is notably rounded off, as if it had been slewed.

Transistors not sufficiently matched?

I will keep tinkering with it.

[yusynth]

Yes probably

[alanwilder81]

thanks Yves,now it makes more sense !

[alanwilder81]

hello Yves,

i finally managed to build the keyboard circuit published by Thierry Rochebois.
It looks it works, i am immensely happy with that.
I would like to thank you for this and share this success, my synth now is complete

[yusynth]

Excellent

[alanwilder81]

thanks Yves. another question.
at the moment i am using an extra -10 V power supply cable connected to the ""echelle 1 V octave"" trimmer. it works but it's only temporary.
What would it be a better and definitive solution to raise the voltage from -12 to -10 in that section?

many thanks!

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[yusynth]

Or you can use a resistor, a 10V zener and a capacitor to create the 10V reference

[alanwilder81]

thanks Yves !