ARP Odyssey Oscillators

isak · Posted: Sat Jan 11, 2014 2:45 am Post subject:

Hi xpmtl

i used regular Fairchild ones, 2N3904/06, didnt matched them at all.
if it helps i put them together with thermal grease.

maybe my test is not so clear, i'll explain better.
i have the lite ,midi2cv, it gots only 5 octaves.
http://www.acxsynth.com/midi2cvlite/midi2cvlitefr.htm
when i change the Tune of the ody VCO, to high i got a great scale track up to 9 oct Smile

meaning...say i play C1 it will be perfect up to C5, then i cant get any higher cause the midi2cv lite wont let me, then... changing the Ody VCO Tune so what was C1 now will be C5 then i get perfect scale for higher notes up to 9 or even more Smile

i hope i explain this better now.

cheers,
Isak E.

xpmtl · Joined: Aug 10, 2007 Posts: 162 Location: Brussels, Belgium

Thanks Isak,

I've soldered thru-hole trannies on the original smd pads (not easy) and now i get 8 octaves perfectly in tune. 9th octave is a tiny bit off.

Used 3904/3906 as you did.

Thanks for your input!

isak · Posted: Sun Jan 12, 2014 6:04 am Post subject:

Happy to hear you got it to work, enjoy this amazing vco Wink

pdman1 · Posted: Tue Mar 11, 2014 6:08 pm Post subject:

Been off these forums for a while. Does anyone sell already etched PCB's for this Arp VCO?

Thanks

isak · Posted: Wed Mar 12, 2014 12:24 am Post subject:

Hi, I pm'd you.

cheers.

xpmtl · Joined: Aug 10, 2007 Posts: 162 Location: Brussels, Belgium

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

xpmtl · Joined: Aug 10, 2007 Posts: 162 Location: Brussels, Belgium

I didn't

Results are pitiful with smd transistors for the expo pair but quite good with thru-hole 2N3904/3906. I had matched a series of transistors so i used a pair with the same values and epoxied them together. So it's not a matched pair per say but it should be really close. I get 8 octaves of usable tracking, 9th octave is a bit off but stll usable.

I've ordered some matched pairs in sot-323 format (BC846bpn & mmdt3946) to test, If it doesn't work i'll stick with the thru-hole pair.

Don't think the fets need to be matched.

I read somewhere that the expo pairs in the oddy weren't matched, so....

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

xpmtl · Joined: Aug 10, 2007 Posts: 162 Location: Brussels, Belgium

Well matching is for temperature stability so it won't affect tracking anyways, what i look for is having the two but in one package possibly on the same die (i doubt they will).

BTW why do you think the FETs should be matched?

I'll keep you inform of the results.