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 Forum index » DIY Hardware and Software
simple but pretty stable/precise vco ?
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synth_ollie



Joined: Sep 11, 2006
Posts: 149
Location: sweden

PostPosted: Tue Oct 31, 2006 3:14 am    Post subject: simple but pretty stable/precise vco ? Reply with quote  Mark this post and the followings unread

it need to be pretty precise over at least +/- 1 oct (2 octaves)
I was thinking of the t.h xr2206 vco, any other ideas... ?

OLLIE
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fluxmonkey



Joined: Jun 24, 2005
Posts: 695
Location: cleve

PostPosted: Tue Oct 31, 2006 10:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Music from Outer Space VCO.

I just built a couple of the Henry/Stites xr2206, using bugbrand's PCB... the swept/VC skew is a cool sound... but the MfOS would win by a whisker, not least because of the quality PCB available--etching boards is not my favorite.

these are both pretty much simplified to their cores... probably start compromising quality/stability w/ anything simpler...

bbob
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toppobrillo



Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1

PostPosted: Tue Oct 31, 2006 1:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

don't skimp on the CV summation/current conversion stuff, temperature compensation is critical. [there are a few different approaches to do this]

if you're going the 'electro-notes option whatever' saw-core route with a FET [like MFOS], apparently the MPF-102 isn't the best choice. I haven't had any problem with it, but some do. I have used also a J112 which, apparently, is the same transistor used in the Moog [E112]. in the integrator, i guess it's good to use a low-leakage cap like polystyrene.

[I have this philosophy: if it's good enough for _____ {insert synthesizer manufacturer} it's good enough...]

all that other stuff is wave-shaping circuitry. at the core the VCO is pretty simple. Rene Schmitz has a very simple VCO built around a single 4069 Hex Inverter. check it out...

http://www.uni-bonn.de/~uzs159/


edit::: here is what Takeda has to say about this VCO

http://www.aleph.co.jp/~takeda/radio/farmVCO4069E.html

[[regarding the first line of my reply]] he says: "This circuit didn't use active parts for summing stage for getting simple. It causes something bad for CV inputs. It will going to make a gap of an octave or something. This type not matches for modular type. But it should OK for IN-BOX type."

he also says: "I think 4069 VCO is hot (I mean double in this word) and good, but if it use more less current to work, then I like it more." heheh
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