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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
The CGS VCO
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numbernone



Joined: Aug 16, 2006
Posts: 477
Location: new york city

PostPosted: Wed Jul 30, 2008 2:45 pm    Post subject: The CGS VCO Reply with quote  Mark this post and the followings unread

I am now pretty interested in the CGS VCO, but am finding not a lot of info as to how others have built it. Surprising, as it seems to offer a hell of a lot of options to float most all folks boats.

Anyhow, I would love to hear some feedback about this oscillator. What parts did you implement, would you do it the same again?

I want to know more about the staricase section.

Also has anyone used an Analog Devices 2210 in place of the 394? I have some 2210's that I got as samples before the clampdown, and would prefer to drop them in instead of hunting the 394s down.

I will definitely be using the waveshaper section, as I LOVE the skew on the Thomas Henry XR osc.

Lets hear about your VCOs...
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Rykhaard



Joined: Sep 02, 2007
Posts: 1290
Location: Canada

PostPosted: Wed Jul 30, 2008 8:59 pm    Post subject: Re: The CGS VCO Reply with quote  Mark this post and the followings unread

numbernone wrote:
I am now pretty interested in the CGS VCO, but am finding not a lot of info as to how others have built it. Surprising, as it seems to offer a hell of a lot of options to float most all folks boats.

Anyhow, I would love to hear some feedback about this oscillator. What parts did you implement, would you do it the same again?

I want to know more about the staricase section.


I've only built 1 of them and I attemplted to implement every single option. The only thing that wasn't / isn't working is the Staircase function. Though, I haven't debugged it either.
Outside of that, the VCO sounds wonderful, especially with it's waveshape control. Smile
However, having 2 more of that VCO board, I'm building them for +/-5V Sawtooth only. (Same thing with my currently built Bi-N-Tic as well as my 2nd unbuilt Bi-N-Tic).
I'm going to be building my own waveform converters again in the near future. This way, keeping the VCOs simple, I'll be able to put 4 of them into a 3U 19" rack panel. Smile

Quote:

Also has anyone used an Analog Devices 2210 in place of the 394? I have some 2210's that I got as samples before the clampdown, and would prefer to drop them in instead of hunting the 394s down.

I will definitely be using the waveshaper section, as I LOVE the skew on the Thomas Henry XR osc.

Lets hear about your VCOs...


I used the SSM2210 in my Bi-N-Tic as well as VCO from Ken. They worked wonderfully in both. As well as metalized polyester film caps for their 1nF positions. Solid tuning over quite a few octaves for both of them.

If you haven't bought 1 of those VCO PCBs from Ken yet - go for it! Wonderful piece of work from Ken! Well worth it. Very Happy
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numbernone



Joined: Aug 16, 2006
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Location: new york city

PostPosted: Thu Jul 31, 2008 7:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Rykhaard, as my usual VCO problem, it will likely be 3.
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CJ Miller



Joined: Jan 07, 2007
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PostPosted: Thu Jul 31, 2008 8:09 am    Post subject: Re: The CGS VCO Reply with quote  Mark this post and the followings unread

I have been building two, but completing them has waited as i was missing a few resistor values. Having washed the boards, I'll let them dry today, and by weekend should be able to have the trimmers and styrene cap soldered in. And then, the big bench test! There are so many connections on these PCBs that I'll need notes handy to even remember what they are. So, I'll probably hear them this weekend!

Rykhaard wrote:
As well as metalized polyester film caps for their 1nF positions.


Hmmm.... I might just be too tired now, but I can't find 1nF caps on here! I used tantalum for the polarized caps, except an electrolytic for the 47uF. A polyester 4n7. Monolithic 100nF and ceramic discs for the pF values. I was guessing that the main timing cap was the crucial one to make stable. The decoupling caps I'd suppose needn't be great. I wonder about the pF caps if these might worsen the sound quality, since they have that reputation. Where are the 1nF? Tomorrow I'll recheck the schematic.

I hope to buy another few of these VCOs later, so maybe I'll compare the caps then. I can hardly wait!
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Rykhaard



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PostPosted: Thu Jul 31, 2008 9:18 am    Post subject:  2n2 poly cap. Not 1nF. My mistakened memory! Reply with quote  Mark this post and the followings unread

Sorry about that CJ! I was going from rough memory, whilst _I_ were half asleep this morning! Sad

The cap for both of Ken's VCO and the VCO in the Bi-N-Tic are 2.2nF. Not 1nF.

That cap. IS the critical one for tuning stability. IIRC the other caps that you had stated that you used, are fine. Smile
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neandrewthal



Joined: May 11, 2007
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PostPosted: Thu Jul 31, 2008 9:36 am    Post subject: Reply with quote  Mark this post and the followings unread

The CGS VCO is incredible! I didn't leave off any options(besides the DC outputs) and I don't regret a thing.

With nothing connected to the staircase out acts as independent ramp lfo, the speed of which is controlled by the sub octave division knob(up the the low audio range) It is lots of fun to modulate the waveshape and frequency(with reversing attenuator) with this. Feed one of the outputs into it and you can modulate the VCO with divisions of it's own frequency.

Those are just a few fun things you do with the VCO all by itself.

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fluxmonkey



Joined: Jun 24, 2005
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PostPosted: Fri Aug 01, 2008 6:23 am    Post subject: Reply with quote  Mark this post and the followings unread

would love to see pics of anyone's "maxed out" vco front panel... anybody done one in frac/euro format?

b

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Luka



Joined: Jun 29, 2007
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PostPosted: Fri Aug 01, 2008 6:33 am    Post subject: Reply with quote  Mark this post and the followings unread

ive got one in cardboard, it has everything except the sub-osc. i had it with the sub-osc on a 3U panel but decided it could be condensed.

sorry for the bad picture

it is the one in the middle with the two big silver knobs

rolls like this,
big silver knobs - fine and coarse tune
small knobs at top - fm ac & dc with cv atten
small knob to the right of tune is pwm
small knob to the left of the tune is waveshape
small knob under tune is linear cv atten

jacks roll like this
pwm, fm ac, fmdc, Waveshape Cv
sync, linear cv, clk
sine, 1v/0, 1v/0, waveshape
pulse, saw+, saw, stair

our drill press broke otherwise i woud have made the plate for this by know
and ill find some nice ex-ham radio bakelite knobs for it too
those silver ones were just lying around


cgsvco.jpg
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cgs_vco ala problemchild
cardboard proto plate
rusty version coming soon :)
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numbernone



Joined: Aug 16, 2006
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PostPosted: Fri Aug 01, 2008 8:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice!!

Now I know I am probably not thinking straight, but whats the advantage here to have both AC and DC FM inputs?
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neandrewthal



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PostPosted: Fri Aug 01, 2008 10:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Here's my "maxed out" version. Just missing the above 0-5v outputs I think.


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Rykhaard



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PostPosted: Fri Aug 01, 2008 10:40 am    Post subject:   Reply with quote  Mark this post and the followings unread

Coloured nuts and washers for 1/4" jacks???? THAT looks VERY impressive! Very Happy

How much do they cost, per jack??
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neandrewthal



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PostPosted: Fri Aug 01, 2008 11:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Rykhaard wrote:
Coloured nuts and washers for 1/4" jacks???? THAT looks VERY impressive! Very Happy

How much do they cost, per jack??


haha, I wish you could buy them.

But, it was $30 for 6 cans of spray paint.

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Coriolis



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PostPosted: Fri Aug 01, 2008 2:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well well...looky here:

http://www.cliffusa.com/datasheet/S1%20MINI%20JACK.pdf

Perhaps they'll sell those as spares if asked?

C

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Rykhaard



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PostPosted: Fri Aug 01, 2008 8:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Whoa! CLIFF is doing it! If I were still early in building my machine, I'd convert back! I'm prolly over 300 jacks now though in my machine, with the current panels being built so it'd be a little too costly now. Oh well.
Whether purchased or painted, they sure look great! Very Happy

THAT reminds me - I want to email Johnson and see about the possibilities of getting a custom run of CLEAR banana jacks. Wondering what they'd want for a minimum order. Wink (Then LEDs could be strung behind them / etc. Very Happy )
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neandrewthal



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PostPosted: Sat Aug 02, 2008 1:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Coriolis wrote:
Well well...looky here:

http://www.cliffusa.com/datasheet/S1%20MINI%20JACK.pdf

Perhaps they'll sell those as spares if asked?

C


Oh neat! That's a nice red nut! I'll have to see what other colors they have as well.

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Luka



Joined: Jun 29, 2007
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PostPosted: Tue Aug 05, 2008 5:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

im having a couple of stumbling blocks while trying to tune my cgs vco, i was wondering if there are some kids out there who have done this that can help me out.

ok so i disconnected my course and fine tune pots.
used the zero centre trim to pull voltage down to 0

then i grabbed 9v batter and scaled the current down to 1v with a pot.
i used a pot to do this and then ran the wiper and ground through a patch cable. first stumbling block. the voltage was measured at 1v without connection to the vco. (i had a dmm connected to the pot as well). Once i connected the patch the voltage dropped to 0.45V. It wasnt the pot turning by itself, as when i disconnected it, the voltage came back up to 1V. So im curious about this, do i need up up the voltage so it is 1V when it is connected? If someone could explain this for me it would be great.

so i assumed that i didnt need to re-scale the voltage and i tuned it roughly to a octave separation with the span trim. i used ableton's analog synth as a reference and did it by ear. i think i got it in there with only a few cents difference. i listened for a phasing effect and then tuned it a little more till it stopped and i got a unisen kinda sound.

anyway, so i didnt bother trying it for 3 octaves yet, i wanted to check what it was like, so i reconnected my tune pots and found that the range of the course pot was completely fuxed. The whole audio range was located in a degree or 2 of the pot. So this is obviously wrong.

this is the first VCo ive had to do this for (haha can you tell?? /noob)
where did i go wrong

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Blue Hell
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PostPosted: Tue Aug 05, 2008 5:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Luka wrote:
ido i need up up the voltage so it is 1V when it is connected? If someone could explain this for me it would be great.


Yes, up it, you'll want 1 V at the control input of the osc for an octave. When the pot is a high value one the 100 k load or so (typically) of the input will make the voltage drop. A drop of over 50% is a lot though, did you use a 1 Meg pot or something? If so the large drop would make sense, maybe better use something like a 1 k pot - it should still drop a bit then but far less - I'd still up it then ... if possible and measurable on the DVM.

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Luka



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PostPosted: Tue Aug 05, 2008 6:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

great thanks.
yeah it was a 1m pot

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ericcoleridge



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PostPosted: Tue Aug 05, 2008 9:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

neandrewthal wrote:
Here's my "maxed out" version. Just missing the above 0-5v outputs I think.


Very nice, great idea painting the washers/nuts. What sort of paint? rustoleum?

Have you had them in use long enough to know if the paint scratches up much?
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neandrewthal



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PostPosted: Wed Aug 06, 2008 1:05 am    Post subject: Reply with quote  Mark this post and the followings unread

ericcoleridge wrote:
neandrewthal wrote:
Here's my "maxed out" version. Just missing the above 0-5v outputs I think.


Very nice, great idea painting the washers/nuts. What sort of paint? rustoleum?

Have you had them in use long enough to know if the paint scratches up much?


I just bought whatever brands had the colors I wanted, which just so happens was mostly rustoleum. I havent been using them very long, but I put them up to repeated scratch tests on a mock-up panel. I have to stab them pretty hard with a patch cord to get them to scratch. Scraping them with a force I am likely to use during patching produces no scratches even after many repetitions. Only time will tell If theyll hold up over the years, though.

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Electronicant



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PostPosted: Sat Aug 16, 2008 6:40 am    Post subject: CGS VCO Reply with quote  Mark this post and the followings unread

Hi, I´d lke to know what´s unique with the CGS VCO. It has many options but except that? does it sound very different?
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CJ Miller



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PostPosted: Sat Aug 16, 2008 11:37 pm    Post subject: Re: CGS VCO Reply with quote  Mark this post and the followings unread

Electronicant wrote:
Hi, I´d lke to know what´s unique with the CGS VCO. It has many options but except that? does it sound very different?


One unique thing is the amount of features which you can interact with. It's based on the ASM-1 VCO, which is well-known as a stable, good-sounding sawtooth VCO which can be made easily without a lot of expensive parts. It has a handy CV processor on the input which is a hugely useful thing which most overlook. And it offers a monster waveshaper on the output for getting "nonstandard" waveforms.

It is not different in being an exotic type of synthesis or unusual electronically. It is special because Ken had the sensibility to include such musical features.

I'm going to try to finish my two this morning! I got sidelined the past two weeks by water in my basement. Here goes!
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Luka



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PostPosted: Sun Aug 17, 2008 1:35 am    Post subject: Reply with quote  Mark this post and the followings unread

so what is the use of the CV processor. im still finalizing my panel and would like to know a bit more about it and what it can be used for.
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andrewF



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PostPosted: Sun Aug 17, 2008 1:47 am    Post subject: Reply with quote  Mark this post and the followings unread

You can use the CV processor to alter the effect of CV signals - for example, usually a rising voltage increases the frequency/pitch of the output signal. The CV processor can cause the opposite effect - rising voltage = pitch goes low.
I love'em and always use these on my CGS VCOs, the 1V/Oct inputs are just spares. In fact, 8 of my CGS VCOs only have the CV processor inputs and no 1V/oct at all Very Happy

Correct me if this is wrong, I think these are based on the functionality of the CV inputs on the circa '73 Serge VCO. (Ken's design is different though.
Check out Houshu's version - http://userdisk.webry.biglobe.ne.jp/000/024/65/N000/000/000/Vco3900_0707.GIF
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Luka



Joined: Jun 29, 2007
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PostPosted: Sun Aug 17, 2008 2:51 am    Post subject: Reply with quote  Mark this post and the followings unread

i can see that gif andrew. is there another link?

so is it like a thru-zero cv processor?

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