VCO-1C #2

tomg vco at
Mon Jan 4 02:49:01 CET 1999

On 03-Jan-99, jhaible wrote:
>> If you really are serious about this. Look at the VCO-3A 
>> again. I used it in the MM and Mini4. After considering 
>> your idea a little more, I think this might actually be 
>> a solution. 
>> Temp-stability is good. It would still require at least a tempco 
>> and maybe 3046s if you were going to gang them up.
>> This is (no offence...really) a pretty nutty idea. Having only 12/16 
>> CEM3340s in a poly they used a cpu to keep 'em almost in tune, some 
>> of the time, and those were Curtis chips.  

>No, no, no - as I said, I would build *linear* VCOs and nothing else.
>Why fooling around with expo converters when each VCO is dedicated
>to one note on the keyboard anyway ?
>(My question was about the stability of the VCO *core*, not the expo 
>And speaking of polysynths, my CS-50 is perfectly in tune for a year 
>or more, without the need of any autotune, and even without touching
>the Manual Fine Tune Knob ! (And I bet a CS-80 wouldn't be much worse
>if it wouldn't produce that much heat on its own !)


Ohhhh...I see (duh) maybe it's not so nutz after all...:-)

In that case I would like to sell you on the 5A ota type 
that's just one LM13600/700, 5 resistors and one cap. 
About $1.50 a key. Probibly the most stable of the bunch.
and very pretty waveforms. You could set up a bank of 
analog switches and flip between the tri/sq. Might even
work out to be cheeper than some of the TOC chips I've
seen for sale these days..

I think the 1C is pretty cool and it's very small but I 
don't think I would use it for what you want to do.

Hope this helps.

poly stuff?

My jp-6 is better than my p-600 but even the mx-6 and
mx-1000 need tuning once in a while and they use DCOs.
Most of the other stuff is right on all the time. Once
in a blue moon the ex8000 (also DCOs) needs a tweek.



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