[sdiy] Weird MFOS VCO max CV problem

[Travis Thatcher]

This is the version, schematics on the page:
http://musicfromouterspace.com/analogsynth_new/VCO200604REV01/VCO200604REV01.html

I have some spare lm13700's laying around. I'm probably going to
replace that and see what happens. Not sure if i have another lf442
though, which is the summing opamp.

T

On Mon, Apr 9, 2012 at 10:06 PM, Olivier Gillet <ol.gillet at gmail.com> wrote:
>> There were some discussions about using a TL07x as an inverting integrator  in an OTA filter, many people had hang-up
>> issues at power up. Using the same part a voltage follower (with the integtator cap to ground) worked perfectly
>> every time...
>
> I have seen this problem, but I think it's the other way round: I have
> seen frequently a phase reversal "crash" with the "cap to ground +
> follower" circuit when signal level was getting too high. Can happen
> when self-oscillation is reached, when cutoff is increased (less
> high-frequency attenuation -> higher level), or simply when a very hot
> external signal is fed into the circuit. I have worked a lot with +/-
> 5V so there's not much headroom and it's easy to hit the rails - and
> in this context seeing a TL072 with its +ve input not grounded raises
> a red flag for me. Neil Johnson has compiled this list of op-amps that
> do not phase-reverse:
> http://www.milton.arachsys.com/nj71/index.php?menu=2&submenu=2&subsubmenu=2
>
> Back to the topic at hand, are there schematics of the offending circuit?
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