[sdiy] Op Amp Replacment for CV and Audio

[Colin Hinz]

On Fri, 16 Jul 2004, Oakley Sound wrote:

> > I'm looking to replace the 1458 dual op amps in an Octave Cat I'm
> > working on. I'll be using LT1013s (as recommended by Paul Schreiber)
> > for the op amps in the CV path in an effort to improve stability
> > especially for the VCOs.
>
> Just to warn you, although the LT1013 is an excellent chip, it probably
> won't do anything for the appalling drift in the Octave CAT's VCOs. Most
> of the drift is coming from elsewhere in the circuitry. I would have
> liked to spend some time looking into this when I had one in the
> workshop a while back. I think the VCO itself is probably OK, although
> it does use a 4093 schmitt as the VCO comparator. My suspicions lie with
> the +/-7V zener regulated lines, but as I say I didn't spend so much
> time with it.
>
> The OP275 is a good all round op-amp for both CV and audio, but it still
> won't beat the LT1013 for its DC specs, or the 5532 for its sound. But
> the trusty TL072 is good one to try first.

This sounds like an excellent application for a few good-quality IC
sockets. Ordinarily, I'm pretty "down" on IC sockets (adding extra
levels of interconnection can only diminish reliability, and $25
spend on a good desoldering tool will last much longer than $25
spent on IC sockets) but in situations like these they'd be really
useful.

- Colin Hinz
  Toronto, Canada