William Sommerwerck wrote:
And even if you do, you're stuck with 1970's
Radio-Shack grade op-amp design.

Actually I opened it hoping I could replace an op amp
but there are no ICs in it at all.

You're probably not looking at quality, then. The 70s
was [sic] awash with grotty discrete kit.

To the best of my knowledge, this equalizer was not an RS design. It came
from a little company called Metrotech, and appeared as a Popular
Electronics construction project. The same circuit was later used by BSR for
a 12-band equalizer.

It should be noted that, even in the '70s, IC designers were still "finding
their way" with respect to op amps. And there are plenty of current
designers who would not agree that ICs are inherently superior to discrete.

The problem is that active filters built on op-amps require lots and
lots of gain.... as a consequence, discrete op-amps in active circuits
tend to be problematic because really high-gain discretes are difficult
to build and keep stable.

It's the one application where monolithic op-amps really _were_ a huge
win, even back in the seventies when monolithic op-amps were... well...
kind of nasty.

Then again, you will still find people who are huge fans of the old ITI
equalizers, which are the typical four-op-amp parametric configuration
built with video-amplifier-style discrete op-amps. Neutral they aren't.
But some people like the interesting weirdness.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."