Make a good (=bad) opamp bad (=good)

[Fancy Lime]

Hi there!

In the olden days, opamps like the 741 or 308 were technically awful for audio but they sound great in distortions. Yet, using modern audio opamps brings with it some advantages, like lower noise and better unit-to-unit consistency. So I wonder, what we can do to approximate the most important of the desirable properties of "bad" opamps.

Slew rate is obviously a factor. No problem if we use opamps with external compensation cap access, but what can we do with "standard" dual opamps?
While slew rate and frequency response are only directly related at one specific amplitude, I find that limiting frequency response of an opamp by putting a large enough cap in the feedback path already goes a long way of replicating the "slowness" of, say, an LM308 in a modern distorting opamp without external compensation cap access.

Has anyone looked at the clipping behavior of the more famous examples in detail? I wonder what differentiates that from, e.g. diode clipping.

What else is important? DC offsets can easily be imposed if clipping asymmetry is an important point. What else am I missing?

Cheers,
Andy

[antonis]

opamps like the 741 or 308 were technically awful for audio but they sound great in distortions.

Maybe 'cause they distorted with even the minute occasion..??

IMHO, a "side-effect" distortion (in the mean of not intentionally designed for this particular purpose) shouldn't be considerd as "great sounding"..

P.S.
If you insist on "replicating" ancient op-amps behavior, place a capacitor inside NFB loop on a unity-gain unstable device..

[Fancy Lime]

opamps like the 741 or 308 were technically awful for audio but they sound great in distortions.

Maybe 'cause they distorted with even the minute occasion..??

IMHO, a "side-effect" distortion (in the mean of not intentionally designed for this particular purpose) shouldn't be considerd as "great sounding"..

P.S.
If you insist on "replicating" ancient op-amps behavior, place a capacitor inside NFB loop on a unity-gain unstable device..

Well no, not replicate their behavior in total. Just identify, which are the factors we find pleasing in their sound and imitate only those without the instabilities, noise, unreliability and so on.

Andy