[sdiy] Discrete Op Amps

[Mattias Rickardsson]

On 9 April 2017 at 12:45, Gordonjcp <gordonjcp at gjcp.net> wrote:
> That doesn't really happen though.  All opamps sound pretty much the same.  All distortion pedals sound pretty much the same too, and it's really only the frequency response - which is not determined by the distortion "shape" - that gives it a particular tone.

Quite an oversimplification. Different distortion pedals typically
have a pre-equalisation that differs, followed by a nonlinearity of
many kinds, followed by a post-equalization that differs.

The pre/post equalizations not only shape the "tone" but affect the
waveshape and hence the result of the chosen nonlinearity, and also
determine parts of the dynamic behaviour.

The nonlinearity (distortion shape) can vary - I can think of at least
5 radically different distortion constructions used in commercial
distortion pedals, and they do give different tones and frequency
responses.

Common for successful distortion pedals is that a good combination of
these parts are chosen, since all of them are affecting the end
result.

> Building discrete opamps to chase a particular distortion shape is the sort of thinking that leads to folk buying specially-imported hundred-dollar rocks to damp out vibrations in their mains cables.

True, locally produced hundred-dollar rocks do the trick just as well. ;-P

When it comes to discrete op-amps and their usefulness today, I do
think that they can be seen primarily as a distortion device - not as
the hi-fi component solutions they once used to be. Using them would
require that you know what particular distortion they give you, and
why you want it. And they could very well be a valid choice, of
course. But today there is no big need of replacing op-amps per se, so
introducing another known type of distortion in the signal path might
be a much more reasonable way than staring at clumsy discrete op-amps.
:-)

/mr