Re: op-amps with wide open-loop bandwidth ?


"John Popelish" <jpopelish@xxxxxxxx> wrote in message news:X_Gdnez8xZPE3YjZRVn-pg@xxxxxxxxxxxxxxx
: Dave Moore wrote:
: > Oops, "unity" isn't what I meant. I mean, I want
: > any op-amp that is flat (more or less) to 20Khz
: > I'm not looking for any specific specs beyond that,
: > so it's V/mv gain curve isn't so important as long as
: > long as it's reasonable to 20KHz also
: >
: > I'm simply looking for a wide variety of op-amp types
: > for sonic evaluation. IOW, I'm attempting to correlate
: > what my ear hears with with the variations in specs
: > from one op-amp to another and sadly deficient
: > in the list of op-amps I've evaluated so far are any
: > that are flat open-loop to 20Khz or higher. The best
: > I have on hand are 10KHz.
: >
: > So far my short list of star performers via the
: > old golden ear test are;
: > THS4022, THS4052, THS4062, THS4012,
: > AD828, LT1363
: >
: > Although it should be mentioned that these are
: > for guitar amplifiers and that Audio Hi-Fi enthusiasts
: > might not agree about the merits of the afore mentioned.
:
: The whole idea of opamps is that, if they have enough extra gain to
: throw away, at the frequencies you are interested in, then they all
: act the same. But the definition of "enough extra gain" is highly
: dependent on the circuit they are part of. In other words, if the
: opamp is fast enough and has high enough gain, it disappears as a
: source of sound color, and the other, more predictable components in
: the circuit, program its output, almost completely. The effect of
: gain on, say, a unity gain follower is very different than the effect
: of gain on a distortion effect generator, at the same frequency. So,
: before any suggestion is likely to help you, we need to understand a
: lot more about what circuit you intend to use this opamp in.
:
: And since, it is fairly obvious that you are not yet a circuit
: designer, you would probably get a more helpful response if you start
: over in sci.electronics.basics
:
: Good luck.

Well John, that's all fine and well in the world of pseudo-intellectual
EE-expertism, however in the real world of empirical eveidence,
it don't pan out. There are op-amps with specs far exceeding your
limited definition of what's necessary to 'dissappear the source of
sound coloration' that sound entirely different in the same circuit
and exhibit very different qualities of dynamics in the feel of a guitar
when you're playing it.

I started out designing guitar amps over 20 years ago and quickly
learned that the op-amps of the era couldn't compare with my discrete
designs. I only recently started to look at op-amps again as a viable
possibility due to recent advances in op-amp design.

I didn't ask for a lecture on tone. I asked for knowledge of any
op-amps that have a flat open-loop response beyond 20KHz
instead of the typical corner of 100Hz to 19Khz.
The open-loop gain in V/mv I don't give a rats ass about other
than that it's relatively flat to 20KHz or higher.

I realize that I didn't do a very good job of communicating
my quest, but cut me some slack here. Ever since hurricane
Katrina waxed my estate, I've been averaging 5-7 hours sleep
per night sometimes even skipping sleep altogether in an effort to
complete a very important project for a rather important person
on schedule in spite of the hurricane induced setback.

I can't tell you about the circuit it's going to go in because it's
not for any circuit in particular but rather for sonic evaluation
for exacly the reason that in the work I do, sonic evaluation is
the only thing that means diddly-poop. I've heard the theories
of the "experts" on the subject of tone fall by the wayside over
the years and watched rather bemusedly as they scramble to
come up with new theories as to why the old theories didn't
account for fact that people can hear the difference in circuits
that so-called experts would logically conclude
(according to the theory du juor) should be sonically
indiscernable.
IOW, the reason I want such an op-amp is to collect empircal
data rather than rely on the opinion of self-proclaimed experts
such as yourself that don't know near as much as they think
they do.
Now, if you want to rail on and hurl insults because I
misinterpreted your question and gave a seemingly non-sequitur
answer, do carry on.

DM


.

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