Re: perceptible audio distortion

In article <6f2i0nF95gi8U1@xxxxxxxxxxxxxxxxxx>, Phil Allison wrote:

"Don Klipstein"

** The LM324 is no audio grade op-amp.

It was designed for single supply, low current applications - ie battery
operation.

The output stage is a real odd ball - requiring direct coupling of the
load ( no caps ) if x-over distortion is to be avoided.

See page 8 of http://www.national.com/ds/LM/LM124.pdf

I was already aware of the LM324 having a high tendency to only behave
well without crossover distortion in single-supply circuits.

** You have it wrong yet again.

The x-over distortion issue is with cap coupling, not single supply.

The issue is handling the current zero crossing - crossover distortion.
I must not have elaborated enough to put coupling caps not preceded by
resistors to ground into the discussion as examples of where the LM324
runs into crossover distortion.

I wonder why you did not cite this along with ua709 before I mentioned
it from actual experience working with it.

** The OP said "some old opamps" - which the uA709 certainly is, having
been around since 1965 and one of the first ever made. OTOH - the LM324
is relatively modern, having appeared in 1974 plus, as I said, not used in
hi-fi audio.

FYI - the popular audio grade op-amp appeared as follows.

uA741 = 1968
LM101 = 1968
LM301A = 1969
uA748 = 1969
RC4558 = 1974
LF355 = 1975
TL081 = 1975
TL071 = 1976
NE5534 = 1977

Most are way older than folk imagine.

Just a little older than I imagined - I thought the 741 came into use in
the very early 1970's and TLO7* and TLO8* came into use in the very late
1970's.

Interesting history!

- Don Klipstein (don@xxxxxxxxx)
.

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