N_Cook wrote:
Bob Larter wrote in message
[...]
Sounds like something's wrong on the input side of the ADC. Have you
tried using a scope to follow a signal from the input socket to the ADC?

I did introduce the sine at the 1/4 inch inputs , and op-amps between but
scoping the ADC inputs , they are fine.

Are you still seeing the sine wave at a pin on the ADC?
I ask because the symptoms you describe sound like something in the ADC
input chain is losing the signal & supplying noise instead.


Curiously my first job in
electronics was constructing a psedo-random sequence generator, filtered
down, to produce peak limited "white noise". For RF transmission line
testing , so requiring MECL logic , rather than for audio. No longer have
access to a spectrum analyser, but would like pass it through one.

I doubt that that would help you. I think that a scope is all you need,
based on the symptoms you're describing.

There are (scope measured) 50K, 400K, 11M clock and other pulse trains and
not determined whether they are as should be , at the moment just an
interesting curiosity. It is stable , invariant to ps voltage change from
4.3V to 5V.

Do you have any data on the correct Vcc for the chips?

Not grey noise or any other "coloured" noises that I can find reference to.
The pk to pk maximum is 1/2 the power rail voltage of 5V, so no nasty short
duration peaky spikes of real noise that cause their own problems over
transmission lines IIRC.

Maybe I'm wrong, but it really looks to me like you're getting noise at
the ADC input, & your tweak is merely coupling it to the output.


--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
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