Sjouke Burry s@b wrote in message
2.10...
"N_Cook" wrote in :

What is the likely cause of this problem.
Just as well I keep repair records as I met this amp 5 years ago with
the same untraceable fault. Owner and me had forgotten it re-appeared
when he used the bass with a different bass amp.
Previously reported as a fuzzy sound when he used the bass E string.
This time just playing the F on the bass E string , a rattly buzz,
like a spiral wound guitar string vibrating against a fret and loss of
the actual F note. I've not seen the bass or transducer , assuming its
a piezo element - make Ashworth transducers, what could cause this
symptom, disappearing for 4 years? Both bass and amp have been around
the world a few times on cruise ships so perhaps excessive heat or
humidity



Input dependend oscillations?
for retain freguencies and /or source impedances oscillations at certain
parts of the waveform.
Sounds just like you described.
And a change of source will make it appear/disappear.
Remedy: carefully changing the HF bandwidth a bit, and improve
dc power decoupling.
A small cap across inputs also is worth trying.

I'm trying to work out what HF means in terms of 44 to 44 Hz, but as the amp
is only used with an acoustic bass then a permanent adaption at the input is
possible