Limited Bandwidth
Eeyore wrote
You're using a 100k 'pot' effectively to drive a cable.. With as
little as 1 nF
of cable capacitance that forms a low pass filter at 6kHz !
Little? 1nF is over 10 metres of ordinary audio coax.
The transistor amps will have a lower input impedance that loads
this which will
push the turnover frequency out of the audible area (just).
Equally, reducing cable length to less than 1m would be just about OK.
You should never drive a cable from a pot or attenuator of high
value.
High is entirely relative.
Try using a 10k stepped attenuator instead. The whole point of
cathode followers
is to drive lower impedances.
Yes, assuming all sources have output resistances of less than 1k, but
doesn't your explanation equally lead to the conclusion that the
problem could be solved by reducing the input resistance of the valve
amps? That would be a much cheaper solution, but not a good one IMO.
All things in proportion.
cheers, Ian
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