Good quality metal films should be stable and distort hardly at all.
Poor quality metal films can be noisy and distort due to
manufacturing defects (eg local heating effects due to thinner parts
of film, and poor lead attachment). I guess the same goes for
carbon, but sometimes I think folk compare good carbon with poor mf
and come to false generalisations.

I suspect that some folk like carbon for the same reason they like
paper and oil caps...harmonic distortion. I don't know what the
mechanism for that is...possibly poor heat conduction and
temperature coefficient on the part of carbon?

It would be interesting to compare typical capacitance and
inductance for the two types. If ringing occurs with one type and
not the other, these would be the parameters to compare I suppose.

I have read lots of times that mf gives a relatively "hard" sound.
I take it that means low distortion rather than high odd harmonics.

cheers, Ian

"Marko" wrote in message
...
I was told that metal film resistors should not be used with tubes
because
they make the circuit ring. Carbon films sound better.

I see no basis for this in specifications for metal films. Any
opinions or
facts? Thanks, Mark