"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.

Hi Mark,

I have seen some concern about inductive and capacitive aspects of certain
types of metal films in certain applications -- even though most specs say
they are 'non-inductive' or don't address the issue. Anecdotally, I have
seen RF transmitters, broadcast exciters, etc. with lots of metal films
throughout, and carbon composition resistors retained in the high-frequency
areas. This may be the source of the 'ringing' comment you mentioned . . .

I do think it is safe to say that the level of extra reactance in modern
metal films is low enough to be extremely unlikely a point of concern in
tube audio electronics -- maybe in a tube VHF transmitter you might worry
about it. It is also safe to say that modern metal films definately have
substantially lower noise and tighter tolerances than carbon composition
resistors (even modern carbon comps), and thus it is very possible for them
to change the sound of the device in question.

As a general rule, I believe in preserving the value of collectable and
valuable historic equipment by using original parts when appropriate, but
for new designs or substantial modifications I feel that the more the
artifacts of the parts are reduced, the closer you will be to hearing the
sound of the circuit itself . . . and hopefully if the circuit is doing its
job, closer to the sound of the music.

I recommend that you heed the advice others have posted regarding voltage
ratings, and enjoy the performance of modern resistors -- if there is indeed
any ringing, it can be measured, analyzed, and dealt with through proper
circuit changes rather than blindly swapping parts.

Best regards,

Kirk Patton