Metal film resistors or carbon film in a tube amp?

[G]

Hi all,

I'm about to the point in my project where I need to order some resistors. Should I use either metal film resistors or carbon film. Maybe metal film for biasing and carbon film for signal?

G

[peranders]

First of all: Consider the voltage rating for metal film! Ordinary metal film are 300 Volts!

Metal film are better in amlost every parameter except for transient power handling. Some types carbon resistors are better in this respect.

Which parameters are better:

Noise
Long term stability
Temp coeff
Resistance tolerance
Power handling (vs. volume)

My advise is to use metal film as much as you can.

[dhaen]

Mmm, I'll have to ask Joel which make "sound" better

[halojoy]

Carbon resistor were used before Metalfilm resistor existed.
And before the transistor existed, there was only Tubes.
A lot of those nostalgic traditions in Audio Design Techniques
will be replaced, as time goes by.
A lot of old schematics has not been updated
to modern standards regarding component selection.
I would not go as far as to say that nothing was better
in them good old days.
There is certainly a lot of crappy things
in latest fashion. Never been tested and aproved.

There is too much of "monkey see monkey do",
that has no valid techniqual qualities.
In circuits of yesterday as well as of today.

But what can we do, if somebody wants to use
second best solutions by sentimental reasons?

/halojoy 2002
been watching the years go by

[Damon Hill]

Carbon film resistors predate WWII and were used in some German radios and other equipment. I don't know when metal
film became affordable/popular.

There's also wirewound, though that's kind of expensive and
not readily available in really high values.

I'm starting my first tube amplifier project and have to consider
the same choices.

[jh6you]

Many tube audiophiles still love to use carbon (non inductive) resistors. They say carbon resistors are somewhat noisy but good for warm, soft and thick-mid sounds. Using the carbon resistors is known as not for better sound but for different sound.

JH

[halojoy]

Yes,
We must always remember that diyaudio is not even to 50%
a Hi-Fi Forum.
High Fidelity - to be true - in this case the signal on the output
should have as little difference as possible from the input signal.
This difference is also called distortion. Can be measured in various ways.

This is a diyAudio forum
Not an High Fidelity forum to 100%
Not an High End forum to 100%

Most of us happy homebuilders belong to THE BIG MAJORITY
who simple likes to listen to music, that we like
and that should sound the way WE like.
And we also like to be creative, build things with our own hands.
And get great joy out of that.
This MAJORITY is NOT to be IGNORED

here is where the fun part comes in
/wholojoy
a whole lotta joy

[JoeBob]

Your choice of resistor types won't change much. In a good circuit they will both sound great, and in a bad circuit they'll both sound bad. The choice of resistor won't make or break an amp. I use carbon film because I like brown resistors better than blue resistors.

[halojoy]

Originally posted by JoeBob
Your choice of resistor types won't change much. In a good circuit they will both sound great, and in a bad circuit they'll both sound bad. The choice of resistor won't make or break an amp. I use carbon film because I like brown resistors better than blue resistors.

I have never been able to getta like brown resistors.
I am perhaps simply not used to the color.
I use mostly what I have at home.
This goes for food also. I take whatever I have in the refridge.
Resistors are superior in linearity compared to most other things.
As is wires and cables.

[peranders]

Originally posted by jh6you
Many tube audiophiles still love to use carbon (non inductive) resistors. They say carbon resistors are somewhat noisy but good for warm, soft and thick-mid sounds. Using the carbon resistors is known as not for better sound but for different sound.

JH

G, I forgot maybe the reason for changing resistors. Technically, I think no tube amp really needs metal film. Why?

No low noise application (normally)
No demand for low tolerance (5% is enough)
No need for long term stability (tubes aren't very stable)
Heavy colouration from the tubes and transformers itselves. The contribution from resistors are minimal.