• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Carbon Film Resistor for plate load?

Power tube cathode resistors work hard, everything else can be 1/2w.
Please note that power capability is just one aspect to chose an appropriate resistor. Voltage capability is another one. So a 1 W plate resistor is recommendable in certain cases.
Carbon Comp resistors add something to the sauce in a Guitar amp.
I doubt on that. My theory is: No one knows how a vintage guitar amplifier sounded when it fell from the manufacturer's production line. But all guitarists know how they sound nowadays. As you said:
They don't hold their value when they heat up, or when they get old.
Yes! I bet that the respective then new amp didn' sound any different form a today's new one. Their nowaday's sound is just an acquired taste due to the aged components.

I prefer metal film resistors, where possible, as they're as cheap as carbon films now. Otherwise WW's. Carbon comp is an outdated and unreliable technology.

Best regards!
 
I'm often a contrarian here on DIYAudio, I find many posts long on opinion but short on facts.
For example, the CC R;s are noisey, In 1957 I built this preamp for a General Electric Variable Reluctance Phono
pickup, mV's of signal. Its still here on the shelf but not run for years, Need another for stereo.
While in use it was very quiet.

Next amp your build that needs only a 2 Volt signal has a problem, it may be the
century olde tube making the noise in the cct.
 

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Seen many posts here from the experienced 'smart set' which indicate Comp resistors are the lowest noise. So I've always used them in grid bias/ coupling/ stopper apps. Sure they tend to drift over time, usually higher in value, so might require annual check. Carbon film are used in all other places except PS circuits, which metal film gets the nod- those things are tough
Jim
 
I would instead use a metal oxide resistor as a plate load. They are available in appropriate power ratings from the usual suspects (Digi-Key and the Mouse) and they can be overrated so that the heating due to power dissipation and their voltage coefficient of resistance are low.
The higher the power rating of a resistor, the physically larger it is, and the higher its voltage rating. This helps to cut down the resistance change induced by the voltage gradient across the resistor.
 
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