Question for amp builders re: resistors

[Darg1911]

Hey gents. Quick question.

Marshall style build. The feedback resistor on the board is carbon comp. Adding a feedback selector switch. Resistors at the switch will be in series with the carbon comp on the board and I'm thinking that maybe it would be better to use carbon film or metal film at the switch (additive noise concerns?). But I do have carbon comps I can use as well.

Thoughts / advice?

Thanks

[Lake Placid Blues]

Re: Question for amp builders re: resistors

How much gain? I used all vintage type components in my JTM45 build. It's dead quiet except when a note or chord is ringing out of course. Signal is way above the noise floor. I have been into a few modern high gain Marshalls recently, and it's all metal film regardless of being in or out of the signal path. So if it's a high gain amp, go with metal film. If it's vintage your okay using vintage type resistors. Lead dress and how tightly your heater leads are spiraled will probably have a greater affect on noise.

[Darg1911]

Re: Question for amp builders re: resistors

Thanks for the reply. It's 45-ish. EL34's. Not high gain at any rate. I wasn't looking to build a vintage replica but I might, down the road. I built with metal films. I later replaced a few resistors with AB CC's just on the plates of the preamp tubes and PI and the feedback resistor. Not sure why I bothered with the feedback resistor but some info I came across suggested it and I believe Ceriatone uses one there so I gave it a shot. Amp was quiet from the start and I don't think the 6 CC's I swapped in added any noise. I wouldn't swear on it but I think there was a very subtle difference after swapping in the CC's. I cant really describe it but it was a positive so even if it's all in my head, that's cool with me. They stay. This was all done a while back. It's only the switch that I messed with yesterday.

At any rate, I ended up using carbon films on the FB select switch. I was just going to go with metal film but was missing one of the values. I'll probably just leave it as is. For now anyway.

Thanks.

[Surgeon]

Re: Question for amp builders re: resistors

Use what you have. The routing of your wiring will most likely have more impact on your noise floor than a couple of resistors. Still, they'll be easy enough to swap if you want to experiment later. Imho of course.