Resistor Wattage

[jestaudio]

out of interest what sort of wattages are folks using in there builds, i tend ti use mainly 1 watt carbon film for the preamp section and 2-3 watt metal film in the power section but looking inside some of the modern amps 0.5 watt seems to be more usual

[Phil_S]

1/2 watt resistors are fine in most locations. You'll pretty much know when it isn't, like on the B+ rail. If you need thick leads for some mechanical reason, that is also a reason to go up in wattage -- for example, the 1R cathode sense resistors would be fine at 1/2W rating, but the leads are a bit flimsy for the application.

[sliberty]

I use 1watt everywhere except B+ rail. There I use 3 or 5 watt generally.
The 1 watters are overkill, but it justifies calling my amps Boutique

[Super_Reverb]

I use 1W larger physical sized resistors and appropriately larger for screen and other resistors. Some make the case that they are quiter. They also typically are mechanically stronger and it only costs a dollar or two more for a build to use 1W. Commercially made amps use 1/2W because they are cheaper. I think in many commercial amps, the plate resistors are 1/2W. Plate resistor dissipation is 225mW for a 1.5mA bias current and a 100K resistor, so given the higher voltage and larger resistor area, it seems to me, 1W or more will be more reliable ( I don't have data on this )


rob