Tube Amp Archive

It sounds like you have a grounding problem (50/60Hz buzz) and a power supply problem or two (100/120Hz hum). Do you have access to an oscilloscope?

A friend’s Traynor Guitarmate Reverb measures almost 20 volts higher at idle on the screen of the EL84’s than on the plate. This one is the earliest version I think and the power supply has a 10 ohm resistor between the plate and screen supply instead of a choke. There are no screen resistors on th...

When you consider derating due to selfheating and temperature of surrounding air inside the amp chassie you'll find that 0.65W power dissipation puts a 2W resistor on the low side. 5W resistors derate to ca 3 at 60 degC ambient. Go 5W for the safety margin. Xicon MO Series power resistors are not d...

...= .0635 Watts of power I think you're off by a factor of 10 there ( = .635), but as you point out, 2w is still almost a factor of three margin. Yes, the leading zero was a typo (some would call it a brain fart :) ). I'm also curious why weight is a factor. Component weight is a problem in guitar...

Icetech wrote:express....

The Express has very little clean headroom. It is a distortion machine.

You want a lot of conflicting qualities in an amp. IMHO, you should back off on requirement #5 as it will cause you to make significant compromises on requirements #1-4 (i.e., you will end up with “Boogie Disease”). I have yet to find a high-gain amp that has excellent clean and/or medium gain tones.

IHMO, 5W screen resistors are extreme overkill. An EL34, at full bore, may pull 25ma through a 1K Ohm resistor, which translates to .025 * 1K = 25V drop = 25 * .025 = .635 Watts of power, in the form of heat, that needs to be dissipated (beam tubes draw about half of that amount). Hence, even a 2W p...

Heh...your hunch is correct. Randy and I were working out the values for a cascode stage to replace an EF86 in one of my designs back in 1999. I am glad to see that he went with it! I, on the other hand, had a DC offset that I never bothered to resolve and quickly went back to using the EF86. I bel...

:I saw on another posting where a guy said he quit building amps for fear of being sued. Product liability was one of the big reasons why tube technology was put out to pasture. Solid-state technology has the advantage of having no user serviceable parts and lower operating voltages (i.e., solid-st...

The fact of the matter is that EVERY SINGLE TUBE CIRCUIT IN USE TODAY comes from the RCA/western electric Recieving tube guide. Had Ken Bran and Jim Marshall not "Cloned" a 5F6-A bassman there would be no need for your fake Celestions PERIOD. You know why you can't patent basic tube circuits?? BECA...

I have Xicon electrolytic caps in amps that have been played hard for ten years, and they are still holding up well.

I have been buying stuff from Ted Sr. for close to ten years, and I will not stop because he or his son threatened litigation. People have to realize that there are ramifications for disparaging a vendor's products. It does not take a rocket scientist to realize that "low price" generally means infe...

While grid/plate coupling is a large source of oscillation problems, one also needs to make sure that one does forget to look for plate/ground coupling as well.