Tube Amp Archive

I a glad to know I don't need a new PT. I have an Gibson GA 15 RVT that I had been trying to make sound decent. The preamp tube had started adding a crackling sound. They were not that old. I came up with the theory that the heaters were not Hot enough, ruining the tubes, it must be that the PT was ...

I changed those two resistors, now the supply voltages read 436, 432, 357, 279. Now the plate voltages range from 195 to 204 across the preamp tubes. They started out around 250. To my ears it sounds a little mellower, less brittle. I can turn up the reverb a little more with out it killing my ears....

Here are the readings I am getting off the filters: 436, 432, 409, 356. 436 is a little higher than the schematic, 420. I don't know if that will matter to the 6v6's. Between 432 and 409 it has a 2.7k resistor and between 409 and 356 there is a 10k. I am going to swap the 10k to the 2.7k spot and si...

Thanks, I thought they needed 6.3 at each pin for a total of 12.6vac per tube.

The heater voltage is 2.9 on my DR. The tubes light up and make sound but it seems like it would be good to get them Nice and warm with the right voltage.

Is there anything I can check, or change to fix this ?

Thanks. Brendan

I am measuring AC, the Positive testing the heater wire and The negative lead to ground.

Both, V1, or the normal channel, I originally converted to a tweed channel. A design taken from a different book. It has volume and tone, a .22uf coupling cap. A simple design set up as a high gain channel. It ran on a 12 AX7 and had an extra 8uf 450volt filter cap. I kept the tone stack and the ext...

The dc voltage going to the plates, pin 1 and 6, coming through the 100k 1w resistors.

I recently bought Jeffry Falla's book; Hot Rod Your Fender... and was installing his Vox preamp mod using an EF86 pentode. I Fired it up and it sounded sweet 15 minutes then it stopped making sound. Bummer. I installed it in V1, V2 still works. I don't know what the voltages for the pentode are supp...