Rectifier Tubes
Thu, 10/24/2013 - 08:45
Hi Skip, can you tell me if it's safe to use a 5R4GY in place of a 5AR4 or a 5U4GB, in my Bassman reissue. Maybe if you have the time, you could compile a list of tubes that are safe to use, starting with the rectifiers, output tubes and last the pre-amp tubes, as there are so many different numbers and makes. I tried checking on the web but one guy says you can use a certain tube and the next guy says you can't, so I would like to here it from you, because everyone knows that you know what your talking about. Thanks
Hello Bluez- Yes, it is safe to use those three rectifiers in your amp.
The important thing to realize is that the "B+" voltage (the highest DC voltage in the amp) will be highest with the GZ-34/5AR4 and lowest with the 5R4. The 5U4 is right in between. When the B+ voltage goes up, the current flowing through the power tubes will go up a little as well. This current is what we control by adjusting the bias of the amp, so it is necessary to re-check bias when subbing rectifiers.
I'll remind you that there is some extensive tube-swapping knowledge for the RI Bassman right here at BH.com's Bassman Chronicles.
Bluez, listen to your old buddy...... you are so fired up to work on amps that you may never find time to play it. You REALLY need an additional (less-expensive) amp that you can use to burn off some of that amp-fixin" steam!! One amp to play, and one amp to play WITH. Get a silverface Champ and have some fun!