6L6 to EL34 Mod for Fender Bassman Heads

6L6 power tubes can be a little too clean for the tastes of many. One option is to use 5881's. These are direct replacements for the 6L6 which require nothing more than a rebias after installation. They give a little less headroom, break up a little sooner, and add a little more grind to the amp.

Another option is to swap your 6L6's with EL34's. EL34's have a darker tone, the break up a lot earlier than the 6L6, and their overdriven sound is radically different than a 6L6. If you're looking for a big change in tone, then this may be just what you're looking for. But EL34's ARE NOT direct replacements for the 6L6. You'll need to make a slight modification to your amp so it can use them.

1. Replace the 470 ohm resistor that's between pins 4 and 6 of each output tube socket with a 1000 ohm, 2 watt resistor.

2. Disconnect pin 1 only of the 1500ohm resistor that's between pins 1 and 5 of each output tube socket.

3. Disconnect the wires on pin 1 of the output tube socket.

4. Reconnect the wires that were on pin 1, to the end of the 1500-ohm resisors that are now standing free on each output tube socket.

5. Connect pin 1 to pin 8 of each output tube socket with a solid wire.

6. Adjust the bias of the amp to suit the new tubes. See here for instructions on how to do it.

After this mod you can use either EL34's or 6L6's just by adjusting the bias. I have done this on my Silverface Bassman heads and on my Bassman 100's. Do it on other Fender amps at your own risk.
Home                                           My Tech Page