Transformer Upgrade for Mesa Nomad 55?

[jads57]

Hi, Would upgrading the output transformer( Mercury Magnetics Axiom )and installing a choke, significantly improve the clean tone of myMesa/Boogie Nomad 55? I also should add I`d have a tech do the mod since I`m not qualified to do so. Thanks, John

[sliberty]

I used to own a Nomad 55. I loved the middle channel (classic tones). The clean chanel was a little lackluster, but acceptable (started sounding great when cranked). I suspect that the iron is pretty good, and that replacing it is not worth the expense.

You might try changing tubes though. The Nomad 55 can either use 6L6's or EL34's. I bet that changing the power tubes to EL34's would give a rather different character to the cleans (as well as the distorted tones). Don't forget to switch the bias adjustment on the back of the amp to the EL34 position. I also suspect that some nicer preamp tubes would also bring out some chime. The ones that come with the amp are probably nothing special. Start with the tubes and see where that takes you.

[jads57]

Thanks for the reply. Other than buying tubes from Mesa directly,how do you select power tubes. Being that the amp has a fixed bias. Thanks again

[sliberty]

Well, you have two choices. You can bring the amp to a tech, and let him bias the amp for the new EL34 tubes (it would involve changing a single resistor) or you can buy the Mesa tubes and just use the switch. Many feel that the Mesa tubes would still require a proper bias adjustment, so in my opinion, you might as well buy some nice non-Mesa EL34's and let your amp tech bias it properly.

As for preamp tubes, no adjustments will be needed. So you can experiement with preamps tubes yourself. Based upon the schematic, it looks like the clean channel has only 2 - 12ax7 tubes. If you like the tone from the other two channels, these first two tubes are the only ones you need to experiment with.

[jads57]

Any suggestions for preamp tubes? Thanks!

[sliberty]

For new production, I like the Tung Sol 12AX7 reissue and the Grove Tubes 12AX7M (Mullard clone - hard to get). Or you could buy some new old stock stuff on eBay (RCA, GE, Sylvalia - not too expensive, Telefunken, Mullard - pretty pricey).