Tubes For Mesa DC-3 Amp.......

[zozoe]

Greetings.... What's a good choice for my Mesa Boogie DC-3 tube cooker? It's not necessarily a heavily used amp, so sound quality may be a tad more important than longevity.

I'm looking at either a quad of RI Tung-Sol EL84's or some of the Soviet 6P14P-EV's.
Any thoughts on these 2 choices, or any other comparably priced tubes that would sound fab....??

Thanks in advance ॐ

[Stevem]

And what in terms of your playing needs would as you say “ sound fabulous “?

[JD0x0]

I'm a proponent for using run of the mill production tubes, especially for the power section, more so if the amp is hard on tubes.

Instead, I'd do some mods to keep it from eating so many tubes. You can start with the 470 ohm screen grid resistors, I'd bump these up into the 1.5k-2.2k range.

Unfortunately, adjusting bias on these amps is very tricky because they use the bias voltage to bias the PI, as well. This means, any adjustments to the bias circuits will affect one another. It's a stupid design. I've made one adjustable before, but you need 3 trim pots to balance everything out, and any adjustment to one pot will require tweaking of the other two. Reminds me of tuning up a Floyd Rose bridge. One string is flat, so you raise the pitch, but the tension pulls the bridge forward, and reduces tension on all the other strings, then when you tune up the other strings that went flat, it pulls that original string flat again, rinse and repeat until you're in tune.

There's also a mod where you can move the 2M2 grid resistors on the power tubes. The 220k and 2M2 resistors form a voltage divider which reduces the bias voltage (closer to 0) even more. By moving the 2M2 resistors before the 220k resistors, you can get rid of that voltage divider, which will cool the bias down slightly. This with the upgraded screen grid resistors may give the powertubes a more reasonable life and allow you to use any off the shelf power tube, without much worry of them dying.