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OK so tell me about Mesa matched power tubes. The folks at Mesa seem to think they are the only ones that can produce and match tubes that are suitable for their amps due to the strict bias range. What kind of truth is there to this? I need to replace the power tubes in my F-50. What would you guys recommend? They are 6L6s.

Well, if you want to pay for the ROBOTUBE matching system and a Mesa label on the tubes, they are 100% correct...

...otherwise about any matched set which will sound good with cool bias should do the trick. Most non-adjustable bias systems bias the tubes way cool: my 70's Ampegs were running at about 6-9W dissipation despite fairly high plate voltages; haven't measured my DC-5 but it's set for -50V or so which should be pretty cool. You can either:

(1) pick tubes which sound good with the bias levels likely to be in your amp; Bob at eurotubes, lord valve, and others with mesa experience should be able to pick a pair which will sound good, or
(2) install a bias pot so you can adjust the bias to the tubes you have/ want.

Yeah, a knowledgable tube dealer should be able to sell you a set of matched tubes that will match up with the fixed bias of your amp. Right now, I have Sovtek 6L6GC's in my Mark II and Sovtek 5881's in my Rectoverb. The Rectoverb is about to get a set of the 6L6GC's.

I like JJ's I get mine from Bob at He is very knowledgeable and goes far beyond to help. I'm discussing tubes with him via email right now actually.

Luke

i currently have groove tubes EL34's in the power section of my dual rectifier. it's entirely possible to use other types of tubes in there.

BTW, Mesa Boogie branded tubes are various Russian or Chinese tubes. It's not like Mesa is making the tubes. They're not. They're just putting their name on them and matching them.

So is there a particular brand you guys suggest? Seems like JJs are pretty good.

NOTE OF CAUTION... Mesa will void the warranty of your amp if you run it with non-Mesa tubes! Not sure if your amp is still under warranty.

Personally, I'd still put what you want in there... but SAVE THE OLD TUBES!! If something happens to your amp then put the old ones back in before sending it to Mesa.

As an addendum to one of my previous posts, the current Sovtek equivalent of its 6L6GC is the 6L6WXT.

JJ's have a very middle of the road bias, so you can normally pop them in any amp and they're fine. I like Svetlana too, but one time, I threw a set in, after taking JJ's out, and they practically cooked my amp, they seemed to need a bias adjustment that was lower.

If you click the revolution link in my signature, you'll be getting matched JJ's as cheap as possible. I always recommend GT12AX7C's for highgain amps, since they tighten up the gain better than most others.

If you want to use GT's here is a chart, provided by Myles Rose:
Mesa scale Groove Tubes scale
Red 4
Yellow 4
Green 5
Gray 5
Blue 6
White 6


Originally Posted by GearjoneserJJ's have a very middle of the road bias, so you can normally pop them in any amp and they're fine. I like Svetlana too, but one time, I threw a set in, after taking JJ's out, and they practically cooked my amp, they seemed to need a bias adjustment that was lower.

If you click the revolution link in my signature, you'll be getting matched JJ's as cheap as possible. I always recommend GT12AX7C's for highgain amps, since they tighten up the gain better than most others.

I bought a set of JJ matched 6L6s from Revolution today. He had them on eBay and I snagged them...thanks to all!!

Those tube dealers have a very low profit margin, so they're really focused on customer service and repeat business. It's become a competetive business, since they all have to keep their prices about the same to make any money. They all buy from a large US distributor, so no matter who you buy from, you're getting the same exact thing.