Mesa Dual Rec "mod"

lollygagger8

lollygagger8

New member
Holy Shnikey's......I replaced the turd 5U4 rectifier tubes with JJ GZ34's......wow!!! For about $35 from Eurotubes....well worth the $$!! I would recommend doing this for anyone running in rec mode!

He even put my customer testimonial on his page! <- I'm famous now ;)

I'm thinking about going all JJ's now for the preamp and power tubes. YES, tubes make a differrence!!!
 
I've got a Roadster that I bought off an endorsed buddy of mine. He threw a GZ34 in there for a while, and he too raved about it for the first couple months... Right until his amp died in practice one day. He sent it back to Mesa for repairs, and they eventually traced it to the GZ rectifier tube, which evidently didn't work so well with the internal voltages it was facing. That said, he LOVED how it sounded, and the silver lining here is that he borrowed a friend's Stiletto Stage 2 for a while to hold him over for a couple gigs while waiting for his Roadster, decided it worked better in the band (the other guitarist plays a Triple), and sold me his custom-faceplate Roadster a couple months later for a pretty damned good price. :D

That said, it still has JJ 6L6's in it. I personally dig them, but they're quite a bit darker sounding than the "normal" Mesa 6L6s. If that sounds appealing to you, then go for it. :)

(personally, I'm REALLY curious to try this amp with a set of EL34s, as I always dug the sound of my Rectoverb with a duet of 'em in it. Rip-your-head-off crunch, and it'd probably work quite well on the 3rd "lead" channel of the 4ch Roadster).
 
damn...i cant seem to find the article i'm thinking of which would explain the basis for this opinion... but IMO that's not a good switch... 5U4=GZ32 5AR4=GZ34... i worked on these things for years and was taught not to do this sub... so if your amp roaches come back and post so no one else does this... never realized that rectifiers aren't listed in my tube manuals...
 
Depending on the amplifier, it either works sorta kinda OK or else not very well. It is about voltages. 5U4's can drop up to 70VDC from the B+, depending on the exact 5U4. GZ34's drop maybe 17VDC from the B+. So your Plate voltage goes up, the amp runs hotter, and everyone thinks it sounds like God. I'm always creeped out by Boogie to begin with, and them not having adjustable bias in any amplifier I've seen seems as wrong as two boys having sex. If Boogie actually made tubes, and made them well, that's one thing. But to continually buy crap and silkscreen Mesa Boogie on it isn't consistant with their image and the $$$ they charge.
I'd stick some kind of Bias Probe on those output tubes, and either have some marshmallows handy or some ketchup for this foot in my mouth. If your Boogie was biased cold to begin with, it may be !#$%* cool. If it was on the hot side before, well, it's only gonna get hotter. Amps always seem to sound amazing just before they blow up. Don't ask me why.
 
Haven't had a problem yet, and I play every weekend in a rock band (loud as shit) and prac twice a week. You guys are freaking me out! :( I guess I'll go back to the stupid stock ones then.
 
Hey, don't be freaked out, and don't put the old tubes back in just yet. Spend a couple of buck and buy one of those Bias Probe clones off of eBay. You'll get peace of mind, and you'll also learn how to maintain your amplifier a little in the process. What's to be freaked out by that? The bias may be OK, but I always err on the side of overly cautious wimp.
 
I don't think Mesa's have adjustable bias?

But if you know the hot end of a soldering iron you could make it adjustable I'm sure. Best thing I ever did to my 5150 (for $2).
 
Be careful. Mesa like to crowd their double sided PC board, and give out bogus schematics (apparently to thwart copycats). Unsoldering a resistor is a huge PITA, and almost not worth the hassle. I decided to buy a dozen or two output tubes, match them up into pairs myself, and then further match them to specific amplifiers I have. Expensive? Yep. But I'm good for the next ten years.
 
I had to replace my power cord (cuz the ground fell out....it's an older 90's model dual rec/ it rules) and they packed that shit TIGHT in there. Had to unscrew a few boards to get to it.

I haven't taken the JJ's out....and they are still going strong. Man does this thing sound good.
 
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