Preamp tubes for Mesa .50 Cal+ ?

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bulby

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Hi Guys,

New Mesa user from Bulgaria here! I just bought my first one a week ago. It is a Mesa Boogie .50 Caliber+ head made in April, 1989. :)

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I have to say I was quite disappointed when I turned it on for the first time. It sounded quite lifeless on both channels with the lead channel being quite fizzy and harsh even with the master at 5 or more. I swapped all the tubes - it had some old Sovteks, I put TAD 6L6WGC (great for vintage tones) for the power amp and Mesa Spax at V1, TAD RT001 7025 at V2-3-5, EH 12AT7 at V4. The sound didn't change much, except for the reverb which really sweetened up.

Then I took it to my amp tech to do a bias mod. At stock settings my power amp tubes were running at 19mA :shock: while the TADs are matched at 29. We biased to ~32mA and the amp came to life. I think the preamp tubes are running a bit hotter now as well. Now I can easily say this baby has one of the best clean channels I've ever heard, especially with the master past 4. I love it in combination with my 212 open-back cabinet loaded with Eminence V12 - had some chinese Celestion V30s before which did not click with the Mesa at all.

However, I still don't love the lead channel much. I am wondering what preamp tubes to get to tame it. Currently it is still a bit harsh and very compressed sound. And I'm sure the Mesa Spax at V1 has a lot to do with that... The classic rock crunch is nowhere to be found. It has a great sound for 80es Bay Area thrash metal though, if I only had this amp 10 years ago... :mrgreen:

I want to get a warmer, more open and dynamic sound with less gain and more natural mids. I've been thinking about getting a pair of Jan Philips 5751 and a pair of TAD 7025S and experiment with the V1, V2 and V3 positions.

What would you guys suggest?

I also think to ask my tech to bypass my FX loop as I never use it. I've noticed that there is a volume drop as the send&return jacks collect dust so I have to use contact cleaner quite often.
 
The TAD's I've used before are among the tamest tubes gain wise (12AX7-C's), so you definitely seem to be on the right road to achieving classic rock tones, especially with the AT7 in V4.

If you are thinking NOS, try the JAN in V1, and maybe Mullards in V2-V3 with the AT7 still in V4. It is still going to have alot of gain, but it should sweeten up the midrange alot and darken it up. It should give you alot more EQ and gain control though.
 
Thanks, I was thinking of something similar.

What about the phase inverter (V5 I guess). I know many people consider the PI the most important part of the preamp after V1 but I don't have a clue whether I should be using 12AX7, 5751, 12AT7 or even 12AU7 there?
 
Sorry, i'm not as familiar with the tips and tricks for the caliber series as I am the Marks :?

Easiest trick I use is just control gain with the guitars volume knob, works great with the Marks, it's very responsive when not wide open.

I'm sure someone else can chime in here. Maybe even Monsta-tone, he knows those amps inside and out - literally! lol
 
Thanks anyway, I will get some TAD Highgrade and NOS tubes and experiment :)
 

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