Tube layout for Mark IIB

[Old Cane]

Does anyone have one? From what I see I have 4 12ax7s and 2 6l6gc. Which of the 12ax7s do what? One is in line with the power tubes and 3 are up next to the grill. I know this sounds silly but all I ever find is documentation for Mark Is or IVs.

I had all GTs and last week got a deal on some JJ 6l6s. Fixed my problems. But also got a JJ 12ax7 and a Tung-sol 12ax7. Would I benefit from using these 2 little guys in any certain socket?

 

[Jackkate]

You should have 5 12AX7's (although maybe only 4 if no reverb??...)

My original IIB came with 2 AT7's. I believe at some point Mesa started using all AX7's.

Right to left (looking from back):

Front Row:

V1 12AX7 A: Input amp B: Tone Control Amp

V2 12AT7 A: Effects Return B: Mixer amplifier

V3 12AX7 A: Rev. Return Amp B: 1/2 Lead Drive Amp

V4 12AT7 A: 1/2 Lead Drive Amp B: Reverb Driver

Back Row: 4 6L6's and V5: 12AX7: Phase Inverter/Output Driver

I have the original schematic and Maintenance & Repair Guide. I can scan to PDF's and send them if you want - let me know.

 

[dodger916]

The IIC manual shows the tube layout: http://www.mesaboogie.com/manuals/Mark%20II-C%20Manual%20-%20Maintenance%20&%20Repair.pdf

I believe it's the same for a IIB.

 

[Old Cane]

Ok, mine is a IIB, no reverb as you guessed and 60 watt.

So, according to the IIc I guess I have v1, 2, 3 and 5?

Ok, so my basic question is; will using the tung-sol in one place over another be of any benefit or should they pretty much not matter? I have it now in v5 (phase inverter?) or in other words in line with the power tubes. Good, bad, ugly?

 

[Boogiebabies]

PM me your e-mail and I will send you the Schematic.

 

[dodger916]

Ok, mine is a IIB, no reverb as you guessed and 60 watt.

So, according to the IIc I guess I have v1, 2, 3 and 5?

Ok, so my basic question is; will using the tung-sol in one place over another be of any benefit or should they pretty much not matter? I have it now in v5 (phase inverter?) or in other words in line with the power tubes. Good, bad, ugly?

It definitely will matter, to what degree depends on how sensitive your are to these changes in tone. V1 will have the most overall influence being that it drives the Imput Amplifier and Tone Control. V5 will also have a global affect, but not as profound as V1. Tubes in the other slots will have a more "local" affect in their designated circuits as they are "downstream" in the signal chain.

In my IIC+ I use a 5751 in V1 and a new Mullard 12AT7WA in V5 - both lower gain tubes. I find the Mullard helps smooth out the overall sound and the 5751 made the gain smoother and more manageable. I don't play metal, so the milder growl is just what I'm looking for from the C+.

One of the nice things about these amps is experimenting with preamp tubes. It's a simple, relatively inexpensive way to alter the sound to your taste. Many prefer older tubes (VOS or NOS) to new tubes.

Hope this helps.

 

[Old Cane]

Great. Thanks. So are you thinking the type of tubes makes the most difference which makes perfect sense. But since I have only 12ax7s where would you use the 2 new ones to the best advantage? I have one new TS and one new JJ. and 4 used GTs.

 

[dodger916]

Great. Thanks. So are you thinking the type of tubes makes the most difference which makes perfect sense. But since I have only 12ax7s where would you use the 2 new ones to the best advantage? I have one new TS and one new JJ. and 4 used GTs.

You need to do some "tube rolling" experimentation , which is experimenting with tubes in different positions. I've heard JJs tend to be darker whereas the TS and the GTs should be similar in voicing, so keep that in mind. I'd start with the TS in V1 and GTs in the others. Then try the JJ in V1 just to see the difference. Keep going with whatever sounds best.

Be forewarned: preamp tube hunting can be addictive, and there are plenty of tube junkies here who love to share their habit!

Have fun!

 

[Old Cane]

Thanks. With MY ears there may be no need but I'm sure I'll try anyway.