50/50 pre amp tubes

[monkeychunki]

Hi, im a novice when it comes to this stuff so im after some advice. I have a 50/50 powering an ada mp1 3tm and im concerned the gain levels arent as much as they should be, i can obviously retube the ada however could the tubes in the 50/50 also be effecting the gain levels? I didnt even know until recently that the 50/50 had 12Ax7a's could it be down to these or the 6l6's. As the 50/50 is fixed bias i understand that i'll need to replace the power 6l6's with a matched mesa set, is this the same with the 12Ax7as or can i replace them with JJ tubes.

Reason im going down this route is i also have an engl 520 pre amp (90's pre to 530) and this is meant to have tons of gain and again im struggling with the gain on this.

Apologies if the above doesnt make sense, i just want to make sure i dont waste cash replacing the ada and engls tubes when its maybe the 50/50.

Thanks
Paul

 

[crane]

You can replace the 12AX7's with any brand, but I personnally don't recommend JJ for these spots as they are too dark for my taste. I would rather put some EH or TungSol the PI position for clarity. You can also try 12AT7 in these position for even more clarity.
PI are the 2 tubes on the left side when looking at the 50/50 from the front (on the right is the input tube for both channel).

 

[monkeychunki]

Thanks for the info, would these tubes influence the overal gain of the setup & if so should i be using the high gain versions of the suggested tubes.

Thanks
Paul

 

[Triaxstasy]

You don´t need to replace the power tubes with a matched Mesa set. eurotubes.com offers a complete matched set of JJ tubes for the 50/50.
Stores like TAD or Tube-Town (in Europe) and Dougs, The Tubestore or Tubedepot (in the uS) can also provide matched quads of various brands for the 50/50 if you tell for what poweramp the tubes are needed for.

If there´s a lack of gain when running the 3TM in the 50/50 it´s most obviously the tubes in the 3TM (or the trimpot settings) that need to be replaced/adjusted as the 50/50 (as any poweramp) primarily amplifies the signal that´s fed into it.
For poweramp distortion you really gotta turn the Vol on the 50/50 past 5-6 to notice anything with the fixed (ice-cold) bias.

Crane posted a thread for a bias mod for 50/50 in here that enables you to adjust the bias and run the tubes hotter...

 

[monkeychunki]

Great thanks for this

Paul

 

[talltxguy]

I've found that NOS tubes in the phase inverter position of amps makes as much if not more of a difference than NOS tubes in any other slots. I'm also one who has success using lower gain tubes in the phase inverter slots.

Here's a nice article that says things better than I can:
http://www.guitaramplifierblueprinting.com/files/Phaseinverter.pdf

Hope this helps.