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MB Mark IV Power Tubes

9/16/1999 5:47 PM
DJ Wood
MB Mark IV Power Tubes
Currently have a Mark IV combo, running it in the  
duel 'EL34', duel '6L6' configuration.  
Purchased this set of tubes from MB. Sales person  
said that whether you run this amp with this or the  
4 '6L6' setup, the 2 outer tubes must be a matched  
set and the 2 inner tubes must be a matched set.  
Ok understood.....  
Can I buy other tubes, JJ or NOS in matched sets  
and use them in this amp with good results?  
Mesa probably buys tons of tubes, tests them and  
pairs them up within a certain range.  
Any info on this subject would be appreciated.  
9/16/1999 8:24 PM
John Stokes
You certainly can buy matched pairs of tubes by svetlana, JJ/Tesla, Sovtek, Valve Art, etc..... from several of the respected internet tube dealers at a fraction of the price you'd pay for Mesa's rebranded junk.  
You are correct in that Mesa buys tubes in bulk and matches them into a narrow range of performance values specifically for their non-adjustable bias amps.  
If you want to use other tubes, you may need to have the amp modded for an adjustable bias supply.  
Lord Valve however does sell matched sets selected for use in Mesas. You can email him, he's  
Best luck with the buzz machine.  
9/17/1999 4:20 PM

All we have to do is measure the plate, screen, and grid bias voltages, and the idling current for a set of mesa sanctioned tubes in various mesaboogie amps, then we'd know what parameters are required to be matched in the tube suppliers' tube test rig. A few suppliers match power tubes at realistic circuit operating voltages for a guitar amp anyway. If we could get them to adjust the voltages accordingly, they could supply the tonemongers with really good plug-ins for mesa amps. Same deal with GT's. How about a general correlation in ratings of transconductance and plate current (as labeled on tested matched tubes) with the typical 1-10 /soft-hard GT rating? No patent infringements here.
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