Ok so i bought a jmp1 preamp from this guy for 200 euros, and its loaded with mesa boogie 12ax7 preamp tubes.

Now i also have some jj preamp tubes (same model) lying around that i could throw in and i also have ONE sovtek 12ax7. Now the jmp1 needs two preamp tubes to work so which ones should i load? or should i just leave the mesas in? does anyone know enough to describe what each tube has (and hasnt) and say how my sound would change with each tube?

Also does anyone know how easy it is to change the preamp tubes on the jmp1?

Mesas are rebranded, but I don't know what they're rebranded from. The JJs are probably your best choice. And the amp should has easy access to the tubes, but I'm not familiar with the jmp.


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does anyone know how much work it takes to open the chasis of the jmp1 preamp? any other suggestions as to which tubes to use? i wouldnt mind buying new ones but i d like to just stick to the ones i have.
The MESA 12ax7's are made by Sovtek. I personally find Sovteks to be decent tubes. I have several of the MESA branded ones and they sound good and are reliable. I don't think you are going to hear very much difference between them and some JJ's. Unless the ones in there are microphonic I say leave them in. It shouldn't be that hard to replace them if you must. It is a rack unit correct? Just look for the screws and see how the chassis is assembled. You should be able to figure it out.