Preamp Issues... Which is Which, mesa400+ speaker inputs

**garmenteros** · #1 06-11-2010, 11:25 AM

This may seem like a dumb question, but I need someone to confirm which is which on the back of the speaker inputs of my mesa. On the back we have...

.: :.
4ohms 8ohms

Which are the two 2ohms jacks, which are the two 4ohms jacks, and which are the two 8ohms jacks?

I've always hooked my 4ohms mesa powerhouse into the bottom left jack, since its labeled 4ohms but I just want someone to confirm this.

Im having issues with my preamp tubes. I keep damaging them. So I'm looking at every aspect of the equation. I plug active and passive basses indiscriminately into either input, one and two. I have read on the manual that input one is more catered to active basses and has slightly lower output. But it does say that you can mix and match inputs. Could plugging an active stingray into input two that is more geared towards passive basses fry my preamp tubes?

Help is needed as me and my tech are stumped... He's fixed all my stuff before so I don't doubt his skills... Maybe a bias issue? Let me know what you all think

TONYTHOMAS1956 · #2 06-11-2010, 12:42 PM

Do a search for owners manual. It'll tell you everything u
need to know.

JonPol · #3 06-11-2010, 12:44 PM

The top 2 are the 2ohms, bottom left are 4ohm and bottom right are 8ohm.

johnk_10 · #4 06-11-2010, 01:06 PM

i've never heard of an amp 'frying' preamp tubes, other than one that has a power supply/plate voltage problem that is too high for the tubes to handle. has your tech made sure that your amp is within spec?

RickenBoogie · #5 06-11-2010, 05:09 PM

+1 an active bass won't do any harm to the preamp tubes. There's something else wrong, and it need to be diagnoised by a pro. Good luck, great amp.

**garmenteros** · #6 06-11-2010, 08:02 PM

Quote:

Originally Posted by JonPol

The top 2 are the 2ohms, bottom left are 4ohm and bottom right are 8ohm.

Thanks for the information, I've been looking confirmation for this forever... I've read the manual in and out, but that information managed to elude me...

jhonk_10 I'll mention that to him tommorow as we are going to tear apart every aspect of my rig. Going to measure the cabs ohms rating... going to measure output on my voltage regulator, furman ar1215 by the way... going to put brand new speaker cables in, see if something pops up. I hope the issue is an easy thing to repair.. Im also going to go over my b15n as well.