Got some Mesa SPAX7s

[eudaimonia02912]

I've tried a bunch of tubes in my Mark V so far, including Tung Sols, an NOS EI, JJ high gain, JJ long plates, Sovtek LP, Pentas, Rubies, and more. To be frank, pre-amp tube changes on the Mark haven't had as much of an effect as they did on some of my previous amps. (My Peavey XXX was much more responsive to pre-amp tubes.)

I decided to give the SPAX7s a try, partly out of curiosity, and partly because I wanted to see what effect they'd have on noise. So, I got 4 of them, for V1-3 and V7. (I have stock Mesa 12AX7s in V4-6.)

My first reaction was that they made the amp sound thinner but cleaner--it had less bass in the sound, but also a lower noise floor and less hum. I wanted to get rid of some of the hum without using too much of a noise gate, but I didn't want to lose as much bass as I had seemed to.

But this was an easy fix. I had my bass knob on about 9:30 on channel 3 before, so I turned it up to about 10:45, and all of my bass came back, without muddiness or flubbiness.

So far, after 1 day, I like this better than my previous combination. (Previously, I had a Tung Sol in V1, NOS EI in V2, high gain JJ in V3, stock Mesas in V4-6, and a JJ in V7.) It actually makes the amp sound a bit heavier. The tubes allow me to put a bit more bass in the sound without turning flubby, and they sound a bit fuller. The harmonics are also superior to my previous combination.

 

[eudaimonia02912]

Hmmm... After another hour of playing them, I don't think I like the change. I'm going to put the previous tubes back in and try those again.

 

[eudaimonia02912]

Ok, final report for the night:

I was reading how someone else decided he didn't like the Tung Sol in V1, and I thought I'd try getting rid of mine there too. So, I replaced the Tung Sol with one of the SPAX7s. Good move. It cut the noise floor, but also reduced the tendency of the amp to get shrill or thin and instead added some fullness. Having 4 SPAX7s in all the noisy spots wasn't so good, but as of right now, it's the best V1 tube I've tried.

So, current line up:
V1: Mesa SPAX7
V2: High gain JJ (adds some fatness to crunch mode on channel 2)
V3: NOS EI (very musical, complex distortion. Much better here than in V2.)
V4-6: Mesa stock tubes
V7: JJ

I still haven't figured out what the best tube is for V7. I've used long plate Sovteks and JJs for my other amps in their PI slots, but the effect on the tone in the Mark V seems minimal.

 

[Mark Fore]

From what I remember a long time ago when talking to Mesa about the SPAX7 tubes, the SPAX7's are only supposed to go into the input stage to quiet things up. The rest should have regular ax7's.

 

[Hendog]

Ok, final report for the night:

I was reading how someone else decided he didn't like the Tung Sol in V1, and I thought I'd try getting rid of mine there too. So, I replaced the Tung Sol with one of the SPAX7s. Good move. It cut the noise floor, but also reduced the tendency of the amp to get shrill or thin and instead added some fullness. Having 4 SPAX7s in all the noisy spots wasn't so good, but as of right now, it's the best V1 tube I've tried.

So, current line up:
V1: Mesa SPAX7
V2: High gain JJ (adds some fatness to crunch mode on channel 2)
V3: NOS EI (very musical, complex distortion. Much better here than in V2.)
V4-6: Mesa stock tubes
V7: JJ

I still haven't figured out what the best tube is for V7. I've used long plate Sovteks and JJs for my other amps in their PI slots, but the effect on the tone in the Mark V seems minimal.

Have you A/B'ed the stock Mesa AX7 with the Mesa SPAX7? In what positions?

 

[Music Power]

I would certainly only use a single SPAX7 in the first gain stage, which you've done now.

Try a matched Mullard in the Phase Inverter. Even the new production ones sound solid in the PI position.