Ever try the Mesa sp12ax7 preamp tubes?

[daveyboy]

Just curious on thoughts compared to the standard Mesa 12ax7.

Thanks.

 

[MusicManJP6]

yes. i tried all spax7s in my Stiletto and two problems were encountered.

1) Clean channel had harshness around the notes (broke up way too early I guess) and distortion was muddy. Swapped V1 for a standard Mesa ax7 and the problem was gone.

2) they are susceptible to failure in the cathode follower positions (V3 and V4 in a Stiletto). I thought maybe since they did not say either 'russian' or 'chinese' that they would work in these positions - not so. (refer to the 'mesa memo' for more info on the cathode follower position problem)

Needless to say I was not impressed with these tubes despite their description of being a 'better' tube than standard ax7s. I traded them in for the new Mesa relabeled JJs at my local boogie dealer and like these tubes ALOT. They work fine in the cathode follower positions and sound great in all slots...

 

[daveyboy]

yes. i tried all spax7s in my Stiletto and two problems were encountered.

1) Clean channel had harshness around the notes (broke up way too early I guess) and distortion was muddy. Swapped V1 for a standard Mesa ax7 and the problem was gone.

2) they are susceptible to failure in the cathode follower positions (V3 and V4 in a Stiletto). I thought maybe since they did not say either 'russian' or 'chinese' that they would work in these positions - not so. (refer to the 'mesa memo' for more info on the cathode follower position problem)

Needless to say I was not impressed with these tubes despite their description of being a 'better' tube than standard ax7s. I traded them in for the new Mesa relabeled JJs at my local boogie dealer and like these tubes ALOT. They work fine in the cathode follower positions and sound great in all slots...

Thanks MusicManJP6! I just wondered at $21 bill a piece if they would be
worth a shot. Like you I'm content with the standard Mesa ax7.

 

[Mark Fore]

I remember those being recommended for the first stage as they were supposed to be quiet tubes and make subsequent stages quiet, but not reco'd for any other stage after the input stage. Do they still make them? I haven't seen them in a while.

 

[daveyboy]

I remember those being recommended for the first stage as they were supposed to be quiet tubes and make subsequent stages quiet, but not reco'd for any other stage after the input stage. Do they still make them? I haven't seen them in a while.

They still show them as being available on the online Mesa store.

Thanks for the info.

 

[MusicManJP6]

Maybe my probs were because I had them in all slots, but in V1 it sounded terrible!

 

[MetalMike]

i had one in V1 and V4 and it made my amp sound so quiet on clean had the master cranked and it was still so quiet couldnt get the levels set with channel 3. Replaced them with standard mesa tubes and my amp is just a quiet no to little background hum and now my clean channel is brighter then ever

 

[Stratocaster]

Yes, I use them. I have them in V1 - V3 inside my RKII.
I'm very happy with them, but let me explain WHY I'm happy...

- First, what is the cost to me...
The standard Mesa 12AX7 costs $17, while the SPAX7-A runs $21 dollars. That's 23.5% more, AKA $12 for the three tubes I use. I expect then to last aprox. 2 years before I decide to re-tube, so that $6/year.

- What do I get for my (est.) $6/year...
Not a miracle. I didn’t purchase these for a different tone, additional gain, or more poon. I bought these because part of the description says “…due to their incredibly low sensitivity to microphonic noise”.

- Why did I do it? A very specific circumstance…
I play loud. I have a house, and it’s never a problem cranking up to club volumes as long as I don’t do anything idiotic and try it at 11:00 at night. I play loud at gigs. So the amp gets to run open. I never know what type of band that I’ll end up in next (hence my choice on the RK, for the versatility).
I was in a band that did some NIN covers, and that’s where I was running into issues. I wanted to get all my distortion from the amp (no boost), and I was shooting for an ‘all gain, all compression, no tone’ sound, so I was doing things in Modern mode that went against the specific advice of the manual...turning the gain up all the way.

The swap to the SPAs did help me control the ‘non-musical’ feedback (lol, that is the most polite term I can come up with for that noise) that I would sometime get under this extreme condition. It reduced, but didn’t totally eliminate, all the accompanying sounds that happen when you’re stupid enough to set your amp to ‘auto-destruct’. I had reasonable expectations, and got what I’d hoped for (While I might set my amp like this for a few songs, there is no way I’d attempt to do an entire set like that).


I am not discounting MusicMan’s experience with the SPAs, and I would definitely take into account his findings. I can say that I did not notice any negative tonal/characteristic change from the 12AX7, nor have any of the three ‘given up the ghost’ on me in the aprox. 10 months they’ve been in place. And they’ve been abused on occasion.



Strat

 

[daveyboy]

Yes, I use them. I have them in V1 - V3 inside my RKII.
I'm very happy with them, but let me explain WHY I'm happy...

- First, what is the cost to me...
The standard Mesa 12AX7 costs $17, while the SPAX7-A runs $21 dollars. That's 23.5% more, AKA $12 for the three tubes I use. I expect then to last aprox. 2 years before I decide to re-tube, so that $6/year.

- What do I get for my (est.) $6/year...
Not a miracle. I didn’t purchase these for a different tone, additional gain, or more poon. I bought these because part of the description says “…due to their incredibly low sensitivity to microphonic noise”.

- Why did I do it? A very specific circumstance…
I play loud. I have a house, and it’s never a problem cranking up to club volumes as long as I don’t do anything idiotic and try it at 11:00 at night. I play loud at gigs. So the amp gets to run open. I never know what type of band that I’ll end up in next (hence my choice on the RK, for the versatility).
I was in a band that did some NIN covers, and that’s where I was running into issues. I wanted to get all my distortion from the amp (no boost), and I was shooting for an ‘all gain, all compression, no tone’ sound, so I was doing things in Modern mode that went against the specific advice of the manual...turning the gain up all the way.

The swap to the SPAs did help me control the ‘non-musical’ feedback (lol, that is the most polite term I can come up with for that noise) that I would sometime get under this extreme condition. It reduced, but didn’t totally eliminate, all the accompanying sounds that happen when you’re stupid enough to set your amp to ‘auto-destruct’. I had reasonable expectations, and got what I’d hoped for (While I might set my amp like this for a few songs, there is no way I’d attempt to do an entire set like that).


I am not discounting MusicMan’s experience with the SPAs, and I would definitely take into account his findings. I can say that I did not notice any negative tonal/characteristic change from the 12AX7, nor have any of the three ‘given up the ghost’ on me in the aprox. 10 months they’ve been in place. And they’ve been abused on occasion.



Strat

Stratocaster: Awesome info man!! I wasnt too concerned about the cost either, mostly if there were any tonal
differences which you addressed. I've had good luck with the Mesa standard tubes both pre and power. I may snag
one of the sp12ax7 variety to experiment with next time I place an order. Hmmm come to think of it I really could use a new Mesa Engineering work shirt....teehee.

laters,

 

[Stratocaster]

Follow-up to the above...

I removed the shrink tubing from all three of the SPAs I have, and found them all to be Russian. The markings had worn away, or were never stamped, but I could tell visually (the Chinese have a different physical appearance).

I’ve now moved the SPA that was in V3 (a cathode follower position in a RKII) to V6 (phase inverter/driver). While I wasn’t having a problem, MusicMan brought up a very valid point reminding us of the ‘memo’.

I’ll be sure to post if I have any suspicious activity from placing the Russian (albeit a tight tolerance one) in V6. I already have a Chinese in the other cathode follower position (V5 on the RKII).

Strat

 

[G.I.G.]

What are you guy referring to with the "memo"? Is it posted here or on Mesa's website?

 

[Stratocaster]

What are you guy referring to with the "memo"? Is it posted here or on Mesa's website?

Original thread - http://forum.grailtone.com/viewtopic.php?f=4&t=25102

'Memo' -
---------------------------------------------------------------
SOUND “DROP-OUTS” / INTERMITTENT SIGNAL

One Possible Cause



Most (but not all) Mesa/Boogie amplifiers have one or two “cathode follower” tube
stages in their preamps. Tube selection is CRITICAL in these stages.



Specifically, in a 12AX7 tube used as a “cathode follower”, the voltage difference
between that present at the cathode, as compared with the heater voltage, can be
withstood or tolerated by certain types of tubes, whereas other tubes will fail. The
failure of a “cathode follower“ tube will cause sound dropouts or signal loss.



For the past few years, Mesa has been using two types of 12AX7 tubes: ones
originating in Russia (Sovtek EH), and ones originating in China. The Russian (Sovtek)
tube is NOT reliable as a cathode follower. Of the tubes we are using today (March
2008), ONLY THE CHINESE 12AX7 IS RELIABLE AS A CATHODE FOLLOWER.



In conclusion, if you are troubleshooting for signal dropout in a Mesa/Boogie amp,
suspect a cathode follower tube, and try replacing it with a Mesa 12AX7 that is marked
as “CHINESE” (silk-screened on the tube itself).



Below is a partial list of Mesa amps and cathode follower tube locations:

GUITAR AMPS BASS AMPS

Lone Star & LS Special: V3
M-Pulse: V2
Stiletto: V3 & V4
Venture: V2
Road King I: V3 & V4
Big Block 750: V4
Road King II: V3 & V5
Titan: V4
Roadster: V3 & V5
M2000: V2
Dual & Triple (2ch or 3ch): V3 & V4
Bass 400+: V2
Tremoverb: V3 & V4

ANOTHER POSSIBLE SCENARIO may occur in the “SPONGY” (or on some models,
“TWEED”) power setting: the reduced filament voltage may cause very low output from
a RUSSIAN preamp tube. Again, the recommended fix is to replace the “sagging” tube
with the CHINESE type of Mesa 12AX7 - which are more immune to this type of failure.


----------------------------------------------------------------------------------

Strat