Anyone Using a SPAX7-A in V1? Or Anywhere Else?

[CudBucket]

Hey guys.

Last night I went to a local GC to get to Mesa 12AX7s so I'd have a full backup set (I had 4 others). Anyway, I met a pretty knowledgeable salesperson there (no really) and he told me that the SPAX7-As were special high-gain tubes intended for V1. So I bought one of those and a regular 12AX7.

Anyone using these?

Thanks.

Dave

 

[parsky1]

I'm using an SPAX7-A in V1, I didn't really notice much of a tone change... really its just a regular 12AX7 that has been tested for its superior resistance to microphonics.

 

[NoGlassNoClass]

Got one in V4 (FX driver/return)...the JJ I had there crapped out and the SPAX7 was what I had lying around. No change in tone, but my loop works now.

 

[Boogiebabies]

I'v got SPAX7's from the mid 80's to the last batch of Russian's. They are less prone to microphonics, but have no bearing on the tone the tube will actually produce. I stopped using them and have about six Russians with the heat shrink still in boxes. I rather go for tone with the GT 12AX7M and Ruby 12AX7 C9 or Ruby/Mesa 7025 SS. The ultimate tube in Mesa's for me is the RFT ECC83. Fat, Driven and rated for 10,000 hours of snoochie bootchie.

 

[jbird]

Are they not stock in V-1? I've used them in my two channel for some time now, on recommendation from my dealer!

 

[MasterTrax]

....snoochie bootchie.

8) 8) 8)

 

[Boogiebabies]

They are not stock in the V1 on any Mesa production amps.

Snootch to the Nooch !!!

 

[CudBucket]

Not stock in the V1 of the RKII I know for sure.

Snizooch to the Bizooch.

 

[alejandro]

``The Mesa SPAX7 is a "special" 12AX7 that during our in-house testing processes is found to have a significantly quieter and more stable response to high volume and gain applications. If a fledgeling 12AX7 passes its first test, it is tested a second time under more stringent listening conditions and even higher volume and gain levels. If the young SP passes this second test, it is outfitted with a sleek layer of shrink wrap that helps shield the tube even further from field and transformer noise. We recommend using the SPAX7 in input preamp stages (usually located nearest the input jacks), as the input stage is generally the most volatile. An SPAX7 input tube will lay the foundation for a quiet and stable amplifier in the highest of gain and volume applications, and is a sure winner when playing microphonic musical chairs in search of that troublesome squealing or crackling preamp tube.

Tien Lawrence
Boogie Customer Support"

 

[ol4t]

My RK came with SPAX7 in V1s (I think there are two V1s?).

 

[alejandro]

http://www.mesaboogie.com/manuals/user_manuals.htm

There is only one V1, always. Then V2. Then...

Consider V1 your tone by the pound, and V2 your tone by the ounce, and so on. Mesa'a SPAX7s are formidable, and it's no suprise that you have two in there, as the Road King is their flagship amp.

 

[ol4t]

Then I don't understand what my owners manual is stating on page 43 . Under
descriptions of Tube Functions. It says:
V1 A=First Gain Stage
V1 B=Second Gain Stage
Edit- When my amp came in it was somewhat dark in comparison to another head/cab that came in at t same time. My shop replaced all the preamp tubes with SPAX7s instead of just the V1s, it sounds fine now, but I can't say that was the issue because I think they had the effects loop in different positions on the amps.

 

[Russ]

A and B refer to the two sides of the dual triode. The 12ax7 tube is a dual triode. This means that there are actually two triodes inside that can be wired for different functions or applications.

 

[ol4t]

A and B refer to the two sides of the dual triode. The 12ax7 tube is a dual triode. This means that there are actually two triodes inside that can be wired for different functions or applications.

See, I told you I didn't understand.

 

[Russ]

It is my understanding that Mesa doesn't really grade for gain of a tube outside of it actually working. Their prime concern is noise and microphonics. If they screened for higher actual gm (gain) in a tube they would state that. They merely test a tube for noise and microphonics at higher gain and volume levels. I have a half dozen new in box SPAX7's that I asked them about and they said that they are tested for noise and microphonics. I told them that my tester showed that they didn't even test as new and they said that they are guaranteed to work and be noise and microphonics free. Aside from that there is no other guarantee.

I would suggest a different 12ax7 that is screened for noise and microphonics. GT, Bob, and Doug do a great job of htis. They can even screen for higher gm.

 

[Russ]

They may have pulled a fast one on you too if they charged you. SPAX7's are more expensive than standard Mesa 12ax7's.

 

[ol4t]

They may have pulled a fast one on you too if they charged you. SPAX7's are more expensive than standard Mesa 12ax7's.

No charge. Long standing relationship with these guys.

 

[Russ]

That is good to hear. Keep your business with them. There are a lot of sneaky people out there that might try something like that.

 

[ol4t]

That is good to hear. Keep your business with them. There are a lot of sneaky people out there that might try something like that.

You're right, thanks for the warning though.

 

[alejandro]

Thanks for the info on the gain and grading of the Mesa SPAX7s, Russ. That's something I didn't think about from the Lawrence blurb. I'll pass it on to my fellow Mesa-heads.

I'm in the process of re-tubing some choice positions. A good SPAX7 in the path, probably V2, would lower the collective noise-floor of my JJs and Tung Sol.