SPAX7 for Subway Blues?

[Suave Eddie]

I've had a Subway Blues since 1994, purchased new. This is the first generation model with the two inputs rather than the toggle switch.
It's a rather noisy amp overall. I'm not referring to the "Hum" problem -- I bypassed the effects loop to get rid of that issue -- it's more of a hiss. I've heard that this is to be expected from this amp.

Would the Mesa branded SPAX7 preamp tube help lower the noise level? Does anyone use these?

According to the Mesa site:
"MESA SPAX7 preamp tubes are a super-premium grade substitute for any 12AX7 positions - They are a "Special Requirement Preamp Tube" that possess an even higher standard of overall performance, due to their incredibly low sensitivity to microphonic noise - This is the ultimate preamp tube to use in all critical gain stage positions - It is the absolute best of the best!"
Is this snake oil, or does anyone have experience with these?

If these would help, would I need to replace all four, or just the first position tube?

Thanks for any input.

 

[amrose57]

I've had a Subway Blues since 1994, purchased new. This is the first generation model with the two inputs rather than the toggle switch.
It's a rather noisy amp overall. I'm not referring to the "Hum" problem -- I bypassed the effects loop to get rid of that issue -- it's more of a hiss. I've heard that this is to be expected from this amp.

Would the Mesa branded SPAX7 preamp tube help lower the noise level? Does anyone use these?

According to the Mesa site:
"MESA SPAX7 preamp tubes are a super-premium grade substitute for any 12AX7 positions - They are a "Special Requirement Preamp Tube" that possess an even higher standard of overall performance, due to their incredibly low sensitivity to microphonic noise - This is the ultimate preamp tube to use in all critical gain stage positions - It is the absolute best of the best!"
Is this snake oil, or does anyone have experience with these?

If these would help, would I need to replace all four, or just the first position tube?

Thanks for any input.

I have an Express 5:25+ that had a bit too much hiss for my taste. After rolling over 30 preamp tubes (many NOS) and 4 sets of EL84's, I tried the SPX7A tubes in V1 and V2. Hiss went down by 50% or so. So yes, they do work as advertised. I would buy 2 and start with V1.....

Al

 

[Don]

There's a fix for these amps that involves replacing a capacitor, if I recall.

 

[Don]

http://forum.grailtone.com/viewtopic.php?t=14425&highlight=

 

[Suave Eddie]

http://forum.grailtone.com/viewtopic.php?t=14425&highlight=

"There's a fix for these amps that involves replacing a capacitor, if I recall."

I should have made it clear that I'm not talking about the famous hum that plagued the early Subway Blues. I eliminated that by bypassing the effects loop (mojo module).

This is a hiss, not a hum. I've heard that it is inherent in this amp.

 

[Don]

Definitely experiment with tubes then. I was able to lower the hiss in my 5:50 by trying different preamp tubes.