Noise reduction in Express 5:50

[Room3]

Just bought the 5:50 yesterday and it sounds great! However, I would like to cut down on some of the noise/hiss on some settings without doing a full retube - I'm assuming that this is a mostly a preamp tube issue.
Are there any other Mesa (or other brand of) preamp tubes that I could swap in to help cut the noise a bit? How about the Mesa SPAX7?

 

[Ibanez]

Yes, most of the noise come from the pre-amp tube, and mainly from the V1 pre-amp tube. Mesa is supposed to screen their tube by placing the less noisy tube into the V1 socket. You can try to buy some other tube, other brand and try it in the V1 and see if it helps. It will always remain some background noise though. I'm assuming this is what you are talking about : noise when you don't play. Some noise gate can be good for you if you found this annoying. If you want to try other tube, the Tung-Sol 12AX7 is a good choice.

 

[MusicManJP6]

I retubed my F-30 with all JJ 12ax7's and it killed the noise completely in clean channel and made it 50% or more quieter in the distortion channel. Seeing as the F-series is the predecessor of the Express series, I would highly recommend a JJ preamp tube kit. They'll make it quieter, tighter, and crunchier!!

 

[Don]

My 5:50 makes a slight hiss (it goes "shhhhhhhhh") on the clean mode of the clean channel. It's only slightly loder than the hiss from my '66 Vibrolux Reverb.
It's not loud enough to hear in a room with people in it, though it might be a problem in a recording studio.

When I switch the amp to crunch the hiss goes away.

I was going to replace V1 with a new Tungsol 12AX7 when I noticed that the V1 tube that the amp came with (I pulled this amp out of the sealed Mesa/Boogie carton myself when I bought it) is exactly the same as a new Tungsol 12AX7. The amp performed exactly the same with a Tungsol labeled 12AX7 in it.

I've got some dead quiet RCA 7025s that I might try in it.

 

[Room3]

How easy/hard is it to access the preamp tubes?

 

[Don]

Easy.
They're in the silver cans behind the extruded aluminum bar in the back of the amp near the power tubes.

 

[Room3]

I put in a JJ 12ax 7 in V1 and already some of the noise in the clean channel has been diminished. Also, the amp is a little louder, a little gainier and with a slightly different eq curve. Now I see why people experiment with different combinations of tubes.

 

[Room3]

Well now the amp has developed the hiss and slightly lower volume again - even with the jj in V1. Also there is a very slight rumble when some notes are played. I've also tried swapping out V2 with not much difference. What happened?

 

[NDRU]

Well now the amp has developed the hiss and slightly lower volume again - even with the jj in V1. Also there is a very slight rumble when some notes are played. I've also tried swapping out V2 with not much difference. What happened?

The "rumble when some notes are played" sounds like a microphonic tube. While your amp is on, lightly tap on the tubes with a pencil and see if they make a bunch of noise through the speaker.

They shouldn't. If one does, it's going bad.