Express hiss no biggie

The Boogie Board

Help Support The Boogie Board:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Mar 2, 2015
Reaction score
A while ago I got a well-used but decent condition 5/50. The reverb tank appeared swapped out dead, a new one worked fine. I've seen alot of posts regarding hiss. 99% of the time it's your preamp tubes.

So here's the deal on hiss/no or low hiss on different settings. For example some people experience louder hiss on the clean channel setting than the burn, and are perplexed.

The pre-amp circuit uses 12AX7 tubes, which are dual triode. Dual means that the Tube can be wired to function as two independent components. And that's how they are used in the Express.

What that also means is that depending on what channel settings you use most, the tubes will wear differently. So one side can be "strong" and the other "weak or worn". Also, when replacing tubes you can get variances on sides of the tube, especially with your favorite vintage tubes.

I initially re-tubed my 5/50 until it was as quiet and hissless as I could get it. I left it that way for months. Yesterday it rained all day so I decided to "tube roll". I have a bunch of nos and used vintage tubes. Those tubes are often worn unevenly, strong on side A and weaker on B, especially tubes from organ pulls. I have some favorites and I tried them.

The hiss came back wherever the worn sides landed, but in general, the tone came back pretty much everywhere too. V1, V2, V3 are the main tone and gain impacters in your peamp. Read the manual. Tubes are a major component to tone in my mind. I'm willing to put up with a little hiss at idle if the tone is so much improved it blows away a generic sterile tone. If they could make a toneful tube as quiet as the SPAX7 they would have the guitar world by the balls. I don't know if it can be done, but think it could be, and wish someone would do it.

The old Telefunken, and Amperex tubes have the sound most classic rock guitarists are looking for with American amps. None of the modern tubes have those tones.

For now I'm going to ignore a little hiss. If your amp is hissing, put a new mesa tube or tubes in V1 and V2 and you'll be good to go. They do the job.
Last edited:
The problem with the hiss, is that one can’t record with the amp. That is very disappointing as Mesa amps are very good.

The problem with the hiss, is that one can’t record with the amp. That is very disappointing as Mesa amps are very good.

That must be some loud hiss to be heard over the mix of the entire recording.

Yes, I go out of my way to reduce hiss in my rig, I’ve got a NG out front and in the FX Loop to help squash it in the high gain settings. But I’m sure Pete Townsend and Angus Young didn’t let hiss stop them from recording.

Ok. So the hiss is not audible when playing. So yes recording hiss can be deleted during production. But not worth the extra time to me. Easier to use another amp or modeller.

The his is also dependent on times of the day when there is a lot of interference.

This was a hot topic on this forum when the amp was in production. There are a lot of old threads that describe things that worked/didn't work to reduce hiss. May be worthwhile to read through some of them if you haven't done so already.

Latest posts