MT 15 Hissing - Lead Channel Only

zat48

New Member
Joined
Aug 4, 2021
Messages
1
Hey everyone, this is my first post!

I just got a used MT 15 at Guitar Center about a week ago at an amazing price (for today's market anyway). Its in mint condition, and its one of the earlier models that came with 6L6's- and all the tubes appear to be stock.

My only concern is there's a significant hissing noise that happens on the lead channel only...sounds like static or like a waterfall. The clean channel is quiet and crystal clear. It's pretty noticeable when you're not playing, and even turning down the volume on the guitar doesn't help, its all in the amp. I only run the gain on the lead channel at about 10 o'clock or so. I know some high gain amps have this and that it can be normal, but I just wanted to check and get some opinions.

Considering a tube swap, maybe some 12AU7's or 12AT7's to lower the gain threshold a bit and maybe that will help quiet it down? I tried searching but couldn't find anyone who had the exact same issue, seems like a lot of folks have noise on both channels.

Any help is appreciated!
 
Anytime I have had an amp with too much preamp gain I'll swap a 12ax7 for a 12at or 12au. I was chatting on the phone with John Thompson from Bad Cat once, after I got a 2nd gen Hot Cat 30R. I was telling him it was too much. He suggested swapping for a lower gain preamp tube in V1 and then dropping a 12au7 in the phase inverter. Followed his advice and was MORE than happy with the result.
 
Hi zat48, congrats on your purchase, the MT15 is a beast imho and worth buying ... same here, the gain channel is quite noisy, while the clean is very clean. But when buying the MT15 I think it was meant to be like that, it is a beast and for a reason, it`s Mr.Tremonti`s creation ;) ... but you could tame it with preamp tube swaps, although I don˙t know to what extent you want to change the sound. I fiddled a bit with 5771, and different 12ax7`s and it does make a difference, but you loose a bit of the original character of the amp ... what I did not do was change the power tubes for less powerful ones, but then there are other values to take into account (did buy and try TAD`s 6L6GCSTR, but the Ruby 6L6`s have a better sound for my ear at this time). Also the lead channel master volume knob is somewhat awful as it˙s hard to set a bedroom volume, it goes from 0 to very loud with just a small turn. What about the FX loop, do you get noise there? Do you ever use a 4 cable method to put time effects and noise suppressors in the amps direct signal chain, so that you could use a noise gate for the amp`s lead channel?
As markd21 said try 12AU7, 12AT7, 12AW7 and 5771`s in positions V1, V2 and V6 (phase inverter), it does make a difference. Also see if you have some bad tubes as they can introduce noise into your amp as I found out. Buy some replacement tubes to have near by and test ... and test ... and test ;)
 
Waterfall hissing noises are pretty characteristic of a preamp tube that needs replacement. The fact that it's on one channel would eliminate output tubes as a possible source of the noise.

Have you tried tapping the tube with a pencil or chopstick to see if there's a microphonic tube?
 
Hey everyone, this is my first post!

I just got a used MT 15 at Guitar Center about a week ago at an amazing price (for today's market anyway). Its in mint condition, and its one of the earlier models that came with 6L6's- and all the tubes appear to be stock.

My only concern is there's a significant hissing noise that happens on the lead channel only...sounds like static or like a waterfall. The clean channel is quiet and crystal clear. It's pretty noticeable when you're not playing, and even turning down the volume on the guitar doesn't help, its all in the amp. I only run the gain on the lead channel at about 10 o'clock or so. I know some high gain amps have this and that it can be normal, but I just wanted to check and get some opinions.

Considering a tube swap, maybe some 12AU7's or 12AT7's to lower the gain threshold a bit and maybe that will help quiet it down? I tried searching but couldn't find anyone who had the exact same issue, seems like a lot of folks have noise on both channels.

Any help is appreciated!

Also as I know all MT15`s come with 6L6`s.
 
Back
Top