Loud hum and static on TMB channel

[Jonny fuzz]

Hello, I am new to this forum and and im in search for a solution to my problem. I recently got my first 18w TMB amp. The low gain channel is fine, a little hissing but the TMB channel has a loud hum and a loud hiss. Ive changed the tubes and no luck. I did go in with the chop stick and found that the resister on v1 makes a loud thud noise when i tap it. Also, the "master" or second
stage gain volume pot wires also make a loud thud when i tap them. The rest of the components seem rather quiet. Does anyone have some advise?

Thank you for your time,

Jonathan

[JMPGuitars]

Your lead dress needs a lot of work. You should read the threads in my signature, especially the ground scheme one.

All long leads, especially from input/gain/volume pots, that run to the tubes, should be shielded.

Carbon comp resistors are inherently noisy, and don't add any magic mojo to an amp. I can't see what's on your input jacks, but those 1MΩ resistors must be metal film, or you're asking for noise. I use CMF metal film resistors for all my general resistors.

I'm sure others will chime in too.

Thanks,
Josh

[Bieworm]

What Josh said...
I don't see any metal film resistors in the amp. The grid stopper on V1 is definitely carbon comp. This one alone will provide you with inerasable hiss. Don't forget, this is an "amplifier". Its job is to amplify the signal you put into it, and that includes noise

[Jonny fuzz]

Your lead dress needs a lot of work. You should read the threads in my signature, especially the ground scheme one.

All long leads, especially from input/gain/volume pots, that run to the tubes, should be shielded.

Carbon comp resistors are inherently noisy, and don't add any magic mojo to an amp. I can't see what's on your input jacks, but those 1MΩ resistors must be metal film, or you're asking for noise. I use CMF metal film resistors for all my general resistors.

I'm sure others will chime in too.

Thanks,
Josh

Thank you JMPGuitars, i really appreciate your advice and the time you took to investigate my amp. I will take a look at the thread you suggested.

Jonathan

[Jonny fuzz]

What Josh said...
I don't see any metal film resistors in the amp. The grid stopper on V1 is definitely carbon comp. This one alone will provide you with inerasable hiss. Don't forget, this is an "amplifier". Its job is to amplify the signal you put into it, and that includes noise

Thank you, Bieworm. I really appreciate you chiming in. I am extremely new to this and learning as we speak lol. Okay so from what im hearing. First issued to address is the carbon comp reaistor on v1!. Sounds like its part of my problem. The amp is loaded with carbon comp resistors. I had no idea they would casue so much noise. Now im a guitar player first. i dont mind a little noise but the amp has a rather loud hum and hiss. So it definitely needs to be adressed. I also noticed no matter how many different tubes i put into v1 they all sound microphonic. Could this be because of the carbon comp reaistor.

Thank you for your time,

Jonathan

[Jonny fuzz]

Your lead dress needs a lot of work. You should read the threads in my signature, especially the ground scheme one.

All long leads, especially from input/gain/volume pots, that run to the tubes, should be shielded.

Carbon comp resistors are inherently noisy, and don't add any magic mojo to an amp. I can't see what's on your input jacks, but those 1MΩ resistors must be metal film, or you're asking for noise. I use CMF metal film resistors for all my general resistors.

I'm sure others will chime in too.

Thanks,
Josh

In regards to the lead dressing. And carbon comp resistors. Would you say thats its the un sheilded leads causing the hum and the carbon comp reaistors causing the hiss?

Thank you for your time josh,

Jonathan.

[JMPGuitars]

In regards to the lead dressing. And carbon comp resistors. Would you say thats its the un sheilded leads causing the hum and the carbon comp reaistors causing the hiss?

I'd say there's certainly one way to find out. Those are very likely sources though. The input resistors (the 1M on the jacks, the grid stoppers, etc.) need to be quiet, or they'll introduce noise (including hiss) that will get amplified through every stage of the amp.

Carbon comps should generally be avoided, but PI plates might benefit from them according to some opinions.

If you have to choose a single type for the general resistors, high quality metal film is the way to go.

[Jonny fuzz]

In regards to the lead dressing. And carbon comp resistors. Would you say thats its the un sheilded leads causing the hum and the carbon comp reaistors causing the hiss?

I'd say there's certainly one way to find out. Those are very likely sources though. The input resistors (the 1M on the jacks, the grid stoppers, etc.) need to be quiet, or they'll introduce noise (including hiss) that will get amplified through every stage of the amp.

Carbon comps should generally be avoided, but PI plates might benefit from them according to some opinions.

If you have to choose a single type for the general resistors, high quality metal film is the way to go.

Okay, thank you. I really appreciate your advice abd hour knowledge.

[Jonny fuzz]

I'd say there's certainly one way to find out. Those are very likely sources though. The input resistors (the 1M on the jacks, the grid stoppers, etc.) need to be quiet, or they'll introduce noise (including hiss) that will get amplified through every stage of the amp.

Carbon comps should generally be avoided, but PI plates might benefit from them according to some opinions.

If you have to choose a single type for the general resistors, high quality metal film is the way to go.

Okay thank you, ill start doing the research. I appreciate the advice.

Jon.

[JMPGuitars]

Okay thank you, ill start doing the research. I appreciate the advice.

Jon.

If you want to see what kind of stuff I use, look at the Mouser BOM in the Tremolo TMB section: viewtopic.php?t=25550

It's not all the same as what you need, but there should be plenty of overlap.