Tube Amp Buzzing Noise Varying with Volume and Changes Channels

[Classified]

I couldn't find a match for that board from Glass Audio. Maybe an older version?, or its made by someone else. The voltage regulator circuit using that tube regulator looks like its from Glass Audio though. There may be some printing on the other side of that 4 tube PCB that may identify it.
Like a brand and version number.

I wish I could tell you more or be more helpful on this, I tried to peek at the top of the PCB but the way it's constructed you really can't access it without disassembling the whole thing with some desoldering that likely I wouldn't be able to get back together.

Went through my old messages with the guy, here's all I've got:

"This is built on a TubeCAD 9 pin PCB. The PSU is a VR tube and MOSFET combo."
Topology: https://www.tubecad.com/2004/blog0011.htm
PSU Circuit: https://wtfamps.com/2017/10/19/simple-high-current-vr-tube-regulator/q

It was built by WTF Amps if that helps: https://wtfamps.com/welcome/

 

[Lavane]

I wish I could tell you more or be more helpful on this, I tried to peek at the top of the PCB but the way it's constructed you really can't access it without disassembling the whole thing with some desoldering that likely I wouldn't be able to get back together.

Went through my old messages with the guy, here's all I've got:

"This is built on a TubeCAD 9 pin PCB. The PSU is a VR tube and MOSFET combo."
Topology: https://www.tubecad.com/2004/blog0011.htm
PSU Circuit: https://wtfamps.com/2017/10/19/simple-high-current-vr-tube-regulator/q

It was built by WTF Amps if that helps: https://wtfamps.com/welcome/

I would email WTF Amps and send the pictures you posted and ask if it's one of his, and if it is, what preamp board he used. Also was it meant to be a headphone amp, or a line stage preamp when he built it.
And maybe add that your getting a buzzing noise and if he would know where to look. And add that it stops only when the back two tubes are removed.
It's worth a try if they built it.

 

[Dadbar]

I would be concerned with those unshielded flying leads to what looks like the headphone jack, If it were my amp I would either route those leads to the edges of the amp and/or shield those leads

 

[Classified]

I would be concerned with those unshielded flying leads to what looks like the headphone jack, If it were my amp I would either route those leads to the edges of the amp and/or shield those leads

Heres the headphone jack, sorry I'm not sure what you mean could you please point out what needs to be fixed?

 

[Lavane]

Having those twisted pairs of wires from the headphone jack routed to the left and right sides of the chassis instead of running across the board where they could possibly picup some noise.

 

[Dadbar]

Heres the headphone jack, sorry I'm not sure what you mean could you please point out what needs to be fixed?

Try replacing those cables running to the headphone jack with a longer length of shielded cable and run it out of the way of the board, Ground just one side of the shield, The wires going to the pot are already wired this way and i would do the same with the headphone wires as a precaution,

If the amp is cathode biased I would also suggest tying the cathode lead of one output tube to one of the heater leads to convert the heater AC power to pulsating DC, That trick has solved a lot of buzzing issues in other homebrew amps ive built

 

[Classified]

Try replacing those cables running to the headphone jack with a longer length of shielded cable and run it out of the way of the board, Ground just one side of the shield, The wires going to the pot are already wired this way and i would do the same with the headphone wires as a precaution,

If the amp is cathode biased I would also suggest tying the cathode lead of one output tube to one of the heater leads to convert the heater AC power to pulsating DC, That trick has solved a lot of buzzing issues in other homebrew amps ive built

I tried wrapping those cables in aluminum foil but that didnt seem to help, this'll be the next thing I try

 

[Classified]

Try replacing those cables running to the headphone jack with a longer length of shielded cable and run it out of the way of the board, Ground just one side of the shield, The wires going to the pot are already wired this way and i would do the same with the headphone wires as a precaution,

If the amp is cathode biased I would also suggest tying the cathode lead of one output tube to one of the heater leads to convert the heater AC power to pulsating DC, That trick has solved a lot of buzzing issues in other homebrew amps ive built

Update: I ran with the first half of your suggestion and now have shielded wire around the side of the chassis and the shield grounded only on one side to the body of the headphone jack. I am not hearing any notable difference and it still buzzes with the same behavior.

Could you please expand on your second suggestion? How would you recommend I do that on this build?

Also, I haven't heard from the builder

 

[Dadbar]

Jumper the cathode of the final output tube to one lead of the heater supply for that tube. I'm not sure of what tubes you are running on the amp so I can't give the actual pin designations. It's a very easy mod.

There is also another possibility here- headphones are incredibly efficient and if the amp was designed to be used with speakers which are less efficient, it's possible that the low level noise you are hearing is just an inherent feature of the design, made more noticeable by the use of an incredibly efficient driver.