Humming sound from my audio system

[nutzandvoltz]

I call this sound "rumbling" than a "motor boat". Usually from either cold solder joint or bad tube socket. Since the phono preamp isn't that old, maybe you can exchange it?
Is the turntable's ground connected?

Maybe you need to bond the tube box preamp to the integrated amp by a wire jumper from the thumbscrew the turntable's ground to a ground connection on the integrated amp.

Maybe you have bad rca leads coming from the turntable. Does it act up/ go away if you move around the wire?

 

[Rosenild]

I call this sound "rumbling" than a "motor boat". Usually from either cold solder joint or bad tube socket. Since the phono preamp isn't that old, maybe you can exchange it?
Is the turntable's ground connected?

Maybe you need to bond the tube box preamp to the integrated amp by a wire jumper from the thumbscrew the turntable's ground to a ground connection on the integrated amp.

Maybe you have bad rca leads coming from the turntable. Does it act up/ go away if you move around the wire?

The phono amp is purchased bought and there were no problems with the MM pickup.

The turntable is ground connected. I have tried disconnecting the ground wire, however that doesn't change anything.

The RCA that leads to the turntable must be a bit weary since it's very old.

 

[nutzandvoltz]

The phono amp is purchased bought and there were no problems with the MM pickup.

The turntable is ground connected. I have tried disconnecting the ground wire, however that doesn't change anything.

The RCA that leads to the turntable must be a bit weary since it's very old.

but if a different cart didn't do this, then I doubt its the leads.
What is interesting is your oscillations when you engage the loudness. Which is a sign of poor grounding in a tube circuit. A long time ago people were discouraged to build tube gear on aluminum chassis because of that and its poor shielding qualities.

Switching the operating impedance is only going to change sensitivity to the circuit and exact selection of impedance is really only important if the previous coupling device is a transformer. Which isn't unheard of in some setups to have a step up transformer before the phono preamp.

I would redo the ground wire on the turntable. But I question the build quality of the phono preamp. To test of the preamp is having grounding issues, you take two rca lead, short the wires together, and insert them on a phono input, observe the output. should be nothing. With no device or shorting plus on the input: should be nothing.