audio-talk

Yep, I have to turn off Ethernet over mains if I want to see into the noise floor. The noise on ground is enough to show up on the scope. I assume various inductance on leads and stuff is enough to generate signal voltages that the scope see's

Ahh, hang on, with the heater disconnected the top valve is also off, so the lower valve anode is floating, so its just noise pickup I would expect on a high impedance. There is a lot of noise about in the ether now.

When they are not conducting the anode is a high impedance point, it may be less noise when they are conducting. It could be that you are seeing noise on the power supply line.

Sounds like a big step. I always remember to turn off the soldering iron when trying to find hum. The worst one I has was the jfet phono. While checking for noise I spent ages trying to find the source of low frequency (say 1hz) wandering on the output. I was trying to find the source blaming the po...

It can still be connected to the power supply and working, just not connected to the output of the riaa bit.

Does it do the same if the input to the Aikido is unconnected and its input connected to ground by the input resistor.

May not be the case but remember that the scope will show the signal between the scope's earth and probe tip, so worth considering where the scope earth is and what affect the earth is on the amp and any potential induced voltage on that. Hmm, yes I don't think I've ever had the probe earth in the ...

May not be the case but remember that the scope will show the signal between the scope's earth and probe tip, so worth considering where the scope earth is and what affect the earth is on the amp and any potential induced voltage on that.

Cant offer any help but you have my sympathy. Finding parts is still not recovered from 2020.

Earthing is often a case of try everything and keep what works.

Probably wont make much of a difference but I would not pass the gnd through the boards like that, I would take them all to the same point where the F&S0 connection comes in from the regulator. And I would move the ground point in the power supply at least to the other side of the smoothing caps...

I think those purple wires are the voltage reference for the heater regs. They're taken off the raw DC ground reference lift. I thought this would be adequate for the heater references? Maybe, but every little helps, if the reference is moving WRT the amp 0v there will/may be some coupling via the ...

And going back to the circuit of the regulator. I don't like the way that's drawn. In theory its fine, but in practice, the F0 and S0 need to be bonded together at the common 0v point and the ground connected there not somewhere back on the nominal 0v line. Any The regulator will regulate WRT 0v at ...

Looking at the picture of the breadboard. You seem to have lots of purple wires coming together on the dual cap, I would not treat the -ve teminal of the cap as the earth point, as that will move WRT the output of the regulators if the current in the 0ve line of the regulators in move. I would treat...

I would either make up some phono plugs with 100R resistors in them to make up some shorting plugs to put into the input of the amp, or solder some 100R resistors across the input phono to make sure you are chasing hum in the phono stage not from the inputs floating (which they can, certainly with 4...