audio-talk

Problem is, you have just posted another big chunk of info, but its all over the place again. Simplfy things. 1. The quad II with no input is quiet 2. The quad II plugged into the powered up pre is noisy So from those two we are possibly safe to assume the pre is the source of the noise. Now in that...

was without the common mode choke. I had removed the anode choke completely and the two wires were hanging in free space. Ok, which two wires were hanging? Is this as I said, nothing but the anode, cap and a resistor to ground connecting to the power amp? If so, does the power amp make a noise if i...

Sorry, but I am loosing track with this. Normally I find if something is changed and the result changes, there is a process that explains the cause and effect. What I am missing is the connection between what you change and the result. I think its the problem with reporting this via the forum. It mi...

Only other possibility is the extra gain of the choke loaded anode is amplifying more hum, but I would only expect 3dB or so more gain with the choke at most.

Odd, dont know what to suggest. The implication is the choke is the source of the hum, but then I would have expected it to change as the choke was moved.

Did you try turning them in all directions?

No, he meant one between the choke and the resistor. Does moving the choke make any difference?

But then the cart isn't differential, and you may as well loose half the circuit.

The arm and cart need to be wired floating to do this (and what I originally posted some time ago).

Because the choke is a large coil of wire that will pick up magnetic fields. When the pre is switched off, the choke is connected to the input of the power amp. When the pre is switched on, the choke is then in parallel with the ra of the valve, so the hum and noise pick up will be less. The reason ...

Hang on can I just check what the goal is. Is it to produce something with a 26 in, or to get the original circuit working? We seem to have sidetracked into "it works, keep it". If all you want Phil is a resistor loaded 26, then there you go, if you want to get the original circuit working...

Doesn't have to be exact, anywhere from 20k to 40k should be fine.

No, the problem in that is the total flux is limited by the core size, and the flux needed is in inverse proportion to frequency (as mentioned by Mike in reverse), its already using a ungapped core. Sorry, laws of physics and all that

Easier to adjust the bias DC of the output stage (the DC magnetizing current) until it best matches the particular gap distance, where the transformer is operating at maximum efficiency. Or you can have a second winding and pass a constant current through it to cancel the flux of the normal output ...

No 6em7, may need some values changing for t'other one. Should be doable though. Start with the op points you need and go from there.

Hmmmm.

Yep, it can, all those are well above 100hz