audio-talk

Yes, I wondered that. I even brought the phono and scope downstairs for a completely different environment. But there's no guarantee the kitchen is any better the upstairs with the modem router. The noise looked similar FWIW.

Maybe, but I can't resolve any noise on the HT, beyond the low level mush that's present all the way from the grounded input phono and HT all the way up to the first triode's anode. Or have I misunderstood what you meant about noise on the power supply line?

I'm having a few days away from it, to see what percolates. When I checked it in daylight the noise for want of a better word is still there on the first triode's anode. But it occurred to me whilst unable to sleep that I'd wired the heaters up for E88CC rather than ECC83. Silly boy. So that noise i...

I seem to recall seeing something similar with the iron when I was round at yours a very long time ago now you mention it. Phonos really are a step beyond the average amplifier.

Nick wrote: ↑Tue Mar 21, 2023 6:43 pm It can still be connected to the power supply and working, just not connected to the output of the riaa bit.

Even easier!

I dug out one of the spare Aikido pcbs and attacked the heater tracks with a Stanley knife and the corner of a small flat bladed screwdriver. Pretty it ain't but it worked and the heater pins are now isolated and connected by wires. . 20230321_184159.jpg . Didn't make any difference though. But I di...

I haven't tried that yet - the Aikido needs about 3mA compared to the C3g which is around 35mA so the shunt regs will need resetting.

Probe earth connected to the Aikido earth where the shunt reg attaches - no difference. Perhaps I have tried this previously, can't remember now.

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 ...

To recap, as far as I can tell given the hash that seems to be on the scope/probe when earthed, the noise first appears on the anode of the lower triode in the first valve, circled green below: . Aikido layout schematic.png . I don't know what's causing this but it's the same on both channels. Looki...

Fortunately it was just Q3 (IRF840, the shunt element) that was fried, everything else tested okay. For a sanity check I plugged it in for a listen to make sure it was okay and was pleasantly surprised the noise was much reduced. The reworking of the raw DC PS feeding the shunt regs and the rewiring...

Self inflicted Steve

Best day I've had in about 8 months :-) (probably longer). Thanks for your hospitality Steve, great to meet up again. I thought Steve C's SEP amp was really nice, good enough to resolve the differences in valves. I was a little surprised my MoFo performed as well as it did considering it was a cheap...

A little progress today. PS reworked to two stages with ground reference taken to the output of the shunt reg at the C3g pcb. Heater voltage reference sorted. I'd had the bright idea of changing the referencing of the C3gs to ground rather than elevated the same as the Aikidos. But there's only one ...

Thanks Phil, they look interesting and much cheaper than Farnell et al.

(Am I wrong to be a bit nervous about the legitimacy of high voltage rating of stuff made in China? Probably.)