audio-talk

Well I tried to put DC heating on the amp and what a disaster! A right bleed'n racket of buzzing.
It all went silent when I touched the top caps of the EL38s.
Looks like the RF field coming from the onboard SMPS DC supply is being picked up by the anode leads.
I can't be arsed with anode stoppers ...

10k

So less distortion and you hVe plenty of power anyway. I love my el38 se. I cant beat it with el84 pp


Cheers Paul,
Yep, the EL38 is a great valve. Out of all the combinations I’ve tried, it sounds the most natural and just gets out of the way of the music. There’s plenty of gain using it ...

EL38s have returned to the fold:
EL38.jpeg

This time as a single valve amplifier.
5k output transformer tap on the primary side and the 32 Ohm headphones connected to the 16 Ohm tap. That's as far as the OPTs go.
What impedance that reflects to the primary I don't know. Can't remember the ...

I bought a pair of the General Electric, 6C5, metal tubes Paul mentioned in an earlier post.
At £7.50, you can’t go wrong. I might get around to doing something with them before Owston; we’ll see how things go.

OK,
Heres a pic of the headphone setup as it is now: Looks like the monitor has air extraction
It’s there to get prevent one posting too much hot air.

simon wrote: Sat May 31, 2025 5:58 pm
You mean you're not going to try something else between now and September?

Probably not. Don't want to tempt fate with the respiratory stuff. Can't be doing with the unpleasantness of the symptoms.
However, I will look at the 7A4 option for when I feel up to doing a bit more.

Sarah Jane Morris & Tony Remy Sweet Little Mystery (The Songs of John Martyn) - 2019

Hold the bus!

I've just found a black T-plate 6SN7 from the 1950s by the Italian firm Fivre. It has a broken spigot on the base but getting it the right way 'round in the socket was easy enough. The base can be repaired with one of these from Hotrox:
Screenshot 2025-05-31 at 16.01.33.jpeg

The ...

Paul Barker wrote: Fri May 30, 2025 8:37 pm Langrex are selling Western made 6C5’s fore runner to the 6J5 for £7.50, just saying. Prefer that to Chinese 6sn7 I know you need two but £15 not at all bad for a similar enough valve made properly in the West.

Thanks for that Paul, I'll have a look right away!

Schematics: As advised, I built the input stage without the bypass cap. The gain is just right

OK, here's the amp built:

6AS7 Headphone Amp.jpeg
It's taken me 6 days to build, using on/off working with the mask and the air extraction. No ill effects, but things are taking me far longer than they used to. No bad thing really, now I'm used to the slow pace of work.

The days when I used to ...

Cheers Paul.
I don't take into account what happens at AC. And seeing as how an amp is an AC machine, it seems a bit slack not to.

simon wrote: Thu May 29, 2025 8:29 am If 1 o'clock is your loudest volume Steve it might be worth trying without one of the cathode bypass caps? Might not sound better though.

Yeah, we'll see what happens

That'll do nicely.

So this is what I've got planned out so far:
6AS7AudioCct.png 6AS7HPAPSU.png

With the 6SN7 input stage, I just used the 'Resistance coupled amplifier' charts for a 100k load resistor and interpolated the cathode resistor value for a B+ of 260V rather than the published 180V or 300V.
The 6SN7 has ...