audio-talk

Needed to put in a ground lift switch so that the RTZ and JDS Labs DACs could be used with the amp, otherwise there was an annoying buzz in the headphones.
The MF M1 DAC was no trouble with the primary of the IPT floating, but the other 2 DACs did not like the floating primary at all.

Screenshot ...

I simply put 47K across the push pull pairs as Stephen did with his HPA project:

OK.

Cheers Nick,
I’ll have a look later for 4 resistors.

OK,
I've seen phase splitting transformers used with a resistor across the push-pull pair.
I've drawn one in grey on my diagram.
I'm stumped as to what its function is. Can the panel help and would it be a good idea to install one?

What a bleed’n rat’s nest!:
Never mind

OK,
I've installed the Sowter 3575 phase splitting input transformers: It all sounds great.

izzy wizzy wrote: Fri Dec 06, 2024 9:33 pm Are those Sowter transformers in the background forming an orderly queue for an entrance

Yep

+1

Git down!

There you go:

Just put a Fender jewel light on the front of the HPA. That's better
I can't have a valve amp without a Fender jewel glowing away on the front panel; it's just not cricket!

One of those satisfying moments. When you have a great upgrade lurking in your stash :)


Yep, it makes it worthwhile building stuff.
Just upgraded the sound even further with a pair of Voskhod rocket logo 6N23P I found stashed away in a corner of a dusty old box of small signal tubes. These are ...

OK, so the Sowter push-pull output transformers, I had wound around 2007 have been fitted in the HPA. They have 4 bifilar wound secondaries on split bobbins, cost a fortune back then, and to be honest, the difference these things have made to the sound of this headphone amp has been phenomenal ...

Cheers Stephen

I've got a couple of Sowter 3575s, so might put those on the input to see what the effect might be. It's a good sound as is but an input transformer could be interesting.