audio-talk

Well done Steve, a pat on the head for a successful outcome.

Grand job Steve!

Great result Steve. I've really enjoyed reading this thread, though not had chance to read the Turner Audio pages yet. What make are/were the PP OPTs? I must have missed this.

If you haven’t already, I would loosen the bolts and let the lams clamp together with the amp running then tighten up again (while running).

simon wrote: ↑Sat May 15, 2021 5:46 pm….What make are/were the PP OPTs? I must have missed this.

They were the Danburys I had when I had the push pull amps.

Nick wrote: ↑Sat May 15, 2021 5:54 pm If you haven’t already, I would loosen the bolts and let the lams clamp together with the amp running then tighten up again (while running).

Cheers Nick,
I’ve already done that with the aid of a bloody great long screwdriver, after noting your earlier post.

Sorted - respect Due !

Great outcome, Steve. Domestic peace, I trust, after you ‘interfered’ with the amp?

Greg wrote: ↑Sat May 15, 2021 8:44 pm Great outcome, Steve. Domestic peace, I trust, after you ‘interfered’ with the amp?

I think I got away with it.

simon wrote: ↑Sat May 15, 2021 5:46 pm Great result Steve. I've really enjoyed reading this thread, though not had chance to read the Turner Audio pages yet. What make are/were the PP OPTs? I must have missed this.

Turner made/makes? and sold them.

Someone needs to capture the relevant transformer and choke teachings.... before the pages are lost. I find old search engines like Way back Machine have often found nothing, that I know existed. I tried marrying his teachings with RDH3 but Id not have gleaned the data without Turners interpretation.

That £70 book linked earlier is more likely not as in depth but might be presented better with classy illustrations and step by step photographs. probably though not worth the cost.

I spoke to Turner at length perhaps 15 years ago. I got the impression he is biased push pull, not open for discussion. Hes chosen a different path in audio to me. Probably believed I was deluded about an amp like Steves built.

Such good news those push pull transformers have resulted in better than the ones you started with Steve. Id have expected some early bass roll off. Id have left core alone, wound a choke and found a good cap. primary inductance would be much more. Parafeed is not a second rate SE version. Its different but very nice and was more common in the really early days before matching transformers, the speaker was parafed from the amp raw. Then when matching transformers rose up parafeed was carried on, but died off until Paul Joppa (is that the man?) used it with much popularity.

What would happen if we used the Parafeed cap as part of a crossover? Seems to me that it would be 6dB/8va for free! Would that also not reduce the demands on the choke? With another cap at the input of the amp, we have 12dB for free.

What would happen if we used the Parafeed cap as part of a crossover?

An issue could be that the OPTs primary has a much higher inductance than what would be needed for L for using the OPT as part of x-over filter. Personally I wouldn't trust this kind of operation -even if it were possible - because of all kind of unforseeable (phase) issues etc . Another thing is that the parafeed OPT and a typical 2nd order passive LCR filter might work differently despite the fact that both are connected to ground through a cap/cap and resistor.

Parafeed is not a second rate SE version

And let's not forget that even if we use an air gap and have no saturation of the core for the DC current upto a certain amount we still cannot use the best possible core material for best performance.

we still cannot use the best possible core material for best performance

Why not?