Garp, the output transformer must have the tertiary winding for feedback. To my knowledge, that leaves two choices, Sowter and Cinemag. They are both fine transformers.
I have used the Carnhill inductor and been quite pleased. I had some problems initially with the Vintage Windings inductor, but they have been fixed (see my post about it in this section).
Other important questions are:
- What interstage transformer are you using? If you go with Sowter, spring for the 1475. I used UTC A18 with good results.
- Do you have an audio analyzer to use to tune the Zobel on the interstage to minimize ringing of whatever inductor you’re using?
I’ve not built a unit using all Sowter transformers, the Vintage Windings inductor and the stock interstage Zobel. So I can’t predict performance of that setup. But since no one makes an exact replica of the HS29 (BTW, I wonder why not?), be prepared to adjust the Zobel to suit the transformers and inductor you choose to use. Or just ignore the HF ringing/rise above 26K (if it’s there), since only dogs can hear it anyway. And it only shows up with boost above 8K, you may never use that. But the only way you’ll see it is with an analyzer.