Question about output transformers

[SemperFi]

You will get higher leak inductance using two bobbins. Might be an issue if a PP amp crossing over to class-B.
Interleaving the left-right windings into the two halves will probably solve it tho.

 

[Kay Pirinha]

Yes, that's what I'm intending. I'll have sections 1, 3 and 5 on one, and parts 2 and 4 on the other bobbin. And the McIntosh/Gow Unity Coupling will do the rest !
Best regards!

 

[Kay Pirinha]

However, I think the claimed one ohm section actually is not one ohm, it might be 0.9? ohm, we might not get exact 4, 8 or 16 ohms. However, we should also consider that all speakers impedence will changed in according to the changed in frequency.

I've calculated the sections to 0.9428 ohms. To keep that »Output Impedance Selector Switch« quite simple (see below), I'll restrain to just three impedances, 4, 8 and 16 ohms. A total of eight 0.946 ohms packs allows to be arranged as 2 x 4 each in parallel for 4 ohms nominally, 2 x 3 plus 1 x 2 for 8 ohms, and 4 x 2 for 16 ohms, respectively. Hence all impedances are matched within close and equal (+/- 6%) tolerances.

As suitable mechanical switches (five decks, three positions) that can cope with the currents supposedly aren't available anymore, five SPDT or one SPDT plus two DPDT relays will do the job, driven through a simple diode matrix.
Best regards!