Re: North American Ferrite core supplier for prototypes

Hello Spehro,

Many years ago some outfit in the UK had transformer "kits" with the
primary pre-wound, you just have to add the secondary. Don't know if
they're still available. I bought a few from Maplin.

That was also one of the advantages of taking apart existing transformers. Preferably some with lower voltage secondaries because it was less work to unwind those. Then you had the primary already there, 120V/240V taps and all.

But Sergey wants to create tube amp output transformers and that would almost certainly require a complete rewind. Unless one would find the perfect match where the primary shows just the desired impedance and a 120/240 split if he has to design push-pull.

If I were in his shoes I'd seriously consider one of the hi-perm ferrites. Preferably some huge pot core for easier winding. These materials have come a long way since the days of tube amps. I believe you could get a lot more fidelity out of them. Also, the round bobbins allow to fix them to an electric drill chuck and wind'em up at slow speed. I never really succeeded doing that with square bobbins but in those days the only way to slow down a drill was via a variable transformer and then it would sputter at very low speeds.

Regards, Joerg

http://www.analogconsultants.com
.

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