I needed an audio output transformer for a 30s radio I am working on so I took my last donor out of my parts crib. I hate to have none on hand, so I ordered three of these. Just came today. They are really nice! And less than $4 a piece!

http://www.parts-express.com/70v-10w-sp ... r--300-040

Where have they been hiding all my life?

Mark K8KZ

Hi ark,

Those are line-to-voice coil transformers designed for use on a 70-volt (or 25-volt) distribution line.

They're not meant to connect directly in a tube plate circuit.
The insulation on the primary might not even be suitable for the expected plate voltage.

- Leigh

You don't say?

As Rozqnna Rozannadana would say....never mind.

Mark K8KZ

Who carries those universal audio output transformers any more? You know something 20 bucks or less. I wanted to order a couple to keep on hand.

I thought AES had them, but I can't seem to bring them up.

Thanks,

Mark K8KZ

I think this is what I want.

https://www.tubesandmore.com/products/P-T291

Do you ever feel like you're talking to yourself?

Thanks for the advice Leigh.

Mark K8KZ

EDIT: Oh man, just realized that's a push pull transformer. Not what I want. I'll keep looking.

The best source of modern transformers for tube work that I know of is Hammond Manufacturing in Canada.
http://www.hammondmfg.com

Their products are carried by all major US distributors.

- Leigh

This site makes excellent transformers http://www.edcorusa.com/class-x

+1 Leigh

I was going to suggest Hammond myself, but you got there first.

Mark, those transformers you got...not a good idea to use them for the reasons Leigh pointed out. AES does have audio output transformers for tube equipment, but I generally go to Mouser as they carry a larger variety of Hammond products and generally their prices are a little better than AES.

Good luck with your project

Tony
KC7ZWH

No I get it Tony. I'm not going to use them as audio output transformers.

I paid less than 4 bucks a piece, and it would probably cost me 10 bucks to return them. I'll hang onto them or toss them. Not sure.

Thanks!

Mark K8KZ

Technically 'line transformers' aren't gapped and so should be unsuitable for single ended operation but there are reports of them being used successfully, or should I say 'acceptable enough', as an AA5 OPT. Some folks say they can be used if you're 'in a pinch'.

Since you have them anyway you might as well tack one in and see how they do, or don't do.