audio transformers

John Larkin a écrit : > I believe I mentioned that I don't need the full 60 volts p-p at low > frequencies, since I'm mostly simulating jet-engine alternators. My > customer is currently using a tiny and - no surprise - very expensive > Pico part to do this, and I have at least 5x the available volume to > work in. I would like to get the most voltage at 50 Hz as possible, so > I'd like to use all the iron that will fit. >

Why not trying the obvious, first? You might have luck with small toroidal power transformers (AMVECO).

Digikey carries small ones (down to 1.6VA) which might suits your needs (2x115V2x18V).

There is a circuit on the Lundahl site that puts the tranformer in the feedback loop. Is that an option? It might make a less good transformer acceptable

martin

In message , dated Thu, 31 Aug

But with a turns ratio of 3:1?

Yep. I've used similar arrangements to drive telephone transformers.

...Jim Thompson

John Woodgate a écrit :

Yep.

OK, not exactly 3:1, but sure close enough.

In message , dated Thu, 31 Aug

I doubt that 1.6 VA, or any small transformers, are made with 36 V output. Equally, you don't get BIG ones with 6 V output.

John Woodgate a écrit :

Have a look there, then. I was surprised, too.

Yeah. We're going to order an assortment and see what the high-frequency response is like. Some of the TransEra parts look interesting.

Has anybody used power transformers at higher frequencies?

John

Probably not. Opamp drive and transformer volt-second saturation are going to be my limits, not so much signal precision.

John

Depends a lot on where you are but in the UK you could try St. Ives Windings and Marinair.

Ian

bigger

LOL.

These guys are OK too. In the UK of course.

They do a 1+1:6.45+6.45 which would nicely give you the volts ratio. Quite a decent size too.

Graham

Hello John,

Usually they are the pits, too much in core losses and not very linear. I lucked out at times when fixing grampa's tube radios or an old TV set but it would not pass muster for HiFi-FM.

Anyhow, isn't there another way to do this? Like chopping it up onto a carrier, passing it through an RF transformer and rectifying it back to baseband? That's how we do ECG and stuff.

I think Hammond has an on-line catalogue

Perhaps it might be useful to look at developing a floating power supply, a floating 60v pk-pk output stage, with the ac signal coming up via push-pull optocouplers.

The waveforms these speed probes generate are fairly rubbishy, (and with wide spread on pk-pk amplitude), so a large THD from opto mismatch could be quite acceptable.