Toroids in SET

[Jaime]

In this forum, there were several posts about the use of toroidal transformers in PushPull applications. Now going to SET amplifiers, what is the use of these transformers, as output devices?

Very few manufacturers are using them as OPT in SETs, one of them is Yamamoto:
http://www2.117.ne.jp/~y-s/A-09S-News-E.html

The complicated part I think is making the air gap in the continuous core.
Anybody has the key for it?

Perhaps we can use cheap toroidal power transformers as OPT in SETs.

[Miles Prower]

Originally posted by Jaime
Perhaps we can use cheap toroidal power transformers as OPT in SETs.

No you can't. Toroidal xfmrs are notoriously sensitive to DC offset currents. The DC will saturate that core badly. SET OPTs must have an air gap to prevent DC core saturation.

[Tweeker]

Its no longer cheap once you do that? Labor and/or machining ops are involved to properly gap a toroid. Also the toroid has to be considerably bigger to make up the lost H with the gap, losing HF performance etc etc.

The only way to completely avoid expensive iron in a SET is to use a CCS parafeed at the penalty of ~doubled dissipation. Parafeed with a choke pushes the performance requirements onto the choke (high H, low C).

[Jaime]

Yamamoto do it.

[Tyimo]

Hi!

1. Get a toroid core,
2. cut it to half (with laser)
3. than make the airgap
4. and glue it together.
5. wind with layer and sectioning method as you wish
6. finish.

Greets:

Tyimo

[Elias]

Hello,

It is very well possible to use toroid output transformer in SE. One thing you need to do however, is to compensate the magnetic field caused by DC bias. Like here:
Using mains transformer as output transformer

I'm using toroid at the moment.

- Elias