Looking for choices - affordable PP OPTs

I've used power toroids as output transformers for my amp, but it only puts out a couple watts so I'm not sure how they'd work for higher powered amps. Steve Bench also played around with some donuts for his amp, but again it was a low-powered design. I figure if you have a source of bigger toroids you shouldn't have too many issues getting a 30-50W out of the amp. In anycase, I find toroids to be really nice sounding transformers, much better than the Hammonds I got from the local surplus store.

Zobsky,

You are not going to find any first class OPT's for $60 ea. The power toroid is going to give you about 70% of the performance of an E/I OPT from one of the houses where they actually have a designer who knows what he is doing. If you will email me I will give you further information on a pair of the OPT's that Lynn Olson uses in his Karna, an amplifier that Mahatma Jeeves says represents the finest possible modern tube amp.

This is not BS and I cannot say more here.

Bud

For those that might consider the above linked design as a project beyond it being an example of mains toroids used as audio transformers, I must add that the caution introduction paragraph of the author is a very real warning since the schematic does not include a mains transformer and rectifies directly the mains ac like in old TV sets and radios. I was thinking of doing that too in another circuit idea and the members of DIY audio cautioned me very emphatically that such a practice must NEVER be considered as an option. Its a health risk at all times. See the safety sticky thread.

Used toroidals, very happy with the result. Also used them as phase splitter - less satisfactory, but with the right design these work to. Only putting out about 7watts though.

Shoog

If you will email me I will give you further information on a pair of the OPT's that Lynn Olson uses in his Karna, an amplifier that Mahatma Jeeves says represents the finest possible modern tube amp.>>

I know just what Bud is talking about and you'll be more than very pleased with the results - I second the idea of emailing him! Andy

A toroid power tranny seems like a possibility for a P-P headphone amp too, since normal OP trannies of a suitable ratio seem rare.

What kind of VA should a toroid be for a given power in output wattage? Will a 50VA toroid be able to push 50W of audio? I'm guessing you want a fair bit of headroom for bandwidth/non-saturation purposes, right? I'd love to use a pair of toroids for some 6S19P's in push-pull..

The VA must be about 8 to 10 times larger then the audio power. You have to use a 500 VA toroidal transformer in a 50W audio hight quality amplifier.

A toroid power tranny seems like a possibility for a P-P headphone amp too, since normal OP trannies of a suitable ratio seem rare

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I have done this with a little ECL82 headphone amp using 12V transformers. Works well.

The VA must be about 8 to 10 times larger then the audio power. You have to use a 500 VA toroidal transformer in a 50W audio hight quality amplifier.

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The bigger the transformer the higher the interwinding capacitance and so the more the top end suffers. Also primary inductance is higher the smaller the transformer. The main consideration is core saturation. I think a good compromise is probably 4-8x the output power. Unfortunately no one seems to have tested the theory so its a matter of trial and error.

Shoog

has anyone used toroids for other audio purposes, like MC stepup? or is that an application that is too sensitive?

also, how should one figure out the turns ratio? i'd like an OPT with a primary impedance of around 2K and a secondary of 8 ohms. is the winding ratio around 15.8:1, by square rooting both sides?

You might look into Uncle Ned's (Triode Electronics) Dynaclone transformers. The measurements others have taken look nice, and the price might be in your ballpark. They enjoy quite a following from the www.diytube.com crowd.

http://www.triodeelectronics.com/dytr.html

Some folks like the Transcendar transformers available via Ebay.


good luck,

pj