Trafomatic Transformer

[Diomedian]

Hi all,

I was surfing eBay (standard Sunday afternoon practice), and I ran across a company selling some 10W PP UL toroidial output transformers for US$32. They say they're making a large order and passing along volume discounts to us. Has anyone ever used a Trafomatic transfomer? Opinions, or am I best to stick with a Hammond 1608 for just a little more (probably the same price when shipping is considered)?

Here's the page (linked from an eBay auction):
http://www.engineeringvista.com/trafomatic.htm

I'm not sure - something might be a bit fishy here - one of the transformers they picture on that page is the same picture as a Korato C-Core here:
http://www.korato.com/product.php?id=105

The eBay auction in question:
http://cgi.ebay.ca/Custom-Output-Tra...QQcmdZViewItem

- Jeremy

[pred]

The Trafomatic is making the transformers for Korato. The Korato designs them and the trafomatic makes them. I was only using their toroids for PSU not output so I do not know how the output is made. I was contacting the guys with some questions and they seem nice and polite and have explined and unswerd all my questions. Their PSU thoroid come with screen connection and look really nice. The prices for double C cores in my opinion are quite high for relatively uknown player on transformer market (like more than 160Eur for 6c33c output transformer per piece).

Pred

[agent.5]

Originally posted by pred
I was only using their toroids for PSU not output so I do not know how the output is made.

are you using them for tube psu? what is your opinion of them?

[pred]

I used toroids for tube psu, but for now only the preamp one, so I cann't tell you for higer powers. They are good, well made, and this screen, although maybe not doing much gives confidence that someone gave it some thought, not just simply made them. No buz or whatever, but on the other hand the one I am using is quite oversized.

The only simple thing against is that the screw was shorter than it should be so I had to find another one. But that is minor and I got the apology from them, it was an error in packaging. Now I am preparing to us 600VA thingie for JLH class A, and this "thingie" is built and heavy as a tank

Pred

PS
I do not know what will be the price when you buy them, I got them directly there. They are very good and what is nice you can have as many voltages as you like, the only thing that influences the prices is the VA rating, and that is the freedom I like

[Diomedian]

Well, I wanted to learn a little bit more about toroids in general as output transformers - there's not a lot on diyAudio as of yet. I did find out that they seem to be fussy about current imbalance - see this thread for that discussion:
Toroidals as OPTs?

So I wrote Vista Audio to ask their opinion - Boris Sasic wrote me back within half an hour (!) saying (and I hope I don't do him any injustice by compressing his words here) that toroid cores should be able to take 2-5% of their nominal rating as DC bias, and that we should strive to remove bias anyway as good engineering practice. He also listed many of the advantages of toroids over EI trafos... Well, I'm not a good engineer (at least not a good _audio/electronics engineer :-), so I'll see if I can't get someone to help me out in the thread that discusses the amp I'm going to build.

Anyway, I think that if I get a good enough answer in the other thread, I'll try these transformers out - they're cheaper than anything else rated for 10W with an ultralinear tap. Vista was certainly more impressive that Plitron, which took a week to get back to me, with a price that was more than ten times the Trafomatic unit's. Maybe it's ten times better - who knows, but for my first tube amp, I don't think it matter _that much.

Jeremy

[pred]

I think your approach is good and since the thoroids have only one screw you can easy change if you want to "upgrade". Me, I was more interested in double C cores for SE, and there the prices are quite high...

Pred