neat Toroidal power tf's- Antek Inc.

[imaradiostar]

I swear I'm not trying to drum up business for this guy but I'm totally stoked to have found these things!

Has anyone out there used any of them? The prices are excellent and they appear to be rated very conservatively. I spent some time with Duncan's PSU designer and even after changing values (to make the PT look worse) I was still amazed by the numbers I was getting.

I'm going to order a two- probably a 1T300 for a 2x7189 guitar amp and a 2t200 for a 4x el84 hifi amp.

I'd be interested to hear if anyone has tried them!

Drilling one hole beats the heck out of drilling many or routing a large hole for a z mount PT.

jamie

[Steve Conner]

They are really good. Toroids give about twice the performance-to-weight ratio of EI core to start with, and if they have a single HT coil for use with a bridge rectifier, that makes them perform even better, compared to an old-style EI core tranny with a FWCT rectifier.

I'd have used them by now if it weren't for the cost of shipping them across the pond.

[Enzo]

Toroids are great, and will fit in low spaces. But when drilling that one hole, make sure your mounting bolt only contacts the one chassis surface. If your bolt contacts both roof and floor, then the bolt and the chassis form a single turn through the transformer - and it is a shorted turn.

"Mind the gap"

[Steve Conner]

Yeah, good point Enzo. You really don't want to be around when that shorts out and puts 0.5V at 1000 amps through your chassis. I've never tried it, but I expect it could melt chunks out of a steel chassis like a spot welder.

[black_labb]

i've been planning to use those on builds. they seem extremely reasonable, and the current ratings seem great compared to EI trannies.

[defaced]

At 0.5v and 1000 amps you'll likely get what's called "expulsion" where metal is very violently ejected from the contact point. It will ruin your day, big time.

[Ptron]

Good find! I've been wanting to get my hands on some toroids for an ultra-light amp for a while. All I ever found were the Plitron ones. They were fairly expensive and as heavy or heavier than their E-I counterparts. They may have been potted and I'm pretty sure they were canned like Anteks OTs appear to be.

Which leads me to ask, do they really need to do that? I thought one of toroidal txformers biggest advantages was they were super efficient and didn't radiate much EM badness. Maybe it's to keep noise out? I'd like to use a toroidal OT but the weight they add canning them sort of defeats the reason.

[mr.jetski]

cool

why do they have 0 output at the higher voltage rate?

[Gregg]

The prices are really good - the lowest on toroids I've seen so far. The only explanation for that is obvious but not necessarily a bad thing. Instead of the not needed second high voltage winding they could have included a bias voltage winding thus decreasing the size even more.

[Enzo]

Those voltages are not "selected." They are measured at the various load levels.

Look at the chart, the winding is nominally 300v. The top line in the load test shows that with zero current being drawn the voltage will rise to 310v. Zero current means no load, zero load.

Power is voltage times current. If your transformer is sitting there with nothing connected to the secondary wires, then it is producing no power output. It is up to the load to draw some power from it. That is why there is zero power there: Any voltage times zero current will result in zero power. Power only results if some kind of work is being done - even if that work is just heating a resistor.

The next line shows the winding fully loaded. With a load drawing .4 amps, that 300v winding sags to 296v. The power then is the result of that current flow. (There must be some rounding error, since I get 118 watts with those instead of 116.)

[mr.jetski]

learning

thanks E

[imaradiostar]

Toroids are great, and will fit in low spaces. But when drilling that one hole, make sure your mounting bolt only contacts the one chassis surface. If your bolt contacts both roof and floor, then the bolt and the chassis form a single turn through the transformer - and it is a shorted turn.

"Mind the gap"

Thanks for the tip...that's excellent information!! It would be a shame to blow up a new project or hurt myself or someone else.

jamie

[Enzo]

I don't remember what it was in, but we "discovered" this fact on the job. "My amp blows fuses." But not with the top cover off.

[Robert M. Martinelli]

I' ve been using toroidal PTs in the past, and the ones I purchased ( made in Italy ) came already equipped with a large rubber insulating ring ( rubber thickness was about 2 mm ) - if this is not your case I would make an insulating rubber ring cutting it out of a sheet of rubber for industrial seals building, and punching the center hole with a wad-cutter ( I mean, a wad, NOT a bullet! ).

I use the same rubber to build vibration dampers, pedal FXs rubber feet and the like.

Best regards

Bob

[Enzo]

That won't stop the bolt from becoming a "turn." Good thing to have though.