Transformer source

[dkemppai]

Hi all,

I'm Looking for a sources of Toroid transformers. Preferred is a single 117Vac primary with dual secondary windings 38 to 50vac each.

VA ratings from 400 to 1000.

Preferrably the transformers would be designed for low noise (both mechanically, and electrically).

Wound for slightly lower levels of peak flux density than normal, would be a plus.

Just wondering where you guys buy transformers from, and what your experiences are with the various companies.

Oh, yeah, to pot or not to pot?

-Dan

[Kadin2048]

I recently received two toroids from a place called "Apex Jr." They sell (apparently) surplus and over-run equipment. I bought two very nice Avel Lindberg 150VA, dual 38.4V units for $22 a piece, which I plan to use in a 2-channel psuedo-Gainclone that I'm working on.

What I really wanted was a single 300-400VA unit, but I think the two smaller ones will work just as well, if not better.

He also seems to have a fairly wide variety of other stuff useful to audio builders, including some fairly inexpensive tube sockets (compared to the few other places I've looked).

Doesn't accept internet orders but was very polite when I spoke to him over the phone.

http://apexjr.com/miscellaneous.html#Toroids

-Kadin

[dkemppai]

Ok, found one source... ...prices look good. Although the standard designs are not specifically audio, they do offer audio designs as well.

http://www.tortran.com/standard_designs_117V_60Hz.html

[markp]

Try toroidcorp.com or avel-linberg from Parts Express for good transformers at ok prices. Get a UL approved unit to be on the safe side(avoid no name asian units).

[markp]

Originally posted by dkemppai
Oh, yeah, to pot or not to pot?

-Dan

On larger unit, dont pot. I like unpotted power transformers as they are easier to mount, weigh less, and run cooler in my experience.

[dkemppai]

Originally posted by markp

On larger unit, dont pot. I like unpotted power transformers as they are easier to mount, weigh less, and run cooler in my experience.

What do yo consider larger units? I'm thinking of 600 to 800VA units for this deisgn. (I still need to do a few calculations, before I choose the actual size)


I had the company that I listed earlier quote me a custom low flux audio unit, potted in a metal enclosure. Prices were pretty good, only about $20 more than the standard units.

Mounting is with a 1/4-20 bolt.

I would suspect that the lower flux transformers should run cooler (as there will be less area covered by the B-H curve).

Any thoughts on this?

Thanks!
Dan

[Frazzled]

Don't forget Plitron...

LINK

[dkemppai]

Originally posted by Frazzled
Don't forget Plitron...

LINK

....hmmm, looks expensive... ...you've used them?

-Dan

[markp]

Originally posted by dkemppai


What do yo consider larger units? I'm thinking of 600 to 800VA units for this deisgn. (I still need to do a few calculations, before I choose the actual size)


I had the company that I listed earlier quote me a custom low flux audio unit, potted in a metal enclosure. Prices were pretty good, only about $20 more than the standard units.

Mounting is with a 1/4-20 bolt.

I would suspect that the lower flux transformers should run cooler (as there will be less area covered by the B-H curve).

Any thoughts on this?

Thanks!
Dan

Above about 100va is a larger(non-preamp) unit. The way to run cool is to overspec the power needed by about 20-30%. Toroids are pretty good as far as mechanical noise goes and have a small field than standard units so metal potting is not always needed, save weight and money.

[dkemppai]

Originally posted by markp
Above about 100va is a larger(non-preamp) unit. The way to run cool is to overspec the power needed by about 20-30%. Toroids are pretty good as far as mechanical noise goes and have a small field than standard units so metal potting is not always needed, save weight and money.

I'm not sure if I need the metal, and potting.

I have some transformers now, that are noisy, mechanically. I was thinking that the potting would help to dampen that out a little. I don't konw what the stray flux field looks like, but may pull out the gauss probe, and poke around a little.

I'm already planning on oversizing the transformers. Just wondering where the 20% to 30% rule comes from? Is at rule of thumb?

-Dan