Using "industrial control transformers" for tube power supplies

A few years ago, an unemployed vacuum cleaner salesman with a fetish for "low DC resistance" power supplies decided that you could use common, fairly inexpensive, industrial control transformers for plate supplies for tube audio amps. And, you can. Hams did that for years, as did laser experimenters and people building worm and nightcrawler collecting shockers.

There are upsides and downsides for this. The upside is price, they are not that expensive new, and they are often available for free or very cheap as pulls from building salvage and old air conditioning equipment. They are ruggedly potted and insulated.

The downsides?

They are very heavy and awkward. They usually have the connections on their topsides which in an amp build need to be covered over for safety and long leads have to come through the chassis. The size they come in usually starts at 250VA, meaning they are too big to fit most amp chassis and still have room for other things.

The voltages they put out are usually direct multiples of 120 volts, meaning that you get 120, 240, or 480 volts out. If you need a center tap for a bi-phase half wave rectifier (i.e. you want to run rectifier tube(s))this means you are usually stuck with 240-0-240.

There is only one secondary, in effect, you need another transformer for filament voltage, and a third for bias voltage unless you have one wound. You are already pushing the space and weight budget. This makes it worse.

What this means is that ICTs are better utilized for bench supplies or for providing "foreign" voltages to imported equipment than incorporated into actual amp builds in most cases. But yes, they are a tool in the armamentarium of the DIY builder.

In my opinion, the best source of cost effective power transformers for homebrew and small production tube gear is to use guitar amp replacement units-IF you can get wholesale pricing on these. The music industry works on a pricing scale where "A Mark" (a phrase never to be uttered in a music store unless you want to be kicked out) is fifty percent. Most replacement guitar amp transformers from the bigger distributors are A Mark, sometimes B Mark, items. (B Mark is variously 40, 35 or 30 percent, depending.)