Will this work?

[R.G.]

The weight issue doesn't really bother me that much, ... I can't see happening. ... I'm sure... I do know what doubling the power of an amp does.
The metal that I'm using for the core is indeed low carbon steel suitable for use as transformer iron. It comes in sheets, which will be glued together, and the final result will then be ground and sanded all smooth-like. No, I haven't ever wound a transformer before, but I know how to.

Cool. As long as you already know all this stuff, you're in great shape. I wish I had that much background and info.

By the way, Alex is correct. The reason transformer laminations are in thin sheets and insulated from one another is that his process reduces eddy current losses inside the iron core. Any solid iron core, or one that is laminated but uninsulated, one piece from the other, will have big eddy current losses, and may be unusable because of just that. The higher the frequency of signal ( like treble as opposed to 60 Hz) the thinner the laminations need to be. If you glue and grind iron sheet, your transformer may have disappointing results. But that's just what I read in books and proved in tests back when I designed transformers for a living.

4% silicon iron is usually only sold to transformer makers. That's the only big commercial use of it, so it would be really odd if it was in stock in a shop which didn't primarily make transformers. But it could happen, I guess.

By the way, what interleaving scheme are you planning to do on
(a) your power transformer
(b) your output transformer
and
(c) your power supply choke?

I always wanted to learn from a master.

[Arthur Dent]

I was planning on using the glue as insulation. Just layer it really thick. I guess that might not be the greatest insulation though. I suppose I'll paint all the laminations with a thick layer of enamel, then glue them together. Instead of grinding it down, I could put some kind of filler in it to make it smooth enough, maybe beeswax would work.

No, I don't have access to 4% silicon iron, but that isn't realy entirely necessary. Sure, it's better, but anything magnetically permeable will work reasonably well. The stuff I can get is close enough to work.

What interleaving schemes would you suggest? I really haven't looked into that aspect very much. Your advice would be appreciated. Will I actually need a choke? I know my dad's Ampeg B-15 doesn't have one, and that's a very similar design to my amp. I don't really know anything about choke design. Maybe I should look into that. Again, any advice would be greatly appreciated.

[Steve Conner]

Wiring a second speaker in parallel doubles the power draw from the amp, and (IIRC) it also doubles the efficiency of sound output, so your overall sound power level could go up by a factor of 4.

Winding a tube amp output transformer is one of those jobs that I've never been brave enough to try, though I'm a qualified electrical engineer. You need a lot of very specific knowledge and experience, not to mention some appreciation of music and musical instrument tone, to make one that works well.

BTW, making the transformer laminations yourself sounds like a pretty dumb idea. It'd be so much easier to pick up a couple of old transformers at a scrap yard and salvage the cores out of them. I've seen some big transformers where you can unbolt a steel strap and slide the core out in two or four nice C-shaped sections, after "persuading" the varnish a bit with a blowtorch ;-)

Why not try making the power transformer first and get back to us if you get it running with no smoke or flames. (I remember when I was at high school, my first attempt at making a transformer caught fire when I plugged it into the wall.)

[Arthur Dent]

Ya know, now that I think about it... What specs would I need for a power transformer running a quad of KT88's at 450vdc?
I don't know if I really have the time or patience to wind two transformers of monumental proportions, and I now have the money to buy a few of them. I would consider running higher voltage and just ignoring the free parts I can get, but I already have the circuit boards all ready to be made, with an expected voltage of 450 volts, and I kind of need to get this thing built by the end of the semester in January. I'm not sure I can modify the design slightly to allow more voltage for the power tubes without exploding the preamp tubes. I would like to do that though. How could I get that to work?