How much would that cost? This is usually the follow up answer. We would say, it depends. Because, it really depends. It depends on what power/size and impedance he or she is looking for.
On our no.2 seat in the line, a pair of 300B single ended output transformers, I would guesstimate it to be at whopping of > USD$3000 or more. I'm dead serious. It's no.2 on the seat. I would not say who's no.1 as the sky is the limit. I challenge you to show me what's call no.1!
Recently I embarked on a journey to find out how much would I go in terms of making the ultimate (My ultimate of course, not yours! I believe you could be more extreme than me!) I'm going for the Precision winding method, amorphous double C core with copper magnet wire.
(Wait a minute, that's not extreme! One may say! Just wait and see!)
The extreme part is on the amorphous double C core itself. I'm gong to use Hitachi Metglass cores, with a size of AMCC-400! Some may still ask, what's so special about AMCC-400. I can tell you that it is simply HUGE! Single C-core of AMCC-400 size is already quite hefty. With double C-core of AMCC-400, it is humongous. If you want to be more extreme, go for quad C-core. I'm not going to do that as I would not be able to carry the damn amplifier when it is done.
A single C-core of AMCC-400 is 2820g. Double C-core would be 5650g, just the core itself, mind you. Added with the windings, frame and bobbin, it would be about 7Kg++, just for a single piece of the output transformer alone. This should get me to +/- 0.1dB at 20Hz at full power or more! Now you see what I mean?
Precision winding is already the ultimate. I like warmer tonality and therefore copper wires suits me more. If you like airy highs, then go for silver wires.
Let's talk about price. Hitachi Metglass C-core on AMCC-400 size is USD$568 per piece (2 C's). You can search for the price online and you might find cheaper source but it won't deviate very far. 4 C's are needed to create a double C-core and that would be USD$1136 a piece of output transformer. For a pair for stereo amplifier, that would be USD$2272, just for the cores alone. Shipping + taxes of importing the cores are NOT included yet, not to mention the price to ship the made transformers to you.
Also, do we still have any guys that want silver wires with the cores I'm using? I'm waiting for your email. That's how far I would go. I'm not sure about you. Maybe 1 day someone would email me and ask for Precision Series Hitachi Metglass Quad C Core AMCC-400 Size Silver Wire Output Transformer.
I'm real glad to build you one. The Number One! Don't worry, it would be as expensive (not even close!) as the top transformer from UK, that's £9,695 a piece.
Maybe I should build my ultimate to try it out one day. Stay tuned. Who knows that might happen. Tube amp has always been limited by the quality of the output transformers. Why not change the equation for 1 time and see how it is like to be tube limited 1 day...
P/s: 22 MAR 2014 - my vendor just offered me a batch of used AMCC-400 for half the price. I think I'm able to make 20 sets of 15W SE or 50W PP output transformers out of it. Now that's some good news.
J&K Audio Design
21 MAR 2014