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RE: Alex...

Posted by Alex Kitic (A) on October 28, 2014 at 14:18:43

In Reply to: RE: Alex... posted by Triode_Kingdom on October 28, 2014 at 07:29:20:

If we consider the option to use original secondary wire, we need to provide a 160W unit like you're suggesting. If the amp is stereo, we can use it for both tubes, as 2 secondaries, as explained for 10Y and the 50W unit.

While cheap, it is not at all necessary to use a 160W unit to power a 50W load. If the secondary is removed and a new secondary with adequate wire is wound instead, a 105W unit is literally twice as powerful as needed. Besides the fact that there is no need to burn voltage across resistors (low values of discrepancy can be adjusted by unwinding a few turns from the primary), you would have to burn a lot of W to overload the unit! At 10A, .5 ohms is already 50W, so why throw away all that power and have to deal with huge dissipation? That's what got me to get in the HF AC story in the first place: unnecessary losses in power consumption and heat dissipation - so why would I get back to that once I took a different road?

Once you make it possible for 2x 50W of heaters and a few more W for the drivers to be effortlessly produced by a rather cold (40 degrees C after several hours of operation) and small box... you just cannot get back to burning excess voltage in heat.

As for 50W, imagine 2 "normal" mains transformers. One is 10V 5A, the other 5V 10A. They would be identical size, wouldn't they? The difference would be in the secondary wire thickness and turns number... but if we assume the transformer secondary is bifilar, 2 secondaries of 5V 5A each, than you can do both options with the same transformer. In series 10V 5A, parallel 5V 10A. It's literally as simple as that. The same is valid for the HF AC output transformer, only the size is very much different, as well as the type of wire used (both are frequency dependant).
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