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In Reply to: RE: Choke coupled is going to be inefficient posted by Ralph on April 21, 2015 at 10:35:16
They have to dissipate the energy from the voltage drop across them which means that energy is not available to the speaker.
so does the primary of a transformer.
Additionally, the choke is not offering any impedance conversion, so that has to be done by the power tubes themselves.
tap the choke for your output and you have impedance transformation.
dave
Follow Ups:
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Inductors by nature do not dissipate AC power so I fail to see where the inefficiency comes into play.
dave
It will be dissipating variable DC power, not AC. The output of course is AC.
How is variable DC not AC?
Granted there will be some copper losses from the energy stored and released by the inducance but I'd hardly call that inefficient and the same exact thing happens in the primary of an output transformer. Obviously the ideal solution is to do away with the transformer altogether.... oh now I get it.
dave
An autoformer is definitely do-able but I wonder if the 'secondary' DCR tap can be made small enough to dispense with the coupling cap , maybe even using thicker wire . Obviously there would be a small amount of offset . What do you think ?
Al
Unless I've misunderstood your question... there's a pretty darn good reason to you cannot do what your thinking about...
if you have an autoformer in the output stage of a power amp (i.e., a power tube is driving it) which is hooked up to a speaker load at some tapped point... you would want to use a blocking cap to keep the dc off of the voice coil of your driver, heh?
Or have I gotten your application all wrong?
MSL
Builder of MagneQuest & Peerless transformers since 1989
I did it with the 6C33 for a NY noize. As I recall I had about a quarter of an amp of current and the secondary section had a 0.1 ohm DCR for a 25mv DC offset across the load. I really expected major driver offset and issues from the DC but didn't notice any with my lowthers.
Unfortunately the amp sounded like 6c33's so I moved up conventionally coupled GM-70's for the next year.
dave
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