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In Reply to: Some clarification posted by 13th Duke of Wymbourne on February 10, 2025 at 13:12:24:
As I told you more than 6 years ago, I'm not a SS guy."I see the inclusion of single-ended amplifier load lines. These are not relevant to solid state push-pull output stages, which can produce load current above their bias point as required (but only in one direction, hence the need for push-pull)"
Should I understand, from what you said, that a transistor can't idle at the mid point between cutoff and max current?
The single ended load line may not be relevant as the current moves up from the idle point but isn't it relevant as the current moves down from the idle point?
Or do transistors magically drop all the way to cutoff in a perfectly linear way?
If they don't then that's my point. In a true Class A tube amplifier (single ended or PP) none of the devices are driven into the non-linear regions, up or down. It transistors are linear all the way to cutoff then there is no need for Class AB, Class B with be notchless. (crossover distortion less)
As the dynamic operating curve chart (not a load line plotted on a set of plate curves but derived from that) shows, with a tube circuit Class A only operates the tube(s) in the "most linear part of the dynamic curve". I forget which book I'm quoting but that is a quote.
An AB tube amplifier doesn't do that and neither do SS circuits (unless transistors are linear all the way down to cutoff).
Side note, with a PP Class A tube amp, it you drop the idle current a little to get more power then it's not a Class A amplifier anymore and none of the power is Class A power. Even the part that is still operating in the "most linear part of the dynamic curve". The total rated power of the amplifier has to be power produced while all the tubes are operating most linear part of the dynamic curve. That is what all the old books discribe and show as examples of Class A.
Maybe with SS it's different. If a transistor stays linear all the way to cutoff. Tubes don't do that.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 02/10/25 02/11/25
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Follow Ups
- RE: Some clarification - Tre' 20:09:27 02/10/25 (5)
- RE: Some clarification - 13th Duke of Wymbourne 18:55:10 02/12/25 (0)
- RE: Some clarification - morricab 03:45:17 02/11/25 (3)
- RE: Some clarification - Tre' 07:37:47 02/11/25 (2)
- Hmm, best sounding class B is McIntosh; unity coupled circuit IS brilliant, however-nT - Cleantimestream 07:47:47 02/11/25 (1)
- Vintage Mac unity coupled consumer tube amps - Steve O 09:17:08 02/12/25 (0)
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