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Old 30th November 2014, 07:25 PM   #1
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Default Switched PS Class A

Certainly not an expert on these matters but I had a thought while viewing the Class A 100 watt amp thread... The $700 dollar one with all the transistors on the board. Not a dis....

Anyway, would it be possible to switch the power off until the signal was present to avoid the idle state power dissipation?

I realize this would create noise, that could be dealt with. Perhaps something along the lines of fiber optic switching where the idle state is in the optical realm and the output state is in the electrical?

Optical switching that couples to a power transistor output?

The benefit would be much larger output levels for Class A without the idle state power dissipation.

Ccat.
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Old 30th November 2014, 10:36 PM   #2
DUG is offline DUG  Canada
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Wouldn't that defeat the purpose of a settled, thermally stable amplifier output stage?
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Old 30th November 2014, 10:40 PM   #3
Mihkus is online now Mihkus  Estonia
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Class A was meant to be what it is. Its always half way switched on and theres no crossover noise.
If you want better efficiency with minimal loss of quality go for class ab? Highly biased class AB can be class a to first watt or more...
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Old 6th December 2014, 10:27 PM   #4
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Switching off entirely seems a bit much, but there is no reason why you couldn't build a Class AH amp, i.e. Class A with dynamic rails generated by a SMPS (maybe just for the output stage). This could enable considerable dynamics in power consumption if voltages went down as low as +/- 10 V or so in idle. Obviously the basic amp would need to have good bias stability and excellent PSRR, so its complexity would rival modern AB designs. It certainly wouldn't be a project for the casual DIYer either (complex amp + SMPS) - but it would be doable.
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Old 11th December 2014, 04:00 PM   #5
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Class aAG. That is commonplace for data transceiver amplifiers.

Circlophone has a couple of published mods that could be added for enabling it to operate over a wide and changing voltage range so that it could be used for this. It is already Class aA, and then adding variable power voltage would turn it into a full Class aAG audio amplifier.
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Old 12th December 2014, 09:59 AM   #6
AndrewT is online now AndrewT  Scotland
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Is there a more appropriate section for this Thread?
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Old 13th December 2014, 01:54 PM   #7
Mihkus is online now Mihkus  Estonia
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Class A has nothing to do with chipamps indeed. Passlabs/Solidstate rather solidstate

Last edited by Mihkus; 13th December 2014 at 01:57 PM.
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Old 13th December 2014, 06:56 PM   #8
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Default Fine with me

Wherever the best fit is..

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Old 16th December 2014, 07:05 AM   #9
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If done with chips, it would make a merry list of almost everything not to do with a chip amplifier; however, the prospect would do just fine in the discrete amp solid state forum.
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