Just stumbled upon this remark form Mr. Pass in a thread about SiC transistors:
This would be a nice thing, no doubt!
This would be a nice thing, no doubt!
Most of the smaller Pass DIY designs are only Class A up to a point, and then go into Class B.
AFAICT only the SE designs remain in Class A throughout their useable ouput capacity.
Nelson used to strive to keep the "First Watt" in Class A. 1 Watt can be surprising loud with efficient speakers.
AFAICT only the SE designs remain in Class A throughout their useable ouput capacity.
Nelson used to strive to keep the "First Watt" in Class A. 1 Watt can be surprising loud with efficient speakers.
Hi,
are you sure?
F4 and F5 are in PP = PushPull design with complementary transistors in the output stage and the others are SE = Single Ended, but always in cass A
May be I'm wrong...
But a A/B pushpull design with a little more efficiency and less power consumption will be interessting
cheers
Thorsten
are you sure?
F4 and F5 are in PP = PushPull design with complementary transistors in the output stage and the others are SE = Single Ended, but always in cass A
May be I'm wrong...
But a A/B pushpull design with a little more efficiency and less power consumption will be interessting
cheers
Thorsten
All Push-Pull amps will eventually run into Class AB if pushed hard enough.
If your bias is high enough this wont happen.
Obviously if the supply is insufficient they will clip before this happens.
The clue is in the class of operation AB.
A true Class B amp would be horrible to listen to as you would hear the crossover from the +ve device to the -ve device.
To compensate for this the crossover region is generally biassed at Class A. How big you want to make the Class A region is up to you, set by the biassing of the amp.
If you set the bias to give you 15W of Class A, then the remainder of the +Vcc - -Vcc swing will still be available but will be in Class B.
The SE designs don't have this ability. They run in Pure Class A until they run out of steam.
All-be-it a lot of steam in the case of the Aleph 4 (100W Pure Class A)
In fact if you go to the Pass site Nelson lists the point at which a few of his amps exit Class A operation.
If your bias is high enough this wont happen.
Obviously if the supply is insufficient they will clip before this happens.
The clue is in the class of operation AB.
A true Class B amp would be horrible to listen to as you would hear the crossover from the +ve device to the -ve device.
To compensate for this the crossover region is generally biassed at Class A. How big you want to make the Class A region is up to you, set by the biassing of the amp.
If you set the bias to give you 15W of Class A, then the remainder of the +Vcc - -Vcc swing will still be available but will be in Class B.
The SE designs don't have this ability. They run in Pure Class A until they run out of steam.
All-be-it a lot of steam in the case of the Aleph 4 (100W Pure Class A)
In fact if you go to the Pass site Nelson lists the point at which a few of his amps exit Class A operation.
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However, the interesting question was about whether there would be any push-pull SiC amps... only N-types available so you need to do some tricks to make it happen.
... but may be possible. If you have a look to Naim Audio power amps NAP180, 200 and 250 (may be others too), there are two not complementary NPN transistors NA007 (BD742? as replacement) build in a A/B push pull design.
These Naim amps are not too bad and have a very low power consumption, arround 10W (NAP180 & 200, 250 not measured yet) wirth only preamp noise as input.
If the schematic is a point of interest a can post it
cheers
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