A couple of years ago I made an amp like that, 100mH 3A and 27V rails. I got over 30W out at full blast.
It never got past the prototype stage because of the required size of the heatsinks. I tried fan cooling but the fans made too much noise.
The benefit of using chokes instead of constant current sources is that we can cut the rail voltage down to 50%, the inductance swings the negative half with it´s stored energy.
This raises the maximum theoretical efficiency to 50% instead of 25%.
So, aim for at least 100mH and make sure that the choke can handle the DC (+ the AC swing, overrating this component is not a bad idea) and cut the voltage down to 50%.
It never got past the prototype stage because of the required size of the heatsinks. I tried fan cooling but the fans made too much noise.
The benefit of using chokes instead of constant current sources is that we can cut the rail voltage down to 50%, the inductance swings the negative half with it´s stored energy.
This raises the maximum theoretical efficiency to 50% instead of 25%.
So, aim for at least 100mH and make sure that the choke can handle the DC (+ the AC swing, overrating this component is not a bad idea) and cut the voltage down to 50%.
DCR: The lower the better, simply.
Stay away from toroids, they usually have no airgaps which are absolutely necessary to avoid core saturation from the DC.
Check this (long) thread, it has plenty of good info about choke loaded amps and how to make your own chokes:
http://www.diyaudio.com/forums/showthread.php?threadid=6338&highlight="first+ever+class+a"
Stay away from toroids, they usually have no airgaps which are absolutely necessary to avoid core saturation from the DC.
Check this (long) thread, it has plenty of good info about choke loaded amps and how to make your own chokes:
http://www.diyaudio.com/forums/showthread.php?threadid=6338&highlight="first+ever+class+a"
EI cores or gapped C cores is to go.
OTOH, in small amps there is not much benefit in using chokes.
Up to a certain power level it´s probably easier to find suitable heatsinks that can handle an ordinary CCS´ed follower than to find (or make) suitable chokes.
In bigger amps the efficiency obviously becomes more important.
OTOH, in small amps there is not much benefit in using chokes.
Up to a certain power level it´s probably easier to find suitable heatsinks that can handle an ordinary CCS´ed follower than to find (or make) suitable chokes.
In bigger amps the efficiency obviously becomes more important.
I didn´t calculate anything, but the numbers are about the same as in a prototype amp I made a couple of years ago.
If you don´t need such high power, decrease the rail voltage and keep the current as high as possible.
All class A amps seems to like plenty of current, and most speakers likes amps that can deliver current.
Battery supply?
12V would be a bit low and 24 seems to be more than you need, so perhaps 3 x 6V?
OTOH, 12V (or 13,8V in reality) might be enough for about 10W, which is close enough to 15W and one 12V battery is much easier to charge than three 6V batterys.
If you don´t need such high power, decrease the rail voltage and keep the current as high as possible.
All class A amps seems to like plenty of current, and most speakers likes amps that can deliver current.
Battery supply?
12V would be a bit low and 24 seems to be more than you need, so perhaps 3 x 6V?
OTOH, 12V (or 13,8V in reality) might be enough for about 10W, which is close enough to 15W and one 12V battery is much easier to charge than three 6V batterys.
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