going bellow +/- 15V in PSU and 1A of quiescent current (for outputs) is against nature of output devices
Judicious use of an attenuator preceding the mini-A will limit its output to 3-4 W 😉
Setting the AC current gain to 0 will also reduce the peak output. This may change the sound character. Pull C2 on BrianGT's schematic and you'll have no AC gain. It's the 220 uf from the output to the resistor leading to the base of the Aleph current source transistor.
Why are you trying to limit your output to 3-4W? A little too much power is better than not quite enough.
Setting the AC current gain to 0 will also reduce the peak output. This may change the sound character. Pull C2 on BrianGT's schematic and you'll have no AC gain. It's the 220 uf from the output to the resistor leading to the base of the Aleph current source transistor.
Why are you trying to limit your output to 3-4W? A little too much power is better than not quite enough.
Thanks for the replies. I want to make power that will consume little power. I want to have a little body and little heat.
I guess it depends on your definition of little power. A mini-A on 15V rails will consume roughly 30W per channel at idle. Not the most efficient way to get 10W, but in the big scheme of things, a couple hours listening uses the same or less energy than leaving a light on while you are doing it.
If minimum power consumption is a priority, then it's best not to look at single ended mosfet designs. Mosfets perform best with fairly heavy bias.
For maximum efficiency in a flea power amp, consider something like a t-amp. Search the forums for tweaks. I've never heard one.
Somewhere in between, look for a small class AB bipolar amp. The Sysmasym is nice, but there are plenty of other options. Many headphone amps are capable of 3-4W into 8R, sometimes without tweaking. Try building something with an opamp driving a push pull bipolar buffer on 15V rails and you've got a couple watts.
If minimum power consumption is a priority, then it's best not to look at single ended mosfet designs. Mosfets perform best with fairly heavy bias.
For maximum efficiency in a flea power amp, consider something like a t-amp. Search the forums for tweaks. I've never heard one.
Somewhere in between, look for a small class AB bipolar amp. The Sysmasym is nice, but there are plenty of other options. Many headphone amps are capable of 3-4W into 8R, sometimes without tweaking. Try building something with an opamp driving a push pull bipolar buffer on 15V rails and you've got a couple watts.
I wanted to make A class. Hence this scheme to remake does not work, so sorry. 🙁
You can't have it both ways, the laws of physics do not allow it.
The most efficient class A would be a push-pull circuit using dynamic current sources.
I don't know what 'two-stroke' means. The theoretical efficiency limit for SE is 50%, and that is using dynamic current sources.
The most efficient class A would be a push-pull circuit using dynamic current sources.
I don't know what 'two-stroke' means. The theoretical efficiency limit for SE is 50%, and that is using dynamic current sources.
I can try to gather power in the bipolar transistors in class A, output of 2 watts. I found such a scheme. Thank you all for your help.
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That would be 25% for SE
Push-Pull topology has doubled efficiency and that's where you can go up to 50%
Hi Juma,
So who's to argue? Is an Aleph amp single ended or P-P? A question of semantics.
Actually, 50% is not the limit for an Aleph.
Best, Bill
So who's to argue? Is an Aleph amp single ended or P-P? A question of semantics.
Actually, 50% is not the limit for an Aleph.
Best, Bill
Last edited:
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Joined 2002
