Aleph Follower

[nobody special]

I was playing with a few circuits today:

1st: 6W single supply
2nd: 25W single supply
3rd: 25W dc output

What do you think? Anyone try this yet?

 

[Nelson Pass]

As a concept it will work fine, but this circuit can do that trick without
driving the Gate of the current source transistor. You can feed the output
of the speaker directly to the top of R6.

 

[nobody special]

I guess I'm not seeing it. What exactly do you mean by the output of the speaker?

 

[nobody special]

I think I have it now:
You have to split R6 up.

 

[nobody special]

Cool! Thank you, Nelson.

 

[Nelson Pass]

Usually the function of Q1 for this is as a constant voltage source (for AC
anyway), so you might want to experiment with filtering its action at audio
frequencies, maybe starting with a big cap across Q1's Collector to Emitter
and maybe increasing R8.

 

[nobody special]

Is the idea to fix the voltage at the gate of the current sink for the DC bias using Q1, and then modulate the Vgs using the speaker current? Is this what the bootstrap is doing on your Aleph source?

 

[nobody special]

How about using a separate bias network, like this? I know that it removes the bias loop, but it seems better than a cap across the bias transistor. I tried a 5V active reference and it looked very good.

 

[nobody special]

Or, is it better to switch to a P-channel and just implement the standard type of Aleph sink?

 

[Zen Mod]

or you can take upper part of ACA and invert polarity , as lower part of this one

 

[nobody special]

What is ACA?

 

[Zen Mod]

http://www.firstwatt.com/pdf/art_amp_camp_1.pdf

you also have few threads around

 

[nobody special]

Thanks!
I don't post much.

 

[Nelson Pass]

Or, is it better to switch to a P-channel and just implement the standard type of Aleph sink?

Both will work, but neither needs R1.

 

[nobody special]

Thank you again, Nelson.
I've learned a lot in your posts, and you were the one that got me started in DIY audio back in 1996 when I found your first Zen articles online for the first time. Before that, it was just desire with no direction. I'm still playing with the simple stuff, have designed / spiced 1000 times more than I've actually built, but it's a nice distraction from the day to day grind. Thank you for your generosity.

 

[Nelson Pass]

 

[needtubes]

Or, is it better to switch to a P-channel and just implement the standard type of Aleph sink?

I played with this type of circuit a couple years ago. Never quite got the THD down enough for my liking, but maybe you can with a gain stage and some negative feedback.