My desk amp - “Amp Camp” - Aleph current source OR???

[Zen Mod]

of course , there is output cap .....

 

[knutn]

Yes, thank you Zen Mod.
And the polarity of C3 must be reversed.

 

[kacernator]

R10, R11

I see that you have changed R10 and R11 to different values than original ACA - 0.22R and 0.33R. So you have now lower distortion?
Why Nelson Pass designed ACA with those resistor values?
What is the THD spectra of 0.82R and 0.15R comparing to original values?

 

[knutn]

They are changed to get lower distortion. If I were you, I would try Nelson's original values. It is not unlikely that this will sound best...

 

[kacernator]

Mosfet input

Hi,

as I cannot find any suitable P-Channel JFET in my country, I tried to redesign the input with mosfet. I am not skilled enough to be sure it is designed properly, but it works in simulator. What do you think about it?

Thanks.

 

[knutn]

In principle it's OK, but a possible problem is that the drain-source voltage is only about 1 1/2 volt. You may reduce the value of R11 and R12 to increase this voltage.

 

[drjbf1]

I am also interested in this type of circuit. How's it progressing, and how does it sound?

 

[knutn]

I have modified the circuit quite a bit because I want it to drive some new loudspeakers - not yet built.

So if you study the diagram, you will see
1) C4 and R5 is a zobel network
2) R16 is used to raise the output impedance, the loudspeaker is connected between OUT and FB

These two modifications are used to adapt the amplifier to the loudspeaker (a full range Fostex)

I have built the amplifier and done some initial testing, but I have not had the time to go on.

 

[knutn]

The build