Aleph P current sources?

[stefan]

Hi all,
Can I use in Aleph P current sources with
bipolar transistors (i have a lot of them)?
Will this change the sound performance?

 

[wuffwaff]

Hi Stefan,

yes you can. Wouldn´t know why not. As for sound differences it´s not so difficult to try both isn´t it.

I assume you´ll have to buy more fets than you need anyway

william

 

[Nelson Pass]

For all I know they will sound better.

 

[stefan]

Thanks, mr. Pass!
I'll try and if all is OK I'll post schematics here.

 

[stefan]

Simplified schematic - how will work?

Here is simplified schematics for Aleph P
with bipolar current sources.
I still didn't made it and I need your opinions.
Do you think this will work well?

 

[Nelson Pass]

Your input source is going to see some DC, so you might
consider caps for that. Also, some nice caps across the
Zeners will take out some noise. Maybe a few hundred
ohms in series with the transistor bases to keep them
from loading down the reference when they saturate.

 

[Peter Daniel]

How would it affects the circuit if feedback resistors R11 and R14 would be removed? I mean, is there a way to get rid off the input coupling caps?

 

[stefan]

I think that it's too dificult to make in this circuit.
In all cases input capacitors are simplest and safest way.

 

[jan.didden]

How would it affects the circuit if feedback resistors R11 and R14 would be removed? I mean, is there a way to get rid off the input coupling caps?

I would try connecting R11 *after* C2, and R14 *after* C3. That would give you AC feedback only, but I would expect the circuit to auto-equillibrate with the input gates drifting to ground. Mr. Pass?

Jan Didden

 

[Nelson Pass]

The Gates have to be held at a positive potential or
the gain Mosfets will shut down, so some kind of DC
bias for them is required, or use a negative supply
rail instead of ground for your negative current
sources.

 

[Peter Daniel]

So this circuit should work without input caps then?

 

[stefan]

Peter,
if you want 0 v at gates you have to provide
about -4 V at drains.
I think that this circuit cannot guarantee this in all conditions.
You must supply some negative feedback to hold gates at 0 V and this will make the circuit complicated.

 

[stefan]

Sorry for mistake, I mean sources (not drains) in previous post.