First Watt F5 vs Aleph 5

[a.wayne]

Originally Posted by bobodioulasso

The value of the feedback resistors have to increase when paralleling outputs?
I did not realize that.

Up or down ?

[bobodioulasso]

Originally Posted by Botte

Since adding additional outputs increases the open loop gain and I didn’t change the closed loop gain it had more feedback.

Does that means we need to decrease NFB and so increase the feedback resistors values in order to keep the stock close loop gain?

[Nelson Pass]

Originally Posted by bobodioulasso

The value of the feedback resistors have to increase when paralleling outputs?
I did not realize that.

Neither did I.

[a.wayne]

[joho]

Originally Posted by Nelson Pass

I think this would be the preferred topology.

Thank you Mr.Pass for your response.

I was thinking about 2 zeners to ground to keep a fixed voltage to the base of the cascode transistor. Bad idea?

My rail voltage is around 30 volts (at 225Vac) so I'm using a variac to make the primair AC voltage lower(24V rail).

Last Monday the man with the golden ears was in my listening room and we compared a F5 with an Aleph X (no parallel output fets).
He was impressed by both amps and his only comment on the F5 was;
- sometimes too detailled.
- mids a little bit too cold.

He preferred the Aleph X (more musical) mostly but it strongly depends of the recording you are playing.

Both are great amps.

[Nelson Pass]

I think your friend spotted the relative differences pretty
accurately, and of course one man's accuracy is another
man's "too detailed and cold midrange".

As to the Zener's, I don't think you need them, but they
won't hurt. probably.

[joho]

Yes, at this level it's a matter of taste (like good wine).