transistor ?

[AudioFreak]

The capacitance of the Mosfet is an issue for
two reasons, first because (of course) it will
limit the high frequency bandwidth given a
particular source impedance. This is not a big
problem, but must be considered.

More importantly, the capacitance of the device
varies with voltage, and this creates non-linearity
at high frequencies.

The capacitance of the Mosfet is the reason for using
fairly low impedances in the input networks of the
original Zen amp.

You might think that paralleling devices exacerbates
the capacitance effect, but this is compensated by
the increased transconductance, and is not such a
big problem until you parallel LOTS of devices.

Does the X-1000 output stage classify as LOTS of devices? 🙂 What did you do to compensate?

 

[Nelson Pass]

I believe we could classify the X1000 as being
on the edge with 4 banks of 20 parallel devices
per channel.

Compensate? HAHAHAHAHA

 

[AudioFreak]

OK, let me reword my question... did having so many devices in parallel cause a capacitance problem?

 

[Nelson Pass]

Not really. The X1000 and X600 simply have
more current going through the front end, so
the capacitive effects are minimized. Also, it's
a simple circuit with minimal feedback (none around
the output stage) and isn't trying to be particularly
fast anyway, so it came out about the same speed
as the smaller amps, which is a slew of about 40 V/uS.

 

[PassFan]

ON THE EDGE

Nelson:
You really enjoy extremism, and I admire that. Amps that drive .1 ohm, 4 banks of 20 parrallel devices. Your like the mad scientist all locked away in a room stirring the pot. It's refreshing, and fun for all of us. Thanks🙄

 

[AudioFreak]

Thanks Nelson....

 

[Nelson Pass]

You're welcome. It's a lot of fun.