Hybrid tube/MOSFET headphone amp

[davygrvy]

Hi,

I was messing around in SPICE and think I solved the PSRR problem with a white cathode follower using depletion-mode MOSFETs. I appear to have given it a 26dB improvement.

Is it elegant or another lame-o dud?

The top jfet gets the current sense relative to the supply and send it to the bottom one that inverts and adjusts for matching swings.

 

[davygrvy]

Here's a slightly different one that can bring a 25 ohm Denon AH-D2000 to its full 1.8 watts.

I changed the VAS p-device to a Supertex VP0550 which allows the I-to-V resistor to be larger as the D-MOS turn-on is much higher. This gives much more open-loop gain. Each output device dissipates just 900mW at full load or 1.3W at idle.

 

[davygrvy]

That CCS with the LND is superfluous

 

[davygrvy]

PSU will look something like this using a Hammond 12.6VAC or similar TXFMR

 

[hpeter]

i like how its done. +1
been thinking similar but with semelabs lateral

 

[davygrvy]

Those are enhancement mode. I guess you could do white cathode follower with them, but it won't self-bias

 

[hpeter]

triodes are like self fb, plate is signal out, but at same time could be used as fb input.
when triode is working into opt, that´s easy.
how to make it work in other schemas..quite hard

 

[davygrvy]

Interesting.. A small change to get the bottom biased, and this might just work.

Possibly not tempco stable, though.

 

[davygrvy]

Ooops, Semelabs... sorry.. The spice I did for the Semisouth power SiC JFETs. I was wondering why you asked about.. give me a few moments. a BUZ900, okay?

 

[davygrvy]

For a BUZ901P. I like it