Another no overall NFB amp

[npnp]

Hello!

Here's my idea for an amplifier without overall NFB. Output power is about 35W @ 8 ohm.
Output stage is Hawksford E.C. topology.
VAS has a diamond structure.
DC servo circuit is taken from here.
Simulation results are promising.


Any suggestions are welcome!

 

[Bigun]

Looks very interesting. Is this to be operated in Class AB ?

 

[npnp]

Yes. Quiescent current is 50mA.

 

[AKSA]

A tour de force, no less.....

Have you built it, npnp? Does it sound sensational?

 

[npnp]

A tour de force, no less.....

Have you built it, npnp?

Not yet 😉

 

[ontoaba]

Does it sound sensational?

Buffered current amplifier.
OnlyC5200 & A1953 has linearity, and there is local feedback in pre-driver stage low linearity V->I conversion and some low linearity mirror gain.

 

[darkfenriz]

What's the current in VAS stage? I think you could reduce it while kepping the same gain.
Overally a nice schematic with a terribly overengineered servo 🙂

 

[bogdan_borko]

I made similar input (voltage amplifier) and it sounded lot better with 6dB feedback (taken from the VAS output) then with zero feedback...
Also tried (open loop) mosfet error-correction output stage but it can`t come near bipolar "simple" triple EF.😉

 

[npnp]

Buffered current amplifier.
OnlyC5200 & A1953 has linearity, and there is local feedback in pre-driver stage low linearity V->I conversion and some low linearity mirror gain.

According simulator nonlinearities is not that great (THD 0.02% @ 1kHz @ 30W).

What's the current in VAS stage? I think you could reduce it while kepping the same gain.
Overally a nice schematic with a terribly overengineered servo 🙂

Q8, Q17 - 1mA
Q5, Q19 - 2.5mA
Q9, Q16 - 7mA (to work permanently in class A mode)

 

[npnp]

I made similar input (voltage amplifier) and it sounded lot better with 6dB feedback (taken from the VAS output) then with zero feedback...

You're right 🙂
THD decreased twice!
Thanks!