Fully Differential Headphone Amplifier

Simulation using LTspiceXVII and OPA1656 @48kHz
 

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The "VUELO" schematic calls it a Fully Differential Hybrid Amplifier but doesn't mention headphones at all. Maybe the title of this Forum discussion is incorrect?

I checked mouser.com to see whether C2 and C4 (245 pF) were in stock. Unhappy news: Mouser doesn't even have a part number for those capacitors. You'll have to buy them elsewhere (attachment below).

What's the advantage of connecting resistors R23 and R24 (each are 741Kohms) in parallel as shown here? Why not simply use one 370K resistor instead? With 15 volt supplies those resistors can't possibly dissipate more than 2 milliwatts; cutting the power dissipation in half by installing two parallel resistors seems unnecessary ... ?

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ideal op amp infinite input resistance
But yours Vuelo have 1k input impedance, and resistor tolerance aren't specified, so probably you need at least good-CMRR input based on something like LT5400 or put any instrumentation opamp as good-CMRR input.
Next you need to have a volume reg.
And last will be your Vueno in single-ended input config.
So what's the deal?
 
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They have found their place on the trannies graveyard.
FQT5P10/FQT4N20 pair are matched for transconductance and can be used in headamp output follower.

Perhaps you should look closer at the schematic for those 'really nice audio grade mosfets'

Truly appreciate Dr. Vossen at Berkeley ;]

And perhaps rethink Profusion PLC ECX10N20-S and ECX10P20-S

:boggled::boggled: