QRV-02 - The high performance headphone amplifier with multiple feedback

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I designed this amplifier as a result of reading postings at HeadWize. The forum is I'm afraid closed down.

I call it "underkill amp" or "Cmoy deluxe". The performance is outrageous in headphone amp terms. See the technical data!

Interesting features:

1. The pcb fits virtually any single opamp with or without offset trim.
2. Room for good coupling caps (if you must or like)
3. Input LP-filter if you have problems with RF interference (you should have a filter though).
4. Room for DC removal cap (if you need this).
5. Crossover distortion reducer for the opamp.
6. Current limitation inside the feedback loop (choose the value you like)
7. Local feedback for stable performance (only if necessary)
8. High quality power supply with large smoothing caps. No transformers on the pcb.
9. Fits any headphone (except for electrostatic of course).

My design goal was to make a simple but well balanced amp in terms of component choices and a well-tested topology. The amp needs only high quality industrial parts in order to work good. No special (or odd) audiophilic parts are needed but if they fits, no harm in using them as long as they have minimum performance in electrical terms.

The amp works in class A as much it's possible.