Electronics Headphone amp schematic

Anyone got a good schematic for a relatively hi-fi headphone amp?

I'm lazy, so a nice monolithic stereo amp IC would do nicely, but I'd be looking for about 200 mW per channel. Does anyone have a preference?

 

Here you go

One very good amp.

 

Plenty here to look at, and maybe feedback on some designs in the forums.

 

I've seen that design before and I'd still like to know what the heck Q1 and Q2 are for.

 

Q1/Q2 bias the opamp into class-A, meaning that the output transistors are always on so you reduce IMD significantly as the transistors aren't switching on and off constantly as the voltage swings +ve to ive

g

 

I see what you're saying but... the whole idea behind Class A is to bias the pnp and npn output transistors (or what ever output devices they use) to conduct full output current at idle. Assuming an EF output stage, that design will bias the npn transistor on only, which #1 will really mess with the linearity of the OS, and #2 if that constant current source cant sink enough current at high slew rates the pnp transistors of the OS will turn on causing switching distortion.

 

you don't bias to the current limit of the opamp, otherwise it would drop from class-A operation with any input, 1-2mA will do nicely. Taking the output to the negative rail biases only the NPN transistors, yes, but these are the faster of the two sets of transistors. You don't completely eliminate IMD but it's reduced.

g

 

A list of IC headphone amps: http://para.maxim-ic.com/compare.as...182,133990,133991,133992,133993,143102,143104
Why design a headphone amp from scratch when a semiconductor company already did it for you and put it into a nice, tiny package at the same time?

 

Dropping from class A would mean that the load would use more current than the idle current (active load in this case) and even though the input of the buffer is probably in the MΩ range or even the GΩ range... 1-2mA seems a bit stingy regardless if its first stage is fet based or bipoler based.