For David Eather et al: some "Simple Headphone Amp" ideas

I think the game here may be to design a low-parts-count amp using discrete parts.

And hardly anybody wants to play the game. Talk, talk, talk, and no circuits.

John

What about this...

Simple headphone amp... view with fixed-width font...

.-2.2u--*----< + 24V regulated | | (must be clean) 220K 47 10W (about 300mA, 500ma at powerup) | | >--2.2u--22K--*-220K--*----470uF----. input | | | (bias) | |--' load (32-100 ohms or so) .--82K--*---||

Is it okay to feed the input into the cathode of the zener?

John

No :-)

The zener is just there to keep static from zapping the gate, not really part of the audio circuit. The input must be R+C coupled to the gate for the negative feedback loop to work.

Terry

Okay, I see. I should have estimated some voltage levels. I now see that the zener is biased below its knee.

Cheers, John

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KLA is participating in the DARPA nanowriter project if you want to read more about the rapid e-beam.

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Hmmm. I thought that all the common mosfets were lateral. 30 to 40 = years ago Yamaha has some vertical power mosfets but they seem to have pretty much disappeared since. Of course, i am talking about the orientation of the conduction channel, not whether/how the current flows through the = bulk material.

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I don't get your comment. The current flows in the channel, so how are these cases different? Look at the cross section of a hexfet.

Backwards. Lateral power fets are rare nowadays.

John

Nice little circuit.

The upper 220K could be tuned to null out power supply ripple.

You probably don't need the zener.

John

Thanks :-) but strictly for audiophiles who don't mind consuming 12 watts to produce about a watt output max. Until it gets to clip the distortion products are almost entirely 2nd order (according to LTspice) so it should sound quite "tubey".

I liked your choke-based design... more efficient, cleaner. And bigger! but would have to avoid turning it on with headphones connected (or use time-delay relay or something). Antique Electronic Supply

has some output transformers with 32 ohm secondaries that would probably work fine for the inductors.

Hmm didn't think of that... main function is to hard-bias the mosfet to avoid a huge pop when charging the output cap, which is rather large to be fairly flat down to 20hz.

Unless it has external input wires... fet gate spec'd for +/- 10V which might be exceeded by noise/surge input.

Terry

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Read my post more carefully, cowboy.