Erm... 🙂 I think its a little bit power hungry for headphone use. The concept is fine but I would look at what voltage levels you really need across your headphones (could be just a couple of volts if they are efficient) and perhaps scale things back accordingly. Empirical testing can be good too. Set a limit of say 80 milliamps and alter the values to give that and see if that gives you enough volume.
That would be my first suggestion 🙂
That would be my first suggestion 🙂
make the 22ohm resistor 32 ohm? it was supposed to be a thing to get some extra volume but it looks like i went a bit overkill
looks to be working fine at 15V also the 2nd harmonic is huge. thats why i dont like mosfets. yet i ended up with a pair
i also found an even better solution. just stick an op amp in, and maybe even use a bjt becuse bjts dont have an gate charge
The opamp version will certainly be better on paper but does it sound better? or worse? You might actually prefer the less perfect one.
Gate charge shouldn't be an issue at low frequency (and audio is all very very low frequency in the scheme of things) but MOSFET's do have a major downside on low voltage supplies because of the high gate/source turn on voltage.
Gate charge shouldn't be an issue at low frequency (and audio is all very very low frequency in the scheme of things) but MOSFET's do have a major downside on low voltage supplies because of the high gate/source turn on voltage.
the thing is that the distortion is really significant. lets built it out and see. i also have a bjt version.
In your first version the bias seems wrong, at least for my model of the FET 🙂
Try this one (attached).
Try this one (attached).
You need to bias the FET to give around half supply voltage on the drain so that the output can swing equally in either direction. Gate voltage (its actually the gate to source voltage that matters) is very imprecise and can not be used to set a bias point.
I don't believe you need a big MOSFET like the IRFP240 to drive headphones, and a smaller FET will have a smaller gate charge.
This is almost exactly like my first ever amplifier, only I ran at 12V. I really did enjoy the sound of it in my 32Ohm AKG's, very rich full sounding but in more fast and complex music didn't hold up as well.
I'd recommend using a pot to set the bias and just build it! its a fun easy little amp to enjoy and learn from!
Ow just make sure you use power resistors for R2 and heat sink the FET 👍
So you have a your own design or someone else's design? it is unclear. If you need help or are unclear about anything don't hesitate to ask as I am happy to help with anything I am able to. But please don't loose sight of what all this is about, fun, enjoyment and DIY. whatever makes you happy.