Newby at chip amps, adding a headphone jack to a preamp

[Windcrest77]

Hi,

This is my first post here...

I want to add a headphone jack to a vacuum tube pre-Amp I'm building. Nothing fancy, but low distortion, I'll design the PCB to fit my chassis space, so a schematic would be cool too. How is LM380, LM386, LM1875, TDA7265, etc...? What stereo chip Amp has low THD and a simple circuit that will fit on a 64x64 mm PCB (sans power supply) and makes a fine easy headphone amp? Driving phones is easy so power is not an issue, I can do L Pad attenuation and matching of the phones to an 8 ohm chip Amp.

I just have no experience with chip amps at all, so hoping for some guidance to fast-path a foolproof headphone jack here, looking for a good chip for this application. I was at the headphone Amp forum, but decided I don't want to spend the time on somebody's discreet Amp design which may need troubleshooting. So I thought a chip Amp would be better here, more turn-key.

Thanks!

 

[NanoFarad]

You can try TDA2822M or Similar chip. Another good option is multiple NE5532 in parallel (Douglas self 5532 amp) but your PCB size isn't enough for that.

 

[tomchr]

The OPA1622 is intended for that exact purpose. It's hard to solder by hand but the evaluation kit for it is quite affordable. I'd add a buffer before the EVM, though, as it has pretty low input impedance. That's what I do in the HP-22: https://neurochrome.com/products/hp-22

Tom

 

[Mooly]

You can try TDA2822M or Similar chip.

I'll second that, they are surprisingly good.

Lots for sale I see as kits and boards, just do a search for TDA2822 headphone amp. I built one ages ago using a Maplin PCB. I still have it in a drawer for testing stuff, runs off 9v (PP3). What more could you want.

One practical point, be sure to protect any input (and this applies to any solid state/chip device) from possible high voltage spikes from any non terminated output coupling caps in your valve preamp.

 

[Windcrest77]

The OPA1622 is intended for that exact purpose. It's hard to solder by hand but the evaluation kit for it is quite affordable. I'd add a buffer before the EVM, though, as it has pretty low input impedance. That's what I do in the HP-22: https://neurochrome.com/products/hp-22

Tom

Thanks Tom! It was me that just bought a copy of your HP-22 board yesterday.

 

[tomchr]

Fantastic. Thank you.

Tom

 

[No ideas]

I'll second that, they are surprisingly good.

Lots for sale I see as kits and boards, just do a search for TDA2822 headphone amp. I built one ages ago using a Maplin PCB. I still have it in a drawer for testing stuff, runs off 9v (PP3). What more could you want.

One practical point, be sure to protect any input (and this applies to any solid state/chip device) from possible high voltage spikes from any non terminated output coupling caps in your valve preamp.

100 ohm output resistor
EDIT: ok maybe 100 ohms is too much but i would recommend an output resistor when driving headphones with a chip amp