To help kickstart the thread, here is my little headamp that is still waiting for the 3D printed case I wanted to make months ago.
Definitely lot's of things to improve when I look at it now, but overall it works flawlessly (and has been for a year almost). Considering it was one of my first projects, I am pretty satisfied. It's a dual OpAmp in non-inverting configuration, followed by OPA1622 configured as a buffer and everything is powered by LM27762. The switch controls OPA1622's enable pin and everything is mounted on a 4-Layer board. Yes, the coupling caps are too big for the footprint (which was meant to also accomodate SMD film caps). Yes, voltage swing is limited because of USB specifications, voltage drop in the LDOs and the input protection Schottky. And yes, due to the buffer configuration of OPA1622 the capacitive load drive with acceptable phase margin is also limited to around 500pF. I still like it 🙂
Definitely lot's of things to improve when I look at it now, but overall it works flawlessly (and has been for a year almost). Considering it was one of my first projects, I am pretty satisfied. It's a dual OpAmp in non-inverting configuration, followed by OPA1622 configured as a buffer and everything is powered by LM27762. The switch controls OPA1622's enable pin and everything is mounted on a 4-Layer board. Yes, the coupling caps are too big for the footprint (which was meant to also accomodate SMD film caps). Yes, voltage swing is limited because of USB specifications, voltage drop in the LDOs and the input protection Schottky. And yes, due to the buffer configuration of OPA1622 the capacitive load drive with acceptable phase margin is also limited to around 500pF. I still like it 🙂
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I'm going to regret posting:
19 years ago I had a career in portable concert recording. I did not always have a "booth" so I used headphones for quality checking. The onboard phone output on recorders is usually very lame around live performances. I built a 400mW class-A phone amp to fit in the gig-bag. Just for me, not dressed to impress. Worked great. But ran HOT!! So it named itself. I had calculated, but numbers are not the same as laying your hand on it between movements.
19 years ago I had a career in portable concert recording. I did not always have a "booth" so I used headphones for quality checking. The onboard phone output on recorders is usually very lame around live performances. I built a 400mW class-A phone amp to fit in the gig-bag. Just for me, not dressed to impress. Worked great. But ran HOT!! So it named itself. I had calculated, but numbers are not the same as laying your hand on it between movements.
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Look really nice!
Do you have problem with the lm27762? I design a power supply for headphone amp around the lm27762 too, the first time, negative side doesn't start up well, it stuck at -2V, i need to use a long usb cable or put 1R resistor to the input 5V to make it work. But after that, when load current is increase ( power 1 opamp opa1688 at 1Vrms at 32R, mean about 70ma load current) the power supply buzzing very loud, it's kind of 17,18khz frequency. At smaller load, it still buzz but it's quieter.
Four "creatures" I've soldered so far:
1st - Marsh headphone amp with integrated B1 buffer
2nd - Marsh with a small box on top- Class A single Mosfet "buffer" HPA
3rd and 4th the famous WHAMMY
5th - temporarily without enclosure - High speed HPA from Bruno Carlsson
1st - Marsh headphone amp with integrated B1 buffer
2nd - Marsh with a small box on top- Class A single Mosfet "buffer" HPA
3rd and 4th the famous WHAMMY
5th - temporarily without enclosure - High speed HPA from Bruno Carlsson
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Translation: Its own wiring, but very good. close to the author'sОбратите внимание, это англоязычный форум.
To be honest I didn't have problems with LM27762, not that I know of. Since current draw is very low, most USB powerbanks shut off. That is my main problem. But that isn't the LM27762's fault and there are ways to fix that. I will probe around LM27762 and let you know if I find anything suspicious. You can also ask TI directly in their forum about your problems.
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Thanks! I look around TI support and seem like they are very active but not helpful at all, everytime they just refer to their EVM.
I started a build of this amp,but then I lost my mind.....
So many and so small components.
If anyone wants it I´ll send it to them....🙂