Portable 3-channel CMOY with 200 mAh Ni-MH battery and recharcing circuit, plus thumbweel volume...

I took smallest case I could find for this project, 3xAA battery holder with switch.

The circuit is CMOY with Buffered Virtual Ground. Op amps are OPA2132PA (40 mA output current) in left and right  and TLE2082 on ground (160 mA output).

There is 10K thumbwheel volume control and 3.5 mm input and output jacks.

3.5 mm DC plug to recharging circuit that is LM317 CCS set to ~20 mA trickle charging the 200 mAh 9V battery  in 10 hours.

Playtime is with 10 mA Iq 20 hours.

Input caps are plastic

Gain 3

Case is sealed with hot glue which mean that you cannot change op amps or the Ni-MH battery very easily. But that shouldn't be a problem because long life of Ni-MH and nice op amp choices.

EU style 230VAC->17VDC wall wart provided. That is not regulated which would be preferable.

I can ship worldwide but buyer pays the shipping. Located in Finland

Payment with Paypal or bank transfer

Price is 40 €.

PS. Support beginner DIYer!

Dimensions

69x48x18,5 mm = 2.72"x 1.89"x 0.73"

Unknown (generic) battery case. Very solid plastic. If it falls right into the switch then it might brake, but I think it is otherwise very sturdy.

This amplifier has similar sound quality than 150$ amplifiers.

Why pay more than this, for such basic wire-with-gain principle?

The signal path in this amplifier is like this

-> 10K volume control -> 0.1 uF polypropylene capacitor -> input resistor to ground 150 Kohm -> OPAMP -> headphones

Solder joints are all shiny.

I have used this amplifier on bus trips and I noticed that it doesn't take interference from cell phone networks or anything. Very short, as short as the SMD resistor, feedback loop ensures that there is very little possibility for RF interference to catch up.

OK this was sold locally in Finland.

I can build custom amplifiers for anybody who is interested in quality sound but at lower prices. PM me!