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needtubes 14th December 2003 06:27 PM

headphone amp in 9V battery case
Hello all-

I was trying to think of a good enclosure that would be ultra-compact and unique... and after a 9V battery blew up in my hand and I disassembled the thing I thought of using that...

It was a tight squeeze to get everything in, but I managed to do so... Pics and more about the amp are located here. Comments welcome


Does anyone have a suggestion for a good opamp to use with it? Power supply is limited to 6V (+/-3V) at about 5mA. Thanks

TNT 14th December 2003 06:36 PM

nice !

if you put the switch etc on the opposite side you could drive it with an other 9v battery. no cables just "mate" them if you see what i mean ...


carlosfm 15th December 2003 11:07 AM

Re: headphone amp in 9V battery case

Originally posted by needtubes
Does anyone have a suggestion for a good opamp to use with it? Power supply is limited to 6V (+/-3V) at about 5mA. Thanks

Very cute idea, needtubes!
The aswer to your question is simple: OPA2228.;)
Very good, BTW.

sek 15th December 2003 12:12 PM

You're challenging me, needtubes! ;)

I'm dreaming of a PiMeta in a 9V battery now. Additional two batteries for supply, beautiful cable between the three, perhaps arranged as a stable and neat looking "battery pack"...

Very nice work!


PS: I'm currently developing an SMT version of Tangent's PiMeta for a smaller-than-mint-can enclosure. But a battery... challenging! ;)

macboy 15th December 2003 06:05 PM

Both the NE5532 and JRC4580 (NJM4580) are suitable for driving headphones directly. Most opamps are not, as you have found. You would usually put a resistor in series with the output, but with such a low power supply voltage, you can probably omit it. Try it both ways I guess. The 4580 is spec'd for voltages as low as +-2 V, and the 5532 is spec'd for +-3 V. Texas instruments makes "clones" of both, and would probably be my first choice of a supplier (Their JRC4580 is a "RC4580").

Also consider using two batteries instead of one, so that you don't need to waste battery power creating a virtual ground using a voltage divider.

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