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A Pocket Headphone Amplifier
A Pocket Headphone Amplifier
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Old 9th October 2005, 12:25 PM   #1
Mad_K is offline Mad_K  Norway
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Default A Pocket Headphone Amplifier

Thought I'd share my newest creation; my portable headamp in Chu Moy style:
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Old 9th October 2005, 12:26 PM   #2
Mad_K is offline Mad_K  Norway
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Here is the inside:
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Old 9th October 2005, 12:30 PM   #3
Mad_K is offline Mad_K  Norway
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And finally, the schematic I ended up with:
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Old 9th October 2005, 12:41 PM   #4
Leolabs is offline Leolabs  Malaysia
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Old 9th October 2005, 12:46 PM   #5
Mad_K is offline Mad_K  Norway
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It is intended to be used with my portable CD-player and my Sennheiser PX-100 http://www.sennheiser.com/sennheiser...nsf/root/05206
(32 Ohm, 114dB)
My first incarnation of the psu was like Chu Moy's two 4K7 rail splitting resistors, but the rails collapsed (not surprising, really) when i started playing loud music with high energy passages. This was not aceptable, so after a little pondering, I used the dual opamp virtual ground driver as drawn in the schematic. Now it simply clips like any other amp when it hits the rail limit. This happens at far louder volumes than I like to listen to.. I delivers a clean 0,5VRMS into my PX-100's, that should be (according to the datasheet) 108dB!

The sound is more dynamic, with more air and detail, when this little amp is plugged in between my cdplayer and the headphones.
A friend of mine also tried it with his Creative ZEN mp3 player and was pleasantly surprised
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Old 9th October 2005, 12:56 PM   #6
Mad_K is offline Mad_K  Norway
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The DC offset is 0,1mV on both channels due to the extreme DC-precision of the OPA2277. The PCB I used is originally designed for my MM phono preamp, but I have found it to be very useful for linear applications as well. You can't really see it from the picture, but the second OPA2277 that creates the pseudo-ground is soldered on top of the one that is soldered to the PCB
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Old 9th October 2005, 12:57 PM   #7
Mad_K is offline Mad_K  Norway
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Quote:
Originally posted by Leolabs
nice

Thanks
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Old 9th October 2005, 01:22 PM   #8
Mad_K is offline Mad_K  Norway
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I just listened to Black Label Society;Mafia;Fire It Up.. Man, what a energy rush!

Does anybody know how many mAh a 9V battery is rated?
I wonder how may hours of operation I will get from it. As I have done what I can (design-wise) to minimize current draw, it depends mostly on the power output.
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