"KiwI" compact CMoy based headphone amp
May 6, 2015 at 8:43 PM Thread Starter Post #1 of 1

mwhouston

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I had a request from a Kiwi friend to make him a very compact and light headphone amp for his super expensive in ear buds and noise cancelling BOSE headphones. He travels regularly back to New Zealand to visit family and loves his music. I have made many headphone amps both portable and home based but he through down the gauntlet to build compact and light. Most off all it had to drive his phones well and sound good. The plane sound system didn't drive his phones well and was very thin.
 
A CMoy knock-off seemed the way to go with the usual Houston twist. No exotic parts here, no room. The OPA2134 is my chip of choice and will work down to +/- 2.5V. Perfect for an amp which could only house one 9V battery. Whiel we are talking of batteries my mate, Bill, tried the amp with various fresh batteries and found the more high powered and expensive the battery the better the sound and longer the play time. He should get 50 hours + even on cheap batteries. The differential PS is also built onto the cct. brd. The enclosure is lined top and bottom with bitumanised heavy Al foil to control resinance and to add some RFI\EMI shielding.
 
As usual I made the amp on prototype brd. all silver soldered, silver plated hook-up wire and a socketed build. A faint LED indicates "on" and I presented to him in a tight fitting black valvet slip. I also made him the inter-connect from plane to amp. This was also made from three strands of thin silver plated wire, hard twisted. Definitely no shielding to dull the sound. There are two earth wire but only one is connected at the destination end. Gold plated 3.5mm phone plugs were used and again silver soldered. Heat shrink covers the fine wire and doubled at ends to act as a strain point with the springs for the plugs.
 
The two-tone ABS enclosure looks understated and smart. Bill used the amp on his New Zealand flight with the BOSE and said it work perfectly. I have since made myself one. It is a little bigger than the palm of your hand and weighs 153gms with battery.



 

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