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Homebuilt Cmoy + Koss = Wahoo!

post #1 of 3
Thread Starter 
After much sweat, blood, soldering iron burns, sore typing fingers, and help from the helpful people in the DIY Amps forum, I finally finished my Cmoy Portable Headphone Amplifier. IT ROCKS.

Hooking it up to my McIntosh amp (thru the headphone out) and my Koss TD/70 phones, it makes them sound as good as my (dad's) Grado SR-80's without the amp (with the amp they have residual hiss due to their low impendance)! It adds so much more 'presence' to the sound (in the words of my dad, who was amazed when he heard it). Now my dad wants me to make him one! (Where can I get one of the Hansen PCBs?)

The Cmoy has a very nice sound, however because it's relatively difficult to build if you aren't exactly Apheared when it comes to electronics, I'd dock a few points, giving it mebbe a 9/10 or so.

Anyhoo, my dad was so proud he let me order the Etys from SageArts (How fast is their shipping?)
post #2 of 3
Eric, congrats on finishing the amp! I just saw your posts in the DIY Amps forum. It did not take you long to troubleshoot. When you get the chance, you might want to transfer the amp to a case with a true battery compartment. Then if you use the amp while travelling, the battery will not hit the board and possibly cause a short.

You can get the Hansen pcb direct from Carl Hansen. His email address is shown in the addendum of my article. (I wonder how many of these pcbs does Hansen have. He must have sold hundreds by now ). The more electronics DIY that you do, the easier it will get - although you will still have to troubleshoot circuits. Rarely does anything work on the first try.

As for the best headphones to pair with this amp, DIYers have created all sorts of variations on the basic design to go with just about any headphone. The OPA134 is an excellent opamp (see the article by Ben Duncan in the June issue of Stereophile.) With lower impedance phones like the Grados, configure the amp with a load resistor to reduce hiss. Also, try Apheared's 47 amp which is designed to drive Grados. If you are going to use high impedance phones (like the Senn. HD600) then use a power supply higher than 9V.

Great work, eric! Congrats again.
post #3 of 3
Thread Starter 
The battery is held VERY securely in place by a bit of rubber foam. This way it's nice and easy to change the battery (and I don't have to devise an elaborate battery compartment).
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