Post by Steve Deckert on 02/29/08 at 19:21:45
If you recall back in October I gave a sneak peak at the protoype Decware personal headphone amplifier.
Well received, but it had issues driving certain headphones and I really wanted it to work well with almost anything. Turns out the capacitance vs frequency of some phones, or even the phone cords created a condition where the voltage rails would become unbalanced leading to premature clipping. Even though this only seemed to happen on 2 sets of phones - I've only tried it on 20 different pairs so to me that's a potential incompatibility factor of 10%.
I redesigned the power supply portion of the circuit to include regulation from the 120+ miliamp BUF634P buffer chip by Burr Brown which turns out to be almost impossible to find. (Lead times on this chip are running 28 weeks. Meanwhile you can pay up to $45.00 each for them from you favorite parts brokers.)
This had the desired effect in keeping the rails steady under adverse conditions and dropped the current draw significantly since the virtual ground reference is now 10 times it's prior value. So battery life is likely to improve beyond the 50 hours it had been.
Probably not so surprising is that it also improved the fidelity by an obvious amount.
Anyway, here is the final result, and I've renamed it ZEN HEAD for Zen Headphone amplifier
And the link: https://www.decware.com/newsite/zenhead.htm
We hope you like it!
Steve