Here some quick pictures of a recent project. This is a pretty modified DDDAC1543 (16 instead of 8 parallel DACs), sporting custom power regulation for the XO clock, as well as several other circuit modifications over the original design. The most obvious one is the direct headphone output (i.e. the headphones are directly driven by the DAC, no opamps, no tubes, nothing but a pair of blackgates beween the DAC output and the Neutrik jack. There's also a stepped attenuator that is outside of the signal path, which doubles for headphone and line-out volume control. The DAC is essentially a passive preamp for the digital sources, although it's a little loud for that right now - I will need to add a toggle with a single high grade series resistor to match my amps better. That'll be in the next build which will also have a modded M-Audio USB input inside the box. The thing plays for well over 18 hours before you need to recharge (8 hours for a full recharge). Just about all the components used are highest grade available: Silver wiring, Stillpoint ERS paper lining, Auricaps and Blackgate N/Nx caps, etc.
Sorry for the big pictures - there'll soon be a web page with more info and with big images linked from thumbs
Finished DAC:
Inside:
The Elma switch 24-step stereo attenuator - just because it looks so cool
Backside - top left are the main battery and charger connections. The weird plug below came with the enclsosure and powers the fan only. Inputs are toslink and SPDIF via proper 75 ohm Neutrik BNC connector.
18ah SLA battery with smart charger: you'd never know this thing runs on batteries. Portable? No
This is the batch I built for a few head-fi'ers - no, there are currently no plans to do this again. This thing isn't cheap (over $600 in parts alone), and the time that went into each of them.... don't ask.
Anyway, folks with AKGs need not apply - this thing won't drive them. Works fine on Sennheiser 650s and Grados and other less difficult to drive headphones.
Peter