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also how will I bypass the amp inside to just use the DAC?
From what I know, you can't. Even the RCA output at the back go trough the amplifier. And since audio-gd has an unconventional way of building amplifiers and DACs, you can't just go in and bypass stuff. For starter, all the signals before the amplifier are kept in the current domain, as opposed to the conventional voltage signals. I think even the filters between the DAC chip and the amplifier works on current signals. The volume potentiometer is used as a variable resistor to limit current, as opposed to a voltage divider to attenuate a voltage signal.
But honestly, it's not like it's a bad thing. Even the most over priced stand-alone DAC usually use Op-Amps on the analog outputs. Take for example Calyx DAC, it goes for 1800$, uses ES9018 Sabre DAC chip, and a bunch of NE5332 Op-Amps for the analog output. As long as it sounds great and works, why care about it? Using an amplifier between the DAC chips and the analog outputs serves to protect the DAC chips if nothing else.
As for filters, I've been using the 4X oversampling , Minimum phase 'soft-knee' filter ever since I received the unit, but last week I switched to 4X oversampling , Linear phase 'brickwall' filter. I noticed better treble extension, aka less treble roll off. There seems to be something different to string instruments, but I just can't quite explain it. It just sounds different. I used the soft knee filter because it tamed the treble on my cans and gave them a more "comfortable" sound. Now that I also have a tube amplifier, I thought I could use the better treble extension, if only to widen the difference between the NFB-12's headphone out and the tube amp. I enjoy changing things every once in a while, to keep them interesting. Though I don't have the switches to change the filters on the go, I bought some switches to hack on the case. It's still on my to-do list though, as I can't make up my mind as to how I should mount them without ruining the aesthetics.
Ah and just for fun...
The Hammond 1455T2201 enclosure fits perfectly on top of the NFB-12:
If you guys think the NFB-12 gets hot, you should try a Starving Student. Just look at the heat sinks needed for this thing! It gets so hot I can use it to keep my tea warm. The MOSFETs alone dissipate 20W of power as heat. The whole thing gets so hot, it actually makes the NFB-12 bellow it significantly warmer.
And here it is, at the Montreal August 2012 meet. I did get questions regarding the artsy breathing holes.
