Nicely done Brian!
Yeah, AMB's workmanship are top notch! I know he likes FrontPanelExpress and it looks like he used one of the Chinese enclosures for the base instead of a Pars. Very Clean! Been really meaning to ask where he gets his boards done because they seem to be reasonably priced and fantastic quality. I have been using the SeeedStudio or BatchPCB service ad while nice are no comparison to the beauty of those AMB boards.
You might want to seriously look into using one of the I/O expander ports and connecting in to the TPA Buffalo or Opus to enable the digital filters. The code is simple enough, but an easy connection module would likely do a lot to make it easy on the non-coders.
If you want to do an android app that controls over Wifi, let me know. I can certainly get a good start on that since I have been wanting to do it for AMPs?DAC's to converge everything.
Another possibility of a cool module is a set of digital potentiometers that could snap in for the trim pots in the AMB designs. Use an A/D tied in with voltage tolerance so that you could have a dynamically adjusting amplifier. This would be VERY cool for the Beta22 for those of use using it as a low-imp, high-imp, and speaker amp - plus it could account for drift. This board could have helped when my left amp board blew and caught fire (same spot as a few other people). It would be insurance that also ensured the best possible SQ.
All the Best man! You certainly do keep up the good work!
The Spec issue.... yes I understand. Most of the time, audio is not limited by the hardware, but by the software. You need to remember that every bit of mastering takes something out, especially in the digital game. God forbid though to many audiophiles that you use software to your advantage to fix something. I mean, do you think that PSA or Meridian is NOT using software to make it sound better? C'mon.
There really is no need to use the 0.1% or 0.5% resistors in many cases and a LOT of the audio game is all about overkill. I can see how someone may really want an R-2R ladder if you want to make a custom set of impedances, but why not just go with one of the REALLY nice digital pots from TI or Maxim? Most are SPI and the ones that use digital serial are pretty easy to make your own interacting protocol (done it). If your amp draws 2A, why always make PSU's with 50 filters and running up to 15A? There are a Million headphone amps doing this right now and someone put it in their heads that because a headphone amp that only needs to drive at most 100mA/channel should be using an 1amp or more of power. Some have also forgotten that simple is sometimes the best and that a clean, accurate simple circuit will beat an overly complicated design any day (tube and hybrid designs show this all the time).
Headphones do show the details, much better than speakers do. I have the Stax, CD3K, and the AKG's (had the HD580's - just were not my favorites). in those cases, headphones are extremely sensitive to noise floors and ground loops (however small) because of the sensitivity and well, just how intimate your head is with the transducers. Only really use them at work now though...
Still, keep working at it!