I have now had my Grant Fidelity Tubedac-11 for a few days and I must say I'm very impressed with the performance and how much dac / pre-amp this is for the money. Nice build quality and quality feel. The sound is transparent and the dynamics and signal-to-noise ratio impressive. The background is almost a dead quiet even with the volume at max level. I was a bit worried about the high 6V RMS output but thanks to the non-linear volume control this causes no problems (I have tried different power amps with input sensitivity between 0.5 to 1.4 V). The volume pot feels very nice as well.
The only negative I've found is that it emits click noise when switching between songs that have different sampling rate which is a bit annoying and that the DAC fails in the intermodulation test below:
If you're curious about the performance of your own system, the following samples contain a 30kHz and a 33kHz tone in a 24/96 WAV file, a longer version in a FLAC, some tri-tone warbles, and a normal song clip shifted up by 24kHz so that it's entirely in the ultrasonic range from 24kHz to 46kHz:
30kHz tone + 33kHz tone (24 bit / 96kHz) [5 second WAV] [30 second FLAC]
26kHz - 48kHz warbling tones (24 bit / 96kHz) [10 second WAV]
26kHz - 96kHz warbling tones (24 bit / 192kHz) [10 second WAV]
Song clip shifted up by 24kHz (24 bit / 96kHz WAV) [10 second WAV]
(original version of above clip) (16 bit / 44.1kHz WAV)
Assuming your system is actually capable of full 96kHz playback, the above files should be completely silent with no audible noises, tones, whistles, clicks, or other sounds. If you hear anything, your system has a nonlinearity causing audible intermodulation of the ultrasonics. Be careful when increasing volume; running into digital or analog clipping, even soft clipping, will suddenly cause loud intermodulation tones.
I hear noises in all the above tracks, noises that I suppose should have been filtered out by the DAC...
Because of this I have to restrict sample rate to 44.1 KHz in the software player (Audirvana+). If the DAC can't handle samplerates correctly, then the feature becomes pretty useless...
Then I wonder if anyone knows if you can just disconnect the tube because I believe that the tube does not add anything but noise and literal warmth.
Edited by WinstonOboogie - 6/27/13 at 5:55am