Musiland 03 I2S to Buffalo II DAC: Playing 352.8Khz Music
Hurray! I can pass 352.8K Music to the Buffalo II DAC. Even with the limitations of the older 80MHz Buffalo II, I was able to hear super clean music by optimizing some of the parameters in the DAC. Here is proof:
Downloaded a 24bit/352.8K file from 2L
(Photo of artists taken from: http://www.flickr.com/photos/arvola/5692730311/in/photostream)
Played the file with MusicBee (to allow automatic switching of sample rates through WASAPI exclusive mode). Notice that the sample rate is measured to be exactly 352,800 hertz.
CLICKS and NOISE with 352.8Khz FILES
There is absolutely no underlying noise when playing the track, except there is an occasional “click” sound. The clicks are very short, low volume, sort of like a static “click”. Reminds me of the clicks when playing analog LPs. This was somewhat due to the wiring configuration I used. When I twisted the LRCK and DATA lines together (in addition to having previously twisted the BCK and GND lines), the clicks were largely reduced. In the above track I couldn’t hear them. In another solo piano track, the clicks were also gone.
The other factors in getting rid of the clicks are the settings for the DAC. I used the slow FIR filter and 8-bit true differential in the quantizer setting.
Strange noise: when the track is paused, stopped or during the gap between songs with the sample rate remaining at the high rate (352.8K), the DAC will emit a loud hissing sound. The level and tone of this hissing sound changes with the DAC digital volume setting with some setting giving more volume than other settings but not related to the amount of volume attenuation. In addition, FIR sharp filter results in a louder noise than the slow filter. The quantizer bit depth also changes the amount of noise coming from the DAC. The IIR filter and the notch delay don’t seem to have any effect.
The situation can be replicated if you digital reduce the volume to zero using the volume control of the application, the OS or the device driver. If the volume is reduced to near zero, clicks and cracks noise will emerge.
Because of some of these issues related to rendering ultra high sample rate files, The Buffalo II DAC was upgraded to 100 MHz clock.
Unfortunately I was not able to get drop-free play with the DPLL setting at “lowest”. The level of jitter (as determined by the DPLL setting) seems equal to the modded Musiland MINI. Keep in mind that I disabled the power to the analog section and replaced the regulators with low noise types in the MINI. The Musiland 03 is in stock form with the analog power section intact. So overall, there could be some improvements with regards to jitter.
Although disappointing, this level of jitter is expected as the FPGA has an inherent minimum amount of jitter when processing the clocks. Similar levels (as indicated by DPLL setting) have been reported with different USB interfaces.
Personally, this “quest” for lowest DPLL setting is pretty much “academic diy” as I hear no differences in sound with the different DPLL settings. In addition, one of my goals is to keep the headphone amp so removing the power to the analog section is out of the question.
Note: for 352.8KHz material I set the DPLL to “BEST”
SAMPLE RATE PRECISION
As seen in the display above, the sample rate generated by the FPGA is pretty much exact. The Musiland MINI had a variation of 4-5 Hz for 44.1K material. This is probably due to the fact that 24Mhz oscillator is used instead of the 24Mhz crystal that was used in the older models.
I paired BCK with GND and twisted the wires to provide some shielding. The Buffalo locks to BCK
The wires are probably much longer than they need to be in this first iteration. LRCK and DATA are just single wires with no shielding. Even with this “rudimentary” setup, I did not experience any noticeable problems such as noise or dropouts.
Update: I also twisted the LRCK and DATA lines together and the occasional “clicks” went away…
Al in all I am very happy with this device. Just as the Buffalo II sets a price/performance benchmark for high-end DACs, so does the Musiland 03US set a price/performance benchmark for high-end USB audio interfaces. On top of that, you also get a good headphone amplifier and another DAC