Amanero Long Term Measurements (I)
Here are a couple of measurements for the Amanero USB board that I did for many hours. I also measured the Musiland 03US again for comparison.
- Measurement consist of counting the number of unlocks per 10 minute interval for several hours
- Connected to the Buffalo II DAC with 80 MHz clock in asynchronous operation and DPLL set to “LOWEST”
- 44.1KHz sample rate music continuously being played with the latest version of iTunes on a Windows 7 Laptop
- Capacitor mods applied (100 uF added to the input capacitors of each of the two on-board regulators) to the Amanero board
The first chart records the unlocks from the late night to early morning hours (click to enlarge):
Since I had removed the putty on the Crystek oscillator since I did the Musiland tests, I decided to put some mechanical isolation under the feet of the DAC case. I used pieces of gel insoles (those used for shoes).
Here are the results:
For comparison, I measured the Musiland 03 again under similar circumstances:
Note: the “burst” of unlocks in the middle of the night for the Musiland device is likely due to some “unusual event” not related to the normal working of the Musiland and BII DAC.
I also compared the power-on behavior for the Amanero-BII by consolidating the results of the 4 tests I did for the Amanero board, 1 new test for the Musiland board (Musiland 2) and the last test I did for Musiland device:
- Initial unlocks are pretty “well behaved” and likely relates to settling time of the clocks on both the BII and Amanero boards. The capacitor and isolation mods don’t seem to have any effect during this time which further indicates that the unlocks are caused by internal disturbances and instabilities during power-on/warm-up.
- A long stretch for several hours with zero unlocks is definitely possible with this board. This indicates that unlocks outside of this area (and with the exception of the war-up period) seem to be caused by external disturbances such as electrical and mechanical noise.
- I did not do a long term test without the capacitor mod (too impatient to try modding the board :-)), but I do believe the board responds well to this mod.
- As the second long term test shows, adding mechanical isolation also seems to help reduce some of the unlocks.
COMPARISON WITH MUSILAND
- During warm up, the Amanero board settles at a faster rate compared to the Musiland board. The multiple tests show that each board has a “signature” warm-up behavior.
- Perhaps the lower complexity of the Amanero board allows it to “settle” faster than the Musiland device.
- The Musiland looks cleaner (less unlocks) after the warm-up period. Notice the number of unlocks during the morning hours.
- Around 4:30 AM I was awaken because the volume had increased from around -60 db to -35 db …by itself! The IR sensor/Arduino got affected to such a degree that the software thought a valid code was generated by the IR receiver (the code only responds to valid codes). During that time, the DAC experienced a series of unlocks as recorded in the graph. I would consider this an anomaly and not the regular behavior of the Musiland/BII combo.
DOESN’T QUITE MAKE SENSE
The observed behavior doesn’t quite make sense. I would have expected that the Amanero board would test “cleaner” -less unlocks after warm-up, but this was not the case. The Amanero board does the one thing I thought Musiland compromised: namely deriving the clocks from discrete oscillators. The Musiland, on the other hand, derives the clocks in the FPGA’s DCM’s (from the clock signal that is passed down by the USB receiver), which results in higher amounts of jitter.
Further, the Amanero power section uses Ultra low-noise linear regulators (ADP-150) whereas the Musiland uses what appears step-down switching regulators.