Full Potential of Buffalo II at Last!
For over two years, I’ve been trying of figure out why I was getting unlocks with the DPLL bandwidth setting at “LOW” and “LOWEST” with I2S input. I had attributed this to jitter from the interface. I’ve tried different interfaces (within my budget), tried modding the power sections of the interfaces, tried using different player software and whatever the audio community was experimenting at the time.
I think I am finally able to use the “LOWEST” DPLL setting without any unlocks. The latest “mods” consist of further shielding and vibration damping. This is starting to look like the type of mods people used to do to their CD players: damping, shielding, power cord/filter mods… I never thought those mods would make a difference…
The reason to go after the DPLL bandwidth setting “LOWEST” is to maximize the jitter rejection capability of the DAC. With this setting you can achieve the ultimate performance that the DAC was designed for.
Although I am not sure how repeatable the results are, here they are nonetheless:
Put some damping material on top of the clock (I think it is some kind of office-type of erase-putty)
Here is the additional shielding: a thin copper plate with two female pin connectors affixed to the plate and plugged into the exposed GND pins of the AVCC module
The following graphs record the number of unlocks per each 10-minute interval for 24 hours. During the first 60 minutes, the DAC will unlock many, many times. During this time the clock (etc) is stabilizing. Diyaudio wisdom indicates that it will take ~one hour for a good crystal to stabilize [link] so this is consistent with observation. Thus, for the Buffalo DAC, it will sound its best at least one hour after power-on
After the “warm-up time, the unlocks are seen clustered in bursts. One burst of 3 unlocks at 9:00 PM (I was listening the music at the moment and they happened within a few seconds of each other). The next two groups of unlocks during the second 6-hour interval and third 6-hour interval were recorded while I was sleeping or away, and they do seem to show up as a burst of unlocks.
I captured more data for another 6 hours (for a total of 30 hours). There were no unlocks in the last 6-hour interval
After that I did some focused listening comparing the sound between DPLL bandwidth set at MID-LOW (my previous reliable setting) and LOWEST. I used the track “Happy Now” of Poncho Sanchez’s “Conga Blue” album. After repeated non-blind A/B listening sessions, I am able to distinguish subtle differences. In particular LOWEST produces a “sharper”/”less soft” sound on certain instruments (for example, the sound from the cowbell). I think people call this “more focus” and “more layered” music.
More sensitive listeners may find bigger differences, but for me the differences are very subtle. In “normal” listening I would not have heard any differences.
The shield a bit modified
Heat exhaust holes
Making sure nothing is shorted by the shielding cage