vibrations and NAS

[luigip]

I have tested the effect of anti-vibration/resonance devices (Nordost Sort cones AC) below the NAS (QNAP TS219PII) that feeds my Klimas DS/2.
Results:
1) The sounds is distinctly different
2) With the cones there is more focus, micro-detail allows to identify and follow each of the instrument and in general the rhythm /tune of the mid and bass can be followed more easily. Without the cones the mids and lows are louder, the sound seems more punchy but it is more difficult to follow the line/tune of the instruments
3) The sound changes immediately, i.e. as soon as you put the cones in (or out)
4) Same experiment with the QNAP HS251, the effect is still present but much less evident. One has to note that the TS251 has a plastic based structure with a vent, and is more prone to vibrations, while the HS251 has a more solid structure, and it is less sensitive to vibrations. Roughly the “sound” of the TS251 with the cones is close to the HS251 without cones

Assessment:
From point 3 one derives that vibrations are NOT affecting the digital stream (e.g. bit errors), but the analogic downstream chain. Here is why I come to this conclusion. The DS has a buffer of a few tens of seconds (let’s call DT its duration). If one inserts (or pulls away) the sort cones at a time T0, any variation affecting the bit content in the NAS would happen at such T0, but would be reproduced by the DS with a delay, i.e. at T0+DT. This is not what happens, the change is sensed immediately.
Thus one is left with the only viable solution that vibrations in the NAS affect the analogic chain. One reasonable explanation of why this happens is that vibrations change the parasitic capacitance to ground, and because the NAS, Klimax DS and the pre/amp chains share the same ground, the vibrations (produced by the music from loudspeakers) introduce a delta signal correlated with the musical signal. This hypothesis is also consistent with point 2 above, i.e. that without the cones the mid/bass is louder but less focused.

Hope this helps

Luigi

[beck]

I agree that unwanted vibration reaching the analog chain of a hifi system is a big problem. It changes the original sound to something else.
We have to be even better than today to isolate each part of a system from each other to reach a natural sound being careful that vibration does not travel via the cables.
This is a lot easier with a simple analog system than with a more complex digital/analog system.