My own reservation against this kind of gear with this kind of price tags has a similar background: How can effective damping require such a sophisticated high-tech design with expensive materials and thousands of hours of development efforts? I strongly suspect that the same effect can be achieved with a cheap DIY design – maybe you just have to do some experiments to get this far or almost as far for a fraction of the asked price – which borders on usuries in my book.
I'm not even disputing the benefit from such damping tools, since some trustworthy Head-Fiers confirm it. But one thing I wonder: Is there also an effect in the case of pure headphone listening, or are the reports exclusively referring to speaker listening? In the latter case the benefit from damping against vibrations through solid-borne sound from the furniture on which the DAVE stands, which on its part is excited by air-borne sound waves from the speakers, is kind of plausible. The only question is how it can have an impact on the electronics and thus the analogue signal emitted by the DAVE. From what I know Rob acknowledges such a possiblity, and maybe he's willing to explain. But in the case of headphone listening, I don't see a possiblity of a furniture anywhere in a living/listening room not affected by aircraft or traffic noise to transfer some vibrations to the DAVE that are neither felt nor heard. So how is your take for this second scenario? Is the DAVE (without any moving parts in it) supposed to develop some vibrations itself that need to be dampened?
Dave, in common with all electronics, is (very slightly) microphonic. You can hear this using the AP - set it up so the -128 dB background noise from Dave is a roar from the AP loudspeaker monitor (that would be about 120 dB of gain), then tap Dave's PCB and you can hear tiny clicks through the loudspeaker. On headphones you can't hear it with the Nighthawks but you can just hear it with Noble Kaiser K10 IEM. Note if this was a valve or tube DAC or pre-amp the clicks would have been extremely audible.
So using Dave with loudspeakers one can reasonably expect it would be (slightly) sensitive to vibration - after all I can hear the effects of noise shapers at -350 dB affecting depth, so this is way bigger than that. Also I experimented a lot in the 1980's with vibration control - my turntable was in an 1 inch thick oak double glazed (with half inch thick plate glass) enclosure, and this made a huge difference to turntable sound. My electronics were on stainless steel springs and Italian slate - so I know vibration is important. That is one reason why Dave is in a solid aluminium billet, so I can control vibration. Reducing vibration gives smoother sound, with better depth.
So I am not surprised about it being slightly sensitive with loudspeakers. But I admit I was very surprised to hear reports about it being sensitive with headphones - this I can't see making a difference. That said I have two favorite quotes relating to audio - "There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy." And somewhat more recently "You know nothing Jon Snow". So yesterday I puzzled over what may be a reason and thought of skirts. When a DAC or oscillator creates a sine wave, when you do an FFT you do not get a straight line indicating a pure tone - it will have skirts. Now these skirts are important subjectively - you hear them as a hardening of the SQ, so reducing the skirts and making an individual sine wave more pure and sharper on an FFT makes it sound smoother. And the ear/brain is very sensitive to this problem. Skirts are caused by low frequency jitter problems, and if you can measure a skirt it is audible. This is why I do not use fempto S clocks or atomic clocks; these have low cycle to cycle jitter, but lots of low frequency jitter, as these oscillators use PLL's - which have poor low frequency jitter performance. So using a fempto clocks measurably increases skirts, and sound much brighter - and its easy to confuse the brightness as more transparency. With Dave, I have no measurable skirts - at least I am at the residual level of skirts that you get with the windowing function of the FFT within the AP.
But the action of low frequency vibration may add more skirts, and so this is a
potential mechanism for making very small changes to the SQ when you are just using headphones - but it would only have the effect of making it sound a little smoother with lower vibration levels.
I am in Moscow tomorrow, then Dusseldorf, Singapore, Shanghai, Tokyo and finally Ho Chi Min. When I finally get back I think it will be worth investigating, as I am intrigued.
Rob