on cleaner spdif...


2008-05-29 11:46 pm
I think this has worked...it has taken some years of progress, thought and investigation but the results are worth it.

The answer for me is to look at the spdif route to the DAC (DAC64). I have used a Meridian 518 DSP/enhancement as a volume control with the DAC64 driving the amps (heavily modded NVA A80's built from kit 10 years ago) powering Wilson Benesch Arcs thru silver cabling. (This amp/speaker comb is incredibly revealing and the slightest improvement to the source is very evident) My own conclusion in reading many articles about the arduous spdif transfer of data is, as well known, degradation of the synce/clock intoducing dreaded jitter, and intoduction of any rf through the ground which becomes very audible as a heavy or plodding delivery of the sound with a noticeable soundstage flattening and narrowing with jitter introducing harshness and also diminishing soundstage/separation. So the spdif out is taken to a Monarchy dip via toslink (in measurements it only lowers jitter via toslink, again hinting at rf induced via ground links being a culprit) which rebuilds the clock. Then coax spdif is output, as short as possible with a generous cable ferrite, to the 518 which uses some very clever Meridian invented techniques to match word length, rebuild a very accurate clock, introduce high resolution noise shape dither (I use shape D and add emphasis) for the volume control to make the most of the subtlest low level audio info, and add word length to 24bit (not resample!). Then to the DAC64 via shortest possible coax to the bnc, here I added a pulse transformer for more iso to the bnc connector itself. The reason I know when each stage is a definate improvement is that the buffer on the DAC64 reduces in length when it sees a better quality spdif and you get less delay through the buffer (set to maximum buffer always!).

What it essentially boils down to is rebuilding/isolating from stray rf, the spdif data stream right up the dac as much as possible. The sound is quite staggering from this set up...at the moment I'm just using a hdd media player (Freecom) as the source with my CD collection digitised using the usual secure recover error with multiple passes etc. to wav.

Hope some of this is useful to anyone, and it's not too "we know all that already!!"