Treble harshness - interconnects as culprits?

The only culprit here is the power. You would need high quality power cords like a Transparent Audio Reference power link or a good Regenerator like a Pure power or a Monarchy. I have gone through this exact situation. Any attempt to cut down harshness through interconnect will only lead to coloration and softening of transients because the problem doesnt exists there and you are trying to forcibly cure it there. POWER POWER POWER !!!!

There was a thread on this the other day. Get rid of the Radio Shack ICs and get the free ones that come with your oldest and cheapest CD or DVD player. If it sounds worse you know that is the problem.. The other way to approach this is to buy a very high quality Cardas Golden eference IC and use those. That will almost certainly fix the problem but you will be out about $850 for a meter. Not the highest price in the world but not cheap. You should alsp get Dream Weaver Speaker Cables from Jen Labs I use the cheapest but the all copper braid is a great cable and the higher up you go the better. This will solve the problem but the price of admission here is fair considering all the labor but firmly up there.

Some good ideas so far, but one thing that has not been mentioned is jitter.

Mizuno - You said in the OP that your dac is being fed by the S/PDIF output from Sonos. Sonos' S/PDIF output has a high level of jitter. Jitter results in frequency modulation that is audible as harshness in the high frequencies, which is exactly what you are reporting. If your dac does not reclock, then you are probably hearing the results of jitter. What dac are you using?

Bryon

what about the room (reflections), or the unforgiving nature of the integrated amp and /or speakers ?

i'm not saying it isn't a cable problem. the obvious solution is to try other cables.

you have not mentioned the brands you use for speaker or integrated amp.

perhaps a tube integrated in lieu of a ss ?

cables are less expensive, maybe, or as has been suggested , another dac, with a tube might be another thought.

asked this in your other thread on the same topic what speciifc equipment do you have? the other thread noted spendor speakers - what integrated and DAC are you driving these with? what speaker cables are you using?