Getting rid of harsh, shrill treble

As others have responded, changes are system dependant..
however, I had great success using a JPS Labs digital cord powering my CD player and it greatly reduced brightness and sibilance..

I agree with Tvad that more information would be helpful and I would add that harshness can also be due to, among other things, cables, plugs, dirty contacts, power line issues, RFI, interaction between your components, need for vibration control, etc. My own experience has been that it could well be a combination of a few or even many of these factors - every one of which I have experienced at one time or another myself. I would suggest an approach where you deal with these issues one at a time in order to see what helps or hurts in your system.

Your MD 308 amp is known for a balanced presentation and is probably not the source of the harshness and shrillness (unless it hasn't been broken in for long enough). Your Rega Jupiter is probably also not the problem. Per your question, switching to a tube amp could smooth the highs somewhat, but I suspect the better answer would involve a combination of different speakers and some room treatment.

Alternatively, a cheap and dirty fix would be to buy an equalizer and use it to reduce the treble energy. This is pretty sure to work, but you have to accept the compromise in signal quality that would be incurred.

Unless you have a harsh component (s)...it's probably room acoustics as others have mentioned. That said, I find good violin recordings (at least on cd) far and few between.

Dave

I considered suggesting the equalizer but am afraid everyone will think I am a Behringer salesman! But, since Jameswei raised the subject, I think that you should spring for a Behringer DEQ2496...about $350 with mic and cable. The analyser function will tell you what your system is doing, and help fix it as much as possible with room treatments and such. Then, when all else fails, use the equalizer function. Finally, don't assume there will be any audible signal quality degradation. Only your own ears can inform you about this.