How do I smooth out violins?

I have never heard your speakers, but this sounds to me like a speaker issue. Your speakers cross over from midrange to tweeter at 3 KHz. Its possible that your tweeters beam more than your midrange which would tend to make the upper frequencies stand out more. I have also heard harshness in some speakers at the cross over point. If you have a test disk that plays warble tones at various frequencies, it may be easier to diagnose if this is due to a tweeter beaming than with music playing. Just go back and forth between the frequencies above and below the crossover point and see if you notice a lack of coherence, that is, an obvious shift of sound from the midrange to the tweeter. My Magnepan 1.6QRs used to do a similar thing in the violin range where the violins would jump from the planar magnetic panels to the quasi ribbons. That lack of coherence drove me nuts.

I think there are a lot of good comments above. I am especially appreciative and supportive of where frogman was going, in that you really want to diagnose and address the problem rather than throw bandaids at it. Who among us appreciates the auto mechanic who fixes our cars by sequentially replacing parts until the problem goes away?

When I read the OPs comments, I focused more on lack of integration than lack of smoothness. I think most of you focused on smoothness rather than integration. This is where the comment above that this may be due to more than one issue is also relevant. Further clarification from the OP is required with respect to what he means by "smoothness." Does this mean you are experiencing excessive grain or excessive brightness? If it is excessive grain, I strongly urge you to replace the aq4s. They are very grainy, but I did not find them overly bright. If the problem is brightness, then some of the comments regarding power treatment and IC's may well be relevant to this problem. If dirty power is exacerbating the problem, it will probably be variable. Most people have cleaner power in the evening than during the day. If the problem is not variable, you may not want to address power treatment first.

My guess remains that the "integration" (coherence) problem is speaker related. I have no knowledge of this speaker. If those who do can indicate that coherence is a strong point with this speaker, well, I guess the problem must lie elsewhere. I can tell you this. I had major issues with integration (lack of coherence) and also a minor issue with stridency or harshness in reproduction of violins (at the crossover frequency) that pretty much completely went away when I went from Magnepan 1.6QRs to 3.7Rs. I have an extensive library of orchestral and chamber music, and I would have to go back to cds recorded in the early 80's to find examples of recordings where the violins are excessively bright. Granted, certain recordings can make a violin sound larger than life due to close miking, which I suppose could be a part of the problem here. But I find it difficult to believe that the OP has somehow managed to selectively collect a large number of bad recordings.
I do have a tubed CD player, but I do not have a tubed pre amp. I have nothing against tubed preamps, but they are not a panacea, nor is vinyl. Digital can get this right, and will not require investing in a top notch vinyl rig and phono preamp. Resorting to vinyl is not really a viable option for those who have a substantial investment in CD's, and I would suggest most fans of classical would not be satisfied with the quantity of music that is available on vinyl as compared to digital.
One other possible issue here is jitter. I don't know the Marantz, but in my experience jitter will for some reason manifest itself as most objectionable with music that is rich in high frequencies.

Pity the pour soul who asked for advice. So far we have:
It might be the speakers and its probably not the speakers.
Buy a tubed preamp and it is not necessary to have a tubed preamp to tame digititis.
Purchase new speaker cables, ICs, power cords and power treatment.
All your recordings are bad, go vinyl.
Start by replacing the source.

I'm sure at this point he is clear on how to proceed. I guess he is fortunate, in that he gets to keep his amp (so far), and no one has invoked demon possession as the only reasonable explanation.

What would be helpful would be comments relating direct experience with the actual components in question, or diagnostic approaches that would allow him to narrow down the field without running megabuck experiments.

I think a reference recording, recommended by the group as being innocent of the offending attributes has a great deal of value. If Charles1dad has a recording of violins that exhibits good coherence, lack of grain, and lack of excessive brightness in his system, and the OP finds the recording still has issues in his system, then it is system related and not an inherent fault of digital reproduction. If, on the other hand, this recording is found by the OP to be satisfactory, then he is going to have to live with the fact that he has somehow selected a bunch of bad recordings. The idea is to help the poor fellow narrow things down without running a series of megabuck experiments.

Tarp, I agree with your comments re Praga and Audite, but I am surprised by your comments regarding Hahn's Sony recordings. My ModWright Sony 5400 captures quite well the sweetness of her live performances. Anyone who thinks digital is an unmitigated disaster really needs to hear a ModWright player.

Zd,
I agree with your post but my comments about replacing the AQ4 speaker cables was based on having used them for several years. Have you used them in your system? They are extremely grainy, and really don't do strings any favors. Another person suggested replacing them with Cardas. I can't answer for why they made that recommendation. I can say that AQ 4 is the worst wire I have ever had in my system. Chances are pretty good that replacing AQ 4 with Cardas, or for that matter something else selected at random would be an improvement. Its really not good wire.

Zd, I think we are on the same page. I really don't like the change this buy that approach to spending other people's money. Luck is a poor plan A for making improvements in one's system. In the case of the AQ 4, I had direct experience with the cable and didn't like it. Inexpensive cables like anticable and signal cable were way better, so its not likely that loosing the AQ 4 would be a waste of money.

Jult, Well said. However, we can't do anything about how a performance is miked and mixed. It is what it is by the time it gets to us. Redbook limitations may be partially addressed by upsampling and purchase of DSD/SACDs. The system limitations is where we have the ability to significantly impact the end result, where those system limitations exist. At the end of the day, nothing we do can mitigate a recording that flips back and forth between 5th row center and dress circle perspecives, or mikes a Bach Partita from 6 inches, so that everytime the violinist moves the violin jumps from center to right, right to left, center to left, etc. (I prefer the Ehnes Bach partitas and sonatas, partially because he stands still during most of the recordings.)