sharp and piercing high pitch /frequency coming out from Harbeth C7

What's the recording and music? In my experience all Harbeth don't show a sharp piecing treble, even if you use the brightest amp, electronics or cables. Hence I am suspecting the music or recording to be the culprit to the bright sound you are getting with the C7ES3 40th Anniversary. Perhaps the 40th anniversary was tuned to have a treble peak, that I'm not sure but the original C7ES3 actually sounds a bit warm to my ears when compared to SHL5+.

I have had problems with sounds generated by other DACs running when I am using my newest & best one. Be sure that the only equipment powered up is the gear you are listening to. The fact that playing LPs is fine is proof that's it's not your speakers. Pull your RCA phono plug cables in and out of their sockets a few times to get clean connections. If your cables have arrows on them, are they pointing in the right direction (generally, toward the preamp or integrated amp). When playing music when you hear the bothersome noise, one at a time, pull the cables coming into your preamp/integrated amp from unused sources out. That one that stops the noise is the one to investigate. I am using class D amps that run at very high frequencies. That ultra high stuff can leak out of the cabinets and interfere with DACs. If all of the previous checks fail to resolve the problem, pick up each connected source component and rotate it 90 degrees in any (and every) direction to se if it changes the unwanted noise. If it does, be sure you are using shielded interconnecting cables. If you can see three wires wrapping around each other, it's not shielded (like Kimber PJB). Good Luck. Feel free to contact me if none of these things work. Good Luck!

I have the same feeling from my Harbeth C7 in comparison to my Gershman Avant Garde and Tyler Linbrook Signature systems.
The high pitch violin or horn sounds a bit harsh with high volume.  However, at mid volume, I am just OK with Harbeth.

Different cables might help make the sound a bit smoother, or tube amps might help. But then, you might not like other (more dynamic) kinds of music. I guess that is why many audiophiles keep multiple setups for different kinds of music or preferences.

@ryder
it is glad that you did not have this problem on the Harbeth. I tried my cables and another better speaker cables on the Sonus Faber speakers in another shop and the sharp frequency happened too. 

i am checking directly with harbeth to see the spec. difference between 40th anniversary and the regular C7. thanks : )