Possible cause of harsh mids?

Once in a while you get that used album that sounds good except for a static like distortion on some more dynamic vocals, horns, guitar.  Just typical for some old albums?  Listening to Corea - The Leprechaun.  It's a very good sounding album, well balanced with great dynamics.  But, that annoying distortion rears its ugly head once in a while.  
The sound you describe as static like can be caused a number of different ways and goes by a number of different names depending on what exactly is going on. Sorry but you just kind of have to experience it a whole hell of a lot on a lot of different records to get the feel for what is what and which is which. Once you do it is very easy to talk about. Problem is most don't have that same experience, don't use the same terminology, and so people wind up talking past each other. 

Sound familiar?

One of the most common ones is sibilance. That is when vocals, for some reason especially female but doesn't matter, and can be some instruments too, but certain sounds get the ssss exaggerated and splattered and sounds like static. A lot of people blame this on dirty or beat up old records but really it can be on brand new perfectly clean ones. So really what we are talking about is a bad pressing. For proof I have several copies all nice and clean all the same shape but one has massive sibilance the other hardly any. It's the pressing.  

Another cause of this static sound is mis-tracking. The stylus never traces the groove the way we think. It mostly bounces back and forth sampling the groove. Go watch Peter Ledermann's terrific video on jitter where he explains this in detail. Fascinating stuff. Anyway, this tends to be worse with high amplitude and certain sounds excite harmonic resonance in the cartridge/arm system and so you can get this same sort of sound from breakup when this happens. If this is what it is you can try and tweak VTF, anti-skate (if it is more one channel than the other) and record mats or clamps. But these are all work-arounds, the real solution to this variety of breakup is a better arm/cartridge.  

This can also simply be caused by a dirty record. Doesn't take much dust to encourage the stylus to bounce around and if you are tracking dirt it is gonna sound like it. Walker Enzyme 4 step cleaning is the best you can do. No one ever regretted cleaning their records, not that I know of. 

But honestly my money is on the first one. Whole lot of records do this, it is just the nature of the beast. Most of the time it is the pressing, and not much if anything can be done but to find another pressing. The best ones are found at better-records.com but even those can still have this same problem. Nobody likes hearing this but it's true. Playing records is a trade-off. You can have awesome great sound- just not all the time.
What millercarbon sez...

Spitty sibilants and scratchy violin sections have been my audio bete noir for decades.
Can spitty sibilants and “static” in high amplitude passages also be an amplification issue?  I upgraded my turntable and think I have the alignment of a nice soundsmith cartridge fairly dialed in using Peter Lederman’s instructions and test record.  SQ is way improved and I’m hearing so much more in the music, but sometimes on some records I also what pkatsuleas describes.  Of course one improvement often tempts another, and now I’m looking askance at my 30 year old B&K preamp and amp.  Trying to talk myself (and wife) into new Brystons.
try backing off on the phono preamp gain.....
There's a process for figuring out what is causing what. If it was a gain issue then the problem would be present every single time the volume got loud. That is not at all what was described. So it has nothing to do with gain. 

Likewise, if it had anything to do with the amp then it would be consistent. So the one simple fact that it is occasional tells us it can't be the amp. Then to test if it is what I said it gets a little harder. The way I know for sure is what I said, having heard multiple copies of the same record on the same table so the only thing left to explain it is pressing quality.  

Then having heard it and knowing exactly what it sounds like the next time it happens I know what it is. There's just no doubt any more. But that is because I went through the learning curve. 

sryeager, this is in no way an attempt to talk you out of buying a new amp. I would never ever try and talk anyone out of buying a new Raven amp. Or Decware, for that matter. 

Congratulations on the Soundsmith cart. It will be so sweet with a Raven, you will forget all about the occasional spitty pressing.