Help with Vintage B&K Power/Pre Amps

I have a ST2140 power amp and a PRO 10MC Sonata Series preamp... thought I had trouble with one of my tweeters (right speaker sounding overly bright to the point of listening fatigue)... a friend brought over a pair of B&W monitors and after plugging them in, the right speaker had overly bright highs as well... anyone have any idea what might be causing this... do I need to send the 2140 into B&K to diagnose, or maybe the PRO 10MC, or both... any suggestions appreciated... this journey down the vintage equipment road can be challenging... thanks in advance.
Just the nature of the beast with B&W.The brand is all hype and yes they sound clinical.
What's your budget there are just so many better speakers out there
Hi Tobb... thanks for the reply... just to clarify, my question was related to my B&K components... the B&W speakers were used to swap out my speakers to verify my sound issues weren't related to the speakers... swapped the L/R RCA Interconnects on the preamp and my sound issue in fact moved from the right speaker to the left... so, it appears I have an issue with my B&K PRO10MC preamp... not sure if it's worth sending in for service or to just look for another preamp... maybe a Classe CP50 or stepping into the entry level tube preamp realm...
I would be surprised if it was not more affordable to have the B&K serviced.
However before I went to the Classe I would check out Coda's new 7X.
They are using very high end double gated FETs and with their
high impedance produce a very tube like sound.
I recently attempted to contact B&K/ATI via telephone and email regarding an older model pre pro I was experiencing problems with.

They never bothered to return my phone calls or email.
The Pro 10MC was one of B&K's best products that they produced, it is a very listenable product, most likely worth a repair if not too costly. However, it is valued in the neighborhood of $250 right now. The Classe 50, is clearly a better product, but probably worth somewhere around $500 to $800. Neither of these products are considered bright. Tobb has recommended a terrific product, but it is new, you won't find a used one for quite some time and it runs around $6500.
At under $1000, I like the Muse 3 Signature or maybe a Audio Research LS9, both are single ended and balanced, both sound near dead neutral and both have remote.
You could could try a cables or a little less tow in on your speakers or both, that would effect high end and listener fatigue.... Good Luck, Tim
Finding a Classe CP-50 for $500 is extremely optimistic, unless it is in poor condition. Those go for more like the $900 range in good working and cosmetic condition. The published Audiogon Bluebook value exceeds that amount.
Tapar1, Is your the Pro10 preamp the model with the red/blue or black/gold writing on the black faceplate or the machined black faceplate with grayish inlaid color where its sort of recessed? There were early and late generation pro10s.

Depending on which version pro10 it is, if you decide to let go of it, I might be willing to take it off of our hands if the price is right and to fund your next preamp purchase.
It's the one with the red & blue on the faceplate... just sent it in for servicing... not sure if it is the early or late model...
Hopefully this is not to dated of a response.  I have the same Pro 10 preamp that I took out of a closet after having been stored of about 15 years, cleaned the contacts and connected it last night.  At first the right channel was lacking in high en response.  I tried different input methods, changing cables and continued to have the same result.  I then connected my output to the second set of preamp output and the proble went away.  I guess its limited to the right channel on the preamp output A.  Doesn't solve the problem but at least I am enjoying the preamp again.