B&K harsh sound

I recently auditioned in my system a used B&K 1430 amp, which is 3x200 into 8 ohms. I have monitor audio silver 5i speakers. My current amp is a rotel rb960bx, which is only 60 watts per channel. I almost couldn't listen to the B&K. It was so bright and a little ragged on the top end. Imaging was bad as well, both right to left and depth. Has anyone else had this experience with B&K amps? I wonder if it is just a bad match for the Monitor Audio speakers, or perhaps it is just this model. Should I give up on B&K for my system?
Without knowing more, I'd suspect that the B&K amp you auditioned is not functioning properly, and needs repair, or perhaps there is a propblem with the speaker cables you are using. There are some amp / speaker cable / speaker combinations that cause oscillation in the power amp, which may be heard at a bright, ragged edge to the sound. There was a lengthy thread here on A-gon about 6 weeks ago about Alpha-Core Goertz speaker cable sometimes causing amplifier oscillation. If the oscillation is severe, the amp will overheat and may even shut down. Does the B&K amp overheat? If so, it may be oscillating.

Most of the B&K amps I've heard over the years have a smooth, relatively mellow sound, not bright as you describe. I think the B&K 1430 is the 3-channel version of the 1400, which is a decent sounding amp. In this situation, I'd be inclined to suspect the particular amp is the culprit, and not the B&K "sound" as a brand. If anything, the B&K "sound" tends toward a bit of warmth in the mid-range, and slightly rolled off in the lowest and highest frequencies.
I own a B&K receiver and have listened to Monitor audio speakers. I would suggest that this is not the best match. I found Monitor speakers bright and constricted even when played through a Pass Labs amp. Be aware the B&K is still solid state and a bit dry at the top. I try not to use any cables that add extra detail and use other components that are known to be smooth and musical. B&K makes great gear, but great systems are about synergy. I would rather build around the front end and amplification instead of around the speakers. It's just MHO.
All B&K amps I've heard are laid back, sometimes too laid back.. What cables are you using? Post the info & you'll get input from experienced users here....
Sounds l;ike a speaker cable mismatch.I just had one with CJ MF2500A and Kimber Monocle XL cables.That sound hurt my ears and i thought the amp was broken.Then i tried a number of cables and stayed with Harm.tech.cables.
I've heard B & K with Monitor Audio speakers, nothing wrong with that match.
I'd suspect other things. A bright room, a malfunctioning amp, etc. You've gone from 60 to 200 amps and to my ears, B & K is a little warner sounding
than Rotel -- the extra power may be bringing something out that clashes with the room or with your ears. You may also be playing the music louder
than usual, which could cause problems in the room that you didn't encounter with the weaker amp.
I picked up a new B&K ST2140 2 years ago to mate w/ the B&K PT3 preamp driving some old Polk Monitor 10 speakers. The amp was awful out of the box. I burned it in 24/7 for a week. Still awful, harsh, glaring, distorted, constrained soundstage, you name it. I returned it.

My 20 year old Hafler sounded great. So it wasn't the pre, CDP or the speakers. I eventually got rid of the B&K preamp too. I'm not a fan.
Newer B&K amps sound quite a bit brighter, harder and more sterile than their older counterparts to me. Rotel gear is also somewhat bright, but may be slightly smoother overall.

Having said that, you should have any electronic component that you bring home for audition on for at least 3 days straight. If at all possible, music should be running through the system 24/7 before doing "serious listening". When running the system during this time, low volume is better than no volume and no volume with the power on is better than no power at all.

Not only are we trying to establish thermal stability, but we are trying to pass signal through all of the components that will normally see such operation. Granted, the compononents might not be getting the work-out that they would during normal use and at higher volumes, but something is better than nothing.

If you don't like the sound of what you hear after 72 hours of continuous playing, you probably never will. Things can change after that, but with electronics, you're about 90% of the way there after this period of time / operation. If that last 10% that settles in over time makes or breaks your decision, you're walking a very fine line.

Speakers will continue to alter operation for quite a period of time, especially if you listen at low levels. I have purchased used speakers that were over a dozen years old that still weren't broken in. Throttling the power to them on a sustained basis made a DRASTIC difference in low frequency output. This was because the suspension on the woofers was never stressed and was still "tight" due to never having to make long excursions. Pumping more power through them / playing music that had "basso profundo" made a huge difference after several days. Speakers that were recently re-foamed may also go through a similar "break-in" period all over again. It is not quite as severe or noticeable as with a brand new speaker, but it does occur. Sean
Thank you everyone. I am now wondering if I shouldn't give the amp another try. I actually wondered if it might take more than the 2 hours I gave it to come to life. But that's all the time I could spend with it. I should have left it in the system, even if I was just watching tv, and tried listening again after a day or 2. Someone asked about speaker cables. I am using Synergistic Research Alphas left and right and a new Wire World Oasis v center. I have heard others describe Rotel as having a "bright" sound. My amp does not come across that way, but on the other hand, I've been using it for years and years.
Sean has the right of it.

Let the amp burn in 24/7 for at least 2 or 3 days (don't power it off and on). Then see how it sounds. 2 hours is not enough.

I had a B&K ST1400 that your amp is based on and it was anything but harsh. In fact, the ST1400, like many MOSFET amps, was hardly the last word in transparency and "air", it was quite mellow and warm sounding, even slightly rolled off at the very top of the treble - IMO not necessarily a bad thing considering the speakers & front ends it's likely to be paired with.

Despite the howls from some quarters, I've found burn in to be a factor with most components. My CD player sounded OK out of the box but took about 200 hours (continuous hours, friend) to attain anything like its optimum sound. Bob Crumps power cords famously take a month to burn in. (But they're very entertaining/frightening meanwhile - it's like buying five different PCs in one.)

PCs can make a difference too.

Maybe the B&K was a defective amp or maybe you had a system mismatch. (Synergy is the thing in audio and, as pointed out, not all components mate well together.) Or maybe the B&K sound has really changed that drastically in the last 5 years. But I'm surprised the B&K sounded night and day different from your Rotel. Nevertheless, when all's said and done, you may simply end up preferring Rotel amps, or even preferring what you're used to listening through.
It could be that I am used to and enjoy the sound from my little Rotel. That causes a problem in the power department though. I clearly need more reserve power.