Interesting topic gents,
I have used and listen to Krell stuff over the years and while powerful tanks, i was never really fond of the
sonic's. Recently i was presented with the opportunity via a good friend to play around with a Krell he had and one thing lead to another and we ended up servicing and modding this unit (KSA200)and would like to pass on my most recent experience and address a few concerns mentioned here.
Firstly due to the high class-A bias most Krell products operate at there idle current will always be excessive and of course nothing like CLass-D stuff...
1. There is no necessity to leave any high bias Krell product running 24/7, 1 hr before listening is sufficient IMO, there high quiescent current is sufficient for the amplifier to reach operating temps and a stable Bias.
2. Regardless of what the guys in print will say, leaving any amplifier that runs at such a high Bias/temperature running 24/7 will shorten the life of the components and lead to sound degradation over the years. Amps that are only 7 yrs old can have issues and of course this IMO lead's to that hard, cold , dry sound most associate krell's with, especially used Krell's.
The Krell in Mention KSA200..
The KSA200 was an amp in long service by my friend and over the years it has made 2 trips back to Krell ( enormous expense) for repairs. Of course this beast idled at 15 amps, YES 15amps and ran as hot as a stove.
On it's second trip back to Krell 2-3 years a go my friend decided to try Bel Canto mono bloc's and was immediately impressed and voiced to me that he will not want the Krell back in his system and upon it's return he would put it up for sale. His decision was later reinforced on the amps return as it's sound was promptly condemned after a thorough listening session comparing the 2, to make matter's worst the Krell failed again a few months later..
The decision was then made, for us to take a look at the amplifier and see what could be done. On examination we found that Krell was only replacing the broken parts and never attempted to fix the problems which by now were bad leaky caps all over the amplifier main boards. Long story short, we went through the whole amp , replaced all caps
(upgrade) except the PSU ( perfect when measured ).
We had reduced the Bias on start up as a safety precaution with the intent of re-biasing the amplifier back to class-a as to Krell specs and after the usual precautionary checks all seemed well, good power,sine wave /et al.
The suggestion was then made to try the amplifier at the lower a/ab bias ( since it speced well ) before going to full class-a Bias.
THE DIFFERENCE WAS ASTOUNDING .. much faster and dynamic than we had ever remembered this amplifier, the sound was so much better, the Bel cantos now did not stand a chance.
During the listening session a few thought the top end was better in full class-a , but all agreed that
1. Bass
2. Sound stage
3. Attack and Speed
was vastly improved with better tonality than before.
Anyway we took this behemoth back to the bench and adjusted it back to it's full class-a spec, plugged it in and ........ Yes.... a disaster!
The difference was staggering , dynamics lost, bass pulled back, dead , dead sound ..
Now my friend has a cool running KSA200 barely warm after hrs of listening,fantastic sound and many new Krell friends :) leaving many anti-Krell individuals ( myself included) blown away at the transition and how really good this amplifier sounds.
I have always felt when listening to high bias class-a amplifiers that they did not exhibit the rhythm and or pace of a good a/ab amplifier, always dead sounding to me by comparison, refined sound, Yes , but no music..
I would like to believe this is what most hear when switching to Class-D, but to my ears class-d is a bit Harsh sounding, yes definitely fast sounding and alive , but there is some crudeness there where a good a/ab amplifier does not exhibit that IMO.
Currently looking into modding and comparing a few other Krell models ( FPB series up next) to see if the mods were specific to this one model or will other Krell models benefit from cap upgrades and reduction of it's quiescent bias.
Stay tuned ..
regards
