Krell KSA-100 MK2

[Bigman80]

Ah thanks matey, I thought that was the case. 100w is plenty I think

Yes, it's class A up to its rated output. It's got even more power than that, but not in class A.

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[Bigman80]

You could hang on and see if a KSA50S like mine comes up at some point, but asking price is likely to be around the same as for the KSA100 currently under discussion.

I don't think it is so much the class A operation that makes the amp what it is, it is the ability to double power into lower loads that makes the difference over 'lesser' amplifiers. But that is just my pet theory.

I've used mine playing at pretty high SPL in my fairly large living room for 4 or 5 hours straight and the heatsinks barely get warm. Peter (Petrat) can attest to this as he didn't believe me until he had touched it himself.

Okay it got red hot at the Penkridge bake-off but it was working at PA levels for 8 hours continually. Even then we never got the last set of bias lights to come on so there was more to give if we'd needed it.

There's a huge difference between amplifiers like that and the usual badge-engineered consumer tat that makes up the bulk of the market. People in the UK especially just don't appreciate that which is why you can pick these things up here for a grand. Which in an educated market would never happen.

Take a look how much people are paying for second hand Naim or Exposure power amps and just wonder.

Spot on with its performance at Penkridge. It was just capable and the character never changed all day. Whatever the volume.

Seriously impressed by it.

Maybe I'll hang on a bit, I do have other irons in the fire and really want to get them over the finish line.

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[DSJR]

I haven't trawled through this thread yet, so forgive me here...

These old original Krells do run very hot indeed and lack the plateau bias of macca's sample, which at least will cool on idling in between cooking (literally) music sessions. 1980's caps weren't always as heat or over-voltage tolerant as newer types appear to be and I can assure you that many first gen Krells will be well off spec now. These early models weren't as complex as macca's though, so a thorough recap may be ok for amateurs able to solder to do. Macca's amp has something like twenty caps per channel and I had a panic attack when I counted them up - fortunately, the circuit used will help a lot here in terms of minimising thermal stress and it's a very different circuit from the originals. Macca's amp had had a fairly easy time for most of its twenty odd year life I gather, as a 'second amp' but now, the replacement FPB models are needing attention if they've been thrashed into panel or ML hybrid speakers, so please be warned...

As for Krell Class A, I thought the 50 and 100 ran *mostly* in A but slid onto AB at the top of their power range, but looking again at the Martin Colloms review in 'Choice he indicates the 50 at any rate is run to 50W in Class A. As these amps can go higher than this, anything is possible, but certainly it appears the full specified output is in Class A and the sound is smooth if a touch 'cloudy' for me - something the 50S isn't in the slightest!

Do PLEASE NOTE - Excessive heat does NOT do 1980's electrolytic or tantalum caps any good at all and a vintage large-Krell bargain could easily turn into a massive and possibly expensive headache. Simon (SQ) has rebuilt two KSA250's I recall and both of them had leaking and bulging caps as well as burn marks where one of them failed spectacularly I seem to remember - I'm sure his story on the last one is buried here somewhere in the archives and I apologise if I have it wrong. He did picture the amp in pieces, stripped down to the last screw and credit where due, he painstakingly repaired and rebuilt it, re-set it up and it looked as good (better?) than new after he'd finished...

Old Naims may be tractor like in build and sound, but my Gawd they're easier to service. Old Linn pre's and power amps are for masochists in comparison with these Krells somewhere in between I feel

[Bigman80]

I haven't trawled through this thread yet, so forgive me here...

These old original Krells do run very hot indeed and lack the plateau bias of macca's sample, which at least will cool on idling in between cooking (literally) music sessions. 1980's caps weren't always as heat or over-voltage tolerant as newer types appear to be and I can assure you that many first gen Krells will be well off spec now. These early models weren't as complex as macca's though, so a thorough recap may be ok for amateurs able to solder to do. maccas ampo has something like twenty caps per channel and I had a panic attack when I counted them up - fortunately, the circuit used will help a lot here in terms of thermal stress and it's a very different circuit from the originals. Mavcca's amp had had a fairly easy life as a 'second amp' but now, the replacement FPB models are needing attention if they've been thrashed into panel or ML hybrid speakers, so please be warned...

As for Krell Class A, I thought the 50 and 100 ran *mostly* in A but slid onto AB at the top of their power range, but looking again at the Martin Colloms review in 'Choice he indicates the 50 at any rate is run to 50W in Class A. As these amps can go higher than this, anything is possible, but certainly it appears the ful specified output is in Class A.

Do PLEASE NOTE - Excessive heat does NOT do 1980's electrolytic or tantalum caps any good at all and a vintage large-Krell bargain could easily turn into a headache. Simon (SQ) has rebuilt two KSA250's I recall and both of them had leaking and bulging caps as well as burn marks where one of them failed spectacularly I seem to remember - I'm sure his story on the last one is buried here somewhere in the archives and I apologise if I have it wrong. He did picture the amp in pieces, stripped down to the last screw and credit where due, he painstakingly repaired and rebuilt it, re-set it up and it looked as good (better?) than new after he'd finished...

Old Naims may be tractor like in build and sound, but my Gawd they're easier to service. Old Linn pre's and power amps are for masochists in comparison with these Krells somewhere in between I feel

Thanks Dave,

That's exactly the input I needed. Glad I turned it down as the stress was killing me lol.

Now, where can I find a second Monarchy Audio SM-70???????

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[DSJR]

Going back to the late 80's, Jimmy Hughes had THREE KSA50's used first in an Isobarik active system where they did sound lovely, even with the first generation Naim active crossover. he went passive with one or two speaker models (modified Arcam 2's were notable) before finishing off with his beloved Impulse H2's which sounded great in his odd split level room.

What was his wonder-amp of choice then?

DNM!!!!! 25WPC of cool running greatness I have to say. No idea if any survive now, or how they'd compare today, but back then and driven with long solid core interconnects too, the sound was natural and totally un-fatiguing...

[Bigman80]

Going back to the late 80's, Jimmy Hughes had THREE KSA50's used first in an Isobarik active system where they did sound lovely, even with the first generation Naim active crossover. he went passive with one or two speaker models (modified Arcam 2's were notable) before finishing off with his beloved Impulse H2's which sounded great in his odd split level room.

What was his wonder-amp of choice then?

DNM!!!!! 25WPC of cool running greatness I have to say. No idea if any survive now, or how they'd compare today, but back then and driven with long solid core interconnects too, the sound was natural and totally un-fatiguing...

Not heard of that Dave.

I know it's. Very subjective issue all this hifi but it's great fun isn't it.

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[Macca]

DNM did always have a great rep but you never see any around nowadays.

[hifi_dave]

I believe they/he are long gone.

Back in the day we sold a few DNM pre-amps, which were good but couldn't get along with the power-amps, which were a bit 'tweaky' with their plastic cases, DIN sockets and low output. Very expensive.

[hifi_dave]

It's an old site, though appears to have been updated recently. I was in contact with Dennis for years but I was under the impression he was going to retire.

[Firebottle]

Now, where can I find a second Monarchy Audio SM-70???????