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I have an original Krell ksa 100 that was barely used over the years. The sound is great with no issues. My preamp is a new Audible Illusions 3B and I am powering Hales Revelation 3 speakers which show about 4 ohms to the amp. These speakers need a good amp like Krell. Here's my issue: My old Krell KAV 250, which was NOT a pure class A amp, ran very hot to the touch with this same system. My newly acquired KSA 100, which runs pure class A , never gets that warm. I had read from most people that this beast could heat a room. When I put my hand near the bottom back, where the internal fans are blowing "down" on the heat sinks, I can feel some heat, but nowhere near what the KAV 250 was producing. One side of the KSA does run warmer than the other side, but no issue with the sound. But the lack of heat overall is not what I was expecting. I realize that many complain about the excessive heat from these things, but I'm not getting that, and I usually play my vinyl somewhat loud. Krell, as well as some other amp technicians have stated that as long as the sound is good, don't worry about upgrading any parts. It does sound great, and maybe the lack of heat is due to the fact that this beast was meant to power speakers down to 1 ohm, and views mine as a walk in the park. Would love to hear about this from other Krell owners or those with experience in this area. Thank you.
Follow Ups:
Finally got my KSA 100 back from Krell. They went through it completely and replaced a variety of parts. Parts alone cost me about $500 and about $500 for 4 hours of labor. I took off the top and it looks new! They cleaned everything. Krell stated that the one side that was hot was nearing an overload. This is an original from about 1982, so it was ready for recapping and such. Now the service manager told me that the amp will now run cooler, and that it will take about 30 hours to fully break it in. As far as the amp running cooler, he's not kidding. I've been pushing it now for hours with loud music to my Hales speakers, and the heat sinks are cool! It sounds great even though it's far from broken in, but I'm concerned or surprised at the complete lack of heat. I mean the Boys at Krell must know what they are doing, but I've never had an amp not get hot after driving it like I did. I thought this Krell was supposed to run very hot? Is this due to the break in period? I'm assuming that Krell's own tech's set the bias correctly. Odd.
Which version KSA100 do you have, you said sinks, is it the plateau bias version ..?
post a pic if possible...
Original version Mk I with internal fans on top blowing down on heatsinks internally.
OK,
A Mk1 will have it's most heat with working fans at idle, unless running at 2 ohms..so one like this ..?
https://www.youtube.com/watch?v=kqSkh08AmKM
Best to check its idle current draw , then it wll be obvious where they biased the amp at.
Regards
Edits: 12/22/14 12/22/14
Yes, that's the one. Forgive me, but I have no idea how to check the idle current draw. Hopefully, the boys at Krell got it right and that with fans running, all is well by running cool.
Any updates Samman ........?
Krell stated that with the newer parts, it can now run cool and still be biased for full class a operation. It does seem to go against standard class a operation, which is hot running. Sound wise, it's fantastic. The soundstage is wide and deep with deep bass and beautiful highs. I have been pushing it hard and leaving it on for hours. When I touch the heat sinks from underneath the amp, they are room temperature. I'm just so confused. Why no heat?? Krell must know what they are doing. Is it possible with the upgraded parts that they can now make this amp more musical than before without the effects of heat on this old design? Even the original literature and manual all state that ventilation is critical for this amp. I am confused. Has anyone else had Krell update a amp and find it running cooler than before?
Thanks! for the update samman11.
I drove the KSA 100 to Krell back in early November. They went through it and upgraded many caps and such and brought it back to proper specs. I'm picking it up in a few days and can't wait to have my amp back all ready to go for the next 25 years. Hopefully. Cost me just over a $1000, but Krell stated I have an original (serial 237) that Dan probably made in his garage. Can't wait to hear it.
Krell fan here, keep me posted as you beak-in this amp.
Well, I never owned a Krell KSA, and I'm no technician but my comparatively little, and modestly powered 2 x 18watts SONY TA-N86B pure class A amplifier driving 104dB sensitive speakers with 8ohms impedance runs very very hot even at idle; I would think any pure class A amp that's not burning hot to the touch has bias issues... some class AB amps with strong bias current already manage to produce a lot of heat...
reading some KSA100 reviews seem to confirm that the beast produces "enormous amounts of heat".
True class-a amplifiers run thier hottest at idle ......
I think the early "fan amps" didn't feel nearly as hot as the later heat sink only designs, but they should still feel pretty warm.
I've attached a link with the best description to biasing that I could find.
Would say that I'd probably go closer to 500 mV than the 325 mV suggested. Believe the factory spec was 600 mV.
Great Amp--I owned the KSA50 version--it was as good as Krell got together with your one.
I ran it with Quad 63's and yes it did get pretty hot.
I know the Hales and probably not a tricky load but some warmth-more than you have,
should be evident I'd thought. It's been a while and I'm not certain if the KSA Series had
bias pots accessible on the boards--if so possible yours are wound right back
i.e way out of Class A.
A Tech could advise?
Anyway as you state all sounding fine--so seems performing to Spec.
Good listening
Des
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