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Amplifier necessity
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cmjohnson



Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s

Posted: Wed Nov 21, 2007 2:59 am    Post subject:

Actually, the KMA-400 is the bigger brother of the 160. The 160s have two pairs of heat sink assemblies, the 400 adds a third.


Yes, my 160s each draw about 7 amps from the outlet, whenever they're turned on. The coldest winter nights that Florida has to offer
are completely defeated by having both amps run all night. In the summer, I've got to set the house AC to 72 degrees and set up a fan
at the door and another fan oscillating on the amps in order to keep the room at 80 degrees.

They sound awesome but there is no doubt that the heat penalty is substantial.


Still, I wouldn't trade them for anything less than other, newer Krell amps.


CJ
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Moose



Joined: 09 Mar 2006
Posts: 788
Location: Minnesota

Posted: Wed Nov 21, 2007 3:23 am    Post subject:

Quote:
Actually, the KMA-400 is the bigger brother of the 160. The 160s have two pairs of heat sink assemblies, the 400 adds a third.


Well, actually - yes. I mispoke. I have the brochure for the KSA-80 and KMA-160 before me. The KSA is the stereo version, the KMA is the mono version. For the mono version you had to either buy it that way or send your KSA back to the factory for modifcation and, of course, get another one. No option for bridging on these amps. I owned the stereo KSA-200; the mono version was the KMA-400, as you rightly said. Terrific amps, very well built (and no turn-on trasient, unlike my previous equally heavy Levinson ML-3) but too much overkill for me. The KSA-200/KMA-400 drew 15 amps continuously each. At the time I was living in an older house with older wiring on a 60 amp service! That's ridiculous. I don't know how I ran it for as long as I did and not burn the house down. And the heat! Much too warm in the winter, intolerable in the summer. I only had window air conditioning at the time. Mine made all sorts of noise while it warmed up and cooled down. I suppose yours does the same. Wished I knew what happened to it and where it is now.

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Tom.W



Joined: 09 Mar 2006
Posts: 6635


Posted: Wed Nov 21, 2007 3:47 am    Post subject:

I've got the Krell KAV-500. One of the best 5 channel amps I've ever heard. 100watts into 8 ohms and 200 watts into 4. Found it in a pawn shop for $500. Also no risk of causing a major power outage Wink
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AnalogRocks
Forum Moderator


Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada

TV/Projector: Sony 1252Q, AMPRO 4000G

Posted: Wed Nov 21, 2007 5:18 am    Post subject:

I was running so much power at my apartment one night I made the CRT computer monitor screen shrink and the flourescent desk lamp go dim. Then the phone rang and thuss ended the fun.
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cmjohnson



Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s

Posted: Wed Nov 21, 2007 2:02 pm    Post subject:

My KMA-160s are UTTERLY silent. Not even any creaking or cracking noises when they heat up and cool down. When they're running with the input disconnected, they make NO noise that can be heard from the speakers, even with your ear right up against them.

Newer Krells are supposed to be even quieter, but I think that's a difference that makes no difference.


My amps have a unique story behind them.

They'd been involved in a house fire but they hadn't been burned in the fire. However, they did get hosed down and put out along with
the fire, and got their fair share of ash and durt washed into them in the process.

Then they were left to rot in a store basement for two years. Untouched.

Frightening, I know.


I bought them "as is" for 500 bucks plus shipping. Sight unseen. Frankly I didn't even know what they'd look like.


When I got them, I was impressed and also concerned about their condition.


So, I tore one completely apart and rebuilt EVERYTHING. Resoldered any and all corroded or oxidized solder joints with highly
activated rosin flux and fresh solder, brushed down all components and inspected for damage, checked connectors, cleaned
and replaced as necessary, and went so far as to refurbish or replace every last piece of hardware in the amp. I replaced
terminal strips, connectors, lugs, sockets, whatever wasn't right. And I electrically tested EVERY driver transistor and power
transistor out of circuit to verify that nothing had blown up. I also did cosmetic restoration to the best of my abilities, and that
came out quite nice. I made one cosmetic change to these amps as the front handles had been damaged, but those are huge
chunks of milled aluminum in a finish that's not easy to get duplicated. So I refurbished them and had them anodized black,
and frankly that makes them look a lot more modern.

As a result, if you ever find a pair of KMA-160s with black handles, check with me and see if mine have been stolen,
as I don't plan to ever sell them! They're unique due to this...plus the whole rebuilt from the dead thing. That hasn't
happened very often.

It took 20 labor hours to complete the task for the first amp.

Then I did the same process on the second amp. Another 20 labor hours.

In total, ONE output transistor was bad and had to be replaced, out of both amps.


When the amps were powered up after all my work, they simply started working as if nothing bad had ever happened to them.

It's been about nine years now and they're as solid and steady as any piece of gear you've ever seen.


Refurbishing these amps was a great project, one that has given me continuous satisfaction for almost a decade now.


Krell had declined to repair these amps, saying it couldn't be done. No reference to cost-effectiveness, they simply
thought the amps could never be brought back to reliable service.

Nine years of reliable service says they were insufficiently optimistic. Smile




CJ
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Curt Palme
CRT Tech


Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC

TV/Projector: All of them!

Posted: Wed Nov 21, 2007 3:29 pm    Post subject:

cmjohnson wrote:


Krell had declined to repair these amps, saying it couldn't be done.

CJ


If that isn't the biggest reason to repair something, I don't know what is. I love proving people wrong.. Thumbs Up
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cmjohnson



Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s

Posted: Wed Nov 21, 2007 4:46 pm    Post subject:

Yes, I like doing that and I also love doing "impossible" repair work, like replacing 180 pin flat pack surface mounted ICs with nothing but a pair of tweezers and a hand-held heat gun, resulting in a perfect chip swap and a repaired radio.

Lately I've been getting a lot of practice at surface mount device work, and I'm not afraid to change out ANY SMD component now,
not even BGA devices.


CJ
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