View Full Version : Krell Club
Ali Tait
06-05-2021, 16:53
Picked up a KSA 100 MK 1 in very good nick today, very pleased with it. Of course, once I got it home I had to get it's top off for a good going over..
Good job I did, first noticed the Zobel connection on one of the positive speaker posts had come adrift, and whilst I was doing that, noticed that some utter idiot had taken the speaker protection fuses out of circuit. Who the hell does that on an amp with this capability??
Did he think it would sound better or something..
Other than that it looks in great original condition.
Anyone have a service manual?
https://i.imgur.com/uHi4IMr.jpg
https://i.imgur.com/VjBxbPv.jpg
You've been waiting a long time to collect that. Or seems like it anyway.
E-mail Krell, they sent me the schematic for the 50S right away.
You try it out yet?
Ali Tait
06-05-2021, 18:01
Yeah been ages mate, just the way it worked out.
Thanks, I'll try Krell. Wasn't going to bother, seller needed a new power switch for the amp a couple of years ago, they weren't interested in helping.
Won't get a chance to try it properly for a while, staying at my girlfriends and don't have any gear here, other than my resistor box and my Ether 2 cans, so will have a listen tomorrow.
Heard it at John's place though, sounded great.
well it is an old amp, I suppose they ran out of the stock of spare power switches a long time ago.
Ali Tait
06-05-2021, 18:41
Possibly. They do still service them though, I'd imagine it's a fairly common service item.
I didn't realise that they still offered service on them.
Ali Tait
06-05-2021, 20:02
As far as I know they do.
Ali Tait
06-05-2021, 20:13
KSA250 serviced a few years ago-
https://forum.audiogon.com/discussions/upgrade-krell-ksa-250-to-what
Hope you get her sorted mate, a stonker of a classic amp.
Bit of fettling it'll be back to its best.
Ali Tait
07-05-2021, 05:17
Cheers mate, just a simple soldering job. It sounded great at John's place.
8 hour round trip to get it though..
Ali Tait
07-05-2021, 13:57
Fuses back in service, all is well and I can't hear any difference to the sound on my cans.
https://i.imgur.com/VFKji0C.jpg
Ali Tait
07-05-2021, 15:01
Have to bring it round sometime mate, compare it to the Meridian.
wee tee cee
08-05-2021, 09:41
Look forward to your impressions.
Always fancied a Krell....
Ali Tait
12-05-2021, 13:58
Some more work on the Krell, swapped out the Roederstein Lytics-
https://i.imgur.com/sJ6s19G.jpg
https://i.imgur.com/hU9kKkq.jpg
All back together now. Just letting it warm up before setting bias and DC offset. I measured the bias the other day, one channel is running a bit hot at 673mV, I'll drop both channels to 575mV or so, that'll give the output stage a bit of an easier life.
This gives a good idea of the size of the main PS caps, they are not small-
https://i.imgur.com/pFoWpY1.jpg
These look to be fine so I'll probably just leave them in for now
https://i.imgur.com/AampGk7.jpg
Ali Tait
12-05-2021, 13:59
Look forward to your impressions.
Always fancied a Krell....
Missed this, me too Tony, been an itch to scratch since I was a young lad.
the hyundai kona has an 8 speaker krell system in it :ner:
Ali Tait
12-05-2021, 16:00
LOL how many amps?
Some more work on the Krell, swapped out the Roederstein Lytics-
https://i.imgur.com/sJ6s19G.jpg
https://i.imgur.com/hU9kKkq.jpg
All back together now. Just letting it warm up before setting bias and DC offset. I measured the bias the other day, one channel is running a bit hot at 673mV, I'll drop both channels to 575mV or so, that'll give the output stage a bit of an easier life.
This gives a good idea of the size of the main PS caps, they are not small-
https://i.imgur.com/pFoWpY1.jpg
These look to be fine so I'll probably just leave them in for now
https://i.imgur.com/AampGk7.jpgI had the reservoir caps from my 1975 Accuphase monos checked out.
Still in spec:)
Big old ELNAs and 500+ Watts into 4 Ohms per mono.
Ali Tait
12-05-2021, 18:29
Yeah not surprised, top quality caps Justin. I don't have a scope so can't check mine, will probably lug it to Nicks' sometime to make sure, but they are most likely fine.
Firebottle
16-05-2021, 08:54
I've joined the Krell club:
https://i.imgur.com/xmrmUjs.jpg
Well... not really, just got something meaty to get my brain around.
Pigmy Pony
16-05-2021, 09:08
I've joined the Krell club:
https://i.imgur.com/xmrmUjs.jpg
Well... not really, just got something meaty to get my brain around.
You need to put two of them in the other room, your house is starting to tilt :)
Opti-cal
16-05-2021, 18:46
I've joined the Krell club:
https://i.imgur.com/xmrmUjs.jpg
Well... not really, just got something meaty to get my brain around.
Sounds like you've got a Krell of a week ahead of you Alan....
Ali Tait
16-05-2021, 20:19
That lot will reach critical mass shortly.
That lot will reach critical mass shortly.
Well, the table will :D
Sounds like you've got a Krell of a week ahead of you Alan....
Genius. :lol:
Firebottle
17-05-2021, 14:07
For those of you not aware of the heavy engineering in a Krell, these are the output straps :eek:
https://i.imgur.com/BCIMUDO.jpg
Ali Tait
17-05-2021, 17:37
Busbar output lol.
Firebottle
18-05-2021, 09:57
Putting this here as a reference for others. This is specifically for a Krell 50S but shows the general procedure.
The relays are mounted on the output boards but contact cleaning is possible without removal of the relays, but one particular specialist tool is required.
Shown is a modified stainless steel tweezer, one arm is bent up to provide a very strong but thin hook, the other is a diamond spatular used to do the actual contact cleaning.
https://i.imgur.com/9bAeC1e.jpg
Firstly remove the back plate, 4 torx screws.
https://i.imgur.com/zdLw608.jpg
Remove the two output bus bars to give access to the relay.
https://i.imgur.com/kfKeYZJ.jpg
The speaker terminals need to be loosened as there is no give in the bus bars, to enable removal.
https://i.imgur.com/bnVZwdG.jpg
The relay cover now has to be removed using the hook to lift the plastic edge which slips over the retaining lug on the relay base.
This is the most difficult part of the job because of limited access, particularly on the blind side.
https://i.imgur.com/ECXZcgK.jpg
The return spring on the top of the relay needs to be disconnected from the contact bar, placing finger on the other end so the spring isn't lost.
https://i.imgur.com/EPzzmD7.jpg
The contact bar can now be lifted from the usual position to gain access to all the contact pads. Use the diamond spatula to clean the pads.
https://i.imgur.com/NsWbTLJ.jpg
Reassemble in reverse order then repeat for the other channel. Ensure connections are very tight on reassembly.
https://i.imgur.com/QVne34n.jpg
AJSki2fly
28-09-2021, 09:22
I joined the Krell club with a KSA-80 about 4 months ago after PXing my 300B set in for it and some other gear. I did this after talking with Martin(Macca) and Alan(Firebottle), my main aim was to get more control of the bottom end and perhaps more depth/space to the musical presentation. My reasoning to make the change was that I suspected the 300B was straining to control the WB Vectors at sensible listening volumes, and at times was creating a muddied image, both Martin and Alan confirmed this was extremely likely.
The KSA-80 turned up just as I started looking for a Krell, it was at Audio Emotion and I had a long chat with Gary about it and its history, originally a demo unit for some time at a dealers in Edinburgh and then a single owner unit who owned 3 houses in Scotland and had 3 relatively high-end systems, the system the KSA-80 came from had not been used very much over 20 years and was in very good condition. So Gary and I struck a deal including a 6 month warranty.
The KSA-80 arrived and as reported elsewhere the instant I powered it up I was blown away by the musical presence and sheer power in the musical portrayal, to use the old cliché "It sounded more real", so success at last and a good match for the speakers.
All went well for a couple of months and then one morning I noticed a very low level buzz from both channels, this was not affected by volume in any way, and was still present with everything everything else off and RCA's disconnected. I measured this and the 50-100hz buzz was around around 40-45dB with the mic about 15cm from the speakers, I would add you could not hear anything when music was playing, only went silent and was very low level. Due to the age of the amp I contacted Gary and sent him recordings of the buzz, he immediately agreed it should be investigated and fixed, he was happy to get it collected but I requested that we used Firebottle(Alan) who has worked on several Krells and is an accomplished Electronics Engineer, Gary agreed.
So 3 week ago I took the KSA-80 to Alan's, and he quickly diagnosed that some capacitors on the power control board were nearing the end of there life, not expensive about £2 each for new better ones. Also and quite important was that the 4 main power supply capacitors were measuring at around 25-33% of what they should be, maybe the previous owner had used it more than he said or they were just degrading with time. These Caps are huge, larger than Coke tins with 2 per channel and arranged in a square with massive copper buzz-bars connecting them up across the top. They are rated at 100v and 47000mF, but Alan advised they are running 50v to support the required voltage and current. Alan identified some good replacements which were virtually the same physical size and these were ordered, they were fitted very quickly although Alan had to make some minor mods as the new caps required 6m nuts/bolts fittings not the previous 5m. Alan tested the Krell out and the buzz has abated somewhat and it sounded very good.
I managed to get enough fuel and had a 10l spare fuel can in the boot, so I went up to Alan's early on Monday morning to collect the Krell, this is a round trip of 330 miles and the first 1.5 hours of the journey was abysmal with torrential rain and the MX5 aquaplaning twice even with nearly new tyres rated at A for the wet, some of the worst driving conditions I have experienced for many years. Alan and I were very pleased as Gary at Audio Emotion had already settled the repair bill.
I got home and Sue and I carefully extracted the Krell KSA-80 from the MX5's front seat, it had been carefully packed in place with lots of old towels and resting at the front on some large wooden blocks in the footwell, and tethered to the seat with a webbing strap around the 4 lifting handles for safety. I set it up and powered on and the buzz has subsided greatly. I duly put on a favourite couple of tracks of Shpongle Codex VI and was immediately struck by how much more the depth and bass control had improved, on further listening I feel it has a even more open spaciousness to the presentation. Some would say it could be that it was just the first initial impact and impression, however I listened to the Flower Kings next and noted improved detail, depth and control of the low end IMHO.
So I am very pleased with the result, a huge thank you to Alan, a lovely chap who is very knowledgable and truly helpful. Hopefully the Krell will continue to please for many years now.
Alan is becoming the unoffical UK service agent for Krell :)
Good that Audio Emotion did not mess you about and paid for the repair.
Firebottle
28-09-2021, 11:52
however I listened to the Flower Kings next and noted improved detail, depth and control of the low end IMHO.
So I am very pleased with the result, a huge thank you to Alan, a lovely chap who is very knowledgeable and truly helpful. Hopefully the Krell will continue to please for many years now.
Excellent result Adrian, I myself was struck with an improvement in the bass control.
Thanks for the kind words.
AJSki2fly
28-09-2021, 16:10
Alan is becoming the unoffical UK service agent for Krell :)
Good that Audio Emotion did not mess you about and paid for the repair.
Yes, but from what I saw he is into servicing a variety of gear, he is a busy chap.:eyebrows:
Powered by vBulletin® Version 4.2.3 Copyright © 2026 vBulletin Solutions, Inc. All rights reserved.