Krell KSA 100mkII Clone

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#2,701
AndrewT said:
The Sprague are rated at 50Vdc
That is too low for the ksa100 which at nominal mains voltage and fully loaded is already at 52Vdc.
When mains is high and/or the loading is reduced, the voltage on the smoothing capacitors will rise to way above 52Vdc.

You need to use 63Vdc, or higher, smoothing capacitors.
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Yes I know. I just showed them as an example of an old Sprague that's still has retained its caprating over almost forty years. I took them out of my Levinson ML-2's and put new Cornell Dubiliers in place of them.
I just keep them for potential ML-2 buyers (they are very picky in the Far East) that insist that the original Sprague caps are in the ML-2. Have to reform them probably. But I will keep my ML-2's for now though.
I'm incllined to order two pairs of Rifa PEH200's 100mF 63V for my Krell.
 
#2,704
100 Watt Krell with and without forced cooling

http://www.diyaudio.com/forums/attachment.php?attachmentid=599498&stc=1&d=1487180552

Krell KSA-100 vs KRS-100

The KSA-100 almost looks cute in comparison.
I do not have the KRS-100 but it shows I think how much cooling extrusions you need to get rid of 100 Watts mono with natural convection although the KRS-100 will probably deeper biased into 4 Ohms then the KSA-100.
 

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#2,706
Yes, I know I have the Krell KSA-100 Mk2 and it illustrates so beautiful in my opinion what it takes to cool down a fixed bias Class A 100 Watt amplifier.
Was the KSA-80B also biased to 80 Watts Class A?
I remember those heatsinks exceeded the 19" rackmount width just as the KRS-100 & 200 but had somewhat lower profile.
 
#2,707
Mark Allen said:
Well, KSA-100 had dual forced air cooling by fans which makes the cooling a lot more efficient than the convection Krells and also probably longer lived. I used to own a KSA-80B and that thing ran really hot. My KSA-100 is also fan cooled and stays cooler over all.
Mark
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I'm halfway reading this entire thread so I will probably see some of your KSA-100 clones soon I hope. Most of the information is hard to grasp for me but I do like to read it anyway. Sad, the KSA-100 wiki is no longer available.
 
#2,708
RobertS61 said:
I'm halfway reading this entire thread so I will probably see some of your KSA-100 clones soon I hope. Most of the information is hard to grasp for me but I do like to read it anyway. Sad, the KSA-100 wiki is no longer available.
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If at least one person will end up using a clone board inside an original KSA100 I would be quite happy. I could have merrily used just any old layout method for the clones but I faithfully copied the form factor (with some improvements) to allow drop-in replacements of old boards with clones. Sadly the original owner for whom I had this in mind never followed through.
 
#2,710
PWatts said:
If at least one person will end up using a clone board inside an original KSA100 I would be quite happy. I could have merrily used just any old layout method for the clones but I faithfully copied the form factor (with some improvements) to allow drop-in replacements of old boards with clones. Sadly the original owner for whom I had this in mind never followed through.
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I know that you did this and that was a good rational decision I think.
If I had a Mk1 (I once had in 1989 with the fans blowing downwards and one if them was already wobbling so that I had to shorten the blades with a womans nail file) I would be certainly interested in a dropin replacement.
Especially the goldboards (just like the Thresholds had) look great and the components would be better I think.
 
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#2,711
2SA991 said:
I think about to recap mine with Epcos Sikorel 105 47000mF
68V

Regrds
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Hi, I don't know anything about these Epcos caps to be honest.
I used mostly Cornell Dubilier and now I bought four PEH200 from Kemet (RIFA) because I heard that they were really good on this forum. The PEH169 Series is supposedly even better but very hard to get. The original Spragues are over 30 years old so I think, but do please ask here, it's good to get some fresh ones.
Mine were from RS Components.
http://www.diyaudio.com/forums/attachment.php?attachmentid=599635&stc=1&d=1487256732

The blue Sprague that you see is from another amplifier not from my Krell.
 

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#2,713
Another stange thing I noticed is that the new capacitors I ordered from Nippon Chemicon and KEMET were all 17% (NC) an 13%(KEMET) below their spec of 100.000uF. The four old Spragues I have from 1978 were all 10% above their rating from 61.000uF. The KEMET's should weigh around 800 grams but the only weigh around 625grams and the Sprague and NC weigh around 1000 Grams.
Maybe the electrolytic fluid in the KEMET is more concentrated the in the American ones?
Anyone can explain thttp://www.diyaudio.com/forums/attachment.php?attachmentid=599636&stc=1&d=1487257948his.
 

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#2,716
RIFA vs EPCO 63V, 100mF

These are the differences when you would choose the 100mF from that same Sikorel Series.
I've chosen a large can capacitor that has the same diameter and height as the old cap for easy replacing them.
Maybe a specialist can draw a conclusion which one is the best for using in our Krell KSA-100 Mk2's. I certainly wouldn't know
Maybe another large can?
http://www.diyaudio.com/forums/attachment.php?attachmentid=599643&stc=1&d=1487259489
 
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