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Old 24th January 2009, 05:55 PM   #7841
john65b is offline john65b  United States
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Andrew,

I am thoroughly confused now - please see here...

KSA100s

Shows pics of the KSA100S with 8 pairs output devices. You were even in the posting. Is this not a KSA100s?? It's where I got my pics in my post...

It must be the difference between the KSA100 and KSA100s that is confusing me....could it be the KSA S series has double the output devices than the non S versions??

CORRECTION. My amp has 3 pairs/channel...so as I was saying, at 4ohms, 72 wpc Class A, and at 8 ohms 144 wpc Class A. The 1A per device was correct.
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Old 25th January 2009, 07:06 AM   #7842
AndrewT is offline AndrewT  Scotland
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Hi,
the Krell info in my post7840 is correct.

That spreadsheet is an easy way to avoid the arithmetic.

But it is flawed. This was pointed out at the time and provided users understood what was needed as input data it gave acceptable results.
I posted a modified version.
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Old 25th January 2009, 07:17 AM   #7843
AndrewT is offline AndrewT  Scotland
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Back to your amp.
3A bias dissipates 234W. That's a lot from 3pair of 150W devices.
Considerably worse than KSA50, which uses 1kW of 200degC devices, whereas your plastic packaged devices are rated to 150degC and 900W.

The amp goes into ClassAB when output current exceeds 6Apk.
So the amp becomes a KSA69 and can push a 4r0 load to 128W.
It cannot drive a 2ohm speaker.

and that 2007 post points out the BIG difference between a 100mk2 and 100s.
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Old 25th January 2009, 03:15 PM   #7844
john65b is offline john65b  United States
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Thank you Andrew...I always appreciate your input.

I have made a comparison spreadsheet on all Krells discussed in this thread (I believe I have most of it correct). If anyone knows if values are incorrect we can update the file. I have included mine in the comparison...I think this is the updated spreadsheet Andrew is referring to.
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Old 25th January 2009, 03:19 PM   #7845
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Here is the spreadsheet (zipped). Maybe we can add or update the file with all accurate info and post on the wiki as a working file? Maybe no interest in it, but hey...
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Old 25th January 2009, 03:24 PM   #7846
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And another more informative spreadheet that adds info on heat sink and Junction temps...again, the listed defualt is my krell conditions. I have Kapton Isolator, .1C/W (methinks) and I really feel the 114 Heatsink temp is accurate on my amp...

Understand I did not author this spreadsheet (someone far smarter than I) as it was original for an Aleph build. I merely modified a few items to use it for the Krell...To whoever wrote the sheet, thanks!
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Old 25th January 2009, 07:52 PM   #7847
AndrewT is offline AndrewT  Scotland
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ksa144.xls is set up for a single ended ClassA amplifier and gives the wrong information for a push pull Krell.
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Old 25th January 2009, 07:57 PM   #7848
AndrewT is offline AndrewT  Scotland
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krell various uses the wrong formulae in some cells and labels other confusingly.
eg.
Look at "mine".
max ClassA output power is (far) greater than maximum ClassAB power into the same 8r0 load resistance. Nonsense!
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Old 25th January 2009, 07:59 PM   #7849
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by john65b
And another more informative spreadheet that adds info on heat sink and Junction temps...again, the listed defaalt is my krell conditions. I have Kapton Isolator, .1C/W (methinks) and I really feel the 114 Heatsink temp is accurate on my amp...
Kapton (0.07) 10times better than mica (0.7)? do more reading.
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Old 25th January 2009, 09:06 PM   #7850
john65b is offline john65b  United States
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Quote:
krell various uses the wrong formulae in some cells and labels other confusingly.
eg.
Look at "mine".
max ClassA output power is (far) greater than maximum ClassAB power into the same 8r0 load resistance. Nonsense!
I always thought something was fishy there, but never questioned it...

Quote:
Kapton (0.07) 10times better than mica (0.7)? do more reading.
I was not the author of the spreadsheet...

Quote:
ksa144.xls is set up for a single ended Class A amplifier and gives the wrong information for a push pull Krell.
It appears to yield same results as the one we have been using on this thread (that appears to be still incorrect), that's why I have been using it - dissipation, wattage, etc. Wouldn't a single ended design be lower power output than PP?

I apologize for causing such confusion...I can ask the moderators to remove my posts if required...
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