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Old 28th February 2005, 12:15 PM   #1001
wim is offline wim  Netherlands
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I am talking about Fischer SK 109 heatsinks with alu plates to make a windtunnel (they are optional), 18 cm high, and sorry, i see that it is 0,3 K/W without fans.

They look pretty like the ones in the original Krells.
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Old 28th February 2005, 01:22 PM   #1002
NUTTTR is offline NUTTTR  Australia
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Fans have proved AMAZINGLY valuble....
I was running 60mv bias (approx 88ma of bias = about 3.7w of dissapation per device...heatsink sat at about 58deg after 3 hrs...
I added a 12v 8cm fan running @ 9v...
Now i have 215mv bias (!) on a 2.7c/w heatsink, with fan, the heatsink is a pretty stable 48deg - i am now running 316ma of bias per device... dissapating about 13.6w/device... about 27w for the heatsink!
That's with 43v rails... just in case my maths is wrong... it's not heating the room, but considering it's running 1 set of outputs!!
Not bad! (the outputs would probably blow if i cranked it... but i'm not going to!)

Aaron
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Old 28th February 2005, 01:41 PM   #1003
VT67 is offline VT67  Belgium
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Hi Wim

Just had a quick look at Fischer's website and I think I'm gonna try to get my hands on one of these (see att)
They are even more "Krell look a like"

Cheers
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Old 28th February 2005, 01:44 PM   #1004
K-amps is offline K-amps  United States
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Aaron your calcs are good... but you are only getting 1.6 watts of class-A output (at an efficiency of 5.88%) rest of your output upto 100 watts is class-AB/B. What OP devices are u using?.

Good for testing though. :-).
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Old 28th February 2005, 02:15 PM   #1005
wim is offline wim  Netherlands
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Yes GeWa, they look great and very "Krelly", but they are not very high i see in the datasheet, and i did not see how much K/W they are (eith and witout fan). Do you know this ratings?
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Old 28th February 2005, 02:23 PM   #1006
wim is offline wim  Netherlands
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NUTTTR, i asume you lower the value of C105 and C106 from 330 PF to a lower value, like 33PF or 47PF? Can you tell us what brand and type the new C's have, i can not find good quality C's with that value.
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Old 28th February 2005, 02:29 PM   #1007
VT67 is offline VT67  Belgium
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Okay Wim, some technical mumbo jumbo for you.
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Old 28th February 2005, 03:21 PM   #1008
wim is offline wim  Netherlands
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Whow, as i can see no temp. problems with these!
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Old 28th February 2005, 03:34 PM   #1009
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Default dhole - You missed the group buy, but if your lucky Troy might still have a couple...

His forum user id is rabstg.

Good luck!
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Old 28th February 2005, 03:42 PM   #1010
VT67 is offline VT67  Belgium
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Wim

The heatsink mentioned above costs 50 for 1m lengts. Not all that expensive I think. Delivery is about 2 to 3 weeks.

For the 33pF caps, I'm going for silver mica.
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