Krell KSA 50 pcb - Page 101

wim · 28th February 2005, 11:15 AM

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.

NUTTTR · 28th February 2005, 12:22 PM

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

VT67 · 28th February 2005, 12:41 PM

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

K-amps · 28th February 2005, 12:44 PM

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. :-).

wim · 28th February 2005, 01:15 PM

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?

wim · 28th February 2005, 01:23 PM

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.

VT67 · 28th February 2005, 01:29 PM

Okay Wim, some technical mumbo jumbo for you.

wim · 28th February 2005, 02:21 PM

Whow, as i can see no temp. problems with these!

Repute · 28th February 2005, 02:34 PM

His forum user id is rabstg.

Good luck!

VT67 · 28th February 2005, 02:42 PM

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.

28th February 2005, 11:15 AM	#1001
wim diyAudio Member Join Date: Sep 2003 Location: Nootdorp, Netherlands	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. __________________ Als er "X" artikelen benodigd zijn, blijken er "X" - 1 in voorraad te zijn.

28th February 2005, 01:15 PM	#1005
wim diyAudio Member Join Date: Sep 2003 Location: Nootdorp, Netherlands	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? __________________ Als er "X" artikelen benodigd zijn, blijken er "X" - 1 in voorraad te zijn.

28th February 2005, 01:23 PM	#1006
wim diyAudio Member Join Date: Sep 2003 Location: Nootdorp, Netherlands	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. __________________ Als er "X" artikelen benodigd zijn, blijken er "X" - 1 in voorraad te zijn.

28th February 2005, 02:21 PM	#1008
wim diyAudio Member Join Date: Sep 2003 Location: Nootdorp, Netherlands	Whow, as i can see no temp. problems with these! __________________ Als er "X" artikelen benodigd zijn, blijken er "X" - 1 in voorraad te zijn.

28th February 2005, 02:34 PM	#1009
Repute diyAudio Member Join Date: Jan 2002	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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28th February 2005, 12:22 PM	#1002
NUTTTR diyAudio Member Join Date: Nov 2004 Location: Australia!	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

28th February 2005, 12:44 PM	#1004
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	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. :-).

28th February 2005, 02:42 PM	#1010
VT67 diyAudio Member Join Date: Jun 2004 Location: Belgium	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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