Nice circuit but the original is alot simpler and straight forword.
http://home.ca.inter.net/~lloyd.maclean/Krell/PWRREL.pdf
The 5 ohm/50 watt soft start resistor is on the main schematic here.....
http://home.ca.inter.net/~lloyd.maclean/Krell/MAIN.pdf
The original Krell DC offset sense is also very imple
http://home.ca.inter.net/~lloyd.maclean/Krell/OUTREL.pdf
Mark
http://home.ca.inter.net/~lloyd.maclean/Krell/PWRREL.pdf
The 5 ohm/50 watt soft start resistor is on the main schematic here.....
http://home.ca.inter.net/~lloyd.maclean/Krell/MAIN.pdf
The original Krell DC offset sense is also very imple
http://home.ca.inter.net/~lloyd.maclean/Krell/OUTREL.pdf
Mark
Stuart,
I added the location of the soft start resistor in the KSA... go back to the post above to see R-402, top center of the main schematic. It is just a chassis mount 50 watter that is mounted off the board. This same circuit could also short out a CL-60. Time for cooling down the CL-60 would be needed to effect a soft start immediately again... say in a power bump situation..... or a blown fuse or bridge may result.
Mark
I added the location of the soft start resistor in the KSA... go back to the post above to see R-402, top center of the main schematic. It is just a chassis mount 50 watter that is mounted off the board. This same circuit could also short out a CL-60. Time for cooling down the CL-60 would be needed to effect a soft start immediately again... say in a power bump situation..... or a blown fuse or bridge may result.
Mark
Nice, the softstarter shows the Papst 4800x as the vent for the KSA100.
Should be the same as on the KSA50.
The 4800X is a 5 inch 32dB model at 1750rpm.
European version is 4850N.
the 4800x is a 9 watt model, with 250R in series it is derated to 6.5 watts on the KSA100.
So it is running at around 50% rpm in the KSA100.
Great fan.
Should be the same as on the KSA50.
The 4800X is a 5 inch 32dB model at 1750rpm.
European version is 4850N.
the 4800x is a 9 watt model, with 250R in series it is derated to 6.5 watts on the KSA100.
So it is running at around 50% rpm in the KSA100.
Great fan.
To Mark : Parallel connection of relay contacts is not good, 'cos they don't switch at the same time and so first switched contact " pull " full inrush current and after time is destroyed and function take second switched contact etc., till the time, when is all relay destroyed. Multipilng of contact you can use only in case, when truecoming current is lower than nominal current of one contact. In this case is reliability of relay very high.
I am aware of the disadvantages of parallel relay contacts... there are advantages and dis-advantages of doing so. In the case of the Krell delay turn on it wouldn't matter because of the 5 ohm resistor thats in the line before the relay ever makes contact to effectively short it out. The resistors have already lowered the inrush current and the amp is actually operating through the resistir for a fraction of a second. Hence no inrush current ever passes through the relay contacts themselves. Were there not an inrush limiting resistor when switching AC one would just use a snubber across each set of parallel contacts to eliminate any arcing at the contacts....
Mark
Mark
Upupa - Thanks for that!
Jacco - i agree it will be a tough time keeping it cool, but that's half the point of having the bias switch is to control that... Hopefully it will cut back on the heat a lot! I've found some fans that i want to use, etc they are 20db (!) @ 2500rpm... so if i use those, i seriously doubt i'll hear them, if i do i'll just regulate them to a lower voltage!
I do agree that 80+ is a bad temp to be at, so i plan on keeping it below that... maybe i should use a thermal switch on the heatsink to switch to lower bias if it's overly hot? Unless you can think of a problem with that with biasing, etc.... But i will have the fans running at full speed over a certain temp, etc so should be ok!
Aaron
Jacco - i agree it will be a tough time keeping it cool, but that's half the point of having the bias switch is to control that... Hopefully it will cut back on the heat a lot! I've found some fans that i want to use, etc they are 20db (!) @ 2500rpm... so if i use those, i seriously doubt i'll hear them, if i do i'll just regulate them to a lower voltage!
I do agree that 80+ is a bad temp to be at, so i plan on keeping it below that... maybe i should use a thermal switch on the heatsink to switch to lower bias if it's overly hot? Unless you can think of a problem with that with biasing, etc.... But i will have the fans running at full speed over a certain temp, etc so should be ok!
Aaron
"Maybe somebody else already brought this up but the thread is getting a bit long to look it up. Where can I find the 2SC3955 (Q111)? Neither Digi-Key or RS have the darn thing in there program.
It also seems that it is a discontinued item." Don't know if they've been discontinued but just use another MJE15032 at that spot. I went with that semi and it tracks the temperature very well.
Mark
It also seems that it is a discontinued item." Don't know if they've been discontinued but just use another MJE15032 at that spot. I went with that semi and it tracks the temperature very well.
Mark
Stuut still has the 2SC3955 on stock according to their homepage.
Nuttr,
mind telling the brand and model of the vents you are using ?
The most silent Papst at 2500 rpm still does 40 dBA, and that is a full alloy model that costs +$50.
Rectification on my KSA100 posting: the 4800X Papst in the Krell should be at 85 % MCR speed, too noisy for my taste.
Nuttr,
mind telling the brand and model of the vents you are using ?
The most silent Papst at 2500 rpm still does 40 dBA, and that is a full alloy model that costs +$50.
Rectification on my KSA100 posting: the 4800X Papst in the Krell should be at 85 % MCR speed, too noisy for my taste.
Jacco - sorry - they are 1900rpm! 
http://www.coolpc.com.au/catalog/product_info.php?cPath=127_5_84&products_id=742
That's what i'm ordering... not sure how to fit them on a small heatsink (it's not 80mm deep on the fins!) But i'll work it out
Aaron
http://www.coolpc.com.au/catalog/product_info.php?cPath=127_5_84&products_id=742
That's what i'm ordering... not sure how to fit them on a small heatsink (it's not 80mm deep on the fins!) But i'll work it out
Aaron
Nice ventilator, Aaron.
And they say the Chinese dont make good stuff.
Just a little note:
The props on that vent are turbine-shaped, that means you'll loose plenty air volume displacement when you derate such a vent.
With 3 vents on your heatsinks that adds 5 dB to the noise, giving 25 dB vent noise per channel.
That is probably lower than the original KSA50 and KSA100, some here found those acceptable.
You will need to place these vents in a duct, or your amplifier will be filled with debris within a few.
In my experience Aussies are noisy anyway.
And they say the Chinese dont make good stuff.
Just a little note:
The props on that vent are turbine-shaped, that means you'll loose plenty air volume displacement when you derate such a vent.
With 3 vents on your heatsinks that adds 5 dB to the noise, giving 25 dB vent noise per channel.
That is probably lower than the original KSA50 and KSA100, some here found those acceptable.
You will need to place these vents in a duct, or your amplifier will be filled with debris within a few.
In my experience Aussies are noisy anyway.
Vents need to blow, not suck, ventilators are much better in creating overpressure.
Best is to place a vent under a heatsink, as Mark already mentioned.
Downside is that you have to dust the top of an amplifier often, a reason why amplifier companies as Krell placed the vent on top, i guess.
Best is to place a vent under a heatsink, as Mark already mentioned.
Downside is that you have to dust the top of an amplifier often, a reason why amplifier companies as Krell placed the vent on top, i guess.
jacco vermeulen said:Nice ventilator, Aaron.
And they say the Chinese dont make good stuff.
Just a little note:
The props on that vent are turbine-shaped, that means you'll loose plenty air volume displacement when you derate such a vent.
With 3 vents on your heatsinks that adds 5 dB to the noise, giving 25 dB vent noise per channel.
That is probably lower than the original KSA50 and KSA100, some here found those acceptable.
You will need to place these vents in a duct, or your amplifier will be filled with debris within a few.
In my experience Aussies are noisy anyway.
Yes! We are noisy! I was planning on putting foam filters on the "bottom" of the amp (as the fans will be under the heatsinks blowing up, they will have a "sheild" around them though...) so the amp doesn't fill with dust...
I think 25db is fine and i have no problems with that level at all, i'm running 3 35db fans at the moment... @ 9v and they are reasonably quiet... to an acceptable level, anything less is a definate bonus, but not a total loss!
Aaron
P.S. Just read your last post... I am putting them under
It will blow up, and it will most likely create dust! But no problem, a quick vaccum!