Krell KSA 50 PCB

bikehorn said:
damn, i just missed out on the perfect heatsink on eBay. ahhh well. anyone know a good place to get a proper fan tunnel that would be right for a 50-60 watt version of this amp? actually i'd really love to be able to get 75 watts but that wold probably require even more heatsink....so i'm not very set on 75 wpc.



this might help
http://www.conradheatsinks.com/products/flat_hd.html

allan
 
Hi Bike,
I intend using 0.1C/W in each monoblock to allow Iq=3A from +-42Vrails to generate about 120W of ClassA output into 6r3 load.
Tc max<=56degC.
6r2 just happens to be about the minimum impedance of any of my speakers.
This proposal should never leave ClassA into any of the loads I might hang off the end.
The 0.1C/W comes from three 200by200by50 sinks arranged around three sides of the 190mm enclosing cubic enclosure.

A tunnel could be much smaller and MUCH cooler for the other internals.
 
kmj said:
didn't Troy post some sinks a while back?
Steve at Apexjr.com has some but I don't know how much they can handle thou.


Sorry for dropping off the face of the planet, but I am still trying to find a ladder to climb back up. :(

Troy still has them and they are packed and in storage for the moment while he is in Atlanta renewing some industry certs. (why am I typing in the third person? :confused: )

I moved all of my electrical tools and active audio related projects to Reputes house where I intend on us building our Krells this winter.

Once again I apologize for not being able to help but right now I am still in the middle of putting the puzzle back together.

Side note, the only thing I REALLY miss of the old life is not being able to read with the children every night before bed.
 
Sorry for dropping off the face of the planet, but I am still trying to find a ladder to climb back up.
Once again I apologize for not being able to help but right now I am still in the middle of putting the puzzle back together.

No need for apologizing here Troy, sometimes these things are harder than they seem. I now that in the end when you get all things back in perspective your life will be back on the right track. Good luck to you mate. ;)

Regards
 
AndrewT said:
Hi Bike,
I intend using 0.1C/W in each monoblock to allow Iq=3A from +-42Vrails to generate about 120W of ClassA output into 6r3 load.
Tc max<=56degC.
6r2 just happens to be about the minimum impedance of any of my speakers.
This proposal should never leave ClassA into any of the loads I might hang off the end.
The 0.1C/W comes from three 200by200by50 sinks arranged around three sides of the 190mm enclosing cubic enclosure.

A tunnel could be much smaller and MUCH cooler for the other internals.

I would actually like to achieve something similar, in an ideal world. i'm trying to model my amp sort of after old school 70's/80's Class A boat-anchor poweramps(Marantz SM-6 and the like, and in particular the Luxman M-05) and as they all had a lot of power i think i'd like to as well...so i was going to just increase the number of output devices, however, as i've been trying for a while, i've not been able to catch Mark at a good time for PCB buying, i have tentatively put my name in for 2 PCBs of the upcoming KSA100 boards...so maybe i'll just get my power that way.

i found some interesting fansinks on http://www.coolinnovations.com in the "power modules" section...including one that is rated for 0.07 c/w! they are not tunnels, but it turns out they are not far from me and possibly would make my life a lot easier.
 
Bikehorn
"including one that is rated for 0.07 c/w! they are not tunnels"

Physical Dimensions:
L 5.0"
W 5.0"
H 1.7"


Fan Data (4 fans per heat sink)
fan size in. 2.36x2.36x0.98
air f low CFM 33
static pressure in.(H20) 0.291
noise (dBA) 43
rated cureent (mA) 316
Voltage (V) 12
bearings ball bearing

Yes but 4 fans at 43dBA and 33CFM is a lot of noise.

allan
 
AndrewT said:
Hi Aw,
he's OK with the fan noise. He's going to have enough power going into his speakers that he will never notice!

BTW.
0.07C/W sink is going to be awfully big and thick and heavy.
Are you sure it can achieve that dissipation when passive?


Hi andrew
that was, this one rated
Physical Dimensions:
L 5.0"
W 5.0"
H 1.7"
http://www.coolinnovations.com/pdfs/2-505017R.pdf
except rated with the 4 fans going 33cfm

unfortunately it doesn't mention passive ratings
but looks interesting

allan
 
Passive thermal resistance will be awfull, it needs airflow between the pins to remove the heat.

The pin number and sizes lead to a surface of 329 square inches for the pins alone.
For an efficient heatsink that surface corresponds to ~0.35 C/W. For 0.07 C/W a high airspeed fan must reduce that by a factor 5, sounds fair.
 
i guess i never completed my post last night - you know it's late when...

anyway, the 0.07 c/w rating only applies when it's flat and the fans are blowing down, and that would take up too much space in the 4U rackmount chassis i wanted to use so i'm willing to take a small performance hit by standing it up on its side. also, i had no plans to use the noisy 4-fan complex they supply.

it seems there's a 130mm computer fan(fits 120mm mount) made by Thermaltake called the Silent Wheel rated for 55 cfm at 16 dBa, which is more than quiet enough for me even if i have two heatsinks. with a 30,000 hour life expectancy, i think it should do the job nicely even if the longevity rating is inflated.

here's a link, practically every online performance PC store sells it

http://xoxide.com/thermaltake-silent-wheel-130mm-fan.html
 
Fan Action

I'm not a big fan of fans, :xeye: , but I picked this up for $20 today. I washed it off and now it shines like new. It is machined already for 12 TO-3's. I think a stereo KSA-50 would be fine with just 12 output devices in total? I just picked up a third-hand set of DIY group boards a month or so ago. So this amp is coming together too. Slowly but surely.

Cheers,

Shawn.
 

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Re: Fan Action

TomWaits said:
I'm not a big fan of fans, :xeye: , but I picked this up for $20 today. I washed it off and now it shines like new. It is machined already for 12 TO-3's. I think a stereo KSA-50 would be fine with just 12 output devices in total? I just picked up a third-hand set of DIY group boards a month or so ago. So this amp is coming together too. Slowly but surely.

Cheers,

Shawn.


20$ ?
lucky #$$%%^&*!!!
;)
 
PinkMouse substitutes

Just thinking about ording some of these transistors but I wanted to get the nod that the second column are good subs for the PinkMouse boards?

Q1 MJW1302, MJ15004
Q2 MJW1302, MJ15004
Q3 MJW3281, MJ15003
Q4 MJW3281, MJ15003
Q5 MJW3281, MJ15003
Q6 MJW1302, MJ15004

Q107 MJE15033, MJE15029
Q108 MJE15032, MJE15028
Q109 MJE15032, MJE15028
Q110 MJE15033, MJE15029
Q111 MJE15032, MJE15028

Cheers,

Shawn.
 
Hi,
the MJ15003/4 are To3 devices. They will not fit the output boards.
You need To247 or To264 devices. ONsemi show an L to indicate this. eg MJL4281

The 15003/4 are very robust SLOW devices that were originally used by Krell. The pink selection are 15times faster. Does that make them 15times better? No!! but there may be some sound quality improvement if the speed increase is cascaded all the way back through the schematic.
The 301/281 devices and similar have a high gain at high output current This may be useful in extracting good performance into low impedance loads.
The fast MJLs are also less robust and have only a 150degC Tcmax limit. You need many more of them to equate to the abilities of the 15003/4, That why Pink uses 3pair, but 3pair of 150W devices still leaves the output lacking, That's why I decided to go 5 or 6pair.

Rather than MJE15032/3 I would go the other way to the 4A MJE15034/5 I think the later version is better. But again I decided to go with 2sa649/c669 for extra gain and speed at the expense of missing the power handling.