My Completed Krell KSA 50 Clone - Pics

[IMGDEAD]http://www.parttimeprojects.com/audio/diy/Images/Krell%20Clone/Krell KSA 50 Clone Front1.JPG[/IMGDEAD]


[IMGDEAD]http://www.parttimeprojects.com/audio/diy/Images/Krell%20Clone/Krell%20KSA%2050%20Clone%20front3.jpg[/IMGDEAD]

Building this amp was really a great example of "community" here at DIYaudio.com.
Despite the fact that the "Krell KSA 50 PCB" thread has over 3600
posts a lot of very smart people read it every day and answered
highly technical (and basic, and stupid) quesitons. The Krell KSA 50 Build Wiki contains
all the basic technical information and resources. People on that
thread bend over backwards to help each other out. Its really
been something special, I was very impressed.

Anyway, on to the amp, a few pics were first posted in the
massive Krell thread, but that thread is pretty unmanageable so here we go.
 
[IMGDEAD]http://www.parttimeprojects.com/audio/diy/Images/Krell%20Clone/Krell Clone Wood Panel On.JPG[/IMGDEAD]

[IMGDEAD]http://www.parttimeprojects.com/audio/diy/Images/Krell%20Clone/Krell KSA 50 Clone Front Panel2.jpg[/IMGDEAD]

[IMGDEAD]http://www.parttimeprojects.com/audio/diy/Images/Krell%20Clone/Krell KSA 50 Clone perspective.jpg[/IMGDEAD]
 
Sorry about the size of pics, if you have dialup you are going to be sitting for a while.

[IMGDEAD]http://www.parttimeprojects.com/audio/diy/Images/Krell%20Clone/Krell KSA 50 Clone Cutaway.jpg[/IMGDEAD]

[IMGDEAD]http://www.parttimeprojects.com/audio/diy/Images/Krell%20Clone/Krell KSA 50 Clone Top Cover Off.JPG[/IMGDEAD]
 
info

Ok, so I'm still working on the cover.

Stats-

- switchable from low bias to high bias, currently biased at 50W/8
ohms into 8 for high bias and 20W (??) for low bias.
- heat sink temp is about 61 deg C for high and 50 for low, depending
on how you set the fans of course, but its not overly loud at these temps.
- 4 pairs of MJ21193/94 per channel
- 128,000 uF per channel, plays for >5 sec after turned off even at high bias.
- Aerogate 3 personal computer fan controller and temperature monitor.
This allows for 4 channels of temp to be monitored, and
for speed monitoring and conntrolling of 4 fans.
- two fans, one 40mm on the bottom blowing up and a 120 mm on the
top blowing up.
- Dual mono from the AC inlet onwards, even soft start is dual mono.
- two 700 VA xformers.
- weighs 70 lbs/ 32 Kg.
- 22 mV (left) and 28 mV (right) DC offset
- the amp is bolted to the bottom wood plate. This is to ensure that
the fan intake has sufficient clearance.
- after much debate I decided to keep the heat sinks live.

Just starting to listen to it now, I can tell bass is not going to be a problem.

I'd keep rambling and posting pics, but I already did that on my web site, click Here for a ton of pics and my running narrative.
 
Buzzy said:
by using a fan can the size of heatsink be reduced significantly ?

Sure - just look at CPUs, dissipating up to 130W. Forced air cooling will significantly reduce the size of the heatsink required, but then you have to put up with the noise of the fan and no matter how quiet they are supposed to be, they always make a noise and it tends to get worse with age...
 

wcleungoo

Member
2010-06-09 2:48 am
My KSA50 clone, just finished yesterday and is under stress test. Power: 500W torodial Transformer, 2x100,000uF BHC cap. bi-bridge rectification per channel... natural cooling. How it sound ? solid bass, clean and clear mid and treble In comparing with my DIY Aleph 5, the sound is a "sharp". Aleph 5 sounds much warmer... different style. So, i think it is better for rock music while Aleph 5 better for vocal presentation. It is of course up to the preference of the listener!

ksa50%25283%2529.jpg


ksa50%25282%2529.jpg
 
Nice job wcleungoo. I don't check here anymore but I randomly did today and saw your post. Looks like you have upgraded to a CRC power supply that Krell never used? What else did you modify and improve on?

I agree with your listening impressions generally though I do not like the weak sound of the Aleph amps at all (have built diy and bought the commercial version) - just my opinion that everyone here will disagree with.

I think the KSA -100 was not fully tested/functional from my memory of the related threads here, but the KSA-50 worked just fine for a lot of people. I know mine is sounding great after many years and while it is only 50 WPC, it plays LOUD and with authority, esp. the low end; but generates so much heat that evacuating it from the case is a problem. 100WPC ? I would not want to take on that heat-challenge!

Note- I used this amp to drive Wilson WP 5.1's for 2 years. Sounded fantastic, no need for more than 50 WPC; bass that will shake your windows from their frames. I am not really into audio that much anymore and my collection of impressive overpiced high end items has been mostly sold off though I have all my diy amps and some ok stuff.

Just happy to see some more activity on the KSA 50, nice amp.
 
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Sure - just look at CPUs, dissipating up to 130W. Forced air cooling will significantly reduce the size of the heatsink required, but then you have to put up with the noise of the fan and no matter how quiet they are supposed to be, they always make a noise and it tends to get worse with age...

That is still somewhat true but I am beginning to think that the time of that being a fact is coming to an end. Just take a look at this this fan running at 5V.

AcoustiFan DustPROOF Premium Quality Ultra Quiet Computer Fan - 80mm AFDP-8025B

There are others that are just as quiet as well. I am sure that one day in the near future we will be able to use fans and smaller heat sinks just like the rest of the tech world.

The amp looks awesome. How much of a change is there between high bias and low bias?
 
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