Stolen Trademark Amplifier from Jim's Audio on EBAY

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#2
hello

i dont know why yout got this,but ...im currently building the ksa 100 mkii,& i already got the transformer,its BIG ,has 4 different voltages ,the 38 v is center tapped ....i have all the pieces except Heatsink & case ...& of course have to think of a preamplifier -have any suggestion ?
-if you have any question -ask? (take note that i didnt build it yet )
 
#6
Kaplaars said:
I have ordered the same boards myself. They are good quality if you ask me.

I am far from finished, but the most resistors are already soldred to the PCB.

An externally hosted image should be here but it was not working when we last tested it.


Have you received the PCB's already?
Click to expand...


Excelent boards. Just be careful. There's a misprint on the boards. Look at the schematic. Resistors 20k and 47k next to the 150R should be 4k7 on the right front side of the boards 😉
 
#11
xslavic said:
do you suggest using low ESR caps for the mainboard ?
Click to expand...

I didn't used low-ESR caps, but normal Rubycon's instead. I am sure low-ESR caps arent necessary for the amplifier board. For a switching PSU it's a different story. The 1000uF ROE(derstein) caps used in the original KSA-100 weren't low-ESR neither.

I would advise normal 105 degree caps (instead of 85 because this amp is generating a lot of heat) from a good brand like Rubycon or Vishay.
 
#13
How far are you progressed with building the KSA-100 clone neychi?

I have soldred the last resistor to the board yesterday.

By the way, I am searching for the speaker protection circuit used in the original KSA-100 but haven't found the PCB. Have you already found a PCB for it?
 
#14
Actually, I am building KSA50mk2 which is basicaly the same amp with some smaller differences (a smaller number of output and driver transistors, the difference in the values ​​of several resistors and zener diodes). I have no need for bigger amplifier. It's not finished yet, becouse I don't have much time. I made one KSA50 clone allready http://www.diyaudio.com/forums/solid-state/31077-krell-ksa-50-pcb-783.html. This time I want to be closer to the original layout.
There's no need for original soft start and speaker protection circuits, but if you want to be near to the original KSA100 as far as possible, take a look at this topic http://www.diyaudio.com/forums/solid-state/78129-krell-ksa-100mkii-clone-233.html
Member Fix ordered soft start and protection boards very similar to originals. Maybe he still has some to sell. Ask him😉

Which mosfets you planning to use?
 
#15
Aha. Yeah, I saw that the KSA-50 and the KSA-100 are very similair when it comes to the circuit. WAUW, real nice work Neychi, love the cabinet. A real masterpiece. How does it sound?

I've send Fix a mail. Hope he has some PCB's left.

I try to stick to the original design as much as posible, so I will try to find and use the items described in the original schematic.

By the way, bought some nice caps today on a local radiomarket for just 8 euro's! A real bargain if you ask me.

An externally hosted image should be here but it was not working when we last tested it.
 
#17
A little update from Kaplaars aka Michael ;-)

I've almost completed all the parts necessary to build one KSA-100. I have progressed a lot with building the amplifier. I've orderd the last missing parts (2SJ313 and 2SK2013 which are hard to find!) by another diyaudio member Zhou Fang, so with some luck I can test the amplifier pretty soon from now.

I am a poor chemistry student haha, so a lot of the parts are second handed. For example, I've bought two cooling towers from a chap who took a big *** power supply apart.

Pictures tell more than words so here some photographic material:

One of the cooling tunnels before operating it:
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And after:
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I will replace the fans with 'modern' plastic computerfans because they make a less noise and fan speed is easier to moderate with this fans.

The driver boards almost completed:
An externally hosted image should be here but it was not working when we last tested it.


I've also ordered four new Nippon Chemicon 44000uF caps because I could not find another pair of 39000uF Philips capacitors.

An externally hosted image should be here but it was not working when we last tested it.


And last but nog least; I've ordered two 1KVA Amplimo torodial transformers. I was very lucky with these, bought them quite cheap for 39 euro per piece!

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Have you progressed Neychi? Well I keep you updated!

Kind Regards,
Michael / PA4MW
 
#18
hi,nice

hi,nice build,i just only use Toshiba devices ,ill have to order the pcbs ,the components i bought from digikey,including the 39000 uF caps but ill ad more capacitance intend at least 68.000 parallel per rail -for the output boards,mainboards will have to do with 20.000 uF in paralell from Capxon oil electrolit
 
#20
Hi Xslavic,

Wauw, you have some pretty big transformers over there. Mine are about 7,5cm by 15cm and weight about 10kg. Amplimo specs their transformers much lower than they can handle. The wire diameter of the secondairy side is about 2,5mm2

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


I also use the original Toshiba mosfets and ON transistors for the power stage and driver stage.

I also bought a lot by Digikey they're realy reliable, because there are a lot of fake MJ15003/4 transistors on the market, but Digikey delivers genuine ON transistors. I wouldn't buy them from Ebay.
 
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