KSA 100 from Jim's Audio on EBAY

[Kaplaars]

Originally Posted by xslavic

do you suggest using low ESR caps for the mainboard ?

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.

[neychi]

I use Panasonic FM

[Kaplaars]

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?

[neychi]

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 Krell KSA 50 pcb. 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 Krell KSA 100mkII Clone
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?

[Kaplaars]

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.

[neychi]

Thanks. It sound real nice. Open mids and deep strong bass. But I must have something to compare with

Really good bargain for caps, excellent indeed

[Kaplaars]

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:


And after:


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:


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



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!



Have you progressed Neychi? Well I keep you updated!

Kind Regards,
Michael / PA4MW

[xslavic]

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

[xslavic]

they seem to small for me,i use one thats 3 of these -one on top of the other ,and 1,5 times the diameter

[Kaplaars]

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





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.