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Old 13th November 2012, 02:03 AM   #351
spurlte is offline spurlte  United States
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Hey guys.... I found a sample of the water cooling system at inlowsound.com
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Old 13th November 2012, 04:52 AM   #352
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The original KSA 100 used an orange (not sure maybe ICC ) 250 VDC 0.1 uf polyester cap with 2 watt 5% 5.6 ohm dark brown resistor - not sure who made it, for the zobel mounted at the output jacks - a good film and foil polypropylene with an flame proof 2 or 3 watt metal oxide or caddock power film resistor will be a good upgrade. It was stable with Quad 63s in parallel with 4 ohm Dynaudio subs.

Last edited by ticknpop; 13th November 2012 at 04:55 AM.
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Old 7th December 2012, 05:01 PM   #353
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Amices,

Any progress made ? :-) I am still enjoying the KSA. Glad it is still operational. There have not occured any flaws. It is and stays solid as a rock! It is really the beast amplifier I've ever heard. Krell really is a fantastic brand

I did some further experimenting concerning the optimal bias value. I've found out that 450 mV bias (when using 1 ohm emitter resistors) is the optimum value for my KSA when concerning heat, stability on the long term, noise from the fans and distortion.

Looking back I've learned that using two seperate cooling tunnels is the best solution when going full bias. There is more difference in temperature between the cooling tunnels than I had expected (about 12 degrees). This causes one part to get very, very hot (70+ degrees). Although the trannies would be well within their SOA, I did not feel comfortable.

If I ever would made another one, I think I would buy even larger tunnel coolers and place them upright, just like in the original design. Maybe in the future... I still have some parts left haha

I've also bought a nice, but defective pre-amplifier! Risking of going offtopic, I hope it is still nice to tell you all a bit about it. Got to keep busy aye ;-). I was thinking to use the chassis and replace the intestines with a design from Pass. But I actually liked the amplifier and tought it would be a shame to stripp an expensive amplifier like this one just to use the chassis. Also I did not expect it would cost me a large amount of money to repair it. So I decided to repair it. It is a Pre 6 from Audyn (a Dutch brand). It has been custom made and is pretty expensive (about 1650 euro's!). It has 6 channels, so it is actually a 6 channel pre-amplifier. Two channels did not work. I found out that this was caused by two defective modules, which I tought, were customly designed by Audyn. I was expecting something like a PGA2310 in it, since I was most certain this module must had a function as volume controll.

So I've mailed Audyn and Aaron (Aaron is a sister company derived from Audyn). I've asked both for a schematic and what a new module would cost me. Aaron could not help me because the Audyn amplifier would be completely different than their No.22 device. 'AARON and Audyn are not the same. Even if they are based on our AARON technology, they are all cheaper made and the sound is of course not as good as the AARON amplifiers'. Hmmm, maybe I need glasses, but compaire yourself:

Aaron:
Click the image to open in full size.

Audyn:
Click the image to open in full size.

But well, it does not really matter. After all it is an Audyn so they should be the ones to help me. After many e-mail traffic with Audyn, giving the serial number and so to them, they still refused me to give me a schematic or sell me another module. Even a partnumber of the module was to much to ask. Only thing they they offered me was the option that I would send the device to them, they would repair it for me and charge all the costs (starting with 80 euro's for just 'inspecting the device'). Well you see my friends, price is not a good degree for the level of service you may expect.

Well okay, keeping positive, thus till so far the nagging part. It is time voor DIY. Like I've said earlier in this treat, having little budget forces you to be creative. So I carefully sliced a module open to see what actually was in there. I had to be very, very carefully. Any printing on the electronics inside is erased easily.

Tadaaaa:
Click the image to open in full size.

Whaaat, it was just a plain simple Maxim DS-1808 IC! Not expensive at all

So I've bought a few of these IC's from Maxim and a few SO-16 converter PCB's from Ebay:

Click the image to open in full size.

Resulting in new modules!!!

Click the image to open in full size.

It is almost a crime if you think about what these kind of companies are charging you for what actually turns out to be a prettty simple amplifier.

I am using thes pre-amplifier in combination with the Krell. I have to say, it sounds pretty good. It is hard to describe, and a bit cliché, but I experience this pre amplifier as very open, direct and analytical, but also a little 'cold'.

It also combines very nice with the Krell if I may say myself

Click the image to open in full size.

Click the image to open in full size.
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Old 15th December 2012, 01:03 PM   #354
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Help where can i buy original Toshiba 2SC2238 transistors, 2SA968. Thanks in advance to anyone who can help me.
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Old 7th January 2013, 03:17 PM   #355
spurlte is offline spurlte  United States
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Quote:
Originally Posted by Kaplaars View Post
Good job David!!! I also got a reply from Jim:

Thank you very much for building the boards with patience and shared your experience with other people. I have checked the board, and it seems to be an error that happened during PCB fabrication, since in the first log of boards ( I built two logs, and the first log was done in 2007 - 2008) there is a link from the track ( right below the transistor MJE15033) to the base lead of this transistor. I need to check with our PCB vendor why this happened. But I thank you for letting me know this otherwise I thought the board is as good as it has to be.

Nice that this mystery is solved :-)!

By the way David, there is another thing you have to take into account. Around the holes which are meant to attach the MJE15033/32's to, there is a conductive ring:

Click the image to open in full size.

When you attach a non isolated / non anodised heatsink, which means your heatsink electrically is conductive, chances arise that your heatsink will make short circuit due to a connection with these holes. This holes are connected to the the collectors of all MJE15032/33 devices. Short circuit between the collectors is something you definetely don't want, because your power lines will make short circuit also (V+ and V- are attached to the collectors). So you have to isolate the heatsink from this rings aswell, or use an isolated heatsink. I took no risk, so I chose to remove the conductive layer on the surface around the holes in the front by drilling very carefully the little conductive surface away. Worked like a charm :-).

@Dean: Aha, so you have the red ones too. I thought the blue ones were yours :-D. Hmm, maybe Spurtle is lucky and have his PCB's the tracks aswell.
I finally found appropriate heat sinks for MJE15032/33 devices and somehow luckily ran into your advice. The only thing, I will have to attach the devices vertically. I am still having a hard time finding the appropriate fan type heat sinks for the output devices and since reading Fix's old posts, that he really found that his music went sour with lower bias--below 500mV--to deal with the heat dissipation--he wanted ~625mV because his music was bliss at the higher bias (the bass). I am really thinking of liquid cooling (mineral oil?).
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Old 9th January 2013, 04:09 PM   #356
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Hi David,

I have to say, in all honesty, that I do not share the observation Fix has made. I actually can't hear any difference when experimenting with bias values ranging from 100 mV and up. I begin to experience slight deteriation in sonic quality when I dial the bias far below 100 mV.

But I have to say, I don't listen music at very loud volumes. So the amp has not to deliver lots of power to drive my speakers. That is why, in my case, a lower bias will do just fine. When your speakers draw more power than your bias is set, and you exceed this value, then you can experience more distortion due to crossover distortion, but below it should not occur.

But cooling is very, very important. Lot's op people underestimate it. I for example did haha. That is why I want to add even bigger tunnel coolers because 1) I am bored haha, 2) because this way the fans have to displace even less air to get the same results and 3) because I offcourse want to go all the way ;-). After some evaluation I think it is after all beter to separate the tunnel coolers afterall, and place them upright just as fix did and the original KSA-100 has.

If I am correct the original KSA-100 uses tunnel coolers which are 12cm long. If I am not mistaken Fix is using tunnel coolers which are about the same length. Even then I think the KSA-100 runs pretty hot. So you will need probably more cooling. For my new plans I have bought these beauties (29cm long each, almost twice as heavy as the ones I use right now):

Click the image to open in full size.

I am thinking of cutting them through at about 18CM and place them upright. Does anybody has some experiencing with cutting aluminum profiles like these?

Liquid cooling would be very verry cool David! I would love to see that. Even better, it does not produce a lot of noise. I think for me that would be a little to expensive. I think I stick to aircooling.
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Old 9th January 2013, 04:33 PM   #357
Arick is offline Arick  Canada
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Quote:
Originally Posted by Kaplaars View Post
Hi David,

I have to say, in all honesty, that I do not share the observation Fix has made. I actually can't hear any difference when experimenting with bias values ranging from 100 mV and up. I begin to experience slight deteriation in sonic quality when I dial the bias far below 100 mV.

But I have to say, I don't listen music at very loud volumes. So the amp has not to deliver lots of power to drive my speakers. That is why, in my case, a lower bias will do just fine. When your speakers draw more power than your bias is set, and you exceed this value, then you can experience more distortion due to crossover distortion, but below it should not occur.

But cooling is very, very important. Lot's op people underestimate it. I for example did haha. That is why I want to add even bigger tunnel coolers because 1) I am bored haha, 2) because this way the fans have to displace even less air to get the same results and 3) because I offcourse want to go all the way ;-). After some evaluation I think it is after all beter to separate the tunnel coolers afterall, and place them upright just as fix did and the original KSA-100 has.

If I am correct the original KSA-100 uses tunnel coolers which are 12cm long. If I am not mistaken Fix is using tunnel coolers which are about the same length. Even then I think the KSA-100 runs pretty hot. So you will need probably more cooling. For my new plans I have bought these beauties (29cm long each, almost twice as heavy as the ones I use right now):

Click the image to open in full size.

I am thinking of cutting them through at about 18CM and place them upright. Does anybody has some experiencing with cutting aluminum profiles like these?

Liquid cooling would be very verry cool David! I would love to see that. Even better, it does not produce a lot of noise. I think for me that would be a little to expensive. I think I stick to aircooling.
Due to the size of your heat sink, if you want a nice cut, try to go see a machinist. They will have the proper saw to make a nice cut. You can always use a hand held steel cutting saw, however the result will be proportional to your ability's to handle it. i.e. you might end up with an uneven cut requiring a couple of hours of filing...!
Cheers,
Eric
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Old 9th January 2013, 04:47 PM   #358
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Yes the original KSA 100 used a tunnel heatsink actively fan blown.
It really wasn't big enough for the 2.5 amp bias current and baked the thermal compound under the output devices into dust over time requiring a rebuild of the output stage. It needed a bigger sink or a higher ( noiser) fan speed.

I rebuilt mine as a Borbely Millenium with Hitachi TO3 Laterals biased at 1.5 amps and it's been good for a decade.
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Old 9th January 2013, 09:05 PM   #359
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Hi Eric,

Thanks for your input! I was wondering and also a bit afraid that using a hand held cutting saw is not going to be a great idea. I was hoping it would be possible when using a saw guide, but you got me doubting now :-). Think I have to contact an ironshop indeed. There are some metal shops here in the neighborhood. The profile can be dissassembled into 4 separate sinks by the way. This is one of the four heatsinks per tunnel:

Click the image to open in full size.

I am still enjoying the KSA as it is now, so there is no hurry. My plan is to overhaul the KSA again when summer break arrives.

@Ticknpop; I was really doubting that cooling in the original was sufficiënt. Glad to see that someone can confirm this. Even in my present lay out, there is more cooling capacity than the original, but even now it gets pretty hot. This is mainly due to the large distance cold air has to travel through the tunnel. This results in one side at comfortable temperature, the other side running pretty hot. So I am not really comfortable with going full bias right now. Therefore I dialed bias down to 450mV. I think using the new tunnels and placing them upright (so separated from each other) will be a big improvement. I can also attach larger fans to these tunnels than to the ones I am currently using (12cm or even 14cm with convertor vs 9.2cm right now). I am thinking of using 18cm long profiles. The new profiles are the same size as the original, but mine will be 50% longer compaired to the original. Hope that will do.

I am very curious to your rebuilding! Do you have some more info? Maybe pictures? Did you convert an original KSA-100 or did you convert an DIY KSA-100?
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Old 9th January 2013, 09:28 PM   #360
Arick is offline Arick  Canada
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[QUOTE=Kaplaars;3318507]Hi Eric,

Thanks for your input! I was wondering and also a bit afraid that using a hand held cutting saw is not going to be a great idea. I was hoping it would be possible when using a saw guide, but you got me doubting now :-). Think I have to contact an ironshop indeed. There are some metal shops here in the neighborhood. The profile can be dissassembled into 4 separate sinks by the way. This is one of the four heatsinks per tunnel:

Click the image to open in full size.

If you have a guide, you can use all the way through, then do so as long as you properly hold your heat-sink in place. If you have a piece of scrap you can try on, do so first to get a feel for your saw.
Eric

Last edited by Arick; 9th January 2013 at 09:33 PM.
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