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Old 11th September 2012, 08:30 AM   #321
a.wayne is offline a.wayne  United States
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Chassis does look nice , but IMO your Input and output connectors are two close..
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Old 11th September 2012, 09:38 AM   #322
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Hellowhellow Andrew, I wondered where you would be.

Tell me something I don't know... I know how the Zobel and Thiele network works, it is not rocket science to calculate it. But I was curious why some designers use just a capacitor, like Denon does in their PMA-1500R. Why would they do that? But like earlier you can't give real explanations. That is OK, some people don't have the capabilities to teach. But just don't reply then...

Krell uses a Zobel network in their original KSA-100. This sentences: 'However, some designers can make their amplifiers stable without needing the Thiele Network. Those designers are clever and don't need DIYaudio to teach them how to stabilise amplifiers' gives a bad taste in my mouth. I tried to be nice in the past, but not now. Ehh, Andrew, so Mr. D'Agostini is dumb in your opinion, because he used a Zobel network? Actually most respected brands are crap because they use a Zobel network? Who are you to even imply this kind of amplifiers needs a Zobel network. It is just for safety. Should I not use fuses too because an well build amplifier could never go short circuit? C'mon man.

Andrew if you are a sort of design god, were are your designs? So you don't need a Zobel network, because you are, well you think you are, smart. Why did I read in another topic that your KSA-100 clone is mere an oscillator? I would say that this would be really not clever. There are loads of people who done it before . Why did the people who wanted to help you and asked for a picture got a lame excuse that you could not post pictures of it? Do you even have build a KSA? Even I can post pictures on DIYaudio and I am not 'clever', well in your eyes... . How hard is it to construct a KSA-100. Even a, in your eyes, stupid chemistry student who is not that far away from obtaining his Bachelors degree, and who likes to post a thing or two on DIYaudio now and then, can construct a KSA-100

Oh and Mister T: the KSA is actually very stable WITHOUT the Zobel, as you could have red earlier. It is just a safety option. It would be a shame if my speakers would go down. They have a bit of a complex filter, so it can be complicated to my amplifier. Safety first Andrew. Or is safety 'not clever' too?

Thanks A. Wayne! Why would that be? I think input and output could not interfere with each other. I am more concerned about the softstart which is a bit closely connected to the speaker terminals. Hope it does not interfere with introducing some hum If that would be the case, I think I will have to construct some iron shielding, but I think it will be ok Keep you all updated about this.
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Old 11th September 2012, 09:54 AM   #323
sippy is offline sippy  United Kingdom
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I lived with a real KSA100 for a month years ago.......so I follow this thread when it pops up on the home page.
I noticed your post on handles, http://http://www.hifi2000.it/ have something similar.
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Old 11th September 2012, 10:05 AM   #324
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Thanks for the hyperlink Sippy! I actually ordered my cabinet from HiFi 2000 They sell very nice cabinets. But I did not really like the handles. In real the handles from HiFi2000 are a bit too large in my opinion. I was searching for something a bit more subtile The handles at the back are in my opinion perfect. I really like them. They came from old 19 inch rack equipment. Hope I will find two more
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Old 11th September 2012, 10:51 AM   #325
Rewind is offline Rewind  Sweden
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Andrew T; Do you have a suggestion for a suitable Thiele network for the KSA 100? I did not understand your comment fully. I could try to copy a Thiele network design and begin to understand from there.

Kaplaar: Why do you think this Thiele network is not needed?
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Old 11th September 2012, 11:13 AM   #326
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Hi Rewind,

That is something I can't predict. It depends on your build, physical layout, which outputs you use, speakers and so on. Some amplifiers will gain benefits when using a Thiele network and stability will be improved, from the other hand some don't. The KSA-100 is very stable without a Thiele network, mine even is without a Zobel network. That is why I for example did not really needed a network, but... I want it to last, so it has to be very safe. The reason why I did not use a Thiele network is just that the original does not use a Thiele network either. I know for a fact that the original KSA-100 is very stable, so why changing a proven concept? After all I wanted a clone, so I want to stick as close to the original as possible And I truly believe Dan D'Agostino knew what he was doing, if he was willing to implement it into his designs, it has to be OK.
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Old 11th September 2012, 12:37 PM   #327
AndrewT is offline AndrewT  Scotland
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I posted a Thiele Network spreadsheet using the Cherry paper as the basis for the diagrams and cell calculations.

I have adopted a Pi version with R+C, both before and after the R//L.

I fit the before as close to the output pins of the output devices as the PCB will allow. I fit the after across the speaker terminals.
I fit the R//L in the cable between the amp PCB and the speaker terminals, not on the PCB.
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Last edited by AndrewT; 11th September 2012 at 12:40 PM.
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Old 24th September 2012, 05:21 PM   #328
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Hi friends,

Again some progress from Holland. Yes ladies and gentlemen the finish line is in sight, but I've said that earlier. Reality is that it is not finished yet

It was finaly time to mount the tunnel cooler to the cabinet. I've also thought of a plan to keep this beast a bit cooler. I've stripped the cabinet and mounted two extra large fans underneath the tunnel cooler for extra cooling:

Click the image to open in full size.

These fans have a lot of airflow. I can control fanspeed with my little fan control device.

After mounting the fans I mounted square aluminum bars underneath the tunnel cooler so I could lift it a bit higher. This way it fits perfectly above the fans and can radiate heat from below easier. Next project was to mount the tunnel cooler to the cabinet:

Click the image to open in full size.

That turned out OK. The fans are a nice addition to keeping this beast even cooler. Next hurdle to overcome was drilling two big round holes for the fans (dont mind the mess on the floor ):

Click the image to open in full size.

This was a real hurdle to me. Something I did not looked forward to. I bought a nice, high quality HSS Makita hole saw. But still, it was very hard to drill through the metal. You have to drill at very low speed, but my drill had too little power to drill at low speed. It just could not turn the holesaw. But..... after much patience, it worked. I've also mounted two airfilters to the sidepanels:

Click the image to open in full size.

So it was time to test this beast again. Although it powered on OK, I measured a strange DC offset which dissapeared when I disconnected the rear panel from the cabinet. Also the speaker protection almost instantly intervened when I connected the cabinet to GND. Hmm, how could that be? Did I made a mistake with grounding this beast? After some futher measurements I've found the culprit; one of the AC leads (not HV, but 12VAC) from the little transformer which powers the speaker protection made short circuit with one of the spacers. STUPID. How could I have missed that. Fortunatelly I was lucky, it did not do any damage to the amplifier. After fixing this it was time to test it again and........ IT WORKED!

Well guys only thing that I still have to do is mounting a D-SUB chassis part to the cabinet and wire all the fans, and then it is finally finished I also would like some nice handles in the front, and maybe some nice VU meters in the front. But that is for later. Keep you all updated
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Last edited by Kaplaars; 24th September 2012 at 05:27 PM.
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Old 4th October 2012, 01:11 PM   #329
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Hi Friends,

Again an update, but a very little one. I attached the other D-SUB connector to the chassis:

Click the image to open in full size.

Isn't it pretty :-) But that is not why I post this update. Today I fired the KSA-100 up. Man what a sound. It is my birthday today, yay. So it is time to play some music. But I experienced a strange phenomenom; now and then the mains transformers were buzzing randomly pretty audible, osmething I've never experienced. Also the amplifier seem to draw 0,3A extra current. Hmm, that could not be OK. I was afraid there was something wrong with my amplifier. Maybe an heavy oscillation of something. At the same moment I was printing some papers. And yes it turns out my laser printer causes a large DC component on the net. This triggers the transformers in my KSA-100 to buzzzz. I don't use a DC-blocker in my Krell. Maybe it is time to construct one. Would a DC-blocker be beneficial or are there also some disadvantages using one?

I never thought a DC component could cause so much hum. Another lesson learned :-)
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Old 4th October 2012, 01:20 PM   #330
sippy is offline sippy  United Kingdom
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Happy Birthday Kaplaars.
I cant comment on the DC problem, but well done on getting it up and running AND playing music.
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