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Old 14th February 2013, 08:52 AM   #371
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The best replacement for Toshiba 2sa968/2sc2238 are Toshiba 2sa1837/2sc4793 after lengthy search on the net. Mouser price is $ 0.54, I can buy more for a pair transistors after amplification factor.
I have a question for Kaplaars.
Transformers use the company Amplimo produce any noise?
I used another application 2 transformers TALEMA intro had a noise when idling, bother me.
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Old 19th February 2013, 08:56 AM   #372
neychi is offline neychi  Croatia
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Well, I spent yesterday afternoon in listening and I must say that I'm impressed with the sound. Sound stage is huge. I think that the sound is even better than my first KSA50. Maybe, the reason is higher rail voltage. Bias is set at 325mV/0,5ohm. After two hours heatsinks are warm but not hot
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Old 22nd February 2013, 10:46 PM   #373
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Sorry for my late response Guys, I’ve been very busy .

@Stuart: Thanks for your reply! I've got nice info from an other DIY-audio member about matching resistors, so that would be certainly doable. I've got milspec 1 ohm 1% resistors already. There seems a negligible deviation in resistance between them, so that should be a good thing. That is exactly my problem in the current setup, there is a slight temperature deviation between the different trannies. Although bias seems to divide very nice (about 10 mV difference max between the devices) I think using my new tunnel coolers will tackle this problem even better. Another advantage is that my new configuration has no longer 'live heatsinks', all the TO-3's will be isolated. Disadvantage is that heat transfer to the tunnel cooler will be slightly less.

Also thanks for the explanation about the emitter resistors! How could I forget that. So if I want to upgrade, it is necessary to use resistors with higher resistance. Will consider that!

@Neychi: Good that you tackled the problem! But that would be not good news for me because we are probably using the same devices. Are you sure the problem has been caused by the Polida devices? I have not experienced any problems thus far with them. Drove the KSA with a dummy to the max a few times, but it stays rock solid. Maybe I am lucky, but for how long? Have to say, from the 10 sets I've bought, one of the devices was faulty and thrown away before soldering it to the boards. Maybe there was a device which was faulty already before testing the KSA?

Nice pictures by the way, I like your amp very much!!!

@Vdavidov:
The Amplimo transformers are dead quiet, I realy can't hear them, even when I am 5 cm from them. They are only audible now and then when I connect my laser printer to mains. I think my laserprinter adds a nice DC component on the net. This causes the Amplimo's to hum. But that would probably be the case for every toroid. Have to check my printer soon

I've made some progress too. With a little heartache, I stripped my beloved KSA Like mentioned earlier I want to change thermal design. My main concern was cutting the tunnel cooler in two, so I would get two nice 14,5cm tunnel coolers. But this was actually more easy than I thought! Just the old fashined way, no electrical equipment involved:

Click the image to open in full size.

Basic idea is this configuration:

Click the image to open in full size.

Yuuup almost an exact copy of the original one, not very original from my side, but I think this is indeed the best configuration.
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Old 25th February 2013, 05:32 AM   #374
neychi is offline neychi  Croatia
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Thanks Michael

Yes, I'm afraid so. Without changing anything else, only Toshibas, the problem is gone. I tested them before soldering and they seemed to be fine. Funny thing is that they still show correct readings. I burned another set of mje15032/33, because I didn't want to believe that the problem is in them. I put 2sa1011/2sc2344 for which I know they are original Sanyos and the amp works great. You've obviously had more luck.
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Old 21st March 2013, 07:53 PM   #375
Fix is offline Fix  Sweden
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Just a quick post:

Great thread, Great build !!!!
Congrats with the amp !!!!

I'm thinking of building another amp for myself.
Have most parts... Including Heatsinks and pcb's.

But this time I might build the fan-less version. If i can get hold of the right heatsinks.

Keep posting !!
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Old 24th March 2013, 11:53 AM   #376
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Hi Everybody,

I have amplifiers Nad m3 and marantz Pm11s1 and my speakers sonus faber cremona m I like them but I want to drive my speakers with krell ksa 100

When this read this form. I decided to make my krell Thank you for this sharing.


My project not finish yet becauze some items missing. I bougt them from ebay. I am waiting. When they come I will finish. But now it is working perfect I am very happy.

My krell has big heatsink. Thus not heat to much. It heats max 43 c degree.
First a made a small heatsink but Its needs fan because It heats 65 c

First Ksa 100

Click the image to open in full size.

Second Ksa 100


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Old 27th March 2013, 03:52 PM   #377
spurlte is offline spurlte  United States
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Wink New heat sinks

Well, with the help from Stuart Easson, I think I have the right heat sinks. They are from ADCOM, don't remember the model number. They are square and will have to deal with that later. There is room for five output trans. All I have to do now is get the right heat sinks for MJE15s. I have smaller fin blocks, but I would have to stand the MJE15s straight up rather than "laying down on the job." Hey, maybe they will have "verticle sex." Also known as "dancing."
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Old 27th March 2013, 04:47 PM   #378
AVWERK is offline AVWERK  United States
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I think you will need a fan for these. They look too small. You could lower the bias level however and give it a go with enough room to add a fan later if necessary.

Regards
David
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Old 27th March 2013, 05:16 PM   #379
spurlte is offline spurlte  United States
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Default Heat Sinks

Quote:
Originally Posted by AVWERK View Post
I think you will need a fan for these. They look too small. You could lower the bias level however and give it a go with enough room to add a fan later if necessary.

Regards
David
Yes, I am going to use two fans for push/pull effects.
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Old 27th March 2013, 05:52 PM   #380
tinitus is offline tinitus  Europe
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hey, those heatsinks in post 382, looks like its the type with pressed in fins ?
should be very effective
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