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Old 21st November 2001, 10:32 PM   #1
Fuling is offline Fuling  Sweden
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Hi guys!

Do you think it wolud be a good idea to build a downscaled Aleph 3? The reason Im asking is that I happen to have a 2*12V 500VA toroid that I would like to build something with. Im thinking single MosFets (IRFP150), 6*22000 uF capacitors, 1-1,2 A bias and about 0,5 degrees of heatsinking (one heatsink per channel)
Any comments or ideas??

/Daniel
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Old 22nd November 2001, 12:37 AM   #2
hifi is offline hifi  Sweden
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hello,

i saw i japanese design based on aleph they called it A15 dont remember what page but i can look into it if u want...?

/micke
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Old 22nd November 2001, 12:42 AM   #3
lohk is offline lohk  Europe
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Nice idea.
I would suggest 4 x IRF640 (it is a TO220 device). This Mosfet is quite similar to the IRF240. I have already started some experiments.
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Old 22nd November 2001, 01:50 AM   #4
Fuling is offline Fuling  Sweden
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I think I have seen the Aleph 15 too, it is the one on http://www.diyzone.net/ , right? Unfortunately my computer does not allow me to run that translation thingie, so the text on the page is a complete mess...

Looking at the pictures it seems to be a Zen rather than an aleph, the powersupply seems asymmetric and there are too few transistors on the pcb. But maybe we arent looking att the same aleph 15?? thanks for the input anyways!!

I still think I would go for the IRFP150, they are cheap and easily avaliable here in my region, and Ive figured out that with single Mosfets there is no need for matching (correct me if Im wrong!) I saw some page where some guy was using them for an aleph 3, and it seemed to work fine.

Any ideas of a good value of a surge limiting NTC, by the way?

/Daniel
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Old 22nd November 2001, 04:55 AM   #5
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start your NTC value with 10ohms
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Old 22nd November 2001, 12:32 PM   #6
Fuling is offline Fuling  Sweden
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Ok, 10 ohms there shall be...!

But what about the current rating? The biggest 10 ohm NTC that I can find is only capable of 8A. Thats a bit low, right? The only 30A NTC I can find is 0,5 ohm, and I guess that wont help much as a surge limiter...=(

/Daniel
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Old 22nd November 2001, 12:42 PM   #7
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WOW.... talking about some stiff stuff...30A??? 8A will be more than enough...try a 6A rating. Alephs use a Keystone CL60 rated at 10 ohms 5A. Have them placed in series with the mains live.( check out the Aleph schematics )
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Old 22nd November 2001, 12:53 PM   #8
Fuling is offline Fuling  Sweden
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Hehe ok!!
I can get away with that 10 ohm 8A device, then=)
The one I found is a RhoPoint SG40, I hope it will work with 230 V mains.
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Old 22nd November 2001, 12:58 PM   #9
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SG40's great..and by the way, I've been to the page you mentioned and it's garbled, might me chinese characters and the A15 looks more like a zen to me...

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Old 22nd November 2001, 01:48 PM   #10
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Fuling,
Curiously, I had about the same idea as you this past weekend. In my case, I've got two 16-0-16 EI transformers (I don't get worried about EI transformers the way some people do) that I estimate to be about 100VA. I'll probably use one per channel. I've got a few nice drivers sitting on shelves (no, Geoff, not the KEFs this time; Dalesford 5" and I forget what the tweeter is...Senlab? Dynaudio?) that I thought I'd use to make internally powered, bi-amped speakers. I spent an hour or two looking over my various junkbox parts, and I think I can just about whomp up a pair of monoblock Aleph 3s out of stuff I've already got on hand. For a while I considered dropping back to a single pair of output devices, but went back to 2 pairs. I may yet change my mind and go back to one pair, we'll see.
At the moment, I'm modifying my Aleph 2 circuit board layout. It'll be cute. I estimate that it ought to deliver about 15-18W. The trick will be to come up with two pairs of amps out of what I've got here. Got to go rummage around looking for more transformers. (I take it as a personal challenge to build these things for as little money as possible.) It may not sound as good as a full rail version, but why not have fun with it?
In short...go for it.

Grey
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