NAP-140 Clone Amp Kit on Ebay - Page 2 - diyAudio
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Old 24th November 2007, 03:48 PM   #11
es44 is offline es44  Denmark
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Default Re: I think Aeon is our forum member...not sure...he can tell us something about

Quote:
Originally posted by destroyer X

those amplifiers sonics.

regards,

Carlos
Funny, i think it looks like a wooden cooler underneath the output trannies in post #8. Or is it copper maybe
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Old 24th November 2007, 05:06 PM   #12
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Default It seems to be some finishment applied over the aluminium heatsink dear Ebbe



Those anodising results, that transforms silver aluminium in something that remembers copper or gold.

The one is not very clean, not very polished, not very new....some heatsink he captured from dismounted amplifiers.

regards,

Carlos
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Old 25th November 2007, 02:34 PM   #13
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Hi Carlos,
That schematic looks like it matches the photo. Note that the 10uF and 68uF capacitors are shown the wrong way around: they are reversed biased in the schematic.
Brian
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Old 25th November 2007, 02:44 PM   #14
es44 is offline es44  Denmark
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I'd say You're right about the 10uF, but the 68uF over the c-e at the 2sd786 looks right to my eyes.

best regards
Ebbe
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Old 25th November 2007, 02:47 PM   #15
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Is this topology Class A? Can it be biased into Class A if not?

I am familiar with Naim, but never had/heard one...from a few posts I have read, and pics I have seen, I have never seen one with monster heatsinks, so my guess is they are not Class A amps...
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Old 25th November 2007, 02:50 PM   #16
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Ebbe,
You are right about that. I meant the other 68uF cap, the feedback shunt cap.
Brian
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Old 25th November 2007, 02:57 PM   #17
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John,
You are right. The Naim's are class AB - with output transistor bias current set in the 30mA to 50mA region (as far as I recall). Very good for the environment. I see no technical reason not to bias it higher if you wish. In a real Naim circuit the extra bias doesn't affect the sound much. They are also what would usually be called high NFB designs.

The circuit is deceptively simple, based on an RCA design from the 1970s. But it is not simple at all. To get them to sound as good as Naim does requires a lot of careful selection and matching of parts. The parts these clone circuits use are not all the same ones as Naim uses.
Brian
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Old 25th November 2007, 03:51 PM   #18
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Hello

Yes, Naim amp do used selected parts and the LTP input pairs transistors was matched for HFE and VBE , and take a fast transistor for the VAS.

In the NAP 250 schematic you can see a 10 uf cap in the protection circuit, it's to do a small delay so the protection will get in after that small delay and will do less interferences in the normal high level output signal.

Bye

Gaetan

Here's the NAP 250 schematic;

Click the image to open in full size.
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Old 15th December 2007, 10:42 PM   #19
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I did end up purchasing that kit and I'm providing the schematic that came with it. There is also another sheet included in Chinese. The boards are very nicely constructed with gold traces. The parts are as described in the listing.

I compared this schematic with the one posted by Carlos, some slightly different values, those are highlighted with an asterisk.

I have never built a kit and this looked to be a good first one, not sure when I'll get to it, though. If anyone wants any additional information on what I received, just ask.

There is some writing on the board:

AEON copy NAP140 2007 and hifidiy.net.

I do have one question at this point: I have two power supplies from the Accurian receiver that recently was going for $15. The toroid is a 28-0-28 2A. Would I be able to use these for a dual mono arrangement? If not, what are the power supply needs, they are not indicated in the schematic.
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Old 15th December 2007, 10:52 PM   #20
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Here is a link to some photos of the same kit I received:

http://bbs.hifidiy.net/viewthread.php?tid=78276
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