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Old 14th March 2008, 02:06 PM   #101
cdswift is offline cdswift  United Kingdom
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Default Re: Polarity of DC blocking input capacitor

Andy, why do you say that the connection point between the positive output transistors and the 27R resistor is incorrectly represented on the schematic?

Is it because the original NAP140 was like this, or is it because Douglas Self says it should be like this? I haven't checked my new PCBs to see how they are wired.

To my eyes, either connection would work - I'm just not sure which would be better from a stability or performance point of view.

Regards

Chris Swift
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Old 14th March 2008, 02:28 PM   #102
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Quote:
Is it because the original NAP140 was like this, or is it because Douglas Self says it should be like this?
My amplifier design knowledge is partly influenced by John Linsley Hood (JLH).
JLH employed that realization I drew.
I don't know how exactly Naim did it in their original amplifiers.
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Old 24th March 2008, 10:14 PM   #103
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Redid the speakers wiring so the returns were independant going back to the cap cenre point, and also removed the inductor/resistor part of my psu board. I got my bass back!!!

I really liked what that amp was doing but felt the bass was a bit lacking, away must have been to do with somthing i changed, i imagine the psu mods are the most likely source though it hard to say. Very happy now, though i am waiting for some wet 47uf tants for the feedback so see how they sound in there.
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Old 25th March 2008, 01:11 PM   #104
cdswift is offline cdswift  United Kingdom
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Default Silk Screen legend is wrong!

I was building my NAP140 clone this weekend and when matching my 2n5551 transistors for hfe, noticed that the legend for Q1 & Q2 the long-tailed input pair is incorrect on my board. The transistors need to be rotated thru 180 degrees so that the device is opposite to the outline printed on the board.

Anyone else notice this?

Also, there is no provision for an output inductor in this design. Has anyone built this version (see attached picture)? If so, does it work OK without inductor?

Regards

Chris
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File Type: gif nap140.gif (3.9 KB, 2308 views)
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Old 25th March 2008, 03:25 PM   #105
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On my ncc200 boards i used a 0.22r 3 watt resistor which can be used instead. It is used on some amps, i used it without and it works but apparently the amps work better with a bit of inductance or resistance on the output.
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Old 27th March 2008, 09:21 PM   #106
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Default Re: Silk Screen legend is wrong!

Quote:
Originally posted by cdswift
I was building my NAP140 clone this weekend and when matching my 2n5551 transistors for hfe, noticed that the legend for Q1 & Q2 the long-tailed input pair is incorrect on my board. The transistors need to be rotated thru 180 degrees so that the device is opposite to the outline printed on the board.

Anyone else notice this?

Also, there is no provision for an output inductor in this design. Has anyone built this version (see attached picture)? If so, does it work OK without inductor?

Regards

Chris
This is supposed to be a NAP140 clone so it would not use an output inductor. Naim beleives the inductance of the speaker wire should fill this function. If you use NACA5 (or NACA4 or Avondale's wire or older Linn wire) this will work to your advantage-- one less high voltage component. Most wire works just fine actually, so long as it is fairly ordinary and at least 3.5m in length. NACA5 is really very good sounding and a lot of people swear by Avondale's Black Link.

As for the backward transistor... I noticed this in the Ebay picture of the built PCB. I took it as an indication that one should be very careful and thoughtful when building these up. I am still waiting for my boards to arrive but, if anyone has noticed any other potential pit-falls, the warning would be much apreciated.
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Old 27th March 2008, 09:21 PM   #107
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Default SanKen

Quote:
Originally posted by Flappytango
Just got my kit .

I got pretty blue boards (NAP140C version) but did not get the toshiba transistors...

my transistors look very similar to the ones in post #7 of this thread and are labeled as follows.

SK
C2837
7N P


Does anyone know if these will work? Are they are equivalent tosh transistors that have been coming with these kits?

thanks


I've heard a few amps based on the SanKen transistors including a brief period when Naim used them in the NAP140 (Late 80's? Early 90's?). I liked them alot. Comparing SanKen 140 to a 140 using the proprietary Naim 002 transistor I thought the SanKen amps were a little warmer, friendlier and a little more fun. That's entire subjective though.
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Old 28th March 2008, 05:08 AM   #108
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Default NAC 42

I'm considering buying the NAP140 kit and it only seems natural to add a Naim Preamp circuit. Has anyone else considered this PC board?: NAC 42 PC Board on eBay

Other than Naim preamps, what are people using with this amp?
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Old 30th March 2008, 07:00 PM   #109
cdswift is offline cdswift  United Kingdom
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Default Another PCB error

If you are building the latest (blue) version of this clone, beware of another problem I discovered today. The main ground connection to the board (close to the input transistors) doesnt connect to anything except the zobel capacitor. The board will not set up properly unless the ground is also connected to the signal ground point (which it would normally do when all connected up). I corrected this omission by adding a wire link between these 2 points on the track side of the PCB.

Hope this helps someone

Regards

Chris Swift
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Old 3rd April 2008, 10:27 PM   #110
hoka is offline hoka  Netherlands
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just blew up two of these:

Click the image to open in full size.
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