NAP-140 Clone Amp Kit on Ebay - Page 3 - diyAudio
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Old 15th December 2007, 11:01 PM   #21
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Default Thank you by the schematic and informations


Each channel will have something around 160 watts of consumption when driving full power over 4 ohms.... so.... your transformer, 2A and 28 plus 28 will give a little bit more than 110 watts....not enougth, even to a single channel into 4 ohms...but will operate fine into a single channel when using 8 ohms speakers.

If you have two of those transformers, and accept to use only 8 ohms, using good electrolitic condensers into the supply, you will be happy with them.

regards,

Carlos
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Old 16th December 2007, 06:36 AM   #22
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Default I like the kit, in special the boards colour... i love this blue


my prefered colour and tone...blue... alike swiming pool, alike blue jeans pants... Lee Riders and Levis.

Watch the fan over my monitor...my prefered colour.

This kit is lovely.

regards,

Carlos
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Old 16th December 2007, 06:49 AM   #23
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Default This kit is very nice... if i could i would buy a dozen


Nice... very nice.... very pretty.

regards,

Carlos
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Old 21st December 2007, 05:19 PM   #24
flodge is offline flodge  United Kingdom
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Default kit complete/ speaker acting as switch ????

Hello everybody
I have just completed these boards and boy was I careful to not mix anything up or do any bad joints, not drink too much while squinting at the bands with my out of prescription specs.
one very unusual feature, and almost certainly my error - when connected to my bench supply at 31v per side and rigged to test speaker, the current limiter clicks away and treats the circuit as a short. Now, get this, if I unsolder the speaker terminal and switch on everything fine with bias just nice and then connect the speaker, fine, sounds good. For some reason one of the output trannies is not team playing and this quasi thing seems like a fine way to send some juice through your speaker coils. Beware!
Any ideas,
Thanks in advance for your help
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Old 29th December 2007, 11:35 AM   #25
AcidEye is offline AcidEye  Netherlands
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Fodge,

It looks that your PSU does not like the steep current increase when connecting the amp with speaker load attached. One way to prevent this is to use a PSU without current limiter, or to modify the threshold of your PSU's current limiter.

However, since this current peak is ran through the speaker load during startup, it is advised to use a speaker protection for this reason (many speakers do not fancy DC current, even if it is during a short startup period. Low power full range speakers might die within a few milliseconds when exposed to DC ). In one of the links posted in this thread, describing the building process of this kit with lots of pictures, you can see a speaker protection circuit connected to the output of the amplifier boards.

Please let us know how this amplifier sounds, I'm also interested in one of these kits!
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Old 1st January 2008, 07:36 PM   #26
flodge is offline flodge  United Kingdom
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Hi AcidEye
You were quite correct, the surge at turn-on is quite high and then settles down. They sound good on the bench speakers. I will get them put in the box I have ready and waiting that did house my jlh 75w that did not like my electrostatics at all and got very hot, very quickly.
cheers
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Old 4th January 2008, 10:37 PM   #27
rocky99 is offline rocky99  United Kingdom
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Hi

I am awaiting my parts to build one of these clones.

Has anyone finished building one and if so how does it sound compared to the naim nap140?
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Old 5th January 2008, 06:52 PM   #28
flodge is offline flodge  United Kingdom
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Hi
Yes, I have finished mine and put in a box with a shielded transformer and a very simple power supply. Mine is currently driving my 6 foot high diy electrostatics and the sound is very detailed and balanced. My usual amp is a huge beard valve amp and it compares very well especially in the channel balance. obviously it would find the esl's a tough load for its smallish output but i have to say that there is little evidence of it struggling at quite high volume levels. The heatsinks get slightly warm. I set the bias across the emitter resistors at 6mv. Initially it was way too high, 30mv, and the sinks got hottish. 35 to 38ma seems to be the naim standard, or so I am told.
Anyway, I am very pleased to have built them, take a lot of care with good solder joints.
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Old 6th January 2008, 07:52 PM   #29
rocky99 is offline rocky99  United Kingdom
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Hi flodge

Thanks for the reply.

Did you build yours exactly as supplied or have you changed any components? Would changing the output transistors to BUV20's or MJ15003 give more output without getting hot?

By the way, how long did it take for you to receive yours, I have been waiting almost 3 weeks now, although Xmas probably delays things.

Rocky
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Old 7th January 2008, 07:58 PM   #30
flodge is offline flodge  United Kingdom
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Hi rocky99
Mine took about 3 weeks to arrive which is about normal for the distance. I used the components as supplied as they seem to be pretty good but it is debatable whether increasing the bias and more capable output transistors would make a lot of difference with a quasi-complementary circuit. I have to admit though I am just a hobbyist. There are some tests of the nait circuit on the web and distortion levels with different levels of bias and I think the circuit is similar but I may be very wrong. The sound of mine seems to be improving as things 'burn in' or my ears adjust psycho-acoustically, and I don't know which I believe in, depends how much wine you've had or how your feeling. It is a good amp though, I keep on sneaking back for a listen and neglecting my family and that's a good test.
I hope it arrives soon
flodge
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