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Modified Naim NAP140 Schematic
Modified Naim NAP140 Schematic
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Old 6th February 2019, 10:27 AM   #21
domenico80 is offline domenico80  Italy
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if it is possible to stabilize the offset with the trimmer and with the dual fet, one can then try to eliminate the cap from 220 to ground in the counter-reaction ring
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Old 7th February 2019, 09:37 AM   #22
carlmart is offline carlmart  Brazil
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You know that wouldn't be a NAP140 anymore, do you?
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Old 7th February 2019, 02:34 PM   #23
domenico80 is offline domenico80  Italy
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of course it would no longer be a 140, but a better and more performing amp.
we have done something similar and in fact the 140 remains very little
some capacitors are eliminated for the signal in series, the final power section is enhanced and the important input stage is activated
I think the 140 is not even a final amp that can offer outstanding performances, in my opinion, of course

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Old 7th February 2019, 05:07 PM   #24
domenico80 is offline domenico80  Italy
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Quote:
Originally Posted by domenico80 View Post
of course it would no longer be a 140, but a better and more performing amp.
we have done something similar and in fact the 140 remains very little
some capacitors are eliminated for the signal in series, the final power section is enhanced and the important input stage is changed
I think the 140 is not even a final amp that can offer performances, in my opinion, of course
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Old 7th February 2019, 07:27 PM   #25
carlmart is offline carlmart  Brazil
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Do you have any schematics?

I did simulate NAP140 in LTSpice, so I can modify the parts easily.
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Old 7th February 2019, 08:36 PM   #26
JeffYoung is offline JeffYoung  Ireland
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Modified Naim NAP140 Schematic
Here's my LTSpice sim of the NAP250; I'm pretty sure the amp circuit is the same as the 140, with the possible exception of the feedback cap.

Avondale Audio do a true complementary version (with MJ15003/MJ15004). Schematic here: https://pinkfishmedia.net/forum/prox...6a8f0e040a3d9d
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File Type: asc NAP250.asc (9.3 KB, 43 views)
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Old 8th February 2019, 05:48 AM   #27
Ian Finch is offline Ian Finch  Australia
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Because rail voltages are lower at +/-34V, there are also minor changes to current source resistors and the small signal transistor types used in the NAP140. Over 30 years in production, there were forced changes to several of the semis. There were obviously different cosmetics and PCBs too. I have seen only a sketch (a reverse-engineered schematic) of the real 110/140 model designs. The usual design we see called the NAP140 that is plastered all over the net and modified by Avondale, is actually the 250 model - sans regulated power supply. This is the same as NAP135 and I believe it's also close to the NAP180, a model for safe max. power from an unregulated +/- 40V supply.

Given the high Cob of 30pF for the VAS transistor, this needs to be factored into the value of the Miller compensation cap. It isn't just what it appears to be at all - in fact it varies with the signal as does the output capacitance of the transistor. That's all a part of the distinctive sound quality that you hear. If you were looking for a perfect textbook design with ultra low distortion though, I'm afraid Naim designs aren't for you and simulations might give some strange results that don't agree with expectations.

Can't download your PFM link, Jeff. Could you just link a forum post?
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Old 8th February 2019, 09:15 AM   #28
JeffYoung is offline JeffYoung  Ireland
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Modified Naim NAP140 Schematic
@Ian, does this work: QUDOS - the brilliant new amplifier boards from Avondale | Page 19 | pink fish media ?

(Thanks for the extra info. I didn't realise the actual 140 was that different from the 250.)
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Old 9th February 2019, 12:19 AM   #29
traderbam is online now traderbam  Europe
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It is interesting to see that based on its choice of Darlington networks Avondale doesn’t know what its doing.
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Old 9th February 2019, 12:49 AM   #30
Bigun is offline Bigun  Canada
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Modified Naim NAP140 Schematic
Ian,

FWIW I think the reverse engineered sketches of the 110 are valid, I went through the exercise myself using some very good photos of an open box, it’s in my thread on my Naim clone.
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