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Modified Naim NAP140 Schematic
Modified Naim NAP140 Schematic
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Old 11th February 2019, 01:28 PM   #41
traderbam is offline traderbam  Europe
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In my experience, electrons do not seem to take notice of the aesthetic quality of the schematic diagram of the circuit they inhabit.
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Old 11th February 2019, 02:54 PM   #42
domenico80 is offline domenico80  Italy
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here there is no talk of preferential trails taken by electrons, but of well-traveled signal and with a few selected excellent components
I think
and when in a final I start to see input cap, signal-mass cap in the feedback loop, various compensations in a circuit already of its simplest, well, the circuit does not look like much performante
these Naim are simple, almost basic, can be cloned without problems spending very little because the transistors are always replaceable, but say they sound good, in short, I would say no
I too cloned the 140, and ......

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Old 11th February 2019, 03:16 PM   #43
domenico80 is offline domenico80  Italy
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Has anyone paralleled two couples per channel?
has someone increased the supply voltage to 50 VDC?
and what changes did you make?
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Old 11th February 2019, 09:14 PM   #44
Bigun is offline Bigun  Canada
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Modified Naim NAP140 Schematic
I think you are missing the point if you feel the schematic is too basic or flawed. It is the very flaws that that are important. If you try to improve on them, you no longer have what the designer intended. You might not like what the designer intended, that's fine too, just move on to something else - as somebody else on this forum said once, there's for sure an amplifier available for each persons tastes.

I tried a higher voltage on my clone. Interestingly, I don't think it was for the better. And I had a similar experience with my AKSA clone. I don't have them set up at present so I can't re-check - we're relying on my memory. Nevertheless, my perception is that these amps sound sweeter in the range +/-36V to +/-42V than at anything higher. I have other amps that are happy at higher voltages.
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Old 12th February 2019, 04:12 AM   #45
Ian Finch is offline Ian Finch  Australia
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It's not like many others haven't already tinkered and tried everything possible with NAP designs either. Popularity and recognition of the Naim brand is a strong magnet for audiophiles, curious folk and other manufacturers - all for good reasons. If our own efforts are to be meaningful though, we need to avoid the usual DIY stumbling blocks of guesswork, observer bias, poor test equipment and lacking any reference or even a standard amplifier to make proper comparisons.

I would spend some time reading the Naim and DIY forums at pink fish media before guessing about possible modifications that would probably suit mass produced products rather than the tightly specified Naim products. This useful reference doc. for old Naim models also originates at PFM: Modifying Naim Audio power amplifiers
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Old 12th February 2019, 04:56 AM   #46
Ian Finch is offline Ian Finch  Australia
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Quote:
Originally Posted by domenico80 View Post
has someone increased the supply voltage to 50 VDC?
and what changes did you make?
If you look at the ratings of the ZTX653/753 VAS transistors, you'll notice that the rail-rail voltage limit is around 80V with a safety factor. There are few suitable transistors other than these and their SMD versions, than can match these types for the VAS transistor and current sink, where a high Cob of 30pF is clearly wanted. So, for practicality, it's ~40V max. rails or move on to something else, as Bigun suggests.

The NAP design is based on a generic type anyway and the simplest version is a fully worked example seen in Douglas Self's books and on his website, in an article examining distortion in amplifiers. Check it out if you like to tinker with more possibilities. Distortion In Power Amplifiers - Home Warranty Appliances
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Old 12th February 2019, 06:02 AM   #47
johnego is offline johnego  Indonesia
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Quote:
Originally Posted by domenico80 View Post
well, the circuit does not look like much performante
these Naim are simple, almost basic, can be cloned without problems spending very little because the transistors are always replaceable, but say they sound good, in short, I would say no
I too cloned the 140, and ......

Most people don't have good ears. Those who have, mostly don't understand what causing the difference in sound. Almost any topology can sound special if it meets certain conditions. Knowing this conditions is not something easy to do. It is not as simple as it looks.


If you haven't heard the original 140, don't be sure it will sound the same with your clone. For sure it will not be the same sound. Tell me something, do you know the hfe of the original Naim output transistor? Do you know the hfe of your clone? Is bottom NPN has the same hfe with the top one?


Say you have heard the original 140. If you have good ears, you should be able to hear where the amp excels and where it is lacking. It is then up to you if you think the amp is not up to your taste.


IMO, what you need is to improve the distortion (without changing what it is already good at). With this basic circuit it can be expensive. And you know what? Think about this:


Loudspeaker distortion is often much greater than amplifier distortion. Some amps, especially with special drive like Naims, can easily excite speaker cone distortion. Some other amps, like P3A, will not do that. Take a raw high distortion speaker driver and compare the 140 with P3A. The result is like heaven and earth, the P3A will be so much distortionless. Naturally, you will prefer the P3A right? Of course. Now what if you have a GREAT low distortion speaker? What you think is great with P3A might not great anymore because now you are okay with 140 + your speaker distortion.
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Old 12th February 2019, 07:15 AM   #48
domenico80 is offline domenico80  Italy
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the 140 can be interesting for its simplicity and economy of construction having also dissipates little heat
the 140 can always be replicated, clear, no clone will ever be the same original that even the same Naim, today, not could repeat faithfully
apart from the basic scheme, the Naim sound is also defined by the tantalum capacitors used in the finals and pre-English of the time, in addition to the obvious filter capacitors that are nowadays unobtainable.
Who ever decides to clone the 140 will know with absolute certainty that it will never be able to replicate the sound and that even the original 140 will sound, today, very different from the new original.
That said, the 140 seems excellent to be cloned, within today's limits, spending little.
example, Spectral DMA 50, another world compared to 140, it is almost impossible to clone faithfully, but you can redo

Last edited by domenico80; 12th February 2019 at 07:18 AM.
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Old 12th February 2019, 07:22 AM   #49
domenico80 is offline domenico80  Italy
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ask if anyone has tried to feed the clone 140 to 50 vcc, mean to ask what changes have been made (I know what to do, but I ask if others have already walked the way).
Obviously you have to intervene on the transistors and change them with, I do not know, but I would say 2n 5551 and 5401 that seem optimal and final like the 1302 A and complementary or similar, since the 1302 are out of production
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Old 12th February 2019, 07:25 AM   #50
domenico80 is offline domenico80  Italy
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today redoing a final amp 20 years ago is often impossible because there are no more important transistors (see i jfet 2n 5566)
So a diy is forced to repay on simple schemes and projects and to do what you can with what is around from serious dealers such as Mouser, Distrelec, Farnell, RS:
others are almost always cheats
it happens that on E BAY many sites in the Far East, to sell, falsify the codes of j fet and transistor

Last edited by domenico80; 12th February 2019 at 07:27 AM.
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