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Offline Matt  
#1 Posted : 28 October 2011 13:04:03(UTC)
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I've noticed that there are a lot of Naim NAP 140 clone power amplifier kits being sold on the internet, and was wondering if anyone has heard them?

From what I gather the NAP 140 was based on a 1970's RCA power amp design but with different component values. This might explain why the clone makers have avoided any legal issues. Some people have also mentioned that some of the component values in the clone kits are also different.

Edited by user 28 October 2011 13:10:07(UTC)  | Reason: Not specified

Offline kengale  
#2 Posted : 28 October 2011 15:29:03(UTC)
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Matt wrote:
I've noticed that there are a lot of Naim NAP 140 clone power amplifier kits being sold on the internet, and was wondering if anyone has heard them?

From what I gather the NAP 140 was based on a 1970's RCA power amp design but with different component values. This might explain why the clone makers have avoided any legal issues. Some people have also mentioned that some of the component values in the clone kits are also different.


Had a quick look at the NAP140C circuit - pretty conventional quasi-complementary power amplifier. Differential npn pair, pnp driver with npn constant current load, quasi-complementary output stage with diode linearisation and fixed current limiting. Lots of amps around the period looked pretty much the same.
Offline Pete_w  
#3 Posted : 28 October 2011 20:23:06(UTC)
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I ran a genuine '140 for a while. Was never that impressed. I remember that it did sound significantly better with the current limiting removed, so it must have been intruding. Some nice low-value paralleling caps on the PSU caps helped as well, though I remember they were a bit of a squeeze. Then for a while I used it on treble with a pair of DIY '135 "McBride clones" on bass. Sounded fairly good, but eventually dumped the lot for the DIY Tripath approach, a significantly superior (sounds better, timing's better, much safer) solution IMHO. As indeed did Dr McBride :-). Have still got them all somewhere in the garage, but I suspect I'll have gutted them to get the expensive caps out...
Offline Martin Colloms  
#4 Posted : 29 October 2011 07:19:46(UTC)
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If a generic circuit is any good that is only part of the battle for better sound
next comes optimal ground tracking ,
build quality, electrical and physical ,
cable looms, connector practice, vibration control

Good designers constantly judge their work working interactively with all these variables

You can never make up for poor electrical behaviour, but if the other aspects are neglected you will never know the potential of a given circuit design


Martin C
Offline kengale  
#5 Posted : 29 October 2011 23:59:24(UTC)
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Pete_w wrote:
I ran a genuine '140 for a while. Was never that impressed. I remember that it did sound significantly better with the current limiting removed, so it must have been intruding. Some nice low-value paralleling caps on the PSU caps helped as well, though I remember they were a bit of a squeeze. Then for a while I used it on treble with a pair of DIY '135 "McBride clones" on bass. Sounded fairly good, but eventually dumped the lot for the DIY Tripath approach, a significantly superior (sounds better, timing's better, much safer) solution IMHO. As indeed did Dr McBride :-). Have still got them all somewhere in the garage, but I suspect I'll have gutted them to get the expensive caps out...


If it was the original 2SC2837 transistors, they are not particularly robust - indeed a bit marginal for 4ohm speakers with much reactive content, hence the fairly draconian current limiting ,with only a single-slope safe-area limit. Designed when the norm for speakers was a reasonably kind 8ohms. With a few zeners and resistors you could give it a dual or triple slope safe-area limit with much better current delivery without risking blowing it up. I wouldn't care to run it without any limiting - it only takes a slip with a wire or a heavy bass content at full volume into a nominal 4 ohm speaker to overdo things. I suspect the various clones went for tougher output devices - 2N3773 turned up a lot in power amps of the period.
Offline Martin Colloms  
#6 Posted : 30 October 2011 12:07:07(UTC)
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Naim commissioned their own TO3 output transistors with better thermal coupling and thicker internal chip lead out wires

You cannot judge an amplifier by its circuit

Martin Colloms
Offline Pete_w  
#7 Posted : 30 October 2011 15:13:29(UTC)
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kengale wrote:
I wouldn't care to run it without any limiting - it only takes a slip with a wire or a heavy bass content at full volume into a nominal 4 ohm speaker to overdo things. I suspect the various clones went for tougher output devices - 2N3773 turned up a lot in power amps of the period.


Can't remember what I used now when I built my NAP135 clones - it was a very long time ago - but I've just looked in the cupboard and found a bag of unused TIP35Cs, so I could have used those, or perhaps they're unused because I bought them and then chose not to. Who knows? I was driving benign loads - ES11s and then ProAc Response 3.5s, so high current wasn't really a necessity. Anyway, I do remember that Naim's rather lovely high-current +/-40V regulator circuit saved my bacon on more than one occasion in terms of accidental shorts! It generally shuts the rails down in time to save your output transistors, which is nice... The 140, of course, doesn't have one of those.

To be honest, all this was a major contributor to why I eventually dumped the lot and went for the Tripath solution. As the older and .... I won't say "wiser", let's just say "less gung ho" ... I got, the less comfy I felt about leaving all this lot powered up 24/7 in my living room[1] while we slept upstairs and teething kittens roamed the house... I was aware of just how much less "safe" my clones were than Naim's original, and eventually fear caught up with me. The Tripath boards astounded me with how good they could be got to sound (they had enthusiastic "audiofile" apps support back at base in California, real shame they went belly-up) and their short-circuit protection and current-limiting Just Works, as my little boy has subsequently proven...

[1] And yes, it did have to be powered 24/7, else it sounded like a bag of nails... The Tripaths, by contrast, can be left with the Very Big Linear PSU powered, but the output stage muted (which seems to turn off all the output stage's warm-running driver circuitry as well) so it sleeps safely and relatively greenly, and sounds just fine on being un-muted from "cold"...



Edited by user 30 October 2011 15:21:59(UTC)  | Reason: Not specified

Offline kengale  
#8 Posted : 02 November 2011 15:48:24(UTC)
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Martin Colloms wrote:
If a generic circuit is any good that is only part of the battle for better sound
next comes optimal ground tracking ,
build quality, electrical and physical ,
cable looms, connector practice, vibration control.....
Martin C


but if you tackled vibration control then there'd be no market for vibration-controlling feet, shelves etc.
Offline ashleym  
#9 Posted : 02 November 2011 21:52:45(UTC)
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Quote:
but if you tackled vibration control then there'd be no market for vibration-controlling feet, shelves etc


But what sort of control do you need? My stand is a metal framed affair on a suspended wooden floor with numerous Naim amps on. The rack has glass shelves. Would I need to deal with the same issues as a wooden stand with wooden shelves on a concrete floor with a class D amp with SMP? Or with a valve pre-amp? Close or far away from speakers? wall or floor shelf? Aesthetics? Cost?

Of course if vibration control was tackled by the initial equipment manufacturer this would help but they would be some market resistance to it (ie would YOU pay for it?!?!) and not all manufacturers might agree it is necessary.

Edited by user 02 November 2011 21:53:29(UTC)  | Reason: Not specified

Offline hifistan  
#10 Posted : 03 November 2011 03:54:14(UTC)
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Also all the devices I have tried sound different so it is probably best left to the consumer. To me it is akin to auto tyres, bog standard will suit many but the enthusiastic motorist will select replacement ones that give the performance he/she wants.
Offline kengale  
#11 Posted : 03 November 2011 11:40:22(UTC)
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ashleym wrote:
Quote:
but if you tackled vibration control then there'd be no market for vibration-controlling feet, shelves etc


But what sort of control do you need? My stand is a metal framed affair on a suspended wooden floor with numerous Naim amps on. The rack has glass shelves. Would I need to deal with the same issues as a wooden stand with wooden shelves on a concrete floor with a class D amp with SMP? Or with a valve pre-amp? Close or far away from speakers? wall or floor shelf? Aesthetics? Cost?

Of course if vibration control was tackled by the initial equipment manufacturer this would help but they would be some market resistance to it (ie would YOU pay for it?!?!) and not all manufacturers might agree it is necessary.



Vibration control within an amp is a matter of sound design - there's no need for fancy feet, rubber bits, ebony bits etc etc, just proper attention to component selection, PCB design, physical construction. It's a routine thing in some of the fields of design I have worked in, where sensitive electronics are mounted on bits of equipment which have collosal vibration levels - for instance compressors running at 60,000 rpm, cutting-heads of oil-well drills, probes in the wake of a warship with twin 28,000bhp motors at full throttle, and have managed to get induced vibration effects to well below the lsb of a 16-bit aquisition system (-96dB). Similarly when I was designing active speakers I specifically tested for the INAUDIBILITY of vibrational effects on the commercial amps I used as well as my own designs. I am sure if it was possible 30-40 years ago it should be a doddle for current designers. Of course if you insist on using valves then you really are cutting off your nose to spite your face - there are huge problems with pickup, especially as the audio field usually uses B9A-based and similar valves. But you will need to attack this at the amp design stage, not try and cure the problems externally.

But the real question is - do these effects actually exist? Are they actually audible? There's loads of anecdotal evidence, on this site as well as lots others, where people have listened with and without various shelves, brackets, pods etc. and claim to hear differences. But of properly conducted blinded, randomised placebo-controlled trials virtually nothing. And of course if a particular aftermarket accessory cures the faults on one particularly susceptible product, you can assume nothing at all about its effect on another product, which if it has any of these faults at all will probably lie in a completely different area.

And of course the manufacturer is in an awkward position - if he has eliminated any vibrational pickup effects and then points out this fairly routine achievement in his publicity material "Will work perfectly on any shelf, any floor. No need for fancy feet, special mains cable" he alienates the dealers who actually make a handsome profit from these aftermarket products.
Offline hifistan  
#12 Posted : 03 November 2011 17:57:52(UTC)
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To summarize
1. the problems are imaginary in the first place.
2. they are easily dealt with by any competent designer
3. who would use tubes in this day and age?
4. Double blind testing will solve all problems, both real and non-existent

There use to be a term in the Philosophy of Science called "Hand Waving" when someone spent a great deal of time discussing a subject without ever getting down to a concrete level or actually adding anything to our knowledge of it. You be the judge.
Offline Andrew Ashton  
#13 Posted : 03 November 2011 18:30:24(UTC)
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I wish at this point to use in a completely inappropriate and twisted manner a quotation from Stereophile magazine

"All important differences between hi-fi components can be measured; most differences that can be measured don't actually matter because they are below the limit of audibility, as proven by double-blind listening tests; thus, at least for amplifiers, all competently designed amps sound the same."

Andrew
Offline hifistan  
#14 Posted : 03 November 2011 23:07:25(UTC)
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And if you believe that I have a bridge in New York City you can pick up for a song. [Sorry, don't know the British equivalent]. If you can't measure it it does not exist and if you can measure it it is irrelevant as no one can hear it. I think I'll stick with my lying ears.LOL
Offline kengale  
#15 Posted : 04 November 2011 00:10:04(UTC)
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hifistan wrote:
To summarize
1. the problems are imaginary in the first place.
2. they are easily dealt with by any competent designer
3. who would use tubes in this day and age?
4. Double blind testing will solve all problems, both real and non-existent

There use to be a term in the Philosophy of Science called "Hand Waving" when someone spent a great deal of time discussing a subject without ever getting down to a concrete level or actually adding anything to our knowledge of it. You be the judge.


You've mis-summarized:

1. The problems are PROBABLY imaginary in the first place
2. IF they're not, then they are easily dealt with by any competent designer
3. Agree
4. Double blind testing will tell IF there's a problem - it's only worth trying to solve problems that actually exist.
Offline Togil  
#16 Posted : 06 November 2011 09:49:19(UTC)
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How much can design parameters be changed before they become audible in a db test ?

Or put differently, how incompetently can an amplifier be designed before it becomes obvious in a db test ?
Hans
Offline kengale  
#17 Posted : 07 November 2011 18:50:16(UTC)
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Togil wrote:

How much can design parameters be changed before they become audible in a db test ?

Or put differently, how incompetently can an amplifier be designed before it becomes obvious in a db test ?


It's very hard to know, though I suppose one could do such tests. But there's not really much point - if you design an amplifier from first principles to have an output which is an exact copy of its input except that it's more powerful, (or at least, nobody in a db test can tell the difference), only amplifies signals within the audio band and to be non-susceptible to vibrational input or inteference - radiated or conducted - (again, low enough that nobody can actually tell in a db test), and it passes its db tests, then there's not really much point in spending more design effort trying to degrade the design until it fails and then going back one step. Especially if you're selling into the HiFi rather than mass market, because quantities are low (thus not worth spending more development time to spread across these small numbers) and the small changes in bought-in cost will not have a significant effect on the selling price.

Effectively this is the market I work in, designing products where performance is all, numbers by mass-market standards are infinitessimal and development cost tends to dominate the costings. You go for broke straight away, using the best suited technology for the application, taking all sensible precautions against emc, vibration, over/undervoltage, over/under temperature etc etc. If the prototype works to specification, the last thing you do is to go back and see what you could degrade, becasue nobody would pay you for doing it.

Speakers are another matter- they are still so far from theoretical perfection that the whole design excercise is about playing advantages and disadvantages of technologies, material, geometries, material costs etc against each other to get the best compromises possible within cost and the end-users' environment. But you still need to use db testing - or at the very least single-blind testing - to see if your pet solutions produce differences, improvements or degradation. The hardest thing is to tell whether things that the user says sound "better" (single or db) are actually any nearer to what's within the source - because hardly anyone has any real knowledge of what the original is actually like.
Offline Martin Colloms  
#18 Posted : 09 November 2011 08:26:44(UTC)
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I concur with this post in the main but I am bound to comment !

If it is so easy to design the perfect amplifier, and at moderate build cost, surely there is a fortune to be made?

Why hasn't it been done, especially by our forum correspondent?

Or does he believe that we have no ability to perceive quality for its own sake , that we live in a state of permanent delusion.

To some degree reviewers have unique advantage in being able to sample a vast range of offerings , most it has to be said, pretty average.

Leaving aside petty issues such as favouritism , prejudice and the like, most us us really want to know.

We have extended experience of systems, set ups and of product and tend to know when the sound is better.

Natural selection weeds out most of the rubbish.

I have also found a number of dealers are good listeners, are sincere and really do understand sound quality.

Dogs are discarded.

Anyway this is old news, I refer again to a listening test on a good amplifier , universally acclaimed at the price, a Rotel 820 where I accessed the reservoir electrolytic capacitors and auditioned a number of alternatives .

Each make and type had a unique audio signature which materially affected the rank and characterisation of the amplifier.

But of course this stuff was and is well known to amplifier designers, it had just not been made public before.

Electronic components are manifestly imperfect , how on earth can a perfect amplifier be made with them?

Designers find a good balance of performance and price and live with it.

DB testing will reveal gross differences for loudspeakers but to avoid experimental errors they are notoriously difficult to set up

The more subtle differences affecting long term satisfaction are missed by the sheer bluntness of dB testing

Remember dB testing assured us that DAB would sound as good as FM , the BBC relied upon it to change the broadcast legislation

db testing also told us we could ( probably) not hear 128K MP3 as a loss in sound quality, but once exposed to the real thing most who care are in little doubt that they can hear the quality loss.


Martin C



Edited by user 09 November 2011 08:27:40(UTC)  | Reason: Not specified

Offline kengale  
#19 Posted : 09 November 2011 12:03:43(UTC)
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Martin Colloms wrote:
Anyway this is old news, I refer again to a listening test on a good amplifier , universally acclaimed at the price, a Rotel 820 where I accessed the reservoir electrolytic capacitors and auditioned a number of alternatives .

Each make and type had a unique audio signature which materially affected the rank and characterisation of the amplifier.






This just means that your "good" amplifier had a very poor power supply rejection ratio (PSRR). This is all this test proved - it doesn't enable one to generalise about the effect of these caps on any other amplifier. With attention to detail it is possible to achieve -120dB over the audio range. The 140 circuit that started this thread inherently doesn't have a very good PSRR, especially with reference to the positive rail - it's necessary to seperately decouple the rail to the driver with resistor/inductor and decent low ESR cap(s). The makers of PA chips have long realised this - you will find most bring out the driver and front-end rails seperately from the output devices, just so that you can apply this seperate decoupling. For the same reduction of power-supply effects this is MUCH cheaper than throwing massive capacitors at the main power supply.

Martin Colloms wrote:
If it is so easy to design the perfect amplifier, and at moderate build cost, surely there is a fortune to be made?

Why hasn't it been done, especially by our forum correspondent?


No there isn't a fortune to be made. There are almost certainly quite a few amplifiers already on the market at moderate cost whose output is completely indistinguishable from the input when driving real loudspeakers. But how would you ever prove it to the customer? Virtually all mags use hopeless testing techniques, non-blinded, judged against a purely imaginary view of what the source material SHOULD sound like, judged on things like Pace, Rhythm and Timing without any idea of the Pace, Rhythm and Timing of the original. Equally, all retailers demonstrating can do is play music from an arbitrary source through an arbitrary set of speakers, all coloured by the retailer's own expectations (and probably his commision level). Almost certainly I have designed amplifiers whose performance if used as a Hifi amp (and a lot aren't, they are driving far more vicious loads than any loudspeaker, and over a wider frequency range) would be "perfect", if you mean that no-one could distinguish its output from its input (the very definition of HiFI, surely?). But I long ago gave up on any idea of making money from selling into the Hifi market - you need lots of skills in the styling and advertising-puff area. The latter I find particularly hard to do, selling pseudo-theories and "specialist"-name components into a market that has very little judgement of its own and is almost certainly not looking for Fidelity. I always remember when a fellow engineer ( a mechanical design engineer) left to work as a salesman for a large pneumatics company, my boss saying to me " **** will make a very good salesman - he's got just the right amount of insincerity"
My customers employ me (I now design on a consultancy basis rather than as a direct employee) to design products which meet their specification without any preconceptions as to how I would do it, and for as little expenditure (of course!) as possible. This means that there is a heavy emphasis on right-first-time, because a protracted development time would cost lots of money. Luckily they don't want lots of unnecessary flashy tooling, themed styles etc. Just the actual performance.



Offline alexh  
#20 Posted : 09 November 2011 13:11:19(UTC)
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I have not posted that often here because I am sick to death of this stupid argument that keeps cropping up.

A fact of life is that some will here thing and some will not. Why not admit it if you cannot here some things instead of hiding behind the ABX argument to justify oneself.

Measurements have a big part to play, but you can not go forward without the benefit of trained designers using there ears.

I have now lost the respect of anyone who thinks that an ABX test is the ultimate test due to the dumbing down effect of the ABX test due to our brains filling in the gaps in poor performance.
Alex H
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