Naim NAP135 vs NAP250...which one? - diyAudio
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Old 26th September 2002, 03:33 PM   #1
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Exclamation Naim NAP135 vs NAP250...which one?

Hi Everyone.

After reading about Naim's product, I'm interested in producing a replica but not sure of which design to base my project on.

There's the design of the NAP135 from Neil McBride
www.neilmcbride.co.uk/jknamps.html
and the original schematic of the NAP250 from previous "MEGA" Naim forum.

Neil says the only difference between 250/135 is the PSU. But looking at the original and Neil's one, his is missing a pair of transistor and other associate component. Is this intentionally
and for what reason?.

Naim says that there is no difference in the two in term of quality, only different in power handling (NAP135 has 75W to 70W of 250). Big diffs hey...5Watts!!!, yet the 250 is more expensive...why?. Which one is best model in quality.

I really want to get start on building the thing, but so confuse as to which one to build.



Thanxs in ADV

Minh
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Old 26th September 2002, 04:22 PM   #2
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Default NAP250 NAP135

HI Minh,

The Price of the NAP135s is virtually double the price of the NAP250 this is because the NAP135 is a Monoblock, essentially its a NAP250 with one amplifier channel taken out and a fan added. The actual amplifier circuit is the same, I have owned both so this is truth not opinion.
The Circuit on Neils site has no protection Circuitry (apart from the current limiting on the Regulator Board), that is what those extra transistors are on the original.
As to the sound I do know people who prefer the NAP250 and others who prefer the NAP135s

Mozfet
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Old 26th September 2002, 04:59 PM   #3
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Minh,
All the old (not NAP500) style Naim amps are basically the same circuit. The 250 and 135 have psu regulators. If it were me I'd build the amp circuit first and get that working ok and then add a psu regulator.
Bear in mind that Neil McBride does not understand how the Naim amp circuit works. In other words, following his instructions will get you a working amp but it will not be of "audiophile" sound quality (this high feedback design needs a lot of attention to output devices for it to sound great). In other words it will be a fun build experience and will probably sound pretty good but don't expect it to rival a real Naim - it certainly won't.
BAM
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Old 26th September 2002, 06:48 PM   #4
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Default 250/135 Clones

It's a relatively simple task to build a 250/135 clone from either the details on Neil McBrides site or from my site:
www.users.zetnet.co.uk/avondale

The Naim amps have a couple of generic problems which I've managed to solve simply by the addition of an output inductor and a couple of emitter resistors in the input long tailed pair. The Naim circuit's so called protection circuitry has also been removed as it operates at very much lower levels than at first thought and produces the characteristic Naim 'glare' over the music. Measurements and listening tests indicate it is perfectly possible to improve significantly on the original manufacturers performance.

Cheers,

LesW
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Old 26th September 2002, 07:10 PM   #5
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Default Keep it real

Les,
Judging by your published "NAP Series Amplifiers - Revised Circuit" you also don't know how the Naim circuit works.

"it is perfectly possible to improve significantly on the original manufacturers performance"

Oh please. I think this is a good, honest site that Nelson's set up and is not an appropriate place to make exaggerated marketing claims for your services, especially ones that you cannot back up. Keep it honest here at least.

BAM
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Old 26th September 2002, 08:22 PM   #6
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Default hi traderbam

no need to be rude old chap ....the man is entitled to his take on naim, or indeed anything else...
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Old 26th September 2002, 09:13 PM   #7
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Default Naim Circuit

Judging by your published "NAP Series Amplifiers - Revised Circuit" you also don't know how the Naim circuit works

In that case Bam, perhaps you'd be kind enough to share with this small but select group your understanding of how the Naim circuit works.

I tender my gratitude in advance,

LesW
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Old 26th September 2002, 09:16 PM   #8
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hi lesw ,
have two rather novel totally high end amp. designs you may want to have for small fee
indeed they could form part of an entirely new range for your firm...

see also my paper on VI protection in october issue of electronics world at your local WH Smith....
mikek in chigwell essex...
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Old 26th September 2002, 10:42 PM   #9
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Firstly, shouldn't the removal of the protective circuitry improve sound quality?, on the basis of a purer circuit.

Secondly, what would be the recommending output device, since Naim had theirs' custome made?.

Thirdly, does anyone have PCB layout for this amp?

Finally, can someone verifies that the schematic I've got is the original design?.

I'll now build the amp module first, if that works ok and if budget permitts, I'll build the monoblock.
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Old 26th September 2002, 10:46 PM   #10
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The picture i've got is a bit fuzzy.
Does anyone know what TR5 is...it looks like ZTX108 but can't be sure.
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