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How powerful is a Nait 2?

Oh, is that right, I thought the 1 and 2 had identical circuit topology - very interesting :).
 
flatpopely said:
It’s not the clipping that kills tweeters per se, it the tendency towards a square wave (DC) that does them in.
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Square wave has nothing to do with DC, and clipping doesn't cause DC unless the amp fails badly.
 
flatpopely said:
It’s not the clipping that kills tweeters per se, it the tendency towards a square wave (DC) that does them in.
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I guess you didn't read the page I linked to. Let me quote:

8.2 - The 'Clipping is Like DC' Myth
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Just as a woman cannot be a 'little bit pregnant' - you cannot have little bits of DC. DC only comes in large and prolonged doses, anything else is AC. A battery delivers DC, while a functioning amplifier delivers AC - not DC (unless it is poorly set up and/or faulty). This applies whether the amp is clipping or not.

The whole idea that clipped or flat topped waves have 'little bits of DC' is complete nonsense, as is the even sillier idea that a cone is somehow rendered stationary whenever the drive waveform is flat topped.

Clipping of an audio signal merely limits the peak amplitude and raises the average value - square shaped waves are just combinations of sine waves with many (mostly odd) harmonics. A square wave within a speaker's normal frequency range does NOT cause the cone to stop moving. If you were to apply a 1Hz squarewave, then yes, the cone will move in and out and be more-or-less stationary at the extremes. I know this because I've done it (and no, the speaker didn't spontaneously fail). Very low (sub-audible) frequencies are meaningless for any speaker driven with normal programme material.

Music (or speech) does not have nor can it 'create' 1Hz squarewaves, regardless of how heavily it's clipped. Poorly set up equipment with DC coupled amps and no high pass filters might cause some subsonic energy if you try really hard..
Very low frequencies are not within the speaker's normal frequency range and are usually irrelevant because they should be filtered out. No high power speaker system should ever see power at any frequency below its natural low frequency limit. Note that even a 1Hz squarewave is still AC, and not DC (whether in 'bits' or otherwise).

Note: 1. The pink noise used in the AES test is simply clipped to provide a 6 dB peak to RMS ratio. Natural pink noise has a 14 dB peak to RMS ratio.
In case you missed the significance of that, the test signal recommended by the AES for power ratings is a deliberately CLIPPED signal !!
The idea that a square wave is made of alternating 'bits' of DC just won't go away. It's utterly flawed and nonsensical, but you'll see it in countless forum posts, sometimes refuted by others, sometimes backed up. Remarkably, you'll find people who claim to be knowledgeable (even some 'experts') making this same, wrong assertion. I've seen (usually self-proclaimed) 'experts' deny that a squarewave is the summation of odd-order harmonics (of diminishing amplitudes), and insist that it has a DC component. This merely indicates that the person is not an expert, and not knowledgeable - even 'dilettante' is high praise for some. A good demonstration of the makeup of a squarewave is seen in Figure 3A, above.

A 'true' squarewave has no DC component, but a DC coupled amplifier severely overdriven with an asymmetrical waveform might have a small DC offset. Even with severe clipping it's unlikely to exceed a medium-term average (around 10 seconds) of more than a few volts.
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flatpopely said:
On off on off on off........
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What id your definition of DC?

I assume you don't own an oscilloscope?

Here is a picture (borrowed from Jim Lesurf) of a badly clipped sine wave. Notice 1) it is not square, 2) it goes from -Vc to +Vc, not 0 and +Vc.

fig1.gif
 
The Nait 2 is indeed truly powerful:
(1) Like a first sexual experience it invokes nostalgia in middle age men;
(2) It generates more replies to posts than other pieces of kit;
(3) It brings out the best and worst in all of us and all connected pieces of hi fi kit.

I could go on...(glad I still have mine)!!!
 
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Other Nait 1 and 2 nerdiness things I can think of:
  • Nait1 runs at a slightly higher bias than Nait2
  • Nait2 has 15W into 8 ohms compared to Nait1's 12.
  • The de-facto Nait listening setup at the factory was an LP12/SBL front and back end.
  • Nait2 CB has a constant voltage logo supply circuit, Nait2 olive has a constant current supply. Both are to stop the display dimming with sagging power rails when driven hard.
  • Nait2 amp circuit is exactly the same as all the incarnations of the NAP90. Its compact design meant good thermal feedback between output stage and biasing circuit, the 90 was spaced out and often overheated (later fixed by moving a transistor under the board).
  • I've had a hand in literally hundreds of Nait2s. I have programmed and maintained the machine that populated the PCBs, hand inserted the large components, wired them up, tested them en masse, and repaired and serviced the things. Despite that I still like them.
  • The Naits 1 and 2 have the absolute minimum number of parts necessary to make a working integrated. Despite that they can still hold their own against the bigger amps. They are truly greater than the sum of their parts.
  • A very simple, and reversible, mod turns the gain right down and allows full use of the volume control.
 
Julf said:
What id your definition of DC?

I assume you don't own an oscilloscope?

Here is a picture (borrowed from Jim Lesurf) of a badly clipped sine wave. Notice 1) it is not square, 2) it goes from -Vc to +Vc, not 0 and +Vc.

fig1.gif
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Unfortunately I think amplifiers (particularly solid state amplifiers) may not clip so predictably. In the distant past I recall magazine reviews that showed output waveforms on clipping and on recovery from clipping. They were, IIRC, not all clean and not all symmetrical. So there might be some "DC" offset from clipping. I have no idea if it's a common behaviour or if it's going to be enough to cause tweeters a bigger problem than the higher levels of high frequency audio components, though.

One of the reasons I am doubtful if the Nait2 will drive an 85 dB SPL / 1 W loudspeaker well enough is that I heard an acquaintance's home-built 4 W SET amplifier driving 84 dB SPL / 1W loudspeakers (B&W DM2a). He was delighted with the sound but I was not impressed at all. He captured a SPL vs time file with his microphones and I looked at it in Audacity. Sure enough there was a lot of clipping. Soft clipping and symmetrical which is, IIUC, typical of valve amplifiers - so it was as good as you might hope for, but the combination still clipped at a reasonable volume. And it sounded like that to me.

I concede that the Nait2 has, IIUC, three to four times the power and the ATC SCM12 is nominally 1 dB more sensitive, so the OP's situation will be better. But I still think it will be marginal, and the OP may have to make a test to be sure if it works for him.
 
John Phillips said:
Unfortunately I think amplifiers (particularly solid state amplifiers) may not clip so predictably. In the distant past I recall magazine reviews that showed output waveforms on clipping and on recovery from clipping. They were, IIRC, not all clean and not all symmetrical. So there might be some "DC" offset from clipping.
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Absolutely - asymmetric clipping (and error conditions) can definitely introduce a DC component (but it is normally blocked by the speaker crossover). My point was about the oft-repeated but erroneous "a square wave is short-term DC because the line is flat" argument.
 
Ode to the Nait...

The Nait 1 had three input selector buttons, the Nait 2 had a knob.

I now have a Manley Stingray, which has *two* input selector knobs.

Joe
 
Joe P said:
Ode to the Nait...
The Nait 1 had three input selector buttons, the Nait 2 had a knob.
I now have a Manley Stingray, which has *two* input selector knobs.
Joe
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How about a Haiku?

The Nait1 selected three
Alas, one extra in the two
Neither moving coil
 
My computer science teacher at college was Don Morgetroyd and he was a master of deadpan delivery. He would very solemnly introduce himself as the Senior Head of Information Technology.

His favourite word was burolandshaft though he was also very fond of aktiengesellschaft.
 
John Phillips said:
To get a realistic answer, the question about the Nait2 really needs to be split into two parts:
  1. Is it powerful enough to produce adequate loudness based on the loudspeakers' sensitivity?
  2. Is it powerful enough to drive the worst impedance the loudspeakers have?
Part 1: Maximum possible loudness comes from rated amplifier power and loudspeaker sensitivity. 13W from the Nait2 will barely (at least from my PoV) get good loudness with a rather below average 85 dB SPL sensitivity SCM12. If you listen at fairly low level and/or close to the loudspeakers and/or in a small room it is just possible it will be enough. However, I think something is needed closer to the ATC minimum figure of 50W to be comfortable.

Part 2: As you write, the Nait2 has a reputation for being able to drive loudspeakers having a difficult impedance. Actually most ATC loudspeakers seem to have a reasonably easy impedance, even if they are difficult because of low sensitivity instead. But unless you achieve adequate loudness for your needs, as in part 1, this second part is, IHMO, not likely to significantly compensate.
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The CB NAIT2 is plenty powerful enough for a pair of Yamaha NS-1000M in a 65 cubic metre room. In my opinion, it's pretty much damn perfect fronted by an LP12 (or decent CD-P like a Densen B-440XS). The only concessions it makes to my usual mainstays of Pioneer C-21/M-22 is a slightly coarser texture, but it has all the boogie, engagement and authority that belies its 15W power rating. It's another case where specs don't really matter that much in a practical sense.
 
I can vouch for seemingly mismatched pairings, an old Rotel RA-820AX into Spendor S35/R2’s, 2 x 30 watts into 85db. Plenty enough volume in a 13 x 12’ room. (For openness I do use a 275w sub too).
 
James said:
The CB NAIT2 is plenty powerful enough for a pair of Yamaha NS-1000M in a 65 cubic metre room. In my opinion, it's pretty much damn perfect fronted by an LP12 (or decent CD-P like a Densen B-440XS). The only concessions it makes to my usual mainstays of Pioneer C-21/M-22 is a slightly coarser texture, but it has all the boogie, engagement and authority that belies its 15W power rating. It's another case where specs don't really matter that much in a practical sense.
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I'd love to try the Nait on some NS-1000Ms.

Nait 1 will also drive Audio Note AX2, Klipsch R15-M and Royd Mistrels with relative ease. Problem is I wouldn't want to live with any of those speakers.

I must try it on my Rega ELAs sometime. I reckon that would work and be enjoyable over time.
 
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