Has anyone listened to the NAD C 390DD?

[finnbrodersen]

the 390DD is indeed a very interesting amp. Like a poor mans (e.g. me) M2

check out http://www.youtube.com/watch?v=0jJR-8sv1pM for more info

and http://www.youtube.com/watch?v=Sksqoz1KXGQ and http://www.youtube.com/watch?v=DxXIqDsIzgs for an introduction to the M2

[darrenyeats]

Guys, here is where I was going wrong! I was thinking about that 16 bit waveform and then I was thinking in 16/44 DAC terms (I was sleep deprived!) which should smooth it analoguely.

Obviously these DACs are not 16/44. But, even after getting some sleep, this morning I would expect an upsampling 24 bit DAC to smooth 16/44 digitally.

Now I realise when Stereophile tested the 16 bit undithered waveform, probably they used a file at the highest sampling rate and bit depth...just mimicking a 16 bit waveform within it. So the DAC doesn't treat it to any upsampling goodness...the customer wants a crude staircase drawn in hi-rez, the customer gets just that.
Darren

Sent from my HTC Sensation Z710e using Tapatalk

[Mnyb]

the 390DD is indeed a very interesting amp. Like a poor mans (i.e. me) M2

check out http://www.youtube.com/watch?v=0jJR-8sv1pM for more info

and http://www.youtube.com/watch?v=Sksqoz1KXGQ and http://www.youtube.com/watch?v=DxXIqDsIzgs for an introduction to the M2

Nice videos a truly interesting assortments of amplifiers ,these new NAD's

If I where in for passive speakers I would not hesitate trying either M2 or C390DD .

Seing that the CC390 has a cheaper chassi and a bit less power to make it more economical would make it perform very well for the money this is NAD as i remember them.
The exclusive high end look cost more than we want to know sometimes.
A NAD should be drab grey and cheesy that's the point no money wasted on bling bling

happy to se some more development in in class D especially as we have to reduce the carbon footprint .

if you analyze music you quickly see that the avarage power is a couple of watts but your typical heavy duty class A/B amp is dumping >100-200 watts or similar as heat all the time .

This means that all amps will work this way eventually so it's time to take sound-quality seriously , hopefully others follow and compete .

what they do fudge a bit is the damping factor at higher frequency's this is the weakness of an amp with an output filter .

otherwise the specs are in a context with most of the conditions so they are not just marketting numbers. except damping that is spec below 200Hz
To low damping can slightly modify frequency response and miss-align passive crossovers a bit performance may be slightly more speaker dependent than a traditional amp .

http://www.rane.com/note145.html

[Phil Leigh]

Guys, here is where I was going wrong! I was thinking about that 16 bit waveform and then I was thinking in 16/44 DAC terms (I was sleep deprived!) which should smooth it analoguely.

Obviously these DACs are not 16/44. But, even after getting some sleep, this morning I would expect an upsampling 24 bit DAC to smooth 16/44 digitally.

Now I realise when Stereophile tested the 16 bit undithered waveform, probably they used a file at the highest sampling rate and bit depth...just mimicking a 16 bit waveform within it. So the DAC doesn't treat it to any upsampling goodness...the customer wants a crude staircase drawn in hi-rez, the customer gets just that.
Darren

Sent from my HTC Sensation Z710e using Tapatalk

erm... the sampling RATE won't make any difference to this...

I wouldn't want to speculate too much on how Stereophile created their test data, but as you can't easily record a perfect -90dB sine wave from any analogue source... (too much noise!) my guess is they generated it as a 16-bit wav test tone mathematically on a PC, which is easy enough to do.

Presumably they use 16 bits for this test to represent redbook CD replay into the DAC. Had they generated a 24-bit -90dB sine wave file, the result would have looked VERY different :-)

When a 16-bit file is presented to a 24-bit DAC - as we know from our Squeezeboxes - the "lowest" 8-bits are zero-filled (i.e. ignored). Therefore, the resulting test result waveform would look the same if the Benchmark was a 16 or 24 bit DAC... there's still only 1 bit "wiggling around in value".

Actually, I can't see the point of performing this -90dB test on a real 24-bit DAC... not sure what they are trying to test. Surely they should be doing a -144dB test?


In modern real-world terms this is meaningless because real-world 16-bit PCM streams are downsampled from 24-bit masters with dithering of some form or other which obfuscates the "problem" in the lowest bit by pseudo-randomizing its value. Bear in mind that no actual music files will EVER have consecutive sample values that look like part of a -90dB sine wave !!!!!!!.


Just to be crystal clear on this, when Stereophile talk about the 3 voltage levels... they ARE talking about the AC voltages: zero-crossing, peak and trough for a single bit representing the sine wave. They are NOT talking about anything to do with "jagged" DC ladder steps or anything like that - because with one bit going on or off there would only be 2 DC values anyway (on or off) and those values do NOT EXIST outside of the DAC chip/IV stage/Filter... so they can't be measured by putting any kind of test equipment across the analogue output of a DAC.
regards
Phil

[darrenyeats]

Phil,
See these posts:
Submitted by Miska on Sun, 02/12/2012 - 17:43.
Submitted by Miska on Mon, 02/13/2012 - 02:48.
Here: http://www.computeraudiophile.com/co...2496-not-24192 (search for 'miska')

Which shows graphically what I mean. Upsampling of 16/44 should make a big difference to the smoothness of the waveform - if the data points are interpolated intelligently and in 24 bit.

I expect to see smoothed waveforms out of DAC. From a native 16/44 DAC (my befuddlement yesterday) I expect to see analogue smoothing. From a 24 bit, high sample rate DAC I expect to see smoothing due to the upsampling (and analogue smoothing at that finer level but this would not be resolvable probably). You keep waving this away but I think it's a reasonable expectation.

erm... the sampling RATE won't make any difference to this...

I think it will (see above)

Presumably they use 16 bits for this test to represent redbook CD replay into the DAC....

Kind of, except I don't think it's exactly equivalent (see further below).

....Had they generated a 24-bit -90dB sine wave file, the result would have looked VERY different :-)

I agree with you and they did do that. That is figure 6.

Just to be crystal clear on this, when Stereophile talk about the 3 voltage levels... they ARE talking about the AC voltages: zero-crossing, peak and trough for a single bit representing the sine wave. They are NOT talking about anything to do with "jagged" DC ladder steps or anything like that - because with one bit going on or off there would only be 2 DC values anyway (on or off) and those values do NOT EXIST outside of the DAC chip/IV stage/Filter... so they can't be measured by putting any kind of test equipment across the analogue output of a DAC.
regards
Phil

No. They measured at the analogue output. Hence my initial puzzlement about no smoothing.

I wouldn't want to speculate too much on how Stereophile created their test data, but as you can't easily record a perfect -90dB sine wave from any analogue source... (too much noise!) my guess is they generated it as a 16-bit wav test tone mathematically on a PC, which is easy enough to do.

I proposed what they did in my last post. Please have a read again carefully:

Now I realise when Stereophile tested the 16 bit undithered waveform, probably they used a file at the highest sampling rate and bit depth...just mimicking a 16 bit waveform within it. So the DAC doesn't treat it to any upsampling goodness...the customer wants a crude staircase drawn in hi-rez, the customer gets just that.

IOW I think they created this 16 bit -90db 1kHz sine wave mathematically and placed it in a 24/96 file. It is already at the DAC's native bit depth and sample rate so no interpolation is attempted. The DAC tries to play (as near as possible) a staircase shaped wave which, as we know, is impossible to do exactly.

Had they played an actual 16/44 file of the same amplitude, I expect it would have been upsampled to 24/96 and smoothed. Which is my point.
Darren

[Phil Leigh]

Darren,
My head hurts... I think we are in a semantic loop :-)
What EXACTLY do you think that Stereophile fig 5 trace shows you?

[darrenyeats]

Darren,
My head hurts... I think we are in a semantic loop :-)

Yeah, you're probably right.

You stated there should be no jagged waveforms in digital audio. And actually that sounded sensible. So I expected to see a smoothed output from these Stereophile plots...but I didn't! This was my initial query.

What didn't help was that I was stuck in a native 16/44 DAC paradigm yesterday (brain burp) so I was questioning (wrongly) whether analogue smoothing really happens. But I think we've got there in terms of explaining the Stereophile results.

What EXACTLY do you think that Stereophile fig 5 trace shows you?

A test of real 16/44 audio would have input a 16/44 file and the output would look quite different to what they measured I think - more smooth.

What they did is not representative of 16/44 audio but a test to see how cleanly the DAC can deal with staircase type waveforms (with a simulated resolution of 16 bits) in 24/96.

You are quite right to say that no real music is encoded like that! And I've actually agreed with most of your comments, which makes me think we've been coming at it from different angles.
Darren

[Phil Leigh]

Yeah, you're probably right.

You stated there should be no jagged waveforms in digital audio. And actually that sounded sensible. So I expected to see a smoothed output from these Stereophile plots...but I didn't! This was my initial query.

What didn't help was that I was stuck in a native 16/44 DAC paradigm yesterday (brain burp) so I was questioning (wrongly) whether analogue smoothing really happens. But I think we've got there in terms of explaining the Stereophile results.

A test of real 16/44 audio would have input a 16/44 file and the output would look quite different to what they measured I think - more smooth.

What they did is not representative of 16/44 audio but a test to see how cleanly the DAC can deal with staircase type waveforms (with a simulated resolution of 16 bits) in 24/96.

You are quite right to say that no real music is encoded like that! And I've actually agreed with most of your comments, which makes me think we've been coming at it from different angles.
Darren

OK - I think we are nearly at the agreeing tree... :-)

[Archimago]

Just to be crystal clear on this, when Stereophile talk about the 3 voltage levels... they ARE talking about the AC voltages: zero-crossing, peak and trough for a single bit representing the sine wave. They are NOT talking about anything to do with "jagged" DC ladder steps or anything like that - because with one bit going on or off there would only be 2 DC values anyway (on or off) and those values do NOT EXIST outside of the DAC chip/IV stage/Filter... so they can't be measured by putting any kind of test equipment across the analogue output of a DAC.
regards
Phil

Hmmm, Phil, I'm curious what you said here. If you feed a 16-bit computer generated -90dB undithered 'sine' wave, you're essentially feeding into the DAC a 1kHz (in this case) 1-bit *square* wave. This is exactly what the measurements show.

Since 24-bit DAC's have more dynamic range, they should reproduce the signal very cleanly and this is exactly what we see in good DAC's - clean square waves. Can this not be measured on the analogue output?

If there continues to be alot of controversy over this, perhaps we should post a question for John Atkinson.

[Mnyb]

Stereophile did test the M2

http://www.stereophile.com/content/n...r-measurements

You miss something by not reading the hifi rags afterall

It measures almost like a t DAC

Wonder how the 390DD would score ?