Redbook CD sounds the same as SACD/DVD-A

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*Scotty*

Re: Redbook CD sounds the same as SACD/DVD-A
« Reply #40 on: 7 Nov 2007, 01:21 am »
Daryl,If the lowest distortion in a digital system exists at 0dB what happens to the distortion when you look at the wave form at -60? When pictures of the waveform at -90 are shown the differences between a 16bit and a 24 bit are very obvious. Neither waveform looks good but the 16bit is noticeably worse than 24bit. Can you please explain what reduced recording levels do to the THD and at what point 3% THD occurs?
Scotty

opaqueice

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Re: Redbook CD sounds the same as SACD/DVD-A
« Reply #41 on: 7 Nov 2007, 02:53 am »
Daryl,If the lowest distortion in a digital system exists at 0dB what happens to the distortion when you look at the wave form at -60? When pictures of the waveform at -90 are shown the differences between a 16bit and a 24 bit are very obvious. Neither waveform looks good but the 16bit is noticeably worse than 24bit. Can you please explain what reduced recording levels do to the THD and at what point 3% THD occurs?
Scotty

I'm not Daryl, but I don't understand your point.  Of course if you don't use the full dynamic range available you get more distortion - so what?  That's true of any recording method or medium.

One of the results of Meyer and Moran was that on certain hi-res recordings with extremely low noise floor you could hear the difference between hi-res and redbook - by cranking the volume up in a quiet part.  That's no surprise - redbook will at best have a -96dB noise floor, whereas SACD might have one below that, and so obviously if you turn up the level enough you'll hear the difference.  However the level will be literally ear-splitting on the loud parts.

*Scotty*

Re: Redbook CD sounds the same as SACD/DVD-A
« Reply #42 on: 7 Nov 2007, 03:28 am »
I am not taking about the noise floor, I am taking about rising waveform distortion as the recording level decreases. See link for a comparison between waveforms 16bit at -90 and 24bit at -90
http://stereophile.com/hirezplayers/105dcs/index5.html
It certainly looks like that once you get below a certain level in a digital recording system you will have unacceptable levels of THD. It looks like dither can only substitute for just so much missing data,especially in a 16bit system.
In an analogue recording system as the signal level decreases only the noise increases, the distortion level decreases as well.
Scotty
« Last Edit: 7 Nov 2007, 03:46 am by *Scotty* »

dmckean

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Re: Redbook CD sounds the same as SACD/DVD-A
« Reply #43 on: 7 Nov 2007, 04:04 am »
Its annoying having to use a HDMI to DVI + SPDIF breakout box to capture the SACD layer digitally to add to my music server.

Could you go into a little more detail on how you do that?

You get an Atlona HDMI to DVI + SPDIF converter box. You connect the DVI portion to your TV and the SPDIF into your computer and hit record. You need either a Universal DVD player that converts the signal to 24/88.2 LPCM or the PS3 which will convert it to 24/176.4 LPCM.

opaqueice

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Re: Redbook CD sounds the same as SACD/DVD-A
« Reply #44 on: 7 Nov 2007, 05:38 am »
I am not taking about the noise floor, I am taking about rising waveform distortion as the recording level decreases.

Certainly that does happen.  That "waveform distortion" could be due to quantization errors, but it can also be due to noise or some other source.  In the end all that matters is how different the resulting waveform is from the ideal.

Quote
In an analogue recording system as the signal level decreases only the noise increases, the distortion level decreases as well.

No, I don't think so.  As the S/N decreases, THD will rise.  Think about it - when the signal is around the same size as the noise, the THD will be much larger than one, because the power in each harmonic from noise will be as large as the power in the fundamental.

So I think what you're saying is true for any kind of recording - analogue, digital, whatever.  What it means is that you need enough dynamic range so that the quiet parts (where the distortion is high) are so quiet you can't hear the distortion.  So the question is whether 96dB is enough for that - and according to Meyer and Moran's results, it is.

*Scotty*

Re: Redbook CD sounds the same as SACD/DVD-A
« Reply #45 on: 7 Nov 2007, 04:23 pm »
opaqueice. you are quite correct about running out of signal to noise ratio at some point in an analogue recording system. When that happens
you have lost your signal into the noise floor and you are done until you apply Dolby A processing. I have an awful feeling that in a digital system
waveform distortion sets in when there are not enough bits to describe the waveform accurately and dither ceases to bridge the gaps adequately.
At some point long before the noise floor of the recording system is reached you have gross distortion of an unacceptable level. Pulling a number out of my hat I would say 3% THD is the limit although this figure should probably be lower. Three percent THD on peaks exceeding Zero dB was considered acceptable in analogue recording systems. This figure allowed some headroom for dynamic range purposes.