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In Reply to: Hey, John.. posted by Commuteman on September 27, 2005 at 16:06:46:
Distortion on vinyl decreases with volume, but I have never measured anything less than 0.1%, and that is rare. Distortion on digital increases when volume decreases, but I have never measured more than 0.15% for 60dB signals.Really, the bottom line is sound quality. I can copy an LP onto CD-R and it sounds just like the LP. What more can you ask for?
Best regards,
John Elison
Follow Ups:
Distortion on vinyl decreases with volume, but I have never measured anything less than 0.1%, and that is rare.How low have you been able to measure? Since you can't just create your own LP test signals, it does sorta depend on getting hold of a test record with low-level continuous tones.....
Oh, one more thing to think about:
From your numbers, it looks like the THD may be comparable for these systems at low levels (0.1% vs. 0.15%), but it would be interesting to see the spectra. My guess is that vinyl playback distortion will be dominated by relatively benign low-order harmonics.
I can't find an online reference that will show me what quantization distortion looks like in the freq. domain. Have you ever seen this?
Peter
"I can't find an online reference that will show me what quantization distortion looks like in the freq. domain. Have you ever seen this?"Doesn't really matter as it entirely depends on the original input signal. For something simple like a sine the q-distortion is likely to look like a bunch of discrete spectral lines, or at least a number of cohesive clumps. For a more complex signal the q-distortion will likely become more noise-like, although possibly heavily modulated by the signal.
All moot, as proper dithering turns quantisation distortion into benign noise.
Hi Peter,Actually I made a mistake on the distortion figure for 60-dB digital. It actually has 3rd harmonic distortion of nearly 0.4%. However, all distortion components fall below the noise floor of my system, which I estimate to be about 105-dB below full scale. The harmonic distortion components of a 60-dB, 1000-Hz sine wave fall at the following levels relative to 0-dB full scale.
2nd harmonic 118-dB
3rd harmonic 108-dB
4th harmonic 119-dB
5th harmonic 114-dB
6th harmonic 119-dB
7th harmonic 112-dB
8th harmonic 119-dB
9th harmonic 116-dB
10th harmonic 119-dBHere is the Spectrum plot.
I will try to get some more plots done of vinyl signals. I believe the lowest level sine wave I can find on a test record is only about 20-dB relative 5-cm/s. Of course this would be about 40-dB below the highest recorded signals on records. Second harmonic distortion on this signal is 59-dB or 0.112%. Third and higher harmonics disappear into the vinyl noise floor. I hope to have a picture pretty soon.Best regards,
John Elison
John,do you know if that -60dB track on the test CD was dithered
or not? If it wasn't then please repeat with a dithered track.If you don't have one then tell me and I'll make one for e-mail.
Hi Werner,I don't think this test signal is dithered. It came from Denon Audio Technical CD 38C39-7147, which I bought in 1984. Some of the test signals have something called emphasis, but this 60-dB signal has emphasis turned off.
If youve got dithered test signals, Id very much like to make a comparison. You can send email to me at w.elison@insightbb.com. Its a broadband connection so you can attach files.
Thanks,
John Elison
Sorry to sound so excited.... :-)Thanks for doing this. I think it's really relevant. If you can get the vinyl -20dB plots you should be able to tell what the trend is compared to your 5cm/s measurement.
You know, in any other context a system that generates 0.2% 5th harmonic distortion would probably sound pretty bad. I don't have any way to give you a reference at this point, but I'm pretty sure that's above the threshold of audibility.
Of course, I have no idea where -60dB (relative to digital full scale) falls in terms of typical musical loudness, and therefore I can't really predict the musical relevance. As a thought experiment:
Let's say I'm listening to music that peaks around 100dB in my room, as measured by something like the RS meter in fast mode. Let's assume (and hope) that these peaks are not within 10dB of maximum (allowing for headroom in the digital system plus the inevitable meter error). that puts 0dB on disc at 110dB in the room. That means -60dB is at 50dB in room, right? It's 40dB if there is zero headroom.
Isn't that still well within the range of a lot of musical information? Think solo instrument in a symphony orchestra. Think about the quality of reverb decay in a large room...
Very interesting!
Peter
> > > If you can get the vinyl -20dB plots you should be able to
> > > tell what the trend is compared to your 5cm/s measurement.The trend in vinyl is that distortion increases as amplitude increases. The reverse is true for digital.
> > > You know, in any other context a system that generates 0.2%
> > > 5th harmonic distortion would probably sound pretty bad.While this may be true, we are talking about distortion from a 60-dB signal. In vinyl, the noise floor is 111-dB at 5-kHz on my system referenced to the +18-dB signal on the Hi-Fi News test record. Consequently, the noise floor amplitude is 0.282% of the amplitude of a 60-dB signal on vinyl. In my book, 0.282% is worse than 0.200%.
> > > Of course, I have no idea where -60dB (relative to digital full scale) falls in terms of
> > > typical musical loudness, and therefore I can't really predict the musical relevance.Well, typical music resides in the neighborhood of 20-dB from musical peaks. Therefore, -60-dB is at or near the bottom of recorded musics dynamic range. In other words, you will not be listening to much at 60-dB on vinyl or digital except possibly for very quiet passages in classical music. Those are the passages where the surface noise of vinyl is clearly evident. Digital distortion at 114-dB (0.200%) is probably almost if not totally inaudible, I would think. However, with digital, when the music gets louder the distortion decreases. With vinyl, it increases.
Here is the vinyl spectrum with a 35-dB, 1000-Hz signal in the left channel. You can see the crosstalk in the right channel produces a 60-dB signal. There are no distortion components visible for the right channel, but the noise floor at 5000-Hz is 3-dB higher than the fifth harmonic distortion component of a 60-dB signal for Redbook digital.
Best regards,
John Elison
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