Does vinyl suffer from low signal-to-noise ratio ?

As I know, vinyl records typically offer around 50 dB of the SNR, compared to 90 dB on CD records. The SNR number reminds me that noisy interferences are always present in the records, no matter how hard we try to avoid them. How does this SNR number realize on the playback system ?

In the digital world, digital signal processing can algorithmically lower the noise level or recover the singal from the contamination. The following illustration shows dithering can recover the original signal (a square wave) from the very noisy input.



I wonder whether do we need to do similar signal recovery on vinyl records (recording/playback systems) ? How can we remove such noise from vinyl records, through analog circuitry ?

Is this the major drawback of vinyl ? Is this why many people prefer CDs to vinyl titles ?

 

I dont think there would be a way using only analog circuitry. No analog filtering method would be precise enough due to component limitations. You need some type of counter...some way of assigning objective values to a wave in order to perform the filtering. Even with the less desireable SNR of vinyl, you're not going to get anywhere near the amount of distortion as what happened to that square wave you pictured. Its what you just have to live with in vinyl I'm afraid. You've got a nail dragging along some plastic...theres going to be unwanted surface noise. However, at -50dB.....its easy to get past once you discover the things vinyl does well. For the normal music-listening public, it is a major drawback however.

 

Vinyl typically offers 60-70db SNR, I've never seen an LP with 50db- even a good condition 78 has better signal to noise than that.

Its also important to note that the signal to noise on a record varies depending on the frequency. At 10kz, the SNR is convincingly above 75db.

I wouldn't look at SNR when comparing vinyl to a CD. As you say, CD's have a ratio of 96db, compared to 60-70 for vinyl. If this reflected real world performance, then vinyl would sound compressed and very dull compared to CD. In the real world however, vinyl can contain dynamic contrasts just as strong as CD. If the measurements were right, you would have to compress the LP source in order for it to fit into the limited SNR. Given that LP's sound just as dynamic, and sometimes more dynamic than CD, the measurements would appear to be nonsense.

 

SNR in digital systems is also a measure of quantization noise. This means how much error was there when the digitizer had to make a choice between two adjacent fixed amplitude values versus the real value of the amplitude. This error (noise) can become very dominating when you are talking about low level signals that only use the least significant bits (LSB's) of the digitizer. Dither is especially useful for helping with this type of error although it is not a free lunch, dither actually raises the noise floor in digital recordings. Sigma-delta digitizers (like DSD) greatly reduce this effect but of course they must have high levels of noise shaping.

There is no such problem in an analog system. The noise in an analog system is just random noise caused by all kinds of things. So all you can do is try to keep the noise sources as low as possible turning recording, cutting and playback.

 

You mean you would have to compress it to fit into the limited dynamic range.

In the analog world, SNR and dynamic range vary with frequency. There is no mathematical absolute like there is with digital.

 

Perhaps you meant low-pass filtering? I don't think that a dithering operation, by itself, on the first waveform, can produce the second.

 

You can indeed calculate the maximum dynamic range and signal to noise ratio of a digital system.

 

bordin wrote, "...Is this why many people prefer CDs to vinyl titles ?"


However did you come to that conclusion? Usage never predicts preference in a mass consumer society. It is simply a measure of advertising spent to promote cheaper, easier to manufacture, deliver and store goods. It has nothing to do with the actual quality of the sound reproduction. Amen.

 

As a typical music listener, when I listen to a CD or vinyl, I only think the sounds I hear are the original ones. Once the SNR gets into my mind, the music I hear is the reproduction of the recorded signal and contaminated noise.

From the SNR perspective, would it be resonable enough to say the reproduction from a CD (with a proper mastering and a decent player) is closer to the original music than from vinyl ?

So, the so-called analogue of vinyl is always contaminated, not the truely natural music ?

However, this is nothing to do with whether people prefer vinyl to a CD or vice versa. Any comments ?

 

I came across Bill Otto's article: Frequently Asked Questions About Audio Compact Disks. He answers some questions about CD v.s. vinyl

Bill's explaination makes me think what the analoque sounds of vinyl really is ? Does a CD sound more "real" ?

 

Tony pretty much nailed it, but I can share one thing based on my work in the studio with analog. In the past when we recorded on a good analog tape machine it can capture the sound in the studio as naturally as 24/96khz sampling rates. We do all digital recording now due to ease of editing on the PC and ease of carrying equipment but you would be surprised how much data can be resolved in the analog format.

 

bordin, The quetions you raise have been discussed many times here on the forum and I suggest you search the forums and archives. IMHO, I also uggest that if you can you first educate yourself on what the digital process really is. Although I am not a huge fan of his I can suggest Nika Aldrich's book "Digital Audio Explained".

The terms you use like "natural" and "so-called analogue" are very hard to define and therefore make it hard to discuss specifics.

In general I would say that analog is natural but comes with certain limitations. Digital techniques overcome many of those limitations but do so by introducing a lot of digital artifacts. Some more recent digital techniques certainly improve on the original CD, again IMHO. So each individual has to decide what he likes best and what he can or cannot tolerate.

 

I think that Bill Otto mentions some things worth having in mind when considering vinyl reproduction as the superior medium.

Yet, the comparison mainly with CD, while illustrative does leave out more differences audible at higher digital resolutions.

I agrew with Lee that an analog tape machine can capture sound quite in line with 96/24 sampling rates. Whether that really translates to vinyl is another story.

The way I see it, vinyl often has a nice sound, but in my mind - recording source, mastering, and the like, being top-knotch - it is not the ultimate medium for music reproduction due to limitation inherent to the format. In this case HiRez: 96/24 and above is it at this moment in history. Provided, of course, that the transfer is also done correctly.

 

Very interesting article. Thanks for posting it, Steve. I had not seen it before.

 

Well, if you're only going to focus on the noise aspect, yes. Although CDs have the edge, I say that the reason many of us here prefer the LP is because the sound isn't usually screwed around with during the mastering process. I'm not one of them, but many who like vinyl are able to tolerate the noise inherent in the medium. Some systems do a great job of keeping the vinyl noise low, but it's still there. But, don't be fooled, CD colors the sound just as much as vinyl, but in different ways. It's just less obvious with the CD.

That's about where I top out. But wouldn't the average, run of the mill, consumer pressing be lower, maybe around 65db?

 

In so far as good quality mastering plays a role yes, but much of what's on that tape can be transfered to vinyl and fortunately minus the A-D-A conversion two step.

I was waiting on someone to post that.

 

My applogy, I did but found nothing answered my curiosity. Thanks for the tip.

Thanks, Steve.

 

Well, if all you want is less noise, I guess digital is the way to go. Better yet, you could just play nothing and have an infinite SNR. Audio is all about compromises. Some are willing to give up 20dB in SNR, and the inconvenieces of vinyl, for perceived higher resolution and just the overall sound of vinyl.

 

Look at it this way. I can clearly hear tape hiss on a well made recording when listening to a lp. Assuming that tape hiss can be 70db or more down on a professional master recording, obviously an lp can exceed that. Of course good vinyl is required to get the lowest possible noise floor from a record.

 

As far as I'm concerned, when all is said regardless of the numbers, most LP's sound like they have a bigger S/N ratio than a lot of their CD counterparts. Probably because of the differences in the actual dynamic range in certain frequencies, I would imagine, when it comes to the analog medium of the LP.

 

Noone denies that. CD has incredible capability for dynamics...but these days it is seldom utilized. My LP's have far more dynamics than most new pop CD's, despite having a worse S/N ratio. I guess what I'm trying to say is that, with all else being equal, you are right. But the mastering of vinyl vs CD is rarely equal.

 

I recall recently reading an AES paper from the 60s comparing the dynamic range of vinyl and tape (15ips as I recall), and vinyl pretty much whipped tape, even back then. I've heard tape hiss on vinyl too. That's the whole point of d2d recording, right?

I made a post on this topic on HA a while ago:

http://www.hydrogenaudio.org/forums/index.php?showtopic=47827&mode=threaded&pid=426789

Short summary: On a spot frequency basis, 16-bit CD audio has a guaranteed dynamic range of 151db. Under the same basis, vinyl has an absolute theoretically maximum dynamic range of 123db. So, by my reckoning, CD has at least about 30db more dynamic range than LP, and likely much more.