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Frequency Response of Vinyl, Split from "To get into vinyl, or not?" (TOS #5)
BFG
post Dec 4 2012, 00:16
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This whole conversation has me intrigued about the technical limitations of vinyl. For example, is there a minimum or maximum frequency that can be "encoded" in vinyl (akin to the ~20Hz and 44.1kHz cutoffs on digital CDs)? Does this differ for 33s, 45s, 78s? Is there a way (based on the needle tip and equipment setup) for a knowledgeable person to precalculate the bands that the most noise interference will likely be in, and thus minimize or remove it? Etc.

It's particularly pertinent as I'm planning to attempt a vinyl-to-FLAC encoding soon.

This post has been edited by BFG: Dec 4 2012, 00:17
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mjb2006
post Dec 4 2012, 01:37
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You might want to review the vinyl myths page in the wiki, especially where it talks about frequency limits.

You will find that different records have a different-sounding "whoosh" of noise imparted by the rush of the groove vinyl along the stylus, so I can't imagine any way to predict that noise exactly. Speed is one of many factors in that.

This post has been edited by mjb2006: Dec 4 2012, 01:42
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BFG
post Dec 4 2012, 01:44
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QUOTE (mjb2006 @ Dec 3 2012, 18:37) *
You might want to review the vinyl myths page in the wiki, especially where it talks about frequency limits.

You will find that different records have a different-sounding "whoosh" of noise imparted by the rush of the groove vinyl along the stylus, so I can't imagine any way to predict that noise exactly. Speed is one of many factors in that.

Ah! That makes for an interesting read, and does indeed answer many of my questions. Thanks for pointing it out.
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Axon
post Dec 4 2012, 09:01
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High frequency vinyl noise is strongly broadband, so there's little use shifting that around, per se.

The arm+cartridge resonance defines the low frequency limit. If you're lucky, it will be 8-12hz; if unlucky, 5-20hz.

The HF limit is dependent on many factors, but at the very least, CD4 records go all the way to 45khz. Typically, you'll know if you have a CD4 record. Otherwise, the useful frequency range limit might be as low as 15khz, or as high as 20-30khz.

Hypothetically, on arm+cart combinations which are too low (<8hz), it might make sense to e.g. play a 33rpm record at a much faster speed, so as to shift the signal spectrum away from the resonance, because spot frequency SNR is ludicrously low around resonance. But AFAIK, that's probably more trouble than it's worth.
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cliveb
post Dec 4 2012, 10:33
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QUOTE (Axon @ Dec 4 2012, 08:01) *
The arm+cartridge resonance defines the low frequency limit. If you're lucky, it will be 8-12hz; if unlucky, 5-20hz.

Very few records are cut with any signal lower then about 20-30Hz. Also, all LPs will have their bass summed to mono below about 100Hz to prevent extreme vertical groove modulation.

The thing about the resonant frequency is that you want it to be below the lowest signal frequency on an LP (ie. less than 20Hz) to prevent exciting the resonance. But you also want to keep it above the frequency of the micro-warps that exist on even the seemingly flattest LP (ie. above about 10Hz). This means that the arm/cartridge will ride up & down over warps - if the resonant frequency is too low then the warps will be read as very low frequency signal.

QUOTE (Axon @ Dec 4 2012, 08:01) *
The HF limit is dependent on many factors, but at the very least, CD4 records go all the way to 45khz. Typically, you'll know if you have a CD4 record. Otherwise, the useful frequency range limit might be as low as 15khz, or as high as 20-30khz.

The ultra high frequencies on a CD4 record can only be read by specialised stylus profiles (eg. Shibata). Play them with anything else (eg. a standard elliptical or (heaven forbid) a conical), and the carrier frequency is destroyed. But CD4 is a historical footnote - nobody actually uses it these days (do they?).

Mainstream LPs are often cut with a low pass filter around the 18kHz mark to prevent overheating of the cutting head. Any kind of signal that comes off an LP above 20kHz is pretty much entirely noise and distortion.

QUOTE (Axon @ Dec 4 2012, 08:01) *
Hypothetically, on arm+cart combinations which are too low (<8hz), it might make sense to e.g. play a 33rpm record at a much faster speed, so as to shift the signal spectrum away from the resonance, because spot frequency SNR is ludicrously low around resonance. But AFAIK, that's probably more trouble than it's worth.

I don't see how this would work. Play a 33rpm record at 45rpm and you'll shift the warps higher up the frequency range, and therefore still above the resonant frequency. So they will still be incorrectly read as signal. If anything, the way to avoid this would be to reduce the speed to 16rpm - but then the bass signal is in danger of dropping low enough to excite the resonance.

If your arm/cartridge combination has a resonant frequency in the wrong place, you have these choices:
1. If it's too high, you can add mass to the arm - stick a penny on the headshell. This will drop the resonant frequency. (Don't forget to reset the tracking force correctly. This is NOT the same as the old trick we did on Dansettes to stop them skipping!)
2. If it's too high, replace the cartridge with a lower compliance model.
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mzil
post Dec 4 2012, 19:10
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Unlike CD, vinyl has no inherent high frequency limit, in theory.

In regards to frequency response, FR, don't worry about the overall bandwidth limits, worry about the number of dB that the overall playback system (LP record condition, phono cartridge, phono preamp) deviate from being perfectly flat in the audible region. That's what matters in terms of audibility.

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krabapple
post Dec 4 2012, 20:20
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QUOTE (cliveb @ Dec 4 2012, 04:33) *
The ultra high frequencies on a CD4 record can only be read by specialised stylus profiles (eg. Shibata). Play them with anything else (eg. a standard elliptical or (heaven forbid) a conical), and the carrier frequency is destroyed. But CD4 is a historical footnote - nobody actually uses it these days (do they?).

Mainstream LPs are often cut with a low pass filter around the 18kHz mark to prevent overheating of the cutting head. Any kind of signal that comes off an LP above 20kHz is pretty much entirely noise and distortion.


Just out of curiosity, didn't the Beatles record an ultrasonic signal at the end of Sgt Peppers's -- supposed to make your dog's ears perk up? And if so, has anyone ever checked a needledrop to see how 'high fidelity' that tone was on playback?
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mzil
post Dec 4 2012, 20:31
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QUOTE (krabapple @ Dec 4 2012, 15:20) *
QUOTE (cliveb @ Dec 4 2012, 04:33) *
The ultra high frequencies on a CD4 record can only be read by specialised stylus profiles (eg. Shibata). Play them with anything else (eg. a standard elliptical or (heaven forbid) a conical), and the carrier frequency is destroyed. But CD4 is a historical footnote - nobody actually uses it these days (do they?).

Mainstream LPs are often cut with a low pass filter around the 18kHz mark to prevent overheating of the cutting head. Any kind of signal that comes off an LP above 20kHz is pretty much entirely noise and distortion.


Just out of curiosity, didn't the Beatles record an ultrasonic signal at the end of Sgt Peppers's -- supposed to make your dog's ears perk up? And if so, has anyone ever checked a needledrop to see how 'high fidelity' that tone was on playback?


The frequency which appears on the British lead out groove of Sgt. Pepper, just before "Lucy abbey all the way" [at least that's what I hear] is very high frequency but not ultrasonic. It is perhaps 15 kHz, I'm guessing.
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mzil
post Dec 4 2012, 20:43
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I was close. Geourge Martin says it was 18 kHz.
http://www.youtube.com/watch?v=0WkUgNKOtSE

EDIT: Wikipedia says "15 kilohertz"
http://en.wikipedia.org/wiki/Sgt._Pepper&#...earts_Club_Band

This post has been edited by mzil: Dec 4 2012, 20:48
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krabapple
post Dec 4 2012, 22:35
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should be able to verify off the CD then, yes?
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bandpass
post Dec 4 2012, 23:00
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Here's a 'Blue box' needle-drop:


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Ed Seedhouse
post Dec 4 2012, 23:11
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QUOTE (mzil @ Dec 4 2012, 10:10) *
Unlike CD, vinyl has no inherent high frequency limit, in theory.


This is wrong, i believe. Vinyl has inherent theoretical high and low end frequency limits due to the material medium. It also has inherent limits in other areas such as, among other things, distortion and noise.

What it lacks is a theoretical upper frequency limit due to the encoding. Digital overcomes the inherent physical limits of the medium and replaces these with an inherent high frequency limit due to the encoding.

In practice this allows digital to exceed the inherent limits of vinyl in every respect. In frequency response terms even CD vastly exceeds vinyl in the low end, and clearly exceeds it in the high end in practice. Though a vinyl record system can put out higher frequencies than a CD, this is always in practice about 100% noise. Below it's upper limit CD digital is flatter and cleaner in every way than vinyl recordings.

More importantly, CD is good enough to exceed the limits of human hearing, if only slightly. Once you have exceeded the limits of our ears then further improvement is theoretically pointless so far as playback is concerned.

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mixminus1
post Dec 4 2012, 23:16
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QUOTE (krabapple @ Dec 4 2012, 14:35) *
should be able to verify off the CD then, yes?

15.080 kHz, according to my rip of Sgt. Pepper's that I bought about 10 years ago, i.e. not from the newer remasters.

Looks like that jives with the spectrograph of the needle drop that bandpass posted.


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mzil
post Dec 4 2012, 23:41
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QUOTE (krabapple @ Dec 4 2012, 17:35) *
should be able to verify off the CD then, yes?


There are two different things here. The spiral lead out groove on some pressings of the vinyl. including the original British one (but not US) has the ~ 15 kHz tone. When it then clicks into the central, inner, locked groove circle you get the "Lucy abbey all the way" part and (as we see from bandpass' spectral analysis) the annoying tone ceases.

The "Lucy abbey all the way" part has been released on some CDs, such as Rarities, however the annoying tone part that precedes it has never been released on any CD that I know of.
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mzil
post Dec 5 2012, 00:11
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QUOTE (Ed Seedhouse @ Dec 4 2012, 18:11) *
QUOTE (mzil @ Dec 4 2012, 10:10) *
Unlike CD, vinyl has no inherent high frequency limit, in theory.


This is wrong, i believe....

What it lacks is a theoretical upper frequency limit due to the encoding.

I have no idea where you got that I was talking about anything other than the encoding of vinyl, compared to that of the CD format, which I named, so I wasn't wrong.

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Canar
post Dec 5 2012, 00:38
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QUOTE (mzil @ Dec 4 2012, 15:11) *
QUOTE (mzil @ Dec 4 2012, 10:10) *
Unlike CD, vinyl has no inherent high frequency limit, in theory.
I wasn't wrong.
This is wrong and you should feel wrong.

The big question is precisely how you define that "high frequency limit", as vinyl keeps getting worse the higher you go, unlike digital's perfect bandlimited reproduction.

This post has been edited by Canar: Dec 5 2012, 00:39


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Ed Seedhouse
post Dec 5 2012, 00:45
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QUOTE (mzil @ Dec 4 2012, 15:11) *
QUOTE (Ed Seedhouse @ Dec 4 2012, 18:11) *
QUOTE (mzil) *
due to the encoding[/i].

I have no idea where you got that I was talking about anything other than the encoding of vinyl, compared to that of the CD format, which I named, so I wasn't wrong.


Well I have re-read the message I was replying to and I didn't see any mention of encoding in it.




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mzil
post Dec 5 2012, 01:06
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QUOTE (BFG @ Dec 3 2012, 19:16) *
is there a minimum or maximum frequency that can be "encoded" in vinyl (akin to the ~20Hz and 44.1kHz cutoffs on digital CDs)?

I was responding to this, the OP's opening question. He used the word "encoding" and made it clear he was talking about the mediums of CD and vinyl, not their playback.

Also, I made it a point to emphasize I was speaking theoretically, by italicizing the words "in theory" in my sentence:
QUOTE (mzil @ Dec 4 2012, 14:10) *
Unlike CD, vinyl has no inherent high frequency limit, in theory.


---

The CD format has a hard limit in that only frequencies below 22.05 kHz can be encoded. This is not the case with vinyl. There is no hard limit, upper frequency limit like that with vinyl, in theory.
. I stand by this.

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Canar
post Dec 5 2012, 01:10
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In theory, it's still wrong. There is a theoretical upper bound to vinyl's frequency reproduction. Like I said, precisely how you define that limit will change where you place that theoretical upper bound.

It's not as clearly defined as CD, but that does not imply that there is no theoretical upper bound!

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splice
post Dec 5 2012, 01:17
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QUOTE (Axon @ Dec 4 2012, 00:01) *
... The HF limit is dependent on many factors, but at the very least, CD4 records go all the way to 45khz. ...


The 4 channels of a CD-4 disc were limited to 15 KHz. Each rear channel difference signal was modulated onto a 30 KHz carrier. The cartridges had significant distortion and frequency response variations above 20 KHz or so, but because the modulation method was FM based the demodulated signal was acceptable provided the disc and stylus were in good condition.


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mzil
post Dec 5 2012, 01:46
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QUOTE (splice @ Dec 4 2012, 20:17) *
QUOTE (Axon @ Dec 4 2012, 00:01) *
... The HF limit is dependent on many factors, but at the very least, CD4 records go all the way to 45khz. ...

The cartridges had significant distortion and frequency response variations above 20 KHz or so,

Just a few dB off, even up to 45 kHz, isn't very significant in my book.
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splice
post Dec 5 2012, 06:42
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QUOTE (mzil @ Dec 4 2012, 17:46) *
... Just a few dB off, even up to 45 kHz, isn't very significant in my book.


I agree, so long as you're talking about the frequency range above 20 KHz rather than below it. smile.gif


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mzil
post Dec 5 2012, 07:13
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Yeah (if I'm getting your humor), I guess when neither the test signal nor the deviated version is audible to human ears, terms like, um, "significant" don't really apply. laugh.gif

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Nessuno
post Dec 5 2012, 09:10
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QUOTE (Canar @ Dec 5 2012, 01:10) *
In theory, it's still wrong. There is a theoretical upper bound to vinyl's frequency reproduction. Like I said, precisely how you define that limit will change where you place that theoretical upper bound.

It's not as clearly defined as CD, but that does not imply that there is no theoretical upper bound!

Well, in very strict theory, every time-limited signal has infinite bandwidth, so... wink.gif


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2Bdecided
post Dec 5 2012, 13:29
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QUOTE (mzil @ Dec 4 2012, 22:41) *
The "Lucy abbey all the way" part has been released on some CDs, such as Rarities, however the annoying tone part that precedes it has never been released on any CD that I know of.
I think it's on both stereo CD releases (1987 and 2009). I haven't got the mono ones yet.

Cheers,
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