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Is "Staircasing" present in the grooves of a digitally recorded vinyl record?
Old 17th September 2011
  #1
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Is "Staircasing" present in the grooves of a digitally recorded vinyl record?

If one were to look at the grooves of a vinyl record produced from a digitally recorded source, would one be able to see the "staircasing" from the digital source?

I saw this picture of a vinyl groove under an electron microscope http://www.synthgear.com/wp-content/...ord_groove.jpg

Would vinyl grooves from a digital source look significantly different?
Old 17th September 2011
  #2
there is no staircasing in output of your DA, it`s a myth
Old 17th September 2011
  #3
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Quote:
Originally Posted by cyjanopan View Post
there is no staircasing in output of your DA, it`s a myth
that basically sums it up...
Old 17th September 2011
  #4
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Quote:
Originally Posted by musichascolors View Post
If one were to look at the grooves of a vinyl record produced from a digitally recorded source, would one be able to see the "staircasing" from the digital source?

I saw this picture of a vinyl groove under an electron microscope http://www.synthgear.com/wp-content/...ord_groove.jpg

Would vinyl grooves from a digital source look significantly different?

here is a link to images

Record grooves under an electron microscope

hotlink didn't work
Old 17th September 2011
  #5
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as far as I understand DACs and filtering in audio systems, I'd say the answer is no. For a couple of reasons:
There is low pass filtering on the output of the DAC that's there to pattenuate switching noise and aliasing products. it's bandwidth is basically the audio spectrum plus a couple kHz. the effect of the capacitor in the filter automatically "smoothes out" this stepping effect.

All the capacitors in the audio chain have a time constant (charge/discharge time) much longer than the period of even a couple of these steps, assuming they're a few bits apart. The resolution of any 16 bit audio DAC is so fine that the caps do not have time to charge discharge at that rate, so they ramp up and down almost "dragging behind" the signal.

Again, that's the way I understand it, but I could be way off.

Get an oscilloscope and look at the output of your CD player or whatever digital source playing a sinewave (or even better, a triangle wave) generated by an analog source at 5mV/division and try to look for the steps. I'm sure you won't find them. the staircase has been buried in the smoothing of the LPF.

Good question. Just enjoy the vinyl!
Old 18th September 2011
  #6
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Quote:
Originally Posted by 2N1305 View Post
Get an oscilloscope and look at the output of your CD player or whatever digital source playing a sinewave (or even better, a triangle wave) generated by an analog source at 5mV/division and try to look for the steps. I'm sure you won't find them. the staircase has been buried in the smoothing of the LPF.
And especially a modern delta-sigma DAC won't produce anything resembling "steps" since it's interpolated and filtered at a much higher rate while still in the digital domain.

Last edited by acreil; 18th September 2011 at 06:16 PM.. Reason: fixed embarrassing, brain-damaged typo
Old 18th September 2011
  #7
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Quote:
Originally Posted by acreil View Post
And a specially a modern delta-sigma DAC won't produce anything resembling "steps" since it's interpolated and filtered at a much higher rate while still in the digital domain.
I didn't know that. I'll have to read up on Delta-Sigma converters.

Furthermore, I HIGHLY doubt that the Cutter head would be fast enough to follow the instantaneous level shift of a "step"... Meaning its mechanical construction would not allow such a rapid change. It would be like slamming the brakes on your car and immediately flooring the gas pedal and reaching your cruise speed (let's say 55mph) in like, 200mS.. Over and over.

Last edited by 2N1305; 18th September 2011 at 04:53 PM.. Reason: added part of sentance
Old 18th September 2011
  #8
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1) They don't measure "stair-casing" in the output of D/As because their isn't any there to be found. That output is effectively smoothed and converted to a continuous "analog" waveform by a reconstruction filter. Essentially a low pass filter that removes any HF digital artifacts.

2) Even if HF digital stair-steps were sent to a record lathe, they would first be LP filtered by the cutter electronics, and finally by the mass of the cutter head itself that can't change direction instantaneously.

3) Even if a cutter were able to cut very HF information in the mastering process the elastic medium used before the pressing tool is fixed hard, would probably relax and remove most evidence of HF steps.

Relax

JR
Old 18th September 2011
  #9
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Quote:
Originally Posted by musichascolors View Post
If one were to look at the grooves of a vinyl record produced from a digitally recorded source, would one be able to see the "staircasing" from the digital source?

I saw this picture of a vinyl groove under an electron microscope http://www.synthgear.com/wp-content/...ord_groove.jpg

Would vinyl grooves from a digital source look significantly different?
no
there is no staircasing
the capactitance time constant would limit them
the LP filter after the d/a would round them off
the cutting machine inertia would finish removing them
Old 22nd September 2011
  #10
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Thank you for all of the responses, much appreciated!

Quote:
Originally Posted by JohnRoberts View Post
and finally by the mass of the cutter head itself that can't change direction instantaneously.



Quote:
Originally Posted by oldeanalogueguy View Post
the cutting machine inertia would finish removing them
I'd been thinking about that. Thanks for the confirmation (as well as the other reasons I hadn't considered)
Old 22nd September 2011
  #11
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tutt

Thank's for clearing that up...

JR
Old 22nd September 2011
  #12
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Quote:
Originally Posted by Sounds Great View Post
However it is audible on the vinyl record.

I wondered for a long time (this in the 80's) why my 'Roll With It' record sounded a bit different than my other records. Until I learned it was mastered digitally. Once you enter the digital domain there is no coming back.
I'm sure I'm not the only one here who would choose to disagree with that, but it's certainly true that many digital masters cut to LP sound horrible. The reasons are more to do with well-intentioned but over-excited engineers finding stuff they could do with digital that was not possible (or not practicable) with analogue, and getting carried away, than with equipment - that said, some of the early digital gear was far from blameless as regards anti-alias filters and other practical details.
Old 23rd September 2011
  #13
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Quote:
but I could hear the digital processing from the first time I heard it
This is the clue. You heard the processing. It isn't intrinsic to it being digital, but it was intrinsic to it being a poor implementation. You can't jump from a badly done example to a blanket claim that all digital sounds that way.

The underlying mathematics is quite clear, and unassailable - analog and digital mechanisms are fundamentally identical in their ability to store information - in this case audio. Implementation details and pragmatics of what is acheivable within the technological boundaries will result in different results, it isn't as if analog doesn't have a sound of its own. Early digital had all sorts of problems, and the limitations due to running with the technology as it was only just becoming viable caused all sorts of sonic problems. But that is no different to saying that early tape had problems. Once your audio is converted to tape the conversion becomes part of the music from that point on too.

Modern PCM for all intents has no sound. It has long since passed the point where the basic technology surpasses the resolution needed. Tape has a very clear sound, even in its most advanced implementations. But the final sound of the recording is vastly less affected by these considerations than by the skills and artistic leanings of the production team. In both mediums there remain plenty of scope to mess things up. Misunderstanding the digital domain can lead to many sonic ills, in the same manner as misunderstanding the analog production chain. The sonic results of such misapplication are different, and identifiably so - so in that respect digital is different to tape. But there is nothing intrinsic to digital that sets it apart as fundamentally damaging the sound. The usual blithering in the HiFi press not withstanding.
Old 23rd September 2011
  #14
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Thanks for clearing that up...

JR
Old 23rd September 2011
  #15
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Quote:
Originally Posted by JohnRoberts View Post
1)

3) Even if a cutter were able to cut very HF information in the mastering process the elastic medium used before the pressing tool is fixed hard, would probably relax and remove most evidence of HF steps.

Relax

JR
Hmmm... perhaps you recall the CD-4 quad records? In addition to 20KHz audio recorded in a standard stereo groove, there were two 30KHz carriers recorded along each groove wall which modulated in a complex FM sort of way to produce a bandwidth that went up to 45KHz. Yup, on vinyl. Still there in the grooves today, playable if you had a CD-4 cartridge and decoder. Of course if you didn't, you'd scrub the carriers out of the groove with your standard cartridge. Those 45KHz sidebands were fragile, but present none the less.

The vinyl system is capable of some very high frequencies. No doubt CD-4 records used special cutter heads with resonances tuned out or way up.

Of course there's no staircasing on records for many other reasons, but limited bandwidth of the system isn't probably the biggest factor.
Old 23rd September 2011
  #16
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Quote:
Originally Posted by Sounds Great View Post
You can disagree, but PCM has a sound. True, bad engineering choices make it even more obvious, but the conversion itself becomes part of the music from that point on.


As far as the Winwood record, it really does not sound bad, but I could hear the digital processing from the first time I heard it, just didn't know what it was at the time.

Maybe you aren't hearing digital... perhaps you are just accustom to hearing the sound of vinyl records?
Old 23rd September 2011
  #17
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I doubt it because the cutting machinery runs any signal through an RIAA curve. so it would turn any theoretical squarewave into something closer to a triangle wave.

The inverse RIAA is what a (Phono Deck) input has.. that reconstructs the waveform by applying the inverse curve.

Quote:
Would vinyl grooves from a digital source look significantly different?
Old 24th September 2011
  #18
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Quote:
Originally Posted by Muser View Post
I doubt it because the cutting machinery runs any signal through an RIAA curve. so it would turn any theoretical squarewave into something closer to a triangle wave.

The inverse RIAA is what a (Phono Deck) input has.. that reconstructs the waveform by applying the inverse curve.
Not to continue much further down this esoteric rabbit hole, you have your RIAA EQ a little backwards. The playback EQ exhibits the falling gain with frequency, so encode EQ has a rising HF characteristic. This doesn't really matter one way of the other since RIAA is only specified up to 20kHz, so these hypothetical digital stair steps would be above 20kHz and rolled off by HF LPF built into typical cutting lathe electronics.

JR
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