Do expensive turntables sound better?

[Blumlein 88]

You don't need all those extra steps -- Phoenix Engineering already makes a PSU + Hall sensor to vary the motor speed, accurate out to several digits.

I would think that has the problem Amir pointed out. Absolute average speed yes, random variations I bet are larger. Though I don't know that such would be my guess.

 

[watchnerd]

I would think that has the problem Amir pointed out. Absolute average speed yes, random variations I bet are larger. Though I don't know that such would be my guess.

With a properly regulated speed control, the random variations in speed are far far less than the random variations in pitch caused by eccentricity issues with LPs that don't have the hole punched in the exact middle.

 

[tomelex]

if you digitally record a song from vinyl, no two times will it record the exact information, no matter how expensive the setup, its (vinyl playback) mechanical system with mechanical limitations. The most telling thing, play a test record with tone or even two tones, then do the same with digital, the difference is obvious. That does not mean that the inherent "flaws" in vinyl can not actually make a better sound in the upper mids to highs and in the imaging and the low rumble can cause a "room effect" , so I am not knocking vinyl, in some ways it helps out poor old two channel stereo for listenability.

 

[Fitzcaraldo215]

With a properly regulated speed control, the random variations in speed are far far less than the random variations in pitch caused by eccentricity issues with LPs that don't have the hole punched in the exact middle.

I agree that LP eccentricity is a major potential issue. Didn't Nakamchi make a TT to automatically and electro-mechanically center the disc prior to playback?

But, all the graphs I have seen of TT speed variation on some pricey rigs show rather high rates of variation. For example, Fremer publishes these from time to time. I am guessing, but I assume he takes the measurements multiple times for each TT, adjusting the record eccentricity for best results. Then, he shows us only the best result, being mum about the variations caused by eccentricity. Still, his graphs show substantial speed variation consistently TT to TT. So, I believe speed variation is still high with mechanical turntables even if eccentricity is carefully adjusted.

I am sure this is all part of the mystique about why vinyl sounds "better" than uninteresting, cold, sterile digital which has taken all the excitement out of audio by virtually eliminating speed variations.

 

[watchnerd]

I agree that LP eccentricity is a major potential issue. Didn't Nakamchi make a TT to automatically and electro-mechanically center the disc prior to playback?

They did!

It was a crazy system, with a 2-step process:

But, all the graphs I have seen of TT speed variation on some pricey rigs show rather high rates of variation. For example, Fremer publishes these from time to time. I am guessing, but I assume he takes the measurements multiple times for each TT, adjusting the record eccentricity for best results. Then, he shows us only the best result, being mum about the variations caused by eccentricity. Still, his graphs show substantial speed variation consistently TT to TT. So, I believe speed variation is still high with mechanical turntables even if eccentricity is carefully adjusted.

I have two turntables, one vintage Michell Gyro SE (that I'm refurbishing) and the 'backup system', a Pro-Ject Debut Carbon with Speedbox for speed control. I've done Platterspeed tests on the Pro-Ject and it exhibits numbers embarassingly close to the ultra-expensive decks:

 

[Bill Bainbridge]

Tell you what would be really neat, pointless, and likely have no market at all. Have a TT that takes in the signal from the cartridge via a good ADC. Have embedded in the platter points to be picked up by sensors. This gives nice read out on real time speed. Have software to vary the speed of playback digitally based upon this real-time speed sensing of the platter. You could end up quite a way towards speed stability of playing a CD. At least it should get much closer than PLL's or massive platters have managed. I suppose the old strobe setup with a light sensor for real time speed measurements might do well enough.

Hmm, a good idea. Although I might point out that the digital technique for error tracking that you speak of might require a software implementation of (gulp) a Phase-Locked Loop. Unless you're aware of a different technique for isochronos synchronization?

 

[DonH56]

I thought there were TT's using Hall-effect sensors that did essentially that (analog PLL). I know I piddled with such a circuit ages ago just to see what I could do with it. And of course a number of direct-drive TT's used PLLs for speed control. I would not use the cartridge as the sensor, however, too much else going on and the signal would be hard to pull from the music on the LP. I am not sure a software approach would do much better than an old-fashioned analog design, however; we can get femtosecond precision from a PLL used for radar, EW/ELINT, or the high-speed serial data links in your computer (PCIe, SAS/SATA). I am not sure why it would get closer than a PLL, seems like pretty much the same function to me.

One could argue a massive platter would work against the PLL circuit since you'd need a lot of torque and excellent control loop damping to adjust and maintain the platter's rotation. Back to the endless debates about smaller/lighter/tightly controlled vs. larger/heavier/lightly controlled if at all, just let inertia control speed variations. Another hot topic -- there was a lot of attention focused on making platters (spindles, bearings, etc.) that were homogeneous throughout and perfectly manufactured so the platter (etc.) did not induce its own speed variations. Then all the focus on motors and drive systems (direct, belt, idler, etc.)

Another can of worms, let's all go fishing!

 

[watchnerd]

I thought there were TT's using Hall-effect sensors that did essentially that (analog PLL).

Yes, there are. You can also purchase Hall-effect sensor / controllers as after market devices.

 

[Bill Bainbridge]

I am not sure why it would get closer than a PLL, seems like pretty much the same function to me.

Except that the loop filtering could get much more sophisticated in a digital implementation, given the right DSP algo's; which might be more capable of tracking wider variation (using adaptive filter or similar) such as those displayed in Amir's chart of the Linn turntable that he posted. Might take a pretty screaming DSP rate to achieve this with less phase noise, but it might be possible.
If achievable, this approach might eliminate the need to have more mass (and accompanying motor torque), and the cost savings could translate to the ability to implement something like laser scanning of the platter surface as a means of ascertaining platter position. I can imagine a laser-etched film being attached to the platter edge that would give incredible resolution of its rotation, and with appropriate onboard DSP to simultaneously examine the spectrum of 1/f noise from the grooves, a further input to the ADPLL could massage platter rotation to accommodate vinyl wow and flutter. Might take a sophisticated and fine-grained servo motor to get there.
Nah! Let's jess go fishin'!

 

[Bill Bainbridge]

Of course the next implementation could also be: Laser scanning of the vinyl surface itself, with no need for a platter, mechanical cartridge, or analog rotation at all. Nah! Let's jess go fishin'.

 

[watchnerd]

Of course the next implementation could also be: Laser scanning of the vinyl surface itself, with no need for a platter, mechanical cartridge, or analog rotation at all. Nah! Let's jess go fishin'.

Laser turntables already exist.

 

[Bill Bainbridge]

How do they sound? I'm sure their not as fascinating to watch as a spiral loop in vinyl going 'round and 'round.

 

[watchnerd]

How do they sound? I'm sure their not as fascinating to watch as a spiral loop in vinyl going 'round and 'round.

I've never heard one. They're primarily marketed to libraries.

 

[Fitzcaraldo215]

Of course the next implementation could also be: Laser scanning of the vinyl surface itself, with no need for a platter, mechanical cartridge, or analog rotation at all. Nah! Let's jess go fishin'.

I do no see how you avoid electromechanical scanning by the laser of the spiral groove either by rotation of a laser pickup or by a rotating turntable with a fixed pickup. The latter had been tried and so far, after many years, it has flopped.

Contrary to intuition, perhaps, one secret of the LP is that signal is not on the surface of the lacquer master grooves. It is cut into them via deformation under pressure, and it also plays back from several molecules beneath the surface of the vinyl via deformation of the material under pressure from the stylus. There is an elastic modulous of the materials involved, and part of the trick is cutting the lacquer master to compensate for this in typical vinyl playback. So, would a laser merely scanning the undeformed surface of the LP grooves accurately capture the mastered signal, which actually lies beneath the surface of those grooves via pressure deformation? Stylus pressure at the microscopic actual groove contact points, by the way, is huge on a force/area basis even where tonearm "downforce" seems benign at 2-3-4 grams or so.

Meanwhile, those of us with any brains have gone digital by now so that issues like the above stand no chance of keeping us awake at night.

 

[Bill Bainbridge]

@Fitzcaraldo215 : We may be many years away from successful implementation of this technique, and no, it wouldn't preclude some form of spacial tracking, including possibly an electromechanical interface (at least in the initial generations). However, the idea is that once the A/D/A process had begun, interceding processing, including literal non-realtime and non-linear processes operating so quickly as to become perceptibly realtime, could help to retrieve amazing surface detail, potentially down to the microscopic level, and with normal expectations of playback latency.

I was amazed at the detail achieved by a simple 3-D common video image capture system I recently saw at a technology Tradeshow. After some processing, the scanner system was able to send its output to a 3-D printer and achieve convincing evidence of its accuracy, at least as observed with the naked eye. If the scanning system utilized coherent light (such as from lasers) as its imaging method, the resolution might have gone down to the level whereby even the high-force impression details you speak of might have emerged.

Concerning elastic modulus conditions, a relatively homogeneous material would transfer some of its variable underlying properties to the surface finish, even if it were on the order of a difference of roughness undetectable with the naked eye. An example of this would be metals subjected to work-hardening conditions, whereby the granular structure of the molecular matrixs is changed by the heat and pressure, and therefore changes the level of polish which can be achieved at the surface.