Turntable 101

There are a lot of industry folks current wringing hands and gnashing teeth over the state of the audio marketplace. The only new customers are old. Apple’s iPod & iTunes are killing the hifi. Kids today just don’t care. The sky is falling, cats and dogs are living together, the oceans are rising. That sort of thing. It’s a mess.

I’ve said elsewhere that I think the one thing that Apple simply can’t do is vinyl. They’ve pretty much killed off CDs, but LPs? No way. In fact, I don’t really see any way at all for any lifestyle vendor or computer maker to really make a move on this segment. Sure, there’s some money to be made upselling the iPod Generation on higher fidelity playback, but that market is rather precarious and there’s way too much advertising money being thrown around by the Bose-equivalent companies for any serious strong growth there by Mom and Pop audio startups. I think it’s a sucker’s game. Like I said, I think vinyl is safe. And, interestingly, there appears to be a market for it. Should today’s high-end companies choose to do so, I think some kind of trade association might be able to buy large enough in-line advertising (like putting turntables and LPs into high-profile movies) that the segment might even take off.

Whatever. It’s not like I’m an oracle or anything. Pay me no mind ….

But I think turntables are cool. Retro in the same way that vacuum tubes are. There’s an appeal there, a natural sexiness, and the fact that the sound quality of vinyl playback is routinely (!) superior to digital doesn’t hurt a bit.

Like many Generation Xers, I ditched my turntable when I was in high school. Maybe earlier, I can’t remember. From what I can (dimly) recall from the 1980s was a deep and abiding fascination with mixed tapes, but perhaps the less said about that the better. Since that time, I’ve ditched all my LPs, worn out all of my cassettes, and moved completely and resolutely over to CD only to see Napster suddenly make music playback interesting and fun again. Remember Napster? Yeah, that peer-to-peer sharing program that allowed you unscrupulous folks to suddenly build up a rather impressive music library that you could then burn to CDs for playing in your car stereo or that CD player someone left undefended at that party you had too much to drink at where you decided that tossing back whole habenero chilis as if they were popcorn wa a fine idea. Good times.

Ok, so needless to say, it’s been a while since many of us have had the hands-on with any vinyl. In my case, I think it was 25 years. Sheesh, I’m old! Anyway, last winter, I took the plunge and bought a brand new-to-me turntable, a dealer b-stock of a Pro-Ject 9.1 turntable. The platter is huge and a cool frosted acrylic. The plinth is this charcoal color. There’s a motor that sits off to the side of the platter and drives it with a rubber belt. It’s awesome! It came with a 9” carbon fiber (!) Pro-Ject 9cc tonearm and I got a Sumiko Blackbird cartridge for it. My preamp at that time, a Plinius M16, actually had a fully functioning phono stage in it (it was a surprise to me), and when I hooked it all up, I was – and please excuse the horribly cliché audiophile phrase – totally blown away.

Over time, the glow faded, but only a bit, and I began to make my wish list, should ever find myself in that joyous position of being able to buy another table. One of the things I want is a better way to change speeds. To change from 33RPM to 45RPM on my turntable, I have to move the belt down to the wider ring on the motor-pod. Yes, it works. But it’s inelegant. And I can’t help but wonder how accurate that change up is. Which brings me to another complaint about my ‘table. How do I know that it’s operating at the speed it’s supposed to be? Unfortunately, it seems that this isn’t going to be a problem that will see a simple solution — I’m going to need a strobe of some kind. I know, I know. “Just do it”. I’m getting there. But it does bring up a related problem — what happens if my speed is off? Whoops. On my Pro-Ject, it looks like I’m out of luck — or in for an upgrade. A priority for my next table? Correctable speed.

Some other things I want – a longer tonearm. 9” is fine, but the longer the arm, the less likely the tracking irregularities. If that sentence didn’t make any sense to you, no worries. A year ago, I had no idea either. I mean, for me, all a ‘table had to do was spin the record. I mean, seriously, what’s the big deal with those expensive ‘tables? Why would anyone spend, say, $7500 on a turntable – much less $20k or even $45k? That’s crazy! They either turn the disks or they don’t, right?

Well, it turns out that there’s more going on than meets the (uninitiated) eye. I know, “shocker!”. So, while you roll your eyes, let’s take a few moments to talk about what a turntable actually does.

Platter spinning

Yes, it’s true: turntables spin records. In fact, the most important thing a turntable needs to do is to spin the platter. Interestingly (ok, it’s interesting to me), it seems that this is harder than it sounds.

First, as the platter spins, it’s possible that the spin is too fast or too slow. If the platter fails to spin at the correct speed, well, that can completely change the pitch of the notes being played. From KAB:

To get an idea of the impact of speed accuracy, a 3.3% change in speed will alter pitch one half step. 6% is a full sharp or flat. So, 0.3% is a good margin. Most hi quality turntables will beat this figure.

Ok, so assume that a “good” turntable can hit 33.3rpm and 45rpm and do so with some precision. So far, so good. The question then is, how stable is that? Will the table hold that speed over time? If not, the difference between correct at time zero and whatever it is at time x is drift. Drift is bad and somewhat insidious. You got your table all set up and ready to go and then an hour later, everything is just a bit off. What happened? Drift. So, design goal number one is a turntable that has low (or no) drift, that is, has good speed stability. Now drift is different from “warm up” in that some very turntables, especially those with very massive platters, might take some time to achieve the targeted speed. I suppose you could say that they drift into correct speed over time but generally, designers refer to tables drifting out of speed, not into it.

Second, speed stability is an averaged number. Which means that it’s entirely possible that within a given revolution, parts of that single revolution can be faster or slower than others. For (one egregious) example, it might be that for half of a revolution, the speed of the platter could be 50% faster and the other half of that revolution it could be 50% slower, with the average being 33.3rpms. As you’d expect, this sort of variation in speed would color the sound that the ‘table puts out. Lots of things can cause this, like wobble in the platter, a sagging belt, a fluctuating supply of power, variations in the surface of the platter or even the record itself, if the record has warps or bubbles. But whatever the cause, the result is a variation in pitch called wow and flutter. Wow refers to slow variations in pitch, or rather, variations in the low frequencies (say around 400Hz) while flutter refers to faster variations in pitch, or variations at higher frequencies (say, around 3000Hz). These days, they tend to get lumped together and refer to any instability of pitch due to variations in rotational speed of the platter and are measured as an averaged value in % based off of some stable speed. Whatever. They’re bad. And, unfortunately, unavoidable. It does not appear to be the case that you can design a turntable with zero wow and flutter. What you can do, however, is reduce them to levels that are inaudible to human hearing, which would be about .05%.

So, what does wow and flutter sound like? From Wikipedia:

Wow and flutter are particularly audible on music with oboe, string, guitar, flute. brass or piano solo playing. While wow is perceived clearly as pitch variation, flutter can alter the sound of the music differently, making it sound ‘cracked’ or ‘ugly’. There is an interesting reason for this. A recorded 1 kHz tone with a small amount of flutter (around 0.1%) can sound fine in a ‘dead’ listening room, but in a reverberant room constant fluctuations will often be clearly heard. These are the result of the current tone ‘beating’ with its echo, which since it originated slightly earlier, has a slightly different pitch. What is heard is quite pronounced amplitude variation, which the ear is very sensitive to. This probably explains why piano notes sound ‘cracked’. Because they start loud and then gradually tail off, piano notes leave an echo that can be as loud as the dying note that it beats with, resulting in a level that varies from complete cancellation to double-amplitude at a rate of a few Hz: instead of a smoothly dying note we hear a heavily modulated one. Oboe notes may be particularly affected because of their harmonic structure. Another way that flutter manifests is as a truncation of reverb tails. This may be due to the persistence of memory with regard to spatial location based on early reflections and comparison of Doppler effects over time. The auditory system may become distracted by pitch shifts in the reverberation of a signal that should be of fixed and solid pitch.

Rumblings

A good turntable is a quiet turntable. Noise, regardless of source, when injected into the pickup (cartridge) can be quite noticeable. In a bad way. In an effort to reduce environmental feedback, turntable designers have done some interesting things, including the extensive use of damping material or the use of various suspension technologies to move the platter (and hence, the stylus) out of harms way. “Suspended” ‘tables, like a Linn or an Oracle, basically float the platter and assembly it sits on in such a way that all external vibrations are trapped and drained before they can get to the platter itself. “Non-suspended” tables tend to use massive materials in their construction as a way to avoid the same thing. Each approach has its proponents.

But however the table is sprung, any table is subject to rumble. Rumble is the low-frequency noise usually associated with the table’s own operation. The bearing that the platter spins on is the historical culprit here, and is probably the reason you hear turntable designers spend so much time and effort talking about how well made their spindle or bearing is. Motors and drive systems are another way to get rumble into the pickup. An irregularity on a belt or on the perimeter of a platter or on the o-ring on a drive spindle all can add a nasty “thump” to the sound coming from your vinyl rig. Thankfully, rumble isn’t nearly the problem it used to be – in fact, “rumble filters” like those found on only pre-amps, simply aren’t necessary anymore.

Still, rumble is bad. Just say no to rumble. A good turntable has to incorporate mechanisms to attenuate rumble to (again) below audible levels. “Rumble numbers” (if they’re discussed at all) are usually measured in dB, as in, “this table’s rumble is -10dB”, which is a way of saying that the turntable is quieter than the record it plays.

Today, one common method of addressing rumble (and wow & flutter) is with a very big, dense table assemblies and platters. The bigger and denser the better.

There are other sources of rumble, too — including the LPs. As with wow and flutter, an irregular or warped record can also introduce the most significant (and troublesome) source of rumble. To cope, some tonearm designers have built-in features to address rumble, like the ability to add some kind of viscous damping fluid. Another approach is vacuum hold-down, a sort of suction clamp that flattens out the record for playback, though I have to say that the introduction of a vacuum motor could be problematic (don’t know about you, but running a vacuum while listening to records doesn’t sound relaxing). More commonly, turntable manufacturers ship their ‘tables with some kind of dense clamp that sits on top of the record and spindle (record clamp) that provides some damping as well as some flattening and there are a couple of vendors that sell something that can be used on the edge of the record itself (ring clamp) to flatten troublesome LPs even more.

Sound of the Platter

Many folks say that a turntable has a sound and generally, they mean something other than the negative contributions of wow, flutter or rumble – or even the contributions (or subtractions) of the tonearm or cartridge. You can read reviews about turntables that are called, variously: lively, dead/damped, smeared, forward, uninvolving, or whatever. As far as I can tell, this aspect appears to have more to do more with the platter itself than the turntable as a whole, though I suppose this could be argued.

There are a lot of aficionados that feel that some platter materials simply sound better than others. Note that this bit is probably the most subjective element when comparing tables, as one man’s “lively” is liable to be another man’s “bright”. Anyway, platters can be made from just about anything, like metals such as aluminum, steel, and copper, or plastics and acrylics, or even wood, or perhaps some material that mimics vinyl, like Delrin. Each material has it’s proponents. For those that seem to pay attention to such things, there seems a significant preference of metal over acrylic, though the prevalence of POM (aka “polyoxymethylene”, better known by DuPont’s brand name Delrin) over metal seems to make it’s own case. Almost no one uses wood anymore, though Teres Audio used to make some really beautiful veneered platters before moving to an all-Delrin lineup.

And what about the sound of each of these materials? Well. That’s hard. If acrylic is the baseline, I think many would say that a metal platter sounds better. In what way, you ask? Well. Let’s take a side trip.

I met Wayne Donnelly very briefly at RMAF this past year, and for whatever it’s worth, he’s a very nice guy and at that time appeared to have a complete inventory of all of his marbles, so I see no reason not to take his 2010 review of the VPI Aries turntable upgrades at face value. In that review, he seemed quite taken with the VPI platter found on their Classic turntable. It’s aluminum and it is also offered as an upgrade for the Aries turntable, up from their standard acrylic platter. Quoting: “the entire musical presentation became livelier and more open”. While I’m not sure how this is possible, Donnelly seems quite certain and the differences he comments are were immediate and highly preferable. Interestingly, this review is one of the only that I know of where the comparison between acrylic and metal platters appears valid because everything else stayed the same. Same cartridge and arm, yes, but also the same bearing, plinth, drive and motor. Rather unusual, that.

So, if it can be assumed that metal platters sound livelier (and presumably, preferably better), then what of Delrin? Delrin, it seems, mimics record vinyl, so the theory is (apparently) that whatever the resonances that are found in the record will be the same as those found in the platter. It seems like good reasoning. Taking a quick survey of the higher-end turntables, it seems that Delrin might be more popular with some of the newer tables, which might be taken to mean that the manufacturers feel that it sounds better.

I’m being kind of wishy-washy here because, as the Wayne Donnelly review shows, direct comparison between platter materials is almost impossible.

Turntable 104: Use me!

Lastly, turntables need to be easy to use. This is different from, though related to, being thoroughly reliable. Turntable setup is notorious for being a painful experience, but once done, you want all that hard work to keep producing for you every time you’re ready for a needle drop. Personally, I’d like my turntable to be easy to set up too, but hey, that’s why buying off the Internets is problematic — because this is the perfect opportunity to leverage that dealer of yours. Let them worry about overhang, offset, VTA, VTF and azimuth. Your job is just to enjoy the music, no? That and shell out the cash, of course. Anyway …

That’s probably enough for now. I’ll leave off the discussion of drive types (direct vs belt) for another post.