Hi
I sincerely would like someone to start a thread on what makes a good turntable .. heck! I will start one and expect the experts to chime in ...
When I first decided to get into audio manufacturing, I asked for advice from some trusted guys. One sent me a rather long e-mail that I saved. Here's a part that I'll share...
"...A couple hints- there are almost no true professionals in home audio, regardless of the stature, size of their businesses, or supposed qualifications. Acceptance & success is as much or more who you know as what you have to offer. Watch your backside..."
I have tried to use that e-mail as a business model, and it has worked well, except when I didn't listen to the little bell ringing in my head regarding the last piece of advice he wrote. Hey, we all learn some things the hard way, right?
So, there are no experts, and there are some lowlifes out there, but I don't mind posting some of my basic philosophies, not that I expect total agreement from everyone.
I believe there are some rules to follow, regardless of any technical approach taken.
1) A turntable should be user friendly.
2) It should actually work without undue failures.
3) Whoever made it should back it up, if it does break.
4) It should spin quietly at the proper speed, or at least at a speed accuracy that reflects its purchase price.
5) Setup shouldn't be a dramatic undertaking. It should be straightforward.
6) Once set up, it should stay that way.
7) Maintenance should be extremely minimal, if at all.
8) It should attractively fit in any room with any system.
9) Every part should have a purpose for its existence because a turntable is a lot like the audio chain itself. It is only as strong as its weakest link.
10) It should pass WAF with flying colors. If Mama doesn't like it, it almost isn't worth the grief of ownership for a lot of guys.
Skinning the cat:
There are three drive systems commonly in use these days: direct, belt and idler. There are also endless arguments about which one is best, usually by those who are either biased because of what they happen to own, or by those who haven't actually been exposed to better units of each of the drive types. My experience tells me that units at the top of the food chain can sound a lot alike, depending on the intentions of the designer. Of course, I have my favorites, and they all have an overall sound that is at least somewhat similar to that of my turntable. Wait... Aren't we striving for a neutral presentation, and shouldn't that be every designer's goal? Well, define neutral. Also, realize that every recording engineer who masters a record has to use his judgement when practicing his craft. I believe we have a representation at the end of the day, and he who declares his to be neutral is either terribly misguided, or trying to misguide others. If that was not the case, all our systems would be identical, and we wouldn't need this forum. For me, that's the starting point.
Now that you know my fundamental views, I'll give my opinion concerning speed accuracy and my way of getting there. If someone wants to start that thread, I'll go deeper into my ideas of what I believe makes a good turntable.
No matter how you slice it, speed accuracy is somewhat dependent upon cost. You can't get there for peanuts. So, what do you need?
1) A decent motor is a given. That sounds simple enough, but it is the biggest hurdle to jump when acquiring parts. One really big manufacturer uses a motor that can be bought for around $56...at least that is what a sample costs. I know because we bought six of them at different times for testing. They all had shaft inconsistencies, and they all cogged like no tomorrow. They are very reliable, however. What does that tell you about that manufacturer? A lot of guys use an off-the-shelf motor that is very consistent between samples, but they have a failure rate that is higher than I like. It is an easy replacement, however. Most of those guys stand behind their product, so it is a minor inconvenience. Other guys have motors custom built for them. Those are generally really, really good, but not always because it costs a lot to repeat that exercise when the results aren't dead on. Sometimes, close enough has to suffice. I use a tried-and-true three-phase motor that is insanely expensive to implement in a turntable application, but the payoff is worth the effort to me.
Here's what I like to see from a properly applied motor...
...but will it do it at every speed when under a real world load? I define every speed as any possible setting. Ex: 33.33333334, 33.33334333, etc., etc. Why should anyone care? Some people care because they can hear a one/fifth harmonic, and some can even hear the direction of wire. Also, not all records were recorded at the same pitch, and people who want the best need a way to compensate for that. Some designers try to give the user the flexibility to adjust the speed closely. I know I do. In fact, I may go overboard by offering 200 steps per cycle. My motor changes speed by changing frequency, so I have a microprocessor programmed to handle that. I am paying to have it coded anyway, so the extra adjustment steps aren't a big cost hit. The cost is in regenerating three synchronized AC phases. At the end of the day, I have a stable, but expensive solution. It's one way to skin the cat.
2) As important as a decent motor, is good system inertia. If a platter/bearing design doesn't take into account how inertia is handled, it will fail to maximize the performance of any motor. If the mass is in the wrong place, or just plain wrong, speed can be negatively affected, regardless of the expense of the motor and all its trimmings. This aspect is harder to achieve than getting the motor right because it is hard for a designer to wrap his head around the concept. As a result, a lot of guys design a platter for sex appeal, rather than for sheer performance. They seem to operate by the "whatever is cool" method. The reality of it is that physics come into play whether it is realized by the maker, or not. That's one reason why some turntables with fancy controllers still sound like crap. Some guys do the math, though. They plan the dynamic mass, static mass, spindle drag and everything else that goes into determining the inertia involved. As a result, their turntables don't jitter, lack micro dynamics, or exhibit the effects of stylus drag, etc. They just sound good.
Summary: In my opinion, that's what makes great turntable speed precision. It takes good design decisions for both aspects to get the best result possible. Skip one, and the overall goal suffers immeasurably.
Caveat: You may disagree, and your mileage may vary. I remain totally convinced, however.