$800 Cartridge Shootout and Upgrade Path

Artar, the discussion of DC vs AC motors is a lengthy one.

Primarily, it has to do with AC "cogging" vs DC "non-cogging" regarding the way the motors work.

"Cogging" is the result of the motor behavior when the individual poles of the motor pass the magnets. A 4-pole motor will have a "surge and lag" effect as each pole passes the magnetic parts of the motor that can be noticeable. AC motor makers have increased their number of poles to reduce this effect, and commonly now use 24-pole motors. The effect is reduced, but not entirely gone.

AC Sychronous motors use the AC line frequency(60Hz) that is generated by the power company to use as a speed reference that keeps their motor speed "constant", similar to an electric clock. Since it locks on the line frequency, and not the voltage level, it can remain constant even during fluctuations of voltage. It is a commonly used type of drive for most of the lower cost turntables, and is even used fairly commonly in expensive turntables.

DC motors do not have a cogging effect, but since there is no "line frequency" in DC, there is no reference to "lock" on the speed like an AC motor does. DC motors are speed controlled by the voltage level. So, the DC motors must have some kind of controller, or the TT will constantly undergo minor slowing as you play the LP, due to drag forces. The "best" kind of controller for the DC motors is a subject of great debate.

Obviously, a "quartz lock" or other "hunting" type of controller that uses a strobe as a reference can have the effects of quick speed up/slow down known as "hunting". This is not good. Teres has developed a controller which uses strobe reference on the platter, which senses variations and applies corrections in a very slow manner, which is not really audible. Some may argue this and claim it is audible. The other method is to use a relatively non-referenced controller which sets speed as a constant, and hopes that nothing really slows the platter down along the way. Any slowdowns with this type of controller will be additive all along the side of the LP being played. Some will argue that this is not noticeable, but others say it is. In either case, the platter momentum is critical to the controller not having to make corrections, or not slowing the platter down during play. Neither of these systems is perfect, and the AC synchronous system is not perfect. Nothing is perfect. Since the ear is most senstive to minor speed variations occuring in a rapid manner(flutter), we strive to minimize flutter, but the methods we use may result in more slower variations(wow). "Wow"(in small levels) is less noticeable to the ear. So, the DC motor application is used to provide the smoothest results in flutter, but may have a bit more wow, or a bit more gradual slowdown, depending upon the type of controller used. In addition, belt stretch and rebound, belt slip, and other things may enter into the equation. It is a difficult engineering task to get close to perfection in this area, and there is no solid consensus on the best method to use. However, it is generally conceded that a well implemented DC motor can sound better than an AC synchronous. The individual TT makers use their ideas of what the best method is, and the user must decide which he prefers sonically. Most of the best units are very very good, and will not intrude into the listening experience noticeably.

Regarding the question about platter mats, the Teres is not designed to use a mat, and should be played "bare". If you want a better platter than the acrylic because of the reflected resonance issue, then stepping up to the next higher level of platter will be useful, not adding a mat.

However, be aware that there is no "perfect" platter either, and it remains a choice of imperfections which is most acceptable to you. There are sonic issues with every single type of platter you may select.

In fact, every single choice you make as an audiophile will have plusses and minuses. It is up to you to select equipment which has the plusses in the areas of most importance to you, and has the minuses in the areas of least sensitivity to you. This is the crux of assembling a satisfying system that will meet your needs as a listener, and it is also why there are so many different ideas of what is "best".

Dan_Ed, the lead loading in the Teres acrylic platter could have the effect of improved perceived bass response.

Essentially, the greater rotational mass will improve the ability of the platter to retain its speed through the tall steep peaks that are present in the bass information in the record groove. This will be percieved as faster and better dynamics in these frequencies, and will add impact.

Generally in belt drive systems, high platter mass is desirable. Affording to buy it may be another matter entirely.

In my case, I have selected the plain acrylic platter. This is not because I am not aware of its shortcomings, rather I am aware of them, and settled on this because it provided performance that was acceptable to me for the price I could afford. In nearly all cases, this type of "settling" needs to be done by the purchaser. Most people cannot afford to buy the most expensive product on the market, and even if they could, perfection is not attainable, so some compromise is being made at all levels. Additionally, as time marches on, even the "best" products get beaten out by some new ideas/technologies/implementations that may occur.

While I am not enamored in general of the sonics of acrylic, it has its good points, and my platter(while imperfect) provides a very enjoyable experience, even if I am aware of the slight reflective resonance issue, and its relative lack of mass compared to the higher priced platters. I am also aware of dozens of other imperfections that are present throughout my entire system. There are imperfections abounding throughout my system, and everybody else's systems, for that matter.

What I am saying is that there is a point for everyone that is a good "happy ground" for the ratio of price to performance. This point will differ greatly, depending on the needs and budget of the audiophile in question. I found a good "happy ground" for me.

What I have done personally, is made a lifetime of learning and study and listening experience, as both audiophile and industry insider, to equip myself with the knowledge to understand what is involved in the selection, application, and use of audio systems. I have even engaged in the designing and building of various products in the chain, to further my understanding of the technical aspects of this hobby. All this experience over 30+ years has shown me that nothing achieves perfection, and that everything is flawed in some way. The closer you get to perfection, the more the product costs. I have recognized that this "happy ground" is where the true enjoyment of listening is. I have found that I can recognize that equipment is flawed, understand why and how it is flawed, and still enjoy my musical experience. I simply use my knowledge and my budget to the best of my ability to gain the most sound quality for my money, while being fully aware of all the shortcomings. I select my equipment to be as maximized as possible in the areas that I am most senstive to, and get the least possible flaws in the areas that I am less sensitive to(in accordance with my budget).

I have listend to alot of audio gear in my day, and can recognize a flaw in just about anything there is. The key is to understand the nature of this, and to find things that will make you happy because their flaws are not in your senstive areas that drive you crazy. You will never find equipment without flaw. You just have to learn to live with it. This is the art of the hobby. Because after all, the purpose is to enjoy music, and if the quest for perfection wrecks your ability to listen with pleasure, it is all for naught.

... every single choice you make as an audiophile will have plusses and minuses. It is up to you to select equipment which has the plusses in the areas of most importance to you, and has the minuses in the areas of least sensitivity to you. This is the crux of assembling a satisfying system that will meet your needs as a listener, and it is also why there are so many different ideas of what is "best".

That should be required reading for each of us, every day. Could we get A'gon to paste it at the top of the screen next to their logo?

TWL: Excellent discussion in your two posts above. Thank you.

I would just add reinforcement of your point relative to the AC versus DC motor conversation: in many cases, designers have made careful evaluations/selections for their specific turntable designs. Most of us are aware, for example, that Lloyd Walker and Harry Weisfeld both believe pretty strongly that they are each getting the best possible results for their turntables with AC motor designs. (In fact, Lloyd has been rather emphatic to me on that point relative to his experiments with both kinds of motors. He has concluded that he can better control the speed accuracy and stability of an AC motor and can overcome the cogging effect using a very low torque motor with a very high mass platter. Clearly a design choice.) And, the Teres designers have certainly found certain DC motor/controller combinations to best meet their design requirements (as discussed). These choices are not absolutes; when cost is removed from the equation, they are design synergy choices.

Again, thanks for your very thoughtful and thorough comments.
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Thanks guys, for your kind words regarding my discussion.

I guess that I'm "waxing philosophical" today!

:^)

Rushton, thanks, and I agree that both Lloyd and Harry are getting great results from their AC motor applications.