Building high-end 'tables cheap at Home Despot II

Oregon, a small correction. We are no longer producing any belt drive turntables. For more than a year now our top of the line table has been direct drive.

With all of the noise about rim vs belt, direct I think that the most important point about the Verus motor is being lost. The reason we are adopting rim and direct drive is that we now have a motor that has dramatically less cogging than anything we have seen before. This allows us to couple the motor more intimately with the platter without the detrimental effects of cogging.

Isolation between the motor and platter (from a belt, idler or whatever) is a very good way to reduce the negative effects of cogging. But as this group knows so well it also causes loss of pace and smearing. An idler setup suffers from cogging effects but to my ears it's a better compromise than the smearing you get from the greatly increased isolation resulting from a belt. But it is a still a compromise.

Because the Verus motor is essentially coggless, we are able to couple the motor as intimately as possible to the platter without introducing degradations from cogging. This is why we created a drop in replacement for the Garrard motor. With the major reduction in cogging and more intimate coupling to the platter the improvement is not subtle. It was rim drive both before and after so there is more to the story than just the drive topology.

I have contemplated creating a drop in replacement for the Lenco. Any interest?

First I want to be clear that I am "contemplating" doing a Verus motor for the Lenco. This is not a commitment.

I can see a few ways to do a Lenco/Verus. I suspect that the best approach would be to create an assembly much like what we did for the Garrard. The Garrard assembly consists of a mounting bracket, a pivoting motor block and a motor with a 2" drive wheel installed on the motor shaft. The drive wheel rests against the inside rim of the platter. The motor block has a pivot that allows the motor block to tilt away from the platter. The weight of the motor block establishes the drive wheel pressure. Thats the general idea. A picture would probably help. For this to work on a Lenco the inside of the platter rim would need to be true and smooth.

Another option would be a replacement for only the motor itself. From the pictures I have seen it looks like the Verus motor would fit inside of the existing Lenco motor housing. The tapered shaft could probably be fitted to the Verus motor shaft. I expect that this would be sonicly inferior, but some may wish to retain the original idler.

We have not developed a mechanism for tilting the motor away from the platter for the VRD-Garrard but will probably do so. The motor needs to be tilted for platter installation but not for normal operation.

Chris

Bolson, It would be fairly simple to to a A/B comparison by simply placing a Verus motor so that it drives the outside of the platter.

A comparison has been done with a Garrard 301 and the results are reportedly quite favorable.

Dopogue, thanks for heads up on the vertical extrusions. Back to the drawing board...

Jlln, I do not expect that flat spotting will be an issue. The o-rings we use are fairly hard and also very durable. Much more durable than materials that were available in the 60's. Also the pressure is quite small. If I am wrong replacement o-rings are about $0.50 and are readily available.

Lewm, I have no idea if there would be an advantage to driving the underside of the plater rather than the rim. From a theoretical perspective there would be slightly more "scrubbing" with the Lenco approach since the driven surface is not moving in a straight line. At first blush this would seem less effective, but who knows. I do like the elegance of the approach.

We may be able to come up with a way to use a Verus motor to drive the underside of the platter. Constant pressure would not be a problem but it may require too large of a drive wheel. I need to think about this.

Mario_b, good questions, thanks for asking. You are correct, as the o-ring wears the speed will change. However, as I noted before the o-ring material is quite durable so it is unlikely that after even years of play that the overall diameter of the drive wheel will change more than a few thousandths. So the speed change will be very small. The controller has switches that provide precise 0.16% speed adjustment steps. So maybe it will advisable to check and possibly re-adjust the speed every year or two.

The Verus controller has a torque adjustment. First of all using the term torque is not strictly correct. This adjustment controls the voltage to the motor which in turn affects the maximum torque that can be delivered. However, the actual torque delivered is a function of load. The load is always much less than the maximum torque so the extra energy is just converted to heat. My point is that the adjustment never actually changes the torque. What the adjustment does change is how rigidly movement of the rotor is controlled by the magnetic field in the stator. The effect is very similar to adding compliance between the motor and platter, but on a much, much smaller scale. Higher voltages are analogous to more rigid coupling. A higher torque setting results in tighter more precise sound. But you can go too far with the sound becoming analytical and dry. I am sure that it is all about precision of speed but I do not think that the lower torque settings are necessarily less precise.

Chris

Johnnantais,

A few corrections. While we no longer produce belt drive motors I do still think that they have a place in the industry. But that place is not at the top.

Induction motors are indeed brushless but they are not coggless. Any single phase AC motor by definition will exhibit nearly 100% torque ripple (or 100% cogging). The incoming power is essentially cycling on and off at either 50 or 60 time per second. When the AC voltage crosses zero then the torque produced by the motor also must be zero. When the AC voltage peaks the torque also peaks.

The RPM of an induction motor is determined by the AC frequency and the number of motor poles. More poles increases the frequency of cogging but in no way diminishes it.

While flywheeling from the platter and/or motor does aid in speed stability it is not a cure. Otherwise the heavy belt drive platters would womp on idlers with relatively light weight platters. Experimenting with a 70 pound platter we still found that subtle changes affecting cogging were clearly audible.

Cogging is always detrimental to good sound. What can be debated is if cogging is better or worse than common fixes. A rubber belt is very effective at reducing the effects of cogging. But it introduces it's own problems that many, but not all, find worse than the cure. An idler wheel is far less effective at reducing cogging effects and also introduces a lot less negative effects. It's all about compromises. But if you start with a motor that does not cog then everything is a lot easier, and better.

I am total agreement about the detrimental effects of "quartz-locking". Thats why we don't use any sort of servo circuit in either the Verus or Certus motors.

Johnnantais,

I don't wish to start a debate but I must say that I am a bit surprised by your comments. We certainly have a lot of common ground and I applaud the work that has been done here to bring great sound to the masses.

I have done a great deal of experimenting with motors with varying amounts of cogging. In all cases reducing cogging has a clearly audible, positive effect on sound quality. Even very small changes in cogging are quite easy to hear. I should add that for most, identifying the degradations from cogging is not easy. Not that it is hard to hear but rather that there is for most, no reference point. As a case in point; those that have never heard a good idler will have no reason to suppose that they are missing anything. A trusty belt drive table would likely seem flawless or at least nearly so. Just because nothing objectionable is being identified, one should not assume that there is no room for improvement.

Because someone who heard a Verus motor at a trade show commissioned an idler is hardly evidence that cogging is inaudible. A comparison of motors in the same turntable that exhibit different amounts of cogging would be experience rather than theory.