Let me start this article with one of my favorite motivational sayings:

Everyone said it couldn’t be done! But then someone came along who didn’t know that —and just did it.

But we’ll get to that later. I would like to extend my blog writing about analogue music sources. This applies to both equipment and outstanding recordings. Vinyl records have been my great passion for decades. I think that many people strive for optimizing their own HiFi equipment over the years. The most important component in this context is of course the record player or many say simply turntable. This involves three essential components: the turntable itself (just spinning the records with constant speed), the tonearm and the cartridge. There are only a few manufacturers who produce these three components themselves and then also offer a complete product that can play at the highest level. Therefore, this hobby is often about putting together the best components yourself. This may also be a reason why it never gets boring, because combining different setups can produce very different sound results. For people who have nothing to do with this hobby, it may seem strange that there are a variety of turntables available for purchase, and the only features is to rotate the record at a constant speed and to provide the option of mounting different tonearms. I know three different drive methods to spin the platter: belt drive, rim drive, direct drive. For decades I have always used belt drives units. The belt provides a very good isolation to motor noise but it’s own flexibility is a problem when it comes to speed stability and dynamics and the belt needs to be replaced regularly. So already a while ago I decided to replace my belt drive turntable with a direct drive. I had also decided that it would be my “last” turntable. I know what some people are thinking now and I have to admit that they might be right. You tell this yourself as justification and in the end things turn out differently…

From a technical point of view, Technics has always had a very good reputation when it comes to direct drive turntables. After withdrawing their products from market in the 80’s  there was a revival of various new direct drive turntables a few years ago. If you want to build your own turntable without a Technics plinth and tonearm, the only option left is the SP10R. This is the designated successor to the legendary SP10MK2 and SP10MK3.  Technics also offer a complete high end product with aluminium plinth and tonearm and the option for additional tonearm bases: the SL-1000R. I like the design very much with the satin polished look of the aluminium plinth and the way how the additional tonearm bases can be mounted to the plinth. Anyway, while searching for a suitable plinth for the SP10R, I came across with Lee’s homepage Acoustand Audio (https://www.acoustand.co.uk/). But since I usually use 12″ tonearms, the size of the offered standard plinth unfortunately did not fit for my intended project. It was too small to carry three 12″ tonearms. So essentially a larger size was needed. To my very positive surprise, Lee listened to my wishes and invested the time to changed the design and the result was the XL plinth according to my wishes. At this point, a big thank you again to Lee, who supported me with my project. Finally, we ended up with this basic sketch:

For me the big advantage of Lee’s design over Technics’s is that the tonearm bases can be easily exchanged without removing the drive unit from the plinth. That would actually have been a no-go for me with the original Technics design. I can still remember exactly when the finished plinth arrived some months later. Perfectly packaged in a specially made sturdy wooden box. If the drive ever needs to travel again, I have the perfect transport box. Here are the first impressions after unboxing. When dealing with aluminum it is always advisable to have a pair of gloves ready.

Lee even developed a special grinding technique to imitate the original look of the plinth. I can tell you that pictures in no way reflect the manufacturing quality of this plinth and the precision with which it was milled. I am deeply impressed by the dedication with which Lee manufactures his products. Pay attention to the details, because even the additional bases I ordered were integrated into the grinding process. Finally, some initial impressions with the mounted Technics SP10R and the Reed 2G tonearm:

I bought the Reed 2G together with a previous turntable and think that it is a fantastic performer so it was set for my “final” setup. At this point, I will go back to what I wrote at the very beginning. Ergonomically speaking, the park position of the Reed 2G as the result using the original mount template bothered me a little in this setup. I asked myself whether the tonearm could be rotated slightly outwards so that I don’t have cross the tonearm tube with my right hand to place a record on the platter. But this tonearm has a magnetic anti-skating and its construction plans cannot be described in a simple way when you study the manual. The center of the tonearm bearing is offset to the mounting base which makes things very complicated, In any case, using the provided factory template resulted in the park position shown. So I contact the manufacturer and the sales representee with this question. Essentially, it was apparent that the pivoting range of the armtube and the respective distance between the magnet screw to the two magnets in the tonearm base would be important for answering the question. The feedback was rather disappointing because I had the feeling that they didn’t even want to deal with my question. I have to admit that it was certainly not an ordinary request but with the knowledge of the manufacturer, more could have been said easily about it. So how do you get rid of the customer? We know the answer: that doesn’t work! Use the included assembly template.

Most people would just accept it like that, but unfortunately that doesn’t work for me because I had already thought too much about it and thought that it must be possible. Since I am generally interested in mathematical technical challenges related to my hobby, I started to develop the mathematics for magnetic antiskating in combination with the tonearm geometry and implemented it in Excel using VBA. Anyway, Originally, I intended to develop a program that could automatically calculate the drill positions for the holes for different tonearm bases in order to simply transfer the output to the CAD file. The result then became significantly more complicated than originally planned.

Reed offer three different armtube lengths from 9.5″ to 12″ for this tonearm. I strongly assume that the magnetic construction is the same for the product line. So I simply studied the assembly instructions for the 9.5″ tonearm and especially the mounting template. The smallest armtube must have a swivel range of 52 degrees from park position to center of platter spindle. This fits in very well with the rotational distance between the two magnets in the tonearm bearing base. It should be noted that one magnet in the base attracts the magnet screw and the other acts repulsive. The reason is that the resulting force must be an inertia to the tonearm rotational axes. But again, with 52 degree swivel range for the 9.5″ armtube, you can fully swivel from the park position to the middle of the platter spindle. Well, but the 12″ version requires a lot less pivoting range to do the same job (only 40 degrees). And this is basically the answer to my initial question. You can rotate the park position of the 12″ armtube further outwards away from the platter, precisely by exactly 12 degrees, and you still reach the middle of the platter spindle! And 12 degrees is a lot and, above all, to be seen in a completely different light than: that’s not possible! But let’s take a closer look. This is the park position of the 12″ version using the factory template:

The following picture demonstrates the resulting magnetic forces with the magnetic screw set to a distinct distance. The absolute numbers do not have any meaning here but the sum of the two magnetic forces as black curve is very enlightening:

First off, it becomes apparent why two magnets must be used in the tonearm base.  Only the sum of the two single forces can become linear. But there is only a distinct region where the resulting magnetic force is almost constant / linear. Both magnets in the base have the same force in this demonstration. I know that antiskating should become lower towards the label of the LP. So I assume that magnets with different strengths are used like this:

But the message is that we need to stay within the linear region. Starting at about 10 degrees and ending around 40 degrees. The first non-linear region is no issue because the way from park position the groove will do the job and skip the non-linear region:

And the second non-linear region at end is not relevant because of the defined standard IEC end position of the groove. Besides this, antiskating is no more that relevant when we approach the platter spindle:

Finally, I will rotate the factory arrangement to the full 52 degrees, and it should become apparent what is possible. We fix the tonearm arrangement and rotate it counterclockwise until the affective armtube is crossing the middle of the platter spindle:

Mission accomplished. This is the maximum amount of rotation for a different park position:

It is a good idea to stay away from the extremes, and I finally select a range of 6-9 degrees out-rotation. I am very happy with the result and I have learned a lot about antiskating during this study.

It is simply a pleasure to listen to this setup and it is perfect to evaluate the sound character of different MC cartridges. What I like is the ease of use of the SP10R. Not belt tension issues, not worn belts, speed stability within a few seconds, the internal breaks to stop the platter in about the same short time period, 33/45/78 rpm and 5 different torque settings are essential properties for me. So it’s very likely that it’s actually my final turntable 😉