LP12MF: Installing the Mober DC Motor Kit

Welcome to the latest installment in my LP12 Modification Frenzy series. This time, I install Mober’s DC motor and power supply.

I’ve had my share of troubles with motors and power supplies over the years. When I bought my LP12 way back in 2005, it had a wonky Valhalla power supply, and so the music would randomly speed up and slow down, making everything sound a track from My Bloody Valentine’s Loveless. Eventually I came across Edmund Chan’s Mose/Hercules II system, which has served me well for over a decade. When I “upgraded” to a Linn Lingo 4, I unfortunately ended up with a dud unit with a noisy motor.

Before the experience with the Lingo 4, I’d always struggled a bit to see what all the excitement was about with power supplies. The job of turning the platter at 33.3 or 45rpm didn’t seem that complicated, and I wondered whether I’d even be able to hear the difference between 33.3 and 33.4 anyway. But the Lingo 4 taught me that speed control is only one part of it; the other, major part is how much noise the motor introduces into the system. Given all the microscopic activity and minute voltages involved in vinyl reproduction, any little bit of noise gets picked up by the cartridge and makes things sound noticeably worse. Indeed, after the recent problems I had getting my Dynavector XX-2 cartridge to sound good, I wondered if really good cartridges were also really good at picking up motor noise…

Enter the Mober DC Unit

I’ve already reviewed a bunch of products by Edmund Chan so far on this site: two of his Mober subchassis (for Rega arms and Linn arms) and his SSP12 subplatter. I’ve been using his Mose/Hercules II power supply for every test to this point but one. I have one of his bearings in my basement, ready to be reviewed in the future. I’m a fan of his products, which I find reasonably priced and great-sounding. It doesn’t hurt that he has in turn become a fan of this website and is the first person on the planet to have sent me review copies. (I bought the Mose/Hercules II and the Rega subchassis with my own money; the SSP12, Linn subchassis, bearing, and this DC unit are review units.)

The thinking behind the DC unit is not dissimilar to the thinking behind the Mober subchassis: take something very expensive that Linn makes, come up with your own design, arrange the manufacturing yourself, sell directly via eBay, and sell it for a lot less.

I’ve never tried a Keel, but the Mober subchassis is a similar design, without being a clone. I’ve never tried a Radikal DC power system, but the Mober DC kit is similar without being identical.

Like the Radikal, the Mober uses a Swiss-made Maxon DC motor. According to the eBay product page for the Mober DC unit, the appeal of DC over AC motor is noise. DC motors are much quieter than AC motors; the challenge is keeping them running at a consistent speed, since they’re very sensitive to slight changes in the voltage provided to them.

Edmund’s method of doing this is similar, but not identical, to Linn’s Radikal system. The Radikal uses an optical tachometer attached to the top plate which monitors the movement of a single felt marker attached to the underside of the outer platter, and feeds this information back to a control box which responds with changes in voltage to the motor based on the current speed, compensating when deviations are detected. Edmund’s Mober box does all that, but monitors 16 markers rather than one (see photo above). According to him, this means it’s much more capable of responding quickly to deviations from true speed.

Installation Process

I’ve been waiting to get my hands on one of these for months. Back in January, Edmund was planning on sending me one, but the Covid shutdown in China meant that the factory where they’re produced went off line. When they started up earlier this month, Hong Kong Post stopped shipping airmail to Canada. Finally, we sorted out a FedEx shipment. It arrived last week along with the Linn-cut subchassis. I decided to install the subchassis first, given the problems I was having with the Kore it replaced. That done, it was time to get the DC unit in.

Motor systems are relatively easy to install, since you don’t need to remove the tonearm, subchassis, or anything else to get them in. You don’t even need to turn the deck upside down, which is nice, given bearing oil’s penchant for leaking out. Heck, I didn’t even have to remove the subplatter. (Note the little pieces of cardboard I put under the subchassis whenever I move the deck, to keep the bearing safe from shocks. That’s a tip I picked up from Gary Dilliott.)

Unlike the Lingo 4, which came with a massive and very detailed set of instructions, Edmund’s Mober has 5 pages of relatively vague instructions. Just to be sure I was doing the right things, I reread the sections of Peter Swain’s LP12 setup manual about the Radikal. Even those instructions are pretty brief. It’s really not a very complicated job. You take out the old motor, put in the new one, install the tachometer, get everything wired up, and “dress” the wires so nothing’s knocking against anything else.

I had experience fitting tachometers with the Lingo 4, and knew it would be a bit of a pain with the Tiger Paw Khan top plate, with its cool but inconvenient ridges. I was prepared this time, anyway. I borrowed a spacer from the outgoing Airpax motor’s mounting screws; it was exactly the right height to hold the tachometer level. I did need to shorten a bolt to the exact right length with a hacksaw and file, but that’s a skill I possess from my bicycle framebuilding days. Also bicycle-related, I put a bit of cotton handlebar tape under the tachometer body to stop it from potentially rattling against the top plate. You can see a piece beside the tachometer in the photo above.

Here it is all set up with the tachometer wires routed. I didn’t get a photo of the underside of the table showing the motor orientation or the cable dressing, because I didn’t want to flip the deck unless I had to. I’ll grab a photo next time I’ve got it upside down. Suffice it to say it was really easy and intuitive to get all this set up. While minimal, Edmund’s manual is probably sufficient for anyone with a bit of experience working with an LP12.

A little metal badge comes with the kit to conceal the now-redundant power switch hole. It was actually much harder to fit than any other part of the kit: very tricky to get it through the hole and tighten it up (it was tricky mostly because the Khan has an extra mounting screw that gets in the way). I must say, I’m not very fond of the look of it. I have no issue with the letter M — my partner’s name begins with it, and there are three of them in my full name — but this seems clunky, overly large, and not very well finished. I’ll have to look out for one of those cool Naim Armageddon switch covers, especially if I end up with an Aro.

Here’s a somewhat more artistic shot of the top-side view of the Mober DC kit equipment — and their cousin, the SSP12 subplatter.

As I said, installation was very simple. Start to finish, it took me under an hour.

A few updates

I’m writing this section two weeks after initial installation, and I’ve made a few little tweaks.

I was hearing an very faint “swish-swish” sound from the motor, and wanted to investigate whether it was something with the way I’d set it up. It turns out that it was. The tachometer sensor sits on a brass bracket, the “toe” of which connects to one of the threaded holes previously used for speed adjustment screws. This toe portion sat quite close to the motor, which required me to mount the motor slightly off-centre in the round cut-out in the top plate. The motor is mounted to the underside of the top plate with two compliant bushings, so I wondered if under load it was bending slightly and rubbing against either the cutout of the brass “foot.”

I solved this problem by filing material away from the brass foot (indicated by the green arrow), which allowed me to get the motor dead-centre in the cutout. I also removed the compliant bushings so that the motor is attached directly against the top plate and can’t lean in operation. With these changes made, the “swish swish” is gone.

Having listened to the Mober for several weeks now, I can say that while it is not absolutely silent in operation, it is much quieter than any other motor I’ve used. With my ear pressed against the closed LP12 lid and the motor spinning at 45rpm, I can hear a faint whir. A foot from the deck under normal circumstances, I can hear this if I absolutely strain. Two feet away, I can’t hear anything.

Note the above tweaks may be specific to installing the Mober tachometer on the Tiger Paw Kahn top plate, with its inconvenient ridges. Every other top plate I know of has a smooth surface here.

The Mober DC unit in action

I’ve made a short video to show you how the Mober Unit works. I’d heard that it’s slow to get up to speed and that the motors can be noisy. That’s definitely not the case with mine, as this video shows. The motor gets up to speed quickly, and it’s very quiet. Also clear from this video: the photos on the Mober eBay listing don’t to justice to the very well-finished and stylish control box.

There’s a bit of hum in the background of the video — that’s just my refrigerator, which is right behind the camera. Also, the inclusion of The Pits of Hell at the top of that stack of books is in no way a reflection of how I feel about the Mober DC kit!

One small note on the above video. In the manual, Edmund says that once the screen goes off, if you want to double-check the current speed, press the opposite button to the one the platter’s currently spinning at — so, hit 45 if you’re at 33.3. In the video, I mention this, and show how it works, hitting 33 while the platter’s spinning at 45. But if you look carefully, you’ll see that the speed actually wobbles when I do so: it drops, then speeds back up. I thought this might be a blip, but it’s happened again while listening to music. I asked Edmund about it, and he said that pressing the button actually jars the CPU mechanism. The solution is to turn the trim pots (the 0.1 pots on the right) rather than the 33/45 buttons if you want to check current speed. It’s also a reminder to be gentle with those buttons.

If you want a closer look at the setup I had in place for that video shoot, here it is:

The Mober DC unit in context

I’ve now got the Mober DC unit all set up in my office. Here are a few photos to show you what it looks like. As I said, I think it’s pretty cool looking. And I like that the control unit is compact and fits on my small shelves. I don’t know where I’d put a Radikal, even if I could afford one…

First impressions

I’ve been listening to my system a lot lately, and doing a lot of “critical listening,” trying to figure out why the Ekos/XX-2 combination didn’t sound better than it did, and if swapping out the Kore would improve the situation. I don’t want to jump to conclusions, but it does seem worth recording some initial impressions on the Mober DC unit, which seems to have made a large positive difference.

When I brought the table it back to my office, I could see the bounce had changed a bit and the suspension needed some work — probably caused by my changing the belt while putting in the Mober DC motor, which is enough to throw off the bounce. But I was tired after a long day and decided to put off fixing it until the next morning, and listened to a few records.

First, was Sun Ra, Heliocentric Worlds vol 1. Then Prince Lasha, The Cry!, King pressing, then Graham Coxon’s, The Spinning Top. I noted:

Every single one of them sounds stunning. Strong sense that these are all much better than I’ve heard any of them before — and each of them is a really nice-sounding record. I’m listening to The Spinning Top right now, and it’s just gorgeously springy, bright, lively. I’m hearing details I’ve never heard before. The impression is not of the “noise floor” being lowered — is of it just sounding BETTER: crisper, better-focused, huge, wide, engaging, engrossing. Immense sense of excitement coming from this setup, no question.

Next I put on the Music Matters pressing of Andrew Hill’s Point of Departure. I noted:

Stunning, amazing, like never before. The reed instruments are absolutely gorgeously textured and stunningly present, as are Anthony Williams’s drums. Also, I don’t need to turn it up loud to get the gorgeous sounds. Amazing.

Then I put on my newly acquired red vinyl copy of Stephen Malkmus’s Traditional Techniques, great music but a middling-sounding disc. It also definitely sounded better than ever. So the setup appeared to be making all discs sound better, the perfectly produced and the merely okay.

And all of that was with the suspension set slightly incorrectly and a non-pistonic bounce.

Today, I took the deck downstairs and fixed the suspension and made the above video. I’ve written this post while listening to my first Canadian pressing of Roxy Music’s Avalon, a US first pressing of Can’s Future Days, my OJC pressing of Mal Waldron’s The Quest, and the Giles Martin Sgt. Pepper. All of them have sounded superb — exciting and notably, attention-grabbingly excellent. I think the main difference is a kind of laser focus that brings every instrument into beautiful relief.

We’ll see if my enthusiasm holds, and how my test tracks fare. I’ll give myself a few weeks to get used to the sound of the Mober DC kit before giving my final verdict. But for now, this seems like a really exciting upgrade — one of the best yet. And one that may finally be allowing me to hear how good previous upgrades sound, such as the XX-2.

Time to listen to some more records…