Technics SL-10 Turntable

An image of the SL-10 taken from Technics' archive

Chasing a better experience with vinyl can be a nigh endless tumble down the rabbit hole if you let it.  Although I've been collecting vinyl itself since the late nineties, I didn't buy my first turntable until 2013, and I really had very little idea what I was doing.  For example, I went out of my way to get a deck that would support 78 RPM because I didn't realize that even in the unlikely event I ever came across a 78 RPM disc I still wouldn't be able to play it with a simple flick of a switch.

One of the first things you learn about setting up your your first turntable is cartridge alignment.  When installing the cartridge, it is necessary to adjust the angle of the stylus relative to the tonearm so that as it rides in the record groove, it rides as straight as possible.  In the process of doing this I learned that it's not possible to actually keep the stylus straight the whole way through the record - at least not on a traditional turntable.

In a traditional turntable, the tonearm pivots which means that as the stylus travels across the radius of the disc, it does so in an arc which means that the tip of the stylus pivots as well and can not always be perpendicular to the groove. In other words the stylus will only be at the correct angle for a portion of the record playback, not all of it.  There are different approaches to alignment which all seek to maximize the window of accurate tracking, but they're all compromises.

When I learned about this, I thought "Well, why don't they just make a tonearm that moves the stylus in a straight line across the radius of the record?"  The answer is, of course, they DID - it's called a "linear tracking turntable".

A linear-tracking tonearm moves the stylus in a straight line across the radius of the record while playing so the stylus is always perpendicular to the groove.  Since the lathe that is used to cut the groove into the original masters also uses linear tracking this means that in technical terms, linear tracking is the most accurate method of playback.

That is not to say that linear tracking is not without its own problems.  The arm has to move across a shaft or bar which increases the frictional surface area, and it has to be moved by some kind of motive force.  The mechanism used to move the tonearm is considerably more prone to unwanted vibrations than a pivoting tonearm.  These extra vibrations could theoretically affect the sound.  Personally I've not been able to detect them - but by the same token I've never been able to hear the distortion from a pivoting tonearm not being perpendicular to the groove either.

The complexity of engineering and producing a good linear tracking system and the relatively in-discernible benefit from it means that we'll probably never see a modern turntable employ this approach again.  Unless your turntable budget is in the 10's of thousands of dollars, your only option for getting a linear tracking turntable is to find an old one that still works. 

I've had my eye on a Technics SL-10 for a little over a year now - I believe it was the first image I saw when putting the term "linear tracking turntable" into Ebay, and after looking at a dozen or so other units I kept coming back to the SL-10. 

There is a really wide price range for these which seems to be based more on opportunism than condition.  That is to say that I've seen these in perfect condition sold for about $300, and others with the chrome worn off the buttons and covered in deep scratches or broken clamps going for $600 to $700.  And of course there are the handful of wishful thinkers on Ebay trying to hawk them for upwards of $1100 (as far as I can tell, no one has ever actually sold one for so much).

In the lead-up to my purchase I learned a good deal about what defects to look out for and what the most desirable elements are.

On the topic of defects:

• The rubber in the feet of the decks has been known to deteriorate
• The lid clasps have a tendency to break

As for completeness, the SL-10 originally shipped with a specially designed AV cable with a custom-shaped plug which incorporated chassis ground as part of the socket.  It's not a huge deal, but definitely more desirable to have the original accessory.

Next, and probably the biggest thing to look out for is the cartridge.  The SL-10 originally shipped with a Technics EPS-310MC cartridge.  The "MC" portion of the name refers to a "moving coil".

EPS-310MC "nude diamond" stylus.

All phonograph cartridges work on the principle that motion between a magnet and a copper coil produces an electrical current which is equivalent to the motion - the physical vibration becomes an electrical signal.

The difference between the "MM" (or "Moving Magnet") and MC cartridges is which element is attached to the stylus/cantilever.  In the case of the MC cartridges, the stylus/cantilever moves the coil and the magnets are stationary.  Evidently the MC cartridges are harder to make, but produce cleaner sound with less distortion - at least that's what I've read.  If I had to guess why, I'd say it's because the coil isn't as dense and therefore not subject to as much inertia as the magnet.

Inertia is a big deal because it can exaggerate the motion of the stylus - and remember the motion of the stylus is what reproduces the original sound.  Ideally the cantilever should only move exactly in the shape of the groove without any motion added or missing.  To that end the most desirable styli are those with the lowest "moving mass".

EPS-310MC hollow boron cantilever.
You can also see the moving coils in the background.

Finally there's the additional factor of harmonic resonance.  I'm not terribly well-studied on the topic, but the gist of it is that each material has a resonant frequency - that is to say that if the material is vibrated at that frequency by an outside force it will tend to continue vibrating by itself after the outside force ceases to be applied.  This is the basic principle of a tuning fork.  It will also produce distortions in the playback of a phonograph record.  Some of the more inexpensive cantilevers use aluminum which can, supposedly, create distortions in the high end of the human audible frequency range because of its resonant frequency.

The EPS-310MC cartridge uses a hollow boron cantilever and boasts the lowest moving mass of any cantilever ever made.  Boron is a very rigid material with a resonant frequency well outside of human hearing. For that reason it is still used in high-end cantilevers today. Boron is already very light on its own, but Technics further reduced the mass of the cantilever on the 310MC by making it hollow.  They did this by some proprietary crystal-growing process which no one has ever duplicated and they stopped manufacturing their own cartridges not long after.

From my own personal experience I can definitely detect a little more detail with the 310MC than with my Shure 97x on my traditional turntable, but not much, and I couldn't guarantee that the difference wasn't because of some other factor.  I'm not an audiophile and I don't really go in for debates over subjective minutiae like "warmth", but I have enough of an ear to hear the clarity and detail of a quality recording played back on a quality turntable. Regardless of how much better it is, the desirability of the EPS-310MC cartridge accounts for as much as half of the value of the SL-10.  In other words, don't pay full price for one that doesn't come with the 310MC.

One of the coolest things about the SL-10 is that it doesn't rely on gravity for its tracking force.  The tracking force is controlled by an electromagnet that moves the tonearm down and measures resistance to keep the force consistent.  The upshot of this is that the player doesn't have to be horizontal to play - in fact it can be played in a completely vertical orientation or even upside-down if you are crazy enough to attempt it.  Because of this Technics released an optional set of feet for the player that allow you to prop it up at an angle.  Unfortunately the feet are somewhat uncommon and Ebay sellers seem to expect to get somewhere in the neighborhood of $300 for them.  However thanks to a forum post I stumbled across when looking up information, I was able to purchase a very good substitute for considerably less.

This laptop stand is sturdy, durable, exactly the right size and even matches the turntable's color and brushed aluminum look:

When my player first arrived, I unpacked it, set it up, inspected it and then tried to play a couple of records.  It would get about 3/4 of the way through the record and start skipping.  One touch of the tonearm rail told me what the problem was - the 40 year old grease had gone sticky and the tonearm was getting stuck.  I had to disassemble the underside of the lid, clean off the old grease and freshen it with some modern lithium grease.  There is one tricky part when taking the lid apart so if you have to do this, make sure to watch it done a couple times on YouTube before trying it yourself.  While I had the lid off, I noticed that the drive belt had hardened a little and replaced it.  Turns out this takes the exact same drive belt as the Sega CD Model 1 which you can buy very inexpensively from Console5. Since that this turntable has been smooth as butter.

What a difference being automatic makes!  In addition to being a linear tracking turntable, the SL-10 is about as fully automatic is it can be.  Living in the age of digitally distributed music, smartphones and bluetooth it may not seem impressive to have a music playing device that "just works", but if you've invested any serious time or effort into vinyl, you probably know it's normal for the process to be a little involved.  Setting up the player for the first time usually involves the afore-mentioned alignment as well as tracking force, anti-skating force, and leveling the turntable itself.  With this turntable all of those factors are either unnecessary or handled automatically.  It's essentially the same level of convenience of playing a CD.  Just put a disc of any size onto the platter, close the lid and push "Start".  The player even automatically mutes the first second of playback to silence the "pop" of the stylus making contact with the record for the first time.

Most of the automatic turntables I've seen use little mechanical sensors which push up through holes in the platter to detect disc size.  The SL-10 uses LEDs and photo sensors.  While this is really cool tech - especially for 1979 when this turntable had its debut, it does present a challenge when trying to play transparent vinyl.  I wound up having to cover up the photo sensors on the underside of the lid with a strip of electrical tape - otherwise the led light would pass through the record and tell the photo sensor that the platter was empty.

If you can find one in decent shape I can't recommend this turntable enough.  When I first got seriously involved in collecting and listening to vinyl the manual process was fun, but now that I've been doing it for a few years, sometimes I just want to pop a record on and listen to it without the associated hassle, and this turntable lets me do just that.