Product name: SAT Carbon Fibre arm
Producer: Swedish Analogue Technologies - Sweden
Cost : 11,200 Euro (Currency conversion)
Reviewer: Geoff Husband - TNT France
Published: December, 2013
It seems that far from being dead the vinyl world is in rude health; one sign of that is the increasing number of turntables and arms coming onto the market, both from established and new set-up companies. In what is becoming an increasingly crowded marketplace a new arm needs to stand out in some way and/or be keenly priced. Here we have a new arm, from a new company that aims at the top end of the market where stratospheric pricing seems to come with wierd and wonderful engineering - much of which, I confess, looks decidedly dodgy to me... When I first saw the pictures I was impressed – here seemed to be an arm following sound engineering principles. The problem was that it wasn't really anything new – to me it looked very much like a pumped up Zeta or Mission Mechanic with very bulky armtube and bearing rings and a much steeper price tag. But as I looked into the arm and conversed with its designer – Marc Gomez of Swedish Analogue Technologies (hence SAT for the arm) – I began to realize that that belying its appearance, here was an arm that was very different from the ordinary and which brought a new combination of both construction and materials to the marketplace. From being something that was a bit 'ho-hum – another expensive arm' it became something I was very keen to listen to at home.
A little background - Marc Gomez isn't a typical enthusiast launching his pet arm, but a structural engineer who's specialized in high-tech fields such as automotive and aerospace components and in particular composite designs. It's this knowledge, and bundles of enthusiasm that he brings to the SAT arm, because the first interesting thing about it is that almost all the structure is made from Carbon Fibre...
Over the years many materials have been used for arm-tubes – Steel, Aluminium, Magnesium, , Titanium, Acrylic, Wood, Bamboo – it seems that as long as you can get it long and thin someone will use it.
The parameters for a good material are stiffness (to resist the cartridge moving), light weight (to give a reasonable Effective Mass), lack of 'ringing', consistency (the problem with living materials like wood) and of course sheer practicality and cost.
The go-to material for many years has been Aluminium. It's fairly light, stiff and tubes are available off-the-shelf in every conceivable diameter and thickness. That makes it ideal for the short-run specialist arm manufacturers as they can just choose a tube – the sort of thing tent poles are made of for example – and voila! A major part of the arm is sorted (I've even considered it myself:-)
But of late the material of choice has shifted to Carbon-Fibre (CF) with similar off-the-shelf tubes available. CF is just such a sexy material – F1 car chassis, 'Dreamliner' wings, Helicopter-rotors, high-end bikes, even designer coffee-tables. In fact it's so sexy that people are sticking fake vinyl wrap on everything from telephones to car interiors to coffee mugs – to be honest it's so ubiquitous there is a danger of it becoming rather passe...
CF is a composite – it's essentially a plastic resin with thin strands of pure carbon fibres in it. It's little different in concept to the glass fibre we've seen for years. But CF is a whole order of magnitude more effective than glass-fibre because those Carbon strands are very stiff and give the composite that we commonly call 'Carbon-Fibre' properties well beyond those of glass-fibre.
I guess everyone knows that CF is very stiff for a given weight, but it's a little more complex than that, and it's here that the SAT gets rather more interesting than just another arm with a carbon fibre tube.
CF, unlike a homogeneous material like Aluminium, doesn't have a fixed set of properties. Those properties are defined by the resin used and more importantly the number and configuration of the Carbon Fibre strands, because the stiffness and (very high) strength depends on the alignment of the fibres in the material. In this respect CF mimics natural materials like wood. The 'grain' of the wood is dictated by the alignment of the wood fibres. Any plank will be cut with the grain along the length of the plank to produce a very rigid and strong structure under bending loads. But give that plank a tap with an axe along its length and the plank will split with ease. The structure is very strong and rigid in one direction and weak in another because of the alignment of those fibres. In chipboard – which is essentially a wood based artificial composite - the fibres of wood are short and arranged in a random pattern. The result is a sheet resistant to splitting, but which can be broken apart fairly easily. A piece of plywood on the other-hand (another composite) has layers of wood glued together in such a way that the much longer fibres of one layer run (naturally) in one direction and the next layer is at 90 degrees giving a much stiffer and stronger material.
Going one step further we can look at our own skeleton. Bone is pretty much the same all over our bodies as far as composition is concerned, but because a leg bone (like a femur) has to be very resistant to bending the strengthening fibres are aligned along its length. A vertebra on the other hand has to be strong in compression and so the fibres run in many directions to hold what is essentially a block of bone together.
And that is how Carbon Fibre works. That pretty woven pattern we are all used to seeing in CF is a general use matting, designed to produce sheets of material with good general properties in all directions. The same pattern that you'll see in CF tubes making up the vast majority of CF armtubes. Such a tube is equally resistant to bending and twisting and in such a configuration a CF tube is about 15% more rigid (and considerably stronger) than an Aluminium tube of identical proportions and thickness. Not only does that rigidity help, but the lighter tube also means you've a saving on effective mass that might usefully be employed elsewhere (a more rigid* headshell for example). The fact that such tubes are almost as cheap as Aluminium means 'why not'?
Because not all CF is equal. To really exploit CF's unique properties you need to get away from mass produced tubes and rethink what you really want from an armtube. What if you forgot about just trying to find a slightly sexier replacement for Aluminium tube and start from scratch?
In a perfect world an armtube should be infinitely rigid, carry vibrations away from the cartridge and give a reasonable Effective Mass (EM).
That last point is important. The days when everyone thought the aim was an arm of vanishingly low EM are long gone. Nowadays quality arms are of medium to high EM and high-end cartridges are almost exclusively designed with lowish compliance to match them. A designer producing a wonder-arm in CF with a 2 grm EM isn't going to find a cartridge to match. So an arm NEEDS mass.
Remember that generic CF tube that was 15% more rigid than the same dimensioned Aluminium tube? Well it'll also be between ½ and 2/3 the weight. So why not make the tube the same weight as the Aluminium tube and thus reap the rewards of an armtube maybe 2-3 times as rigid.
But then some top arms aren't straight tubes at all. Arms like the Rega, top SME's, various Kuzma and the like are tapered and the best have variable wall thickness to maximise rigidity where it's needed most and where it won't raise EM too much – the SME V's cast Magnesium armtube being a fine example. And yes, you can do the same with CF, but by now we're getting a long way from the cheap generic tube and into the sort of multi-layered, complex shapes that make the CF used in F1 car suspension systems fabulously rigid, but also very expensive.
By hand laying layers of CF fibres, one on top of another, each layer having the fibres aligned precisely in directions to maximize the resistance to the forces going through the arm (using CAD design techniques), and varying the thickness of the CF composite through the tube you can end up with a complex structure that hardly deserves the description 'tube'. In the case of the SAT there are no fewer that 20 layers of fibre/resin hand-laid and then autoclaved – the resulting structure is unbroken from headshell to the tip of the counterweight stub. On the review arm the headshell is detachable (though a fixed headshell is optional – more on this later) and made of 40 layers of CF.
The result? One measure of an armtubes overall rigidity is the frequency that it resonates when excited by a signal (as a cartridge would do). In the past two arms I'm aware of have claimed very high first resonance – the SME V and Roksan Artemis with 1.3 and 1.4 kHz respectively - some arms coming in at under 500 Hz. The SAT claims a first resonance at 2.8 kHz which is a sensational result. I've not seen the claimed results for every arm in the world but I doubt if this figure is bettered anywhere... The manufacturer claims the arm is 5 times as rigid as an Aluminium equivalent and having done the math I'm quite happy to have this as a minimum figure...
Clearly the SAT is made of a lot of CF – in bulk if you like;-) Unlike almost all the CF arms on the market which use a single layer (there are some very cheap CF arms now available) here the designer has used as much CF as he possibly can to get the most rigid structure possible whilst not getting too high an EM. Even now the cartridge/arm resonance of 8Hz with the DRT-1 is at the lower end of acceptable (and the same as the V-12), despite a big counterweight which sitting so close to the pivot will lower EM.
Here I'm speculating, but with good reason... First the carbon fibres have their dominant direction of alignment along the armtube. I remember Pierre Lurne claiming that because his Septum armtube was machined from a drawn billet, that the crystal structure of the Aluminium was aligned down the armtube and this helped transmission of vibrations away from the cartridge. If that is the case then I would imagine that the same applied to the SAT armtube.
Also by using a lot of CF the arm has a bigger volume of material for vibrations from the cartridge to be damped. Thin CF can be pretty noisy (listen to a bicycle with CF rims rattle past for an example) so I'd expect this to be a significant advantage.
Beyond the armtube this philosophy continues with the other CF components most noticeably the bearing housings which are visibly more massive than any other arm I've seen and likewise made of many, many layers of CF.
On some of the photos here I've used flash – the result is that the layers are clearly visible – in 'normal' light the finish is much more 'stealth' and indeed I'd expect the production arms to be even better in this respect – it's not an easy arm to photograph as it absorbs most of the light...
As tested the SAT came with an adjustable headshell – note - not 'removable' (more on this later).
Look at the pictures – it's very thick and made of many layers of CF as mentioned above. It's nearly twice as thick as the integral Magnesium headshell of the SME V. As the mass of CF is very much the same as Magnesium and yet over 5 times as stiff (and with this quality I'd expect that to be the figure) you're looking at a headshell 10x as rigid as the SME, and as stated before the SME has long been a benchmark... That's phenomenal – or is it overkill? - we'll see...
The headshell is connected to the armtube with an Allen bolted clamp – it's a very strong and solid connection and that is important for two reasons.
Firstly it's no good if you spend a great deal of time and effort on making a super-rigid armtube if there's a wobbly headshell connection – apart from the lack of structural integrity there's the question of noise caused by any movement even at a microscopic level.
Secondly there's the question of the transmission of vibrations within the arm. One reason for a one-piece arm/headshell is that vibrations produced in the cartridge have an uninterrupted path away and into the much more bulky arm where they can better be dissipated rather than interfering with the cartridge. Eventually some of those vibrations will pass into the counterweight and turntable itself – but only if they escape the headshell.
Every material has an Acoustic Impedance (AI) – a function of their internal speed of sound, their density and elasticity. When vibration tries to pass between two structures of different Acoustic Impedance some part of the vibration will be reflected back at the join. If the AI is identical then in theory vibrations will pass unhindered between the two. So headshell and armtube should be of the same material. However in practice no joint is perfect and wherever there is a gap 100% of the vibrations will be reflected back – so any joint will reduce the transmission of vibrations away from the headshell.
These two factors mean that any separate headshell is a compromise. In the case of the SAT the compromise is minimised by the very solid fixing with its large contact area and by the use of a flexible 'filler' between armtube and headshell which eliminated the voids such a design would otherwise have. The 'filler' is chosen to have a similar AI as the CF – it's difficult to fit which is why the headshell isn't removable.
But no matter how well the SAT's headshell is implimented it will still hold a theoretical disadvantage over a solid one-piece design. So why would any one choose this?
The answer is simple... Even high-end cartridges can have their styli misaligned by a degree or so. Being able to twist the headshell allows you to correct for this and unlike minor VTA adjustments minor Azimuth misalignment can be measured – so that perfect Azimuth can be achieved both by measurement or by ear. So that is the dilemma. Which has the biggest effect on sound quality – a small misalignment in Azimuth or the compromise of a two-piece arm/headshell?
I have no idea, but at least with the SAT you have a choice because is is available as a one-piece or adjustable headshell version. If you are the kind of person that wants to swap quickly between several cartridges then you can even have a version which omits the 'filler' between headshell and armtube to enable a completely detachable headshell – your choice, I can't think of another manufacturer that offers the same**.
The arm is a conventional 9” arm and anyone who has read my arm articles will see that Marc follows very similar engineering principles to Pierre Lurne – the arm being close to a 'Perfect-Mass' - symmetrical around the stylus/pivot axis – meaning that the cartridge will tend to move in any direction with equal ease. The principle is that this doesn't introduce parasitic movements into the arm once excited – the arm will deflect in a straight line and return in a straight line – it shouldn't describe arcs and ovals and generally wobble about uncontrollably in response to an input such as a warp. The geometry also means the arm will be free of the VTF changes induced by warps that plague low-hung unipivots.
There are almost as many bearing designs used in arms as there are arms themselves. Of conventional arms there is a split between unipivots and gimballed arms. Many years ago, in the bad old days of the 'Flat-Earth' two companies dominated quality Hi-Fi in the UK (and elsewhere) – Naim Audio and Linn. The two firms shared a philosophy and split the 'high-end' with Naim making amps and Linn turntables/arms/cartridges and speakers. With both wanting to expand, a divorce was inevitable and an early tiff was in 1989 over the Linn ITTOK arm. Naim (allegedly) were unhappy with the Linn LP12, saying that it now limited their amplifiers, and so Julian Vereker of Naim went around shows and Linn/Naim dealers demonstrating his new arm – the ARO.
It was then, and only then that the majority of Hi-Fi enthusiasts first heard of 'bearing-chatter'... You see the 'point' (geddit) of the ARO was that it resurrected an arm construction long out of fashion – the unipivot.
The ITTOK was a beautifully made gimballed arm, and fairly conventional. In order to hold the arm in place and allow free vertical and horizontal movement it used four bearing races – ball bearings assemblies. These were very high quality, but Vereker's argument was that if you adjusted those bearings to take up all slack they possessed too much drag and their rotation as the arm moved generated noise as they rolled. If the bearings were left a little loose to avoid this then the bearings not under load would rattle or 'chatter' e.g those at the top of the bearing race. Thus setting up such an arm was a delicate compromise between having noisy, high-friction bearings and chattering ones – and that no adjustment would be anything other than a compromise between the two extremes.
In a true unipivot the whole arm is simply balanced in a point which rests in a cup of some kind. The point is very hard and there is obviously phenomenal pressure at the contact with the cup, little change of bearing chatter and very low friction – perfect - they also need no adjustment. The arm relies on its inertia to be 'still' at audible frequencies.
In Julian Verekers demonstration everyone was treated to the coarseness of the ITTOK in comparison to the ARO ( indeed the question 'Is The Tonearm OK' could be answered 'no!').
I'm always skeptical of manufacturers demonstrating the superiority of their product in public, but Naim did reopen the debate and from a position where few top arms were unipivots we come to the current position where they probably outnumber conventional gimballed arms, though that might be because they are easier for small companies to manufacture.
Gimballed arms as a breed are not universal in using annular bearing races (those press-in things you get on power tools, bikes, etc) as some will use variations with points nestling in 'nests' of ball-bearings and the like. In all such cases*** the same dilemma occurs. Bearings tight enough to avoid chatter, but free enough to avoid friction and noise (you'd call it 'rumble' in a turntable).
The SAT looks very much as if it falls into this conventional gimballed/ball bearing family, but it is very different. It's not unique, but it is certainly very unusual in that it doesn't use any ball-bearings in its construction. Rather it uses four very large Tungsten-Carbide points, each located in a sapphire 'cup'. You could think of it as four unipivots – two pairs of opposing pivots. You'll see this sort of bearing in quality 'jewelled' watch movements. In the SAT this is scaled up to form an extremely rigid bearing configuration which when properly adjusted should have no chatter and very low friction and noise. But if you want to opimise the contact the bearings are designed to be user adjusted.
Now here I took a step back. Marc has set the arm up specifically for the Dynavector DRT-1, with what he considered the ideal pre-loading. Though adjustment was simple and the required tool supplied with the arm, was I going to fiddle with it? No – it worked great just as it was and I was not going to get lost in an infinite number of settings that I'd almost inevitably screw up... But it is something that can be tweaked, and more importantly tell Marc what cartridge you are going to use and he will set the bearings to the required position.
If you look at the pictures you'll see that the arm pillar, base, and mounting board and beautifully machined from brass. This material also forms a ring around the Lead counterweight which makes it both prettier and more robust. The impression is that the SAT is designed to be massively rigid and to then use mass in its base as a sink for vibration. I am only speculating here, but I would expect such a design to handle a lot of the vibration control 'in-house' as it were – yes the turntable will have an influence, but I suspect that the arm may be less turntable sensitive than some. The caveat is that the combination is a pretty heavy arm – this isn't something you could drop onto an LP12, Orbe or similar suspended turntable – it needs a heavyweight suspended turntable, or more likely a solid plinth design on one sort or another. It worked brilliantly on the Blackbird and would certainly have been nearly as good on the Woodpecker so you don't need a $100,000 exotic to make it sing, though no doubt it wouldn't do any harm;-)
We've already talked about the Azimuth adjustment – adjustment of lateral cartridge alignment is done by the old method of just moving the cartridge in the headshell slots, helped by the excellent supplied template – then of course fine tuned by ear. Arm height is adjustable using a bolt running down to the base and a knurled locknut, but this mechanism is easily removed once arm height is set. Personally I much prefer this to complex and wobbly VTA 'towers' and the like. A similar bolt and lock-nut allows for fine tracking force adjustment, major changes being done by moving the counterweight itself (two are supplied). Lastly anti-skate is a fairly simple, but well implemented thread and weight, with the brass weight being supplemented with tiny brass washers – the addition or removal of which alter the anti-skate force.
Cabling (at least on the prototype – no doubt you could specify something else) was of the very fine, single-strand, low-mass variety; a theme continued by the use of low mass RCA plugs – all in a continuous run from cartridge tags to pre-amp – something I approve of. I did wonder about hum with this set-up as the Nibiru is very prone to this, but it seems both the earthing arrangements of the arm (CF is a good conductor) and the hum resistance of the cabling are excellent.
I've already hinted at this. The arm is a hand-made product built individually to order. You're not going to find a pile of boxes filled with SAT's at your local hi-fi emporium. This inevitably has downsides, but the upside is that Marc can produce arms to fit individual requirements. Tell him what turntable you are going to use and you'll get an armbase to suite. In my case the standard Delrin armbase of the Blackbird was replaced with a massive brass affair that slotted perfectly into place. Likewise you can have the bearings adjusted for a particular cartridge, an armtube with integral, adjustable or removable headshell, counterweights can be custom made and so-on.
Here I'm going to have to duck – the SAT I have here is the pre-production model. In build and configuration it is as the full production arms, but inevitably fit and finish is not going to match the arm you can buy. That said my first impression was of a well finished arm – the main armtube has a black plastic sleeve shrunk-fit which offers both further damping and hides the raw Carbon-Fibre. Standard CF matting and glossy resin finish give the generic Carbon-Fibre look we're all familiar with, but as already stated the SAT is made in quite a different way and so the 'look' would, I guess, be less 'pretty'. The layering clearly visible in the flash pictures is actually quite subdued in the flesh and the finish is pretty good with no rough edges. Of course at this elevated price level people rightly expect finish to be perfect – if this were a production arm I'd say it would be functional and just acceptable but no more – the final version should clear this hurdle with rather more comfort but I cannot comment further.
But as far as the engineering quality is concerned even the prototype is beyond reasonable criticism and there is a certain integrity running through the design backed by a distinct 'rigidity everywhere' philosophy...
An arm with such obvious engineering excellence promises much but it's no guarantee of a good sound. After all is this pursuit of ultimate rigidity a waste of time? Is Carbon-Fibre en-masse even a suitable material from a purely sonic point of view? Does that unusual bearing design make sense on anything other than paper?
There is of course only one way of finding out – bolt the thing to a turntable, add a decent cartridge and see what happens.
For the turntable I chose the Blackbird – it's been my go-to turntable for a long time because it's so consistent, has few faults and allows me to hear clear differences between arms. Marc also seemed happy with this. As for cartridge this is a high-end arm so using the Dynavector DRT-1 exclusively seemed logical especially as Marc was happy to optimise the arm for this cartridge. The rest of the system comprised the aforementioned Nibiru phono stage, my Ayon Crossfire amp and Polaris speakers – components well up to showing small differences in any arm.
The reference arm was the SME V12. It's familiar to many people, consistent and resolutely towards the top of the Hi-Fi arm pile.
To my surprise the most immediate difference was not small. The SAT just sounded so BIG. I was quite astonished. The SME is hardly a small sounding arm, and its power has been something that pulls it ahead of many worthy designs. But the SAT sounded massive. Not only was the size of musicians and the soundstage bigger in all directions, but macro-dynamics were much improved, Leaving the SME sounding a bit restrained. Now you can get a 'big' sound with a 'bloated' combination – any component from cartridge to speakers can do this and it's something that rapidly becomes wearisome as certain frequencies dominate and detail and space is smothered. This is certainly not that sort of 'big';-) Whilst belittling the SME the SAT managed to drag off just as much detail and keep it consistent.
For example I'm going through an 'Acid Jazz' phase and I've one of Blue-Note's excellent triple LP's showcasing some of their catalogue. One track has a triangle played hard and loud through most of the track. It's hard to think of such an unworthy instrument dominating a mix and being so fundamental to it, but there you go... With some arms there is a tendency for this fundamental component to drift in the mix, both spatially and in terms of tone and volume. In fact (as the SAT clearly showed) it is played with a metronomic efficiency throughout the track and it's only when this is replayed perfectly that it's importance in driving the whole orchestra along becomes apparent.
One of my test discs is the old Opus 3 test record and though most of it isn't music I'd listen to voluntarily it is a real workout. One track is of a concert organ (Scandinavian appropriately) going bananas and this has had some arms causing mistracking, big resonances booming out (one CF tubed unipivot was so bad that I actually abandoned the review and sent the thing back) and a blurring when more than a few pipes got wound up. I've never heard this so well produced as with the SAT. My system has a REL Stentor doing bass duties below the horns and so even the 16 Hz produced by the 32 foot bass pipe made a 'sound' in your gut rather than your ears.
In the past a series of reviews of CF tubed arms has found me tempted to ascribe a certain 'voice' to such designs – a certain romance and 'flow'. I now realise that CF doesn't need to be like that – in fact it can be as explosive and dramatic as anything else I've heard.
In the winter when snuggled up in front of the fire I often find myself turning to Madonna's 'Ray of Light' album – I don't know why but there's something bleak about it despite a rather warm mix. The SAT made wonderful music with it, and I fancied that some of the studio produced sounds – the usual squeaks and tings – took on more subtle undertones than I'd noticed before, sometime revealing a certain tunefullness that I'd missed. Likewise the 'Street' on her 'I Love New York' was big and open with kids and cars running round.
Joni Mitchell's 'Kind of Blue' is not just a fabulous piece of music, it's also a fiercely difficult LP to reproduce, not least because her voice is recorded with very little of the compression and general 'buggering about' which plague some more recent recordings. At the same time her voice can so easily take on a 'fingernails down a blackboard' edge if the cartridge isn't absolutely controlled in the groove. Then as she swoops lower a bloom can ring out that can be cause by just about any part of the system (and frequently the room) – my system plays this cleanly but I was worried that the power of the SAT would set off resonances in the system but no, it all remained under control, nothing better shows the lack of resonances in the arm.
Bass, in any record that has it, was seismic and controlled with leading edges clearly defining the attack of a bass guitar string – plectrum or thumb? - easy to distinguish...
Another surprise was the speed of the thing – the world champ in this respect has always been the Roksan Artemis in my book – leaner and faster than the SME, but the SAT seemed to drive on the music with great pace - PRAT meets SAT as it were. My love for Acid Jazz only got worse;-)
With the front end pulling so much from a record, and sounding so meaty it's easy for a system to get overwhelmed further down the line and depending on system/taste this may well be something that can cause a problem. A 'clean' system is essential – something warm and romantic may well have resonances wound up, or all that detail lumped together. In such a system a leaner less powerful sounding arm (such as the SME) would be a better bet.
And of course that brings us to the tricky question of system/room matching. Personally I found the SAT sensationally good, but that's in my system and room and I am extremely reluctant to state that this will be the case for anyone else. What I can state is that the SAT gets a hell of a lot off the record and presents it at an information/power/dynamics-to-the-max kind of way – if it's on the record the SAT will retrieve it and in spades, without colouration or overhang. Strong medicine for appropriate systems/ears.
The only other caveat is that this is physically a very large and heavy arm – as I've said, some suspended tables will struggle, and likewise the height will be a problem for some dust covers, but I honestly can't see this being a major problem for potential owners.
The SAT is a worthy and original debut for the company into the high-end arm market. In my system I became quite besotted and it was a hard thing to pack up in its box last week. Though unusual it's not unconventional in looks or adjustment and anyone should become familiar with its operation with ease – It's no SME 5 in this respect but then what arm is? Currently it's entering a very competitive market, but the SAT certainly deserves to be auditioned with the best of the rest to see if its combination of attributes is what you are after.
*At the designer's request I have made a distinction between 'stiffness' and 'rigidity'. As a materials engineer he considers 'stiffness' to apply to the characteristics of a material (measure by its Young's Modulus) – 'rigidity' being a measure of the resistance to bending of a structure which of course depends on material and design. This seems totally logical to me.
**SME offer both one piece and detachable headshell arms, but they are quite different, the one-piece being in Magnesium, the separate headshell models in Aluminium...
***Roksan's Artimiz (and perhaps others) uses bearings which are designed to be slack and which tighten during transients – it's complicated but I thought I'd ward off the pedants...A very few arms now and in the past use jeweled bearings but they are much smaller than those of the SAT.
© Copyright 2013 Geoff Husband - Geoff@tnt-audio.com - www.tnt-audio.com