Tonearms

The iota-audio-design “Satori”







































Design and development of the Satori range of tonearms....


The iota-audio-design Satori tonearms are the culmination of many years of design, development, and testing, which comes after more than thirty years direct involvement in the design and development of Hifi products. During this time I have been very fortunate to have had an opportunity to both own and  evaluate many of the finest tonearms available.

Throughout this exposure to these many different tonearms I have been able to assess what properties I would like to see in my own designs. The Satori therefore incorporates what basic principles I believe represent the biggest influence to the sound and tonal characteristics of a tonearm.

Many designers eulogize about the virtue of ultimate rigidity and therefore apply it to all aspects of tonearm design, and when they do so I believe they can miss a salient feature of vinyl record sound reproduction. The sound we hear is as a result of vibration, and I believe absolute rigidity at the expense of all else does not always provide the best solution when you are searching for tonal neutrality and information retrieval. I believe vibration control and the channelling of unwanted energy are actually the key elements to consider in tonearm design.


  









































Tonearms

During the design and developed of our turntables we use  a wide variety of tonearms, as a result when it comes to your preferred choice of tonearm  you are the final arbiter as to what principles, appearance or price you feel is best suited to your needs.

Whatever you choose you can be sure that due to the design principals employed in our turntables your chosen tonearm will easily be accommodated and allow you to get the best from your music.

Obviously we now have our own range of  tonearms in the form of The iota-audio-design Satori, The Satori II, & The Satori B, but we appreciate these  may be out of reach for some customers and we therefore offer our turntables with a number of different arm boards, so that we are able to offer more affordable products as well.

Probably from the most successful tonearm range of all time are the products from Rega, these offer a starting point with our turntables especially if our own offerings are not within your initial budget. Then at a later date the standard Rega arm can be replaced by either the Satori B or Satori II as these are both compatable with standard Rega arm geometry on our turntable products.  The iota  Swingweight II the original version of which has been available since 1998 is incorperated in all our tonearm designs.


















The iota Satori B uni-pivot tonearm.

This is the starting point of our tonearm range, and is designated as the Satori “B” as this is our “base” design in the Satori series, as such it is our essential foundation or starting point, forming part of the essence of all our other designs . However its performance is anything but basic!

Our other models share some materials, techniques, and design features with the Satori “B” , but this is not simply a stripped down or basic version of our other designs,its merely a different implementation to achieve the same goals, that of accurately holding a cartridge and extracting as much detail and musical information as is achievable, while adding as little as possible of its own character to the sound reproduced.
 
Key features of the Satori “B” tonearm.

The main body and structure of the tonearm is made from a combination of machined Acrylic/ Delrin, and carbon fibre . The arm wand has a resin composite fixed headshell that uses our “load plate” clamping arrangement for cartridge fixing. The wand itself is manufactured in square section Pultruded carbon fibre, this material is square on the outside and the internal is round in section, thus providing additional structural rigidity. This wand is supported on a hardened single point of stainless steel held in a brass base, the point of the bearing is in contact with stainless steel bearing cup in a uni-pivot configuration. A pair of lateral side pods or weights enclosures are attached on each side of the wand, & above the bearing point on the wand, these pods can be loaded with different mass weights internally to ensure the correct lateral balance of the tonearm.

As with our other tonearms The Satori Swingweight is  again used and bias is applied by attaching a bias weight to the rear stem of the tonearm by mono filament line, this weight is supported on a stainless steel wire support hook attached to the base of the arm.

As with our other tonearms the internal arm wire is once again from Cardas and this exits the top of the arm and terminates at the rear of the turntable in a plug and socket arrangement, as used with our other tonearms, once again with a choice of either XLR or RCA phono connections on the output cable. This ensures ease of cartridge fitting as the tonearm can be simply lifted off its bearing point and unplugged from the output cable.

The arm is fully height adjustable by simply slackening a grub screw in the arm base that acts upon the locking groove machined into the side of bearing support stem.

The tonearm wand and structure is grounded from the base of the bearing support stem to ensure an appropriate grounded connection to a phono stage earthing point.

The tonearm has a fully height adjustable arm lift, and when not in use the arm wand is held in its support cup to prevent accidental damage to the arm wand and cartridge.


To understand the development of the Satori range it may be helpful to establish the first principles as they apply to tonearms.


What does a tonearm do…….?

The basic purpose of the tonearm is simply to hold the cartridge, of whatever type, moving coil, moving magnet, just above the surface of the vinyl record in order that the tip of the stylus is in full contact with the spiral groove that is pressed into the surface of the vinyl record, thus allowing the cartridge to “read” the groove modulations. The subsequent movements of the styli are used to generate electrical energy; this signal is then sent to a suitable phono stage in order to pass through an RIAA equalisation network to reproduce the original sound.

In order to achieve this the tonearm must be able to maintain a suitable pressure or down-force thus ensuring the stylus contact with the vinyl record groove, whilst also accommodating any warps in the record, and to accurately follow the spiral groove on the vinyl as its size diminishes as the record rotates and the groove approaches the centre of the vinyl record.

What's the “conventional” approach to tonearm design?

  • The majority of tonearms on the market whilst varying in materials, dimensions, and appearance, still follow one of three or four basic design fundamentals when it comes to how the arm is manufactured. Most tonearms but by no means all are usually made from metal, often aluminium, magnesium or similar. The most common type of tonearm irrespective of other factors normally have conventional roller bearings arranged to provide movement in both horizontal as well as vertical planes, in a Gimbal bearing arrangement.

  • A smaller number of designs use an alternative construction, these are arranged as a Unipivot where the arm is again commonly manufactured in metal and sits on a single point or spike and pivots in both vertical and lateral planes, in order to limit the maximum excursion of the arm some designs also include some form of control pins or dowels at the side of the pivot point.

  • A small number of other tonearm designs use some form of suspension, often a single cord and then usually employ some additional form of controlling force, for example magnetic attraction or floating the tonearm in a bath of damping fluid etc. once again to limit the excursion of the arm.

  • A fourth and far smaller number of designs are the more rarefied group of parallel tracking tonearms, operating on a fundamental different principal from all the other designs listed above. These allow the cartridge to track the record in a parallel manner as opposed to all other types that are pivoted from a single position and then traverse the vinyl in an arc.


So what's different about the iota-audio-design Satori tonearm?

This is something of a hybrid in that it combines some aspects of two different construction principles. Therefore we would describe the tonearm as a “suspended control point” tonearm, in that the tonearm is suspended from an overhead “suspension bridge” by a pair of mono filament cords, these are attached above the tonearms centre of gravity to a pair of stability outriggers fixed above and at either side at 90 degrees to the main arm tube. At the same time the tonearms excursions are constrained by the action of the upward facing control point spike, this is located below the tonearm and is located in a control cup. This bronze control cup locates on the cone of the upward facing hardened stainless steel spike rather than the tip of the spike, which actually makes no contact with the arm at all.

As a result the arm has controlled low friction movement in both horizontal as well as vertical planes, and from the users point of view when cuing the arm it has the feel and convenience of a totally conventional tonearm, and consequently doesn't “flop around” in all directions as the uncontrolled variants of the unipivot designs have a rather disconcerting habit of doing, that is before making contact with the vinyl surface.

Not only do the suspension cords ensure the free movement of the tonearm; but they also have another role, when you apply a twist to the cords the amount of twist applied provides anti skate or bias. This the opposition force that is essential to overcome the pull force towards the centre of the record, which is exerted by the cartridge tracking the diminishing diameter of the spiral groove of a vinyl record when using any pivoted tonearm.

Another advantage of our bearing design is that because the Satori is located on the cone rather than the point of the control spike, and the position of the suspension cords are able to be easily adjusted, and our counterweight is able to swing to find its correct vertical position after any adjustment. The result is the Satori tonearm also allows for micro adjustment and compensation of Azimuth or left to right tilt of the cartridge body and tip. Normally in a conventional tonearm such as a Gimbal bearing arm this can only be achieved if the head shell can be independently rotated and re-fixed, and most designs don't allow this or for that matter any other form of Azimuth adjustment.


What is the Satori made from?

After a great deal of testing and development we concluded that carbon fibre for the majority of the arm construction gave us the best results. This material choice in its self is nothing new, many designs use this material. However most designs use round“roll wrapped” carbon fibre tubes, made up by wrapping carbon fibres around a former in a combination of unidirectional and bi-directional weave. This produces a strong, light, and stiff structure, these “roll wrapped” tubes were developed for applications that require enhanced strength in multiple axes. For example the tubes that make up the frame of high performance  road racing or mountain bikes, or fishing rods etc. In such applications these tubes will be subject to significant twisting and torsional forces, as well as occasional massive shock forces. As a result manufacturers of such items are prepared to forgo some of the maximum stiffness and longitudinal strength to increase resilience for such applications.

However we have chosen to use an alternative type of carbon fibre, Pultruded carbon fibre. There are other designs on the market that use this material in their products,but we are not aware of any other design that employs Pultruded tubes for a tonearm with a square profile. Think of it as round tube with four additional “stiffening nodes” running along its outside length.

Tube manufacturers quote:

CARBON FIBER SQUARE TUBES
Carbon fibre square tubes are Pultruded resulting in very straight fibres cured at high temperature yielding in high fibre to resin ratios and very stiff parts. Square carbon tubes contain no fillers - ONLY continuous fibres.


Compared to other materials and processes, carbon fibre square tubes are twice as stiff as aluminium of the same cross section. Carbon shapes are 350% stronger in tension and 550% stronger in compression than the traditional wet lay-up with carbon fibre room temperature resin systems.



Unlike roll wrapped carbon fibre, Pultruded tubes are made by a machine pulling continuous strands of carbon fibre through a “die” to form its shape, in our case a round central core with a square outer former with rounded corners; as the fibres are pulled through they are automatically coated in epoxy resin, and as they come out of the “die” the epoxy resin is cured at high speed. Tubes made in this way are exceptionally consistent and have all of their fibre running length-ways down the tube, this means that they are exceptionally strong along their length, and also very stiff,and light, therefore offering excellent resistance to bending forces, much more so than similar roll wrapped constructed tubes.

However Pultruded tubes are not as able to resist twisting forces, we believe a tonearm is not going to be subject to any significant twisting forces what so ever, therefore this is not an issue. The only other slight concern with a Pultruded tube is a requirement to take account of any significant crushing forces that may be applied to the tube. Once again this will not be a problem in any respect with a tonearm. Obviously we have taken full account of this fact in our construction and mechanical bonding techniques used in the design.

So why if as we suggest we believe this is a superior material for a tonearm application, you may ask why doesn't every other tonearm using carbon fibre us Pultruded tubes rather than roll wrapped? Whilst we are very happy with the appearance and finish of our material and delighted with the performance it provides. We can only conclude that perhaps the appearance of roll wrapped tube may be a factor. Our Pultruded tube is uniform and smooth in external appearance, but does not bear the “hallmark” carbon fibre chequer pattern that most people seem to expect to see and associate with carbon fibre material.

This look has become so ubiquitous in so many areas of modern life that “fake carbon fibre look” material is now used for many other consumer commodities, and for most people this appearance alone will be enough to satisfy them in the belief that something that simply has this characteristic, is in fact the real high tech material, even when in reality its simply a photographic image sandwiched inside some very ordinary plastic!

We are not for one moment suggesting any tonearm purporting to be carbon fibre is in fact simply a plastic fake, its just that many designers may feel its vital to comply with the average persons expectations of a carbon fibre products appearance, even if an alternative material make up could perhaps offer some potential performance advantages.

The other reason we have used Pultruded carbon fibre tube is we believe as the fibres are all aligned along its length any unwanted energy has a more direct path to the effective “grounding point” which in our case would be the stainless steel control point below the arm. Our design overcomes the unwanted energy which might, for example, be produced by a moving coil cartridge. We have eliminated any standing waves being generated up and down the length of the tonearm. If these waves are not dissipated appropriately it can result in potentially out of phase frequency affects, or even loss of certain frequencies due to cancellation or possibly induced mistracking

Our bearing design, and the rigidity of the tube material used in the construction of the tonearm, help to control any vibration within the arm structure, and this is also why we have filled the main arm tube with a granulated damping material, this surrounds the Cardas cartridge wires that are run inside the arm tube in a PTFE protective tube sleeve.

The tonearm is constructed using a structural adhesive bonding agent, and is also mechanically fixed where this is required to form the structure.


























We add a clamp plate on the top of the head-shell, this avoids any physical damage to the composite head-shell by the cartridge fixing bolts, as well as evenly loading this area with the applied fixing load of the cartridge mounting hardware, by doing so this also helps to damp unwanted energy that may be generated by the cartridge.

Similar items added on many tonearms are sometimes used when a low mass cartridge is being used with a heavy counterweight, and under these circumstances can be viewed as undesirable, as the load plate could be seen to add unwanted mass to the structure at a critical point, this is because on a conventional arm a standard metal head-shell can easily add up to 12 grams or more in weight, our head-shell is a fraction of this, therefore the load plate does not adversely influence the total overall mass of our tonearm.

The effective mass of our tonearm is at what we consider an ideal of 11 grams, and is therefore considered to be medium mass, and as such ensuring our arm is a perfect match for a significant number of modern and classic cartridges of all types.

Why is the effective mass of a tonearm important?

This is a subject upon which much has much has been written, discussed, and opinions expressed, if you are unsure of how the relationship works I would suggest consulting some of the numerous sources of information within easy access of your preferred search engine, but by way of a quick step guide, see below.

The correct effective mass of a tonearm is vital to produce the best results from any arm and cartridge combination. All cartridge designs have a degree of “springiness” built into their mechanism, this is to act as a suspension, this “springiness” is defined by a set of manufacturer defined numbers, this is the compliance of the cartridge.

The effective mass of the tonearm(inertia), is often expressed as the amount of mass as seen by the cartridge styli under dynamic conditions, this is not to be confused with the down force, that  force is applied by the counterweight, this is a static figure unaffected by changes in dynamic conditions, suspension, and any internal damping. So think of it as the cartridge is a spring and the tonearm is the mass acting upon it, any effective mass figures quoted are calculated without the tonearm counterweight in place.

To achieve the “ideal combination” we suggest a low or medium compliance cartridge (e.g. moving coil) with our medium mass arm, as a high compliance cartridge requires a low effective mass tonearm. We would recommend using an optimising range of 8Hz to 11 Hz as the resonance figure, although some latitude outside the upper range is considered to be acceptable by some sources of information.

If this is ignored and a cartridge is fitted to a tonearm, and the resulting combination exhibit specific resonant frequencies that occur at a critical point, for example somewhere above 20Hz or even at a much lower frequency, this could coincide with the frequency of record warps or rumble, this “boosted” frequency output can be 3db or even 6db or more, and a 6 dB increase represents a doubling of output when related to noise! The result is bloated or very uneven bass response or even mistracking.

Satori Swingweight

For the Satori we have chosen to develop the "Swingweight" that we first introduced as a modification offered for Rega arms some years ago (1998). However we have used the opportunity to build the weight assembly  from gunmetal and the counterweight has a non resonant centre core section made from Acetyl, this material is used as an interference fit within the counterweight to act as additional damping.

The counterweight stem is  manufactured in brass with a lock nut assembly of the same material. The threaded counterweight stem actually passes into the arm tube when the position of the counterweight is adjusted. As a result small changes in the effective mass of the tonearm take place as the position of mass behind the pivot point of the arm changes, however these are very small and consequently do not significantly affect the quoted figure of 11 grams.

As with the stainless steel iota Swingweight II, the gunmetal counterweight is mounted below the centre line of the arm, on the threaded counterweight rear stem, this allows for very fine and accurate weight adjustment. The weight is mounted on an independent bearing assembly and is decoupled from the rear stem, this allows a controlled amount of free movement of the weight. The result is high levels of decoupling from the arm structure, whilst the low mounting point for the counterweight, below the arms centre of gravity produces greater dynamic stability, particularly when encountering record warps.

The sonic improvements offered by the counterweight include greater tracking ability & dynamic stability, more low level detail retrieval, as well as much more precise and solid presentation of the stereo image. In short, more information less colouration!

The tonearm has a rest position that holds the arm when not in use. In order for the tonearm not be accidentally knocked and moved from this armrest, a magnetic lock assembly holds the tonearm so as to avoid accidental damage to the cartridge.

To aid the fitting of cartridges the whole tonearm tube assembly can be simply unplugged from the socket on the top of the arm board and removed, and upon replacement very easily adjusted with the supplied Allen key,to ensure the correct length and tension of the suspension cords. The arm is supplied as standard with the correct control point and arm board spacers so as to easily accommodate a wide variety of cartridges. Inevitably there may be some cartridges of more extreme height dimensions. For these non standard items we are able to supply the addition hardware required to provide a match for any other cartridge on the market.



























The tonearm is internally wired with Cardas cable especially designed for this role. This cable was selected as it provided us with the most outstanding results from all the cables we assessed for the Satori. The headshell is fitted with short cartridge leads that are easily replaced to allow for different cartridge pin dimensions or simply for service replacement purposes. We strongly feel that this is the best option rather than the tonearm being wired in one piece.

Cartridge leads offer the best solution as internal tonearm wires are not robust enough to withstand potentially frequent changes of cartridge, and we concluded the potential very small improvement in performance is simply not worth the loss of convenience and long term reliability that cartridge leads provide.

For connection to your phono stage the tonearm is fitted with a captive output cable fixed to the underside of the arm board top plate. The standard length of cable is 1.5 mtrs, other lengths can be specified. We offer termination of this cable with either XLR balanced plugs or RCA phono plugs at no extra charge.

For customers wishing to experiment with output cables we offer a version of the tonearm where the captive cable is replaced with a termination box, allowing any alternative cable to be connected, the terminator box is fitted to the arm board top plate.


Dimensions and specifications

Tonearm length styli tip to pivot point..................240mm

Tonearm pivot point to centre spindle...................225mm

Overhang ….....................15mm

Offset …..........................22 degrees

Effective mass.................11.2 grams

Standard mounting plate ..100 x 120mm

Headshell Fixed std ½” mount.

Cartridge weights.............4>11 grams



Materials used in construction

Stainless steel 316.“suspension bridge”, arm lift pod, & misc other components.

Acetyl.... arm board spacers and other turned components.

Glass reinforced Ny66....”suspension bridge” lock nuts.

LG-3.... counterweight.

CZ121.....lock nut & misc components.

Pultruded carbon fibre.....Tonearm tube.

PVDF (polyvinylidene flouride) Mono filaments.

Die cast aluminium....Arm mounting plate.

PTFE protection sleeving.

Various....Granular damping.