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The Isolator from The Cartridge Man

Breaking the Cartridge/Arm Feedback Chain
 

 

August 2005

                  



I fell in love with The Cartridge Man (the nom de audio of Leonard Gregory) MusicMaker III phono cartridge immediately. It did its eponymous job so adroitly and with such soul-satisfying grace that I felt it almost boorish to analytically break down its performance into constituent parts. The parts were so well integrated into a larger whole that sound per se was irrelevant: it made more sense to talk about violins, oboes, clarinets, drums and guitars than to talk about high frequencies, midrange or bass. The MusicMaker’s coherence is as it should be: truly great audio products grab you musically. Sonics are a subsidiary matter, a means to an end. If a component forces you to listen to its sound it’s a pretty good indication that something’s wrong.

The MusicMaker III’s inherent musical quality was obvious with all the tonearm and phono stage combinations with which I partnered it in my review, further adding to my high estimation. Being free from high-strung compatibility issues and other thoroughbred neuroses ensured that most users would be guaranteed experiencing its unparalleled musical rightness. My esteem only continued to grow after I completed my review (this was a cartridge I had to own) and when nomination time for our Most Wanted Components Awards for 2005 came, The MusicMaker III was the instantaneous and obvious choice. The Music Maker III is a great cartridge, a true masterpiece.

The cartridge has a reputation for working particularly well with the Hadcock 242 Uni-pivot arm, which I did not have available for my original review. No particular mystery here: The Cartridge Man’s design input into the 242 tonearm range helped optimize the performance of that arm with the MM III. Continued development of the cartridge’s performance has resulted in a new product from Mr. Gregory called The Isolator that aims to solve a core problem of LP playback.

We all know that the stylus’ movement in the record groove does more than simply generate a content-laden electrical signal in the phono cartridge’s generator; it also pumps non-musical mechanical energy into the cartridge body and through it to the tonearm, and thus to the top half of the record playing system. This ‘upward’ component of unwanted mechanical energy is mirrored by its ‘downward’ component: that which is generated into the record itself and thus to the platter and the rest of the turntable. The spurious mechanical energy affects the arm by exciting its resonance nodes and further complicates extracting the wanted signal by dumping vibrations back to the cartridge, stylus, and record surface. To further muddy the waters, the unwanted energy can then go back up into the arm again and cycle the process. Feedback. Since this stray energy is not related to capturing the evanescently small musical signal, its presence serves only as a corruption and distortion.

The most often articulated model of the phenomenon is the old Linn/Rega standby. Their solution to the problem has been rigidity. Firmly bolt the rigid cartridge (Rega even produces a torque wrench to allow this to be done optimally) to a very rigid tonearm with very tightly-toleranced arm bearings, and the mechanical energy generated by the tracing stylus will pass through the cartridge, flow up into the headshell, continue along the arm to its bearings through which it will pass (and magically disappear?) into the turntable itself. Actually the Linn model held that the vibrations generated into the system should be allowed to freely float in a closed loop – upward and downward components meeting so that there is no relative displacement of the stylus. As a model, the Linn/Rega is very attractive, offering a seemingly common sense understanding of the energy/resonance effect.

The problem with all models, however, is that they aid understanding by simplifying the phenomenon they attempt to elucidate. Practically speaking, models are only useful as working models; that is to say, designs based on their principles have to work. The excellent musical results attained by Linn and Rega in LP playback are certainly impressive: for decades now, if one wanted music from one’s LP playback system, Linn and Rega were the default companies to which to go.

The music-making success of Rega and Linn products would seem to validate their working model, though it is clear that some of the assumptions that underlie it are leaps of faith and achieving the model’s goals are more difficult in reality than they appear in the abstract. Although the concept of ‘draining’ energy away from the stylus/record interface is psychologically attractive, it ignores the fact that the energy flow is not a one-way street and there is no guarantee that the rigid solution will deal with all the superfluous energy generated. It is just as likely that some energy, being closer in essence to water than to automobile traffic, will flow back into the cartridge/stylus and be re-radiated back into the tonearm in a kind of feedback loop. The Isolator is designed to break that unwanted energy loop by isolating the cartridge from the headshell. Not only will vibrations be kept from passing into the tonearm, but those originating in the tonearm itself will not pass into the cartridge, and thus, into the stylus. Rather than relying on the arm tube/bearing-drain principle, the unwanted energy is dissipated into heat before it even reaches the headshell. Another way to skin the cat and a most clever, elegant and successful way at that.

The Isolator is a small rectangular sandwich (3/4 “ W x 1” D x 1/8”H) whose top and bottom are two thin stainless steel plates. Sandwiched between the plates is the exotic, purposed-designed, and very expensive isolating material. This material, technically a closed cell, cross-linked ethylene copolymer structure, is somewhat springy and can be damaged from excessive compression. The Isolator fits between the phono cartridge and the headshell, serving as an acoustic filter between the two. The cartridge side has a re-usable, and easily broken, contact adhesive on its stainless steel plate which bonds the cartridge to The Isolator; two protruding shafts slip into the cartridge’s mounting lugs to center and orient the cartridge. These two shafts do not have nuts; the cartridge is not bolted to The Isolator. From the top of The Isolator protrude two captive bolts that attach to the headshell by two nuts. These nuts are to be tightened just barely enough to keep the cartridge and The Isolator from shifting position. Those trained in the Linn/Rega school of brute-force cartridge nut-tightening (and destroying) need particularly to beware. Over-tightening the nuts will destroy the Isolator’s isolating material and will render the device useless.

The Isolator can be used with all tonearms and cartridges where headshell space allows positioning The Isolator (3/4” W and 1” D), and where the cartridge’s top mounting platform is flat and large enough to allow the adhesive to hold the cartridge securely. The arm will also need to be able to compensate for The Isolator’s additional 2.6 grams added to the vertical tracking force, and will also have to allow raising the arm height by 1/8”, or 5.4 mm, to compensate for The Isolator’s additional height when installed.

Since The Isolator was originally developed with the MusicMaker III cartridge in the Hadcock 242 tonearm in mind, I began my auditions there. The 242 Series of Hadcock arms are available with a variety of tonearm wiring choices starting at $859 for the basic Export model and topping out at $1629 for the Super Silver. The 242 Cryo arm that I used uses VdH copper wire that is cryonically treated and retails for $1359. Hadcock arms have, in the past, been a somewhat underground phenomenon in the US, largely due to lack of easy availability. Now distributed by AudioFeil International, who also distribute all The Cartridge Man’s products, the English-made line of uni-pivot arms should make some fine musical noise here: the performance of the MusicMaker III with The Isolator in the 242 Cryo arm sets a high standard for classical music playback.

Spindly and skeletal in construction, the Hadcock 242 arm breaks with some conventions of unipivot arm design. Unlike the absolute tip of the standard unipivot’s pointed bearing, the end of the upward-pointing bearing on the Hadcock is shaped like a cone. The sides of this cone contact 4 miniature (1mm) brass ball bearings within the bearing cup of the arm tube. Using the simile of the tightrope walker (to which the unipivot arm is often compared) the walker is no longer up on one tiptoe, but can use his feet to grip the rope. The arm definitely wobbles less than the common variety unipivot arm, easing the fiddliness of operation, and banishing that heart-stopping vision of the cartridge rocking side-to-side when it first contacts the record – a vision all too likely to raise concern about the long-term effect on the stylus cantilever and the record groove itself.

The Hadcock’s skeletal headshell, available with both threaded and un-threaded screw holes, is completely removable, and attaches to the arm tube via a collar that slides along the outside of the internally-damped stainless steel arm tube. A set-screw fixes its position, allowing both over-hang adjustment and side-to-side rotation for azimuth alignment. The arm tube itself can also be rotated by loosening another set-screw on the bearing cup. Together with the twin balancing counterweights for adding tracking force, and the outrigger rod extending from the bearing cup that serves as the anchor for the thread and bob-weight anti-skate control, there are a wide variety of adjustments possible to make sure the arm is balanced and perpendicular, the bearing vertically aligned, and the cartridge/stylus correctly aligned for overhang and azimuth. There are also almost infinite ways to screw this up and on a unipivot design, this can lead to great uncertainty as to accuracy of set up. Given that a unipivot is inherently unstable once it begins playing a record, making sure all the balancing and alignment is correct is absolutely crucial to maximize performance. There is thus a high degree of fiddliness involved to be sure, but the Hadcock is rather straightforward to set-up and use, as long as one is conscientious. The owner’s manual could use a proofreader, though, as text content and illustrations don’t completely match. The entire arm wand assembly can be removed by detaching the wiring connector on the arm pillar, thus allowing easy cartridge swaps by purchase of an additional arm wand.

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The Isolator from The Cartridge Man