Sunday, January 10, 2016

Phono Cartridge Stylus And Cantilever Construction Materials: What’s Best?

Given that your phono cartridge has an overwhelming influence on the fidelity of the reproduction quality of your hi-fi rig, would the bits that make the first contact on the vinyl disc – the stylus and the cantilever have the most influence on sound quality? 

By: Ringo Bones

For more than a decade and a half into the 21st Century, it seems that the vinyl record had managed to hold its own as the playback medium that is better than Redbook CD – or those downloadable digital music on the internet – by a significantly wide margin in terms of sound quality. Despite being introduced a few years ago, three popular entry-level turntables: the Project Carbon Debut DC, the Pioneer PL-30-K and the Onkyo CP-1050 Direct Drive Turntable are still selling strong. But what about phono cartridges – has there technological progress being made since the early 1990s vinyl record revival? 

Any phono cartridge faces a major problem: how to cover the full three-decade-wide bandwidth (20Hz to 20,000Hz) needed for high fidelity audio playback. High frequency resonances seems pretty well inevitable and mid-band “glitches” are difficult to avoid, too, as the frequency-response and vertical / lateral crosstalk sweeps with the use of test records showed. Not surprisingly, the success with which these are controlled is very closely linked to the cartridge’s overall sound quality.   

Phono cartridge stylus and cantilever construction have significantly – even radically - improved since those osmium phonograph needles used during the introduction of electrically / electronically recorded records to the market back in November 1925. During the post World War II period that lead to the Golden Age of Stereo, stylus dimensions got smaller and smaller to better track the microscopic grooves of the vinyl long-paying record introduced by Peter Goldmark. First it was made of sapphire – a gem quality form of corundum with a hardness of 9 on the Mohs’ scale which was later replaced by micro-profiled elliptical diamond stylus for better sound quality reproduction. While during the Golden Age of Stereo – the material of choice for high quality phono cartridge cantilevers is the most rigid alloy of aluminum that is commercially available, which during the 1950s is typically aircraft / aerospace grade aluminum. 

Then and now, the moving coil phono cartridge – despite of its low signal output - has been considered as the best when compared to its moving magnet counterparts due to its lack of frequency response problems in the upper midband and high frequencies. Traditionally, moving coil phono cartridges have had relatively incompliant cantilever hinges in comparison to its moving magnet counterpart which resulted in poor low frequency tracking. Anyone looking to preserve their record collection find this alarming. Remember those early Decca London phono cartridges with their tip resonances that are notorious for doing damage to vinyl records? So tip resonance control is also a factor in choice of materials in stylus and cantilever construction. 

Ideally, the stylus should be constructed from the same materials to consistently control the inevitable resulting resonances. Given that the microscopic-dimensioned stylus is barely visible to the unaided naked eye and a modern phono cartridge stylus measures around 7.5-mm long or 5/16 of an inch long and 0.5 –mm thick or 1/32 of an inch thick constructing one from a single artificial produced diamond should not carry a prohibitive price premium. Dynavector’s 17D2 Mk. II diamond cantilever MC cartridge is one such beast. With a hardness of 10 on the Mohs’s Scale, solid diamond is the hardest possible material and supreme for cantilever use. And given that diamond is a good heat conductor, any heat friction generated during vinyl playback can easily be dissipated by the stylus and cantilever assembly because they are made of the same material. But since its introduction in the early 1990s, many competing phono cartridge makers have managed to create better sounding cartridges using both more exotic and tried and true materials. 

Solid-boron-rod cantilevers constructed from the crystalline allotrope of the element boron that has a hardness of 9.5 on the Mohs’s Scale has been extensively used for moving coil phono cartridge construction during the latter half of the 1990s due to its subjectively better sound quality when compared to diamond. Used on the Van Den Hul Frog with a specially shaped Type 1S diamond stylus, this cartridge has the highest cantilever compliance and the lowest recommended tracking weight of all the commercially available cartridges and is notable for its ability to ignore vinyl scratches which is very important if you frequently purchase vinyl LPs and 45 RPM singles from used record shops. While the Clearaudio Signature uses a hollow boron cantilever variant.       
Cantilevers made of sapphire or corundum – which has a hardness of 9 on the Mohs’s Scale - was also tried as far back as the late 1970s. The most famous example of these is the Bang & Olufsen MMC 20CL phono cartridge – which a diamond stylus is attached to a sapphire crystal cantilever that resulted in the elimination of audible tip resonance and thus eliminating distortion in music reproduction and it also means it won’t be destroying your precious vinyl records every time you play them. Enthusiasts back in 1981 praised its life-like ability to reproduce choral recordings like never before and it is probably the first cartridge that started the exotic materials construction wars.  

As a go to material for phono cartridge cantilever construction, aluminum has held its own since the Golden Age of Stereo. The mid 1990s era Ortofon Rohman uses a tapered aluminum cantilever and still manages to gain converts unimpressed by the newfangled solid-boron-rod cantilever construction of competing cartridges. While the Lyra Parnassus DCt uses a more exotic diamond-coated, ceramic-reinforced aluminum cantilever said to be stiffer than ordinary aluminum alloys previously used in cantilever construction.  

Sound quality wise, audiophiles weaned on the “dreaded” compact disc tend to gravitate towards boron cantilevered phono cartridges largely due to its wider perceived bandwidth in comparison to ones using aluminum alloy as a cantilever. While those Iron Maiden and Judas Priest fans who extensively listen to vinyl during the early part of the 1980s say that aluminum cantilevered phono cartridges are more neutral sounding in comparison to their boron, diamond or sapphire / corundum counterparts.