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 21^st 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. 

Are Light Emitting Diodes Too Noisy For High End High Fidelity Use?

Though it has become ubiquitous as a power on indicator of consumer electronics since its introduction back in the 1960s, are light emitting diodes just too noisy for high end hi-fi use? 

By: Ringo Bones 

Ever since I started my audio equipment and musical instrument modifying business back in the early 1990s, I’ve noted that some audio equipment – especially very high gain solid state moving coil cartridge phono preamplifiers – will improve its noise floor when you replace the red or green LED power on indicator or light emitting diode power on indicator with a miniature tungsten filament power on indicator light bulb often used in older audio equipment. In my experience, the main beneficiaries from such moddings are vacuum tube based moving coil phono preamplifiers that use the ECC88 / 6DJ8 / 6922 small-signal vacuum tube and those iconing solid-state moving coil phono preamplifiers that use FETs and transistors or a mix of both like the DNM 3B and the Michell Iso and Michell Argo. 

During the first decade of the 21^st Century, I also discovered that organic LEDs are noisier than their plain vanilla LED counterparts. Even though the invention of organic LEDs made possible those relatively affordable and indispensable part of 21^st Century home theater unnecessarily large video monitors, blue LEDs that had become fashionable add-ons of power conditioners like the MIT Z-Center, produce an audible buzz when used with critical high gain moving coil phono preamplifiers. 

What’s weird about organic LEDs – even those green ones that emit a more vivid green light than their plain vanilla counterparts is that they can be as noisy as their blue colored counterparts. Weirder still, when viewed through a diffraction grading – either a CD or DVD surface – organic LEDs lack the monotonicity of their plain-vanilla counterparts. Ordinary green and red LEDs produce a pure green or and red light when viewed through a diffraction grating while their organic LED equivalents produced a distinctive rainbow streak. Though it is only noticeable in practice, do LEDs – organic and plain vanilla ones – produce more noise when compared with those tiny tungsten filament power on indicator lamps because LEDs are solid-state semiconductor devices and in the solid-state semiconductor world, noise is directly proportional to operational current? 

Vinyl Records: An Extraordinary Playback Medium?

Whether LPs or 45s, are vinyl records qualify as an “extraordinary” musical playback medium due to their capacity to “alleviate” screw-ups during the recorded music performance’s mastering stage?

By: Ringo Bones 

Strange how those “wonderful” attributes of the analog vinyl records – whether they be 33 1/3 LPs or 45s - that Stereophile magazine columnist Michael Fremer had been describing about throughout the 1990s still holds true today, well into the second decade of the 21^st Century. With the Marantz TT-15 turntable back in 2004 and the more recent Onkyo CP-1050 turntable, one would think that both SACD and 24-bit 192-KHz DVD Audio would have consigned vinyl records to the “dustbin of history” during the first decade of the 21^st Century, unfortunately it didn’t. But what is it about vinyl records that managed to raise “more mysticism” than even its own 2-channel analog master tape? 

Chesky Records founder David Chesky once remarked that there was something “magical” and inexplicable about the music generated by a stylus coursing through a record groove. Is the magic we love about vinyl records, whether they be 33 and 1/3 RPM LPs or 45 RPM singles, inherent in the analog nature of record playback, or is it something added by that process that allows vinyl records to create a sense of “reality” better than most commercially available prerecorded music mediums and including its 2-channel analog master tape? Or is it a combination of both? 

In my own listening experience, I suspect it is mostly due to how vinyl record playback cartridges – both moving magnet and moving coil – make the vinyl record playback system like they are very transparent sounding analog “dynamic range expanders” due to the way vinyl records tend to sound “more dynamic” in side by side comparison to the first generation open reel copy of the master tape. Given that some of the master tapes of oft-mentioned classic pop rock studio albums recorded during the mid to late 1970s had been recorded with a little too much compression that even though they are multi-track analog studio recordings they sound as if they have that digital sound that Michael Fremer rails against – i.e. everything gets flattened out – including dynamics. Could the stylus and cantilever structure of a typical vinyl record playback cartridge acting as a “corrective dynamic range expander” that makes some over-compressed studio album recordings sound more natural on their vinyl pressing versions in comparison to either open reel tape and CD, SACD or 24-bit 192-KHz DVD Audio copies? 

The ECF80 Triode-Pentode Vacuum Tube: The Integrated Circuit Vacuum Tube?

Given that it contains two different thermionic amplifiers in a single enclosure, does the ECF80 triode-pentode vacuum tube qualify as an “integrated circuit vacuum tube?

By: Ringo Bones 

Multiunit vacuum tubes may not be able to compete in size and component count with their solid-state integrated circuit counterparts, but if your hankering after that good old robust tone vacuum tube sound, post World War II era subminiature vacuum tubes offer those in a more reasonable sized package. The ECF80 triode-pentode vacuum tube is unusual in that this multiunit vacuum tube can run both its triode and pentode sections at about the same current. The ECF80 makes a great Mu-follower with the pentode strapped as a triode on top and it is often described as a medium Mu triode sharp cut-off pentode. 

Even though it is not featured in the 1959 Mullard Tube Circuits For Audio Amplifiers, Mullard says that the ECF80 was designed for operation up to 220-MHz and it was first introduced back in 1954. As 1950s era television receivers tend to use the PCFnn 300-milliampere filament heater vacuum tubes, the production of the ECF80 with a 6.3 volt heater filament suggests that it was aimed at the 1950s era professional VHF communications market. In a typical VHF application of the ECF80, the triode section is often used as a Wien-Bridge oscillator and has to produce a 5-volt peak-to-peak signal which could allow the ECF80 to be used as the active transceiver tube in 1950s era walkie-talkies. The screen pentode is the mixer. The vacuum tube has two cathodes so the two independent amplifiers are enclosed in a single envelope. The twin anode construction is clearly visible with the triode occupying the much smaller anode. The two sections can be used separately if required and thus extending the versatility of this vacuum tube. 

Given that post World War II subminiature vacuum tubes are primarily used as a cost saving preamplifier and phase-splitter sections of power amplifiers that use 1930s era output power tubes, the World Audio Design K6L6 Integrated Amplifier is probably the most famous application of the ECF80 triode-pentode vacuum tube where it was used as a “novel” phase-splitter. The problem with conventional double-triode phase-splitter, like the 12AX7 double-triode phase-splitter section of the ubiquitous Mullard 5-20, is that its high output capacitance caused by the Miller Effect. This causes high frequency loading on the input vacuum tube and reducing bandwidth, making it very difficult to use appreciable amounts of negative feedback without instability due to the phase shifts incurred. A pentode vacuum tube has a very low output capacitance and high gain due to the shielding effect of the screen grid. This means that the loading on the input vacuum tube is greatly reduced, increasing bandwidth and decreasing troublesome phase shifts. And the WAD K6L6 Integrated Amplifier’s use of the ECF80 triode-pentode vacuum tube as a phase-splitter also eliminated the need of an interstage phase-splitting transformer which also kept costs down. 

The 6AU6 Low Noise RF Pentode: The Retro Vacuum Tube?

Even though modern-manufacture vacuum tube makers have yet to reissue it, does the 6AU6 vacuum tube truly qualify as a “retro preamplifier vacuum tube”?  

By: Ringo Bones 

The NOS or new old stock versions were quite plentiful back in the 1990s when I first got serious into vacuum tube hi-fi as a hobby and even until today modern-manufacture tube makers like Electro-Harmonix, Svetlana and Sovtek still doesn’t have an economically viable need to manufacture their own version of the 6AU6 low-noise RF pentode vacuum tube. And from what I know so far in this hobby, I think the primary raison d’être of those subminiature vacuum tubes manufactured after World War II is to lower the build cost of the preamplifier and phase-splitter stages of power amplifiers that uses output vacuum tubes that date back from the 1930s. 

The 6AU6 low noise radio-frequency pentode vacuum tube was developed by RCA Victor Co. Inc. of New York, New York and it is identical to the EF94. Entered into the Electron Tube Registration List back in October 25, 1945 and entered the Manufacturer’s Literature RCA Datasheet back in October 23, 1945. It has a miniature 7-pin base and was often used as the front end sections of radio and television receivers and it eventually gained widespread use in hi-fi audio towards the end of the 1950s. The 6AU6 is an indirectly heated small signal vacuum tube with a 6.3 volt filament and a 300-milliampere filament heater current. The 6AU6 was described as an RF-IF sharp cutoff amplifier for use in sets with series connected heaters and was eventually superseded by the 6AU6A since November 1956. 

It gained popularity back in the 1990s to keep build costs down when used as first stage preamplifiers of power amplifiers that use power output tubes that dates back from the 1930s – like the 6L6 beam power tetrode – which was first manufactured back in 1936. One of the most popular applications of the 6AU6 low noise RF pentode was in the World Audio Design K6L6 integrated amplifier back in 1995. The WAD K6L6 circuit topology is similar to the ubiquitous Mullard 5-20 amplifier but the 6AU6 low noise RF pentode was configured as a high-gain single-ended amplifier stage. But the relative rarity of the use of the 6AU6 was that the original 1959 Mulalrd Tube Circuits For Audio Applications handbook never used the preamplifier tube in its construction guide of its ubiquitous Mullard 5-20 vacuum tube power amplifier.