Up until the late 1950s, commercial music was mixed in mono. Even then, it took some time for stereo to take off, and it wasn’t until the late 1960s that stereo went mainstream.
In the early days of stereo, many engineers took the opportunity to experiment and play with the format. It’s not uncommon for the stereo version of a record to feature entirely different takes or a radically different mix, as engineers took full advantage of the opportunity to work with two channels rather than just one.
Often, the early use of panning from left to right is less than subtle. Hard panning could result in some instruments playing entirely in the left or right channel only, or in some cases—instruments or sounds passing quickly from one side to the other. Eventually, as stereo became to de facto standard, many older mono mixes were left behind, and in some cases, the only way to hear these versions is to find an old mono pressing of the record.
Here’s a classic example:
Listen to the drastic difference between the stereo and mono mix on the outro of Pink Floyd’s Interstellar Overdrive. The original mono mix is a natural dynamic lift on the opening riff, while the stereo version is one of the decade’s most infamous examples of extreme psychedelic stereo panning.
Like any new “gizmo”, or effect, the novelty eventually wears off, and restraint usually prevails. But the nostalgia for these original stereo mixes remains. In some niche instances, modern artists have deliberately paid homage. Check out this 2004 release from one of my favorite artists, John Frusciante, who intentionally referenced some of the early 1960s stereo records by hard-panning the drums to the right and the guitar to the left.
Back to mono. It’s easy to dismiss mono recordings as outdated, or inferior—particularly if you grew up after stereo’s decline, as I did. But contrary to popular opinion, mono records can sound fantastic, and even possess some sonic advantages over stereo records. When handled by a skilled engineer, mono recordings can sound especially focused, and punchy.
…And while modern stereo styli are backwards compatible with mono records, much of the acclaimed fidelity is lost without the help of a dedicated, true mono cartridge.
To understand the difference and potential benefit of using a mono cartridge, we must first understand the difference between each type of groove.
What’s the difference between a stereo and a mono record groove?
Mono records contain only lateral cut grooves with no vertical component. There is only one signal, and in simple terms, the groove goes from side-to-side without also going up and down.
A stereo record contains separate left and right channel information on each groove-wall at a 45-degree angle from each other. The groove is a more complicated shape with both lateral and vertical information.
A mono cartridge should not be used to playback a stereo record unless the manufacturer states that it has both horizontal and vertical compliance; however, a stereo cartridge can easily play a mono record.
Why Bother with a Mono Cartridge then?
A mono cartridge is by far the best way to experience mono records. You could take the easy option and use a mono switch, but this will not fix the errors caused by a stereo cartridge never quite producing the same signal in both channels. In other words, playing a mono record with a stereo cartridge will not achieve the same signal in both the left and right channels. It will not be “true mono”. Imperfections such as crosstalk, phase errors, and tracking errors will result in a degradation of sound quality. Using a mono cartridge eliminates these problems by only producing one signal that is then distributed to both speakers on your stereo system. The signal in both your left and right speakers will be identical.
Using a mono cartridge can also reduce the response to dust and dirt substantially as any vertical element will not be reproduced. Often, the final result is a much cleaner reproduction of a mono record. Again, a mono switch cannot remove this noise—once the vertical element is tracked, it’s tracked, and this signal now has to be processed by the system whether you mono the signal retrospectively or not.
If ever there was a solid case as to why the signal source is more important than the signal output, this is it!
A Note on Stylus Size
Depending on when your mono records were cut, the bottom groove radius may vary. For example, older microgroove records from around 1950 could approach 15µm or larger. For optimum performance, I have read sources that indicate these records should be played using a spherical 25µm (1 mil) stylus to avoid the risk of a stylus “bottoming out” inside the groove and causing poor fidelity.
Depending on who you ask, you’ll get a different answer as to when the bottom groove radius of mono pressings reduced. In truth, the groove size can vary quite dramatically. As a general rule, mono LPs mastered before 1970 were likely intended for playback using a 1mil stylus. After this point, they are probably cut with a modern 0.7mil in mind. That being said, other sources appear to suggest that the radius of mono record grooves decreased over time, firstly down to around 8µm in the mid-50s, followed by 4µm as we approached the dominance of stereo. A modern 18µm (0.7mil) stylus is perfectly safe for playing back records of both specs.
In an ideal world, listeners would own both the wider and slimmer variety to account for different microgroove specs. However, if finances prohibit this, go for a modern 17-18µm (0.6 – 0.7mil) option.
Note: If you choose to own both (or you want to regularly switch from stereo to mono, you will, of course, require a tonearm with a removable headshell to make switching between multiple cartridges practical. Alternatively, you could run multiple turntables or tonearms.
Interestingly, some cartridge manufacturers suggest that, in some case, playing back older mono pressings with an 18µm (0.7mil) spherical, elliptical or line contact stylus may improve fidelity if the record was originally played heavily with a 25µm (1 mil) stylus. The theory works on the basis that a smaller stylus may replay the record in a different, unworn location of the groove.
Trying to determine the perfect stylus size for authentically playing back mono record pressings is somewhat of a minefield. However, in any case using a dedicated, true mono cartridge will invariably produce superior results to that of a modern stereo cartridge.
What Cartridge Should I Buy?
Ortofon, Audio Technica, & Grado all manufacturer a range of mono cartridges designed to authentically replay mono records. Ortofon, in-particular, offer a wide range to suit both purist and contemporary tastes.
For the purpose of this article, we’ll focus on a few select Ortofon models as a taster.
The 2M Mono is their staple offering, with a modern 18µm spherical stylus. Like so much of the Ortofon range, many of the styli are interchangeable. In this case, you could also choose to fit their 78 stylus option designed to play the wider-grooves of older 79 RPM records.
The purist mono enthusiasts among us may prefer the classic design of their SPU range, which feature an integrated headshell, designed to mount directly into classic tonearms with detachable “universal-fit” headshells. With a wider 25 µm stylus tip radius, they are best suited to older mono recordings.
Lastly, Ortofon claims the 2M Mono SE (specifically created as a tribute to the Mono Beatles albums Set released in 2014) is a great option for playing both older and new mono recordings.