The Sound of Nostalgia

What is
Mono cartridges?

Rekindling Memories

True Mono
Cartridges

The history of recorded music on phonograph records spans over a century.

Many music lovers still have a lot of mono records in their collections. Many mono records first released in the 1950s and 60s have also been reissued during the last years.

The era of high fidelity
sound reproduction

Over a half century ago, beginning in the 1940s, modern vinyl began to take shape and to resemble what we know today.

The tape machine had arrived in studios, cutting was made on a cellulose nitrate lacquer with a sapphire cutter, and the V-shaped groove became standard using a lateral cut mono signal.

New and improved cutterhead by Ortofon

High fidelity
sound reproduction

Ortofon also greatly influenced the process by developing and producing a new and improved cutterhead in 1946. This cutterhead made it possible to achieve an upper frequency limit of 14kHz, which was far beyond the former limit of 8kHz. This gave way to the era of high fidelity sound reproduction.

The records of the early 1940s were coarse-groove shellacs, and playback was made with both mechanical and electronic “cartridges” using an extremely high tracking force. Many cartridges now used a sapphire stylus, and for the records produced in this era, a spherical stylus with a 65µm radius was considered state of the art.

Introduction of the microgroove vinyl record

The first series of moving coil cartridges

The process of launching this new record type was very time consuming: It required a new and better material (which became known as what we now call vinyl), new cutterheads, new recordings that lasted an entire record side, and new turntables that could spin at 33 rpm. Even more notably, new lightweight tonearms and cartridges were required to significantly lower the 100+ grams tracking forces that were common for use with 78 rpm shellacs. 

In 1948, Ortofon launched the first series of moving coil cartridges.

The 2M Mono SE

Play old and
new mono records

The release of the Beatles mono box in September 2014 marked a noteworthy moment in the realm of mono audio. The Ortofon 2M Mono Special Edition cartridge was meticulously crafted as a tribute to the Mono Beatles albums set. The Beatles hold a special place in the hearts of many music lovers, and Ortofon is honored to ensure high-quality, modern playback for the Mono Box Set. In our commitment to supporting and embracing the mono culture, Ortofon takes pride in providing an audio experience that pays homage to this significant musical era.

Leif Johannsen, Ortofon's Chief Officer of Acoustics and Research, reveals the story behind the MONO cartridges and features the 2M MONO SE, the one MONO cartridge to play all the old and new mono records in existence, including the latest “The Beatles: The 22 Singles Collection”, released November 22, 2019.

A, AD, and C models

Mono types

The three models: A, AD, and C were built around the same generator, which is still used in our SPU CG cartridges today. The A-type was a rugged standard cartridge with low compliance and high tracking force: up to 15 grams on coarse groove 78s and 7 grams on microgroove 33s. The AD was made solely for the Ortofon A 212 tonearm, and it had a twistable collar to make the change between 78 and 33 rpm easy. This was also a rugged design capable of up to 10 grams on 33s. The last cartridge in the series, the C-type, was designed for professional use and could run at 3 grams VTF on 33s.

Stereo vs. Mono records

The differences
in groove types

A stereo record contains the left-right information on the two opposing groove-walls that are angled at +/-45 degrees, as is seen in the figure. Cutting the groove this way leaves us with a complicated shape with both lateral and vertical information which a stereo cartridge is able to read. A mono record contains only one signal corresponding to left+right which is cut in the lateral direction, so there is no vertical information.

Using a mono cartridge to play mono records

The perfect match

When playing a mono record with a stereo cartridge, various imperfections like crosstalk, noise, phase errors, tracking error, antiskating, and distortion can lead to an unstable and partially fuzzy sound in the two channels. However, using a mono cartridge eliminates these issues by producing a single signal that is directed to both channels. This results in a more forceful and stable sound with greater richness.

Unaffected by vertical movement

The benefit of a mono cartridge

Using a mono cartridge has the added advantage of being unaffected by vertical movement, such as the pinching effect that occurs when the stylus is pushed upward in narrow grooves. It also reduces the impact of dust, dirt, and wear, leading to a cleaner and quieter reproduction of the mono record.

These benefits cannot be achieved solely through the use of a mono switch.

  • The Mono Microgroove

    The mono microgroove geometry is fairly easy to understand, as it only has to contain one signal. That signal is cut in the lateral dimension only, meaning that the V-shaped groove will have constant width and depth. The groove angle of the V-shape will vary a bit from record to record but will always be close to 90 degrees. The top width of the groove will, according to the different standards, have a minimum dimension in order to ensure that the replay stylus can sit comfortably inside the groove. Over the years, this minimum width has varied due to changing standards but has always been close to 50 µm until the mid-1960s. The latest standards from the 1980s were revised for a minimum width down to around 30 µm. This offered a unified standard, congruent to the minimum width of stereo records.

  • Bottom groove radius

    Regarding the bottom groove radius, old microgrooves from around 1950 could approach 15 µm, or even larger if the record stamper was used for too long. Records like that need to be played only by a cartridge with a spherical 25 µm stylus, otherwise there is a risk of the stylus bottoming out and causing poor fidelity. From around the mid-1950s, the bottom radius was reduced to around 8 µm, which corresponds to the IEC98 standard from 1958 where 7.5 µm is stated as maximum radius. Later on, up to the stereo age, this was further reduced down to 4 µm. The bottom radius is one of the important factors determining which styli will replay the record satisfactorily as can be seen by the drawings below.

  • Spherical styli were commonly used until the early 1960s, particularly for records from the first 15 years of microgroove technology. However, it is not necessary to use a spherical stylus for mono playback. In fact, elliptical and line contact types can be highly beneficial for mono records from the mid-1950s onward. Line contact stylus types, in particular, offer improved high frequency response due to their slim shape and effectively reduce distortion caused by the pinching effect in narrow high-frequency grooves. For example, the SPU Mono and SPU CG25 Di MkII models utilize a 25µm spherical stylus.

  • To improve the playback of an old mono record, it is recommended to use a different stylus than the original 25 µm spherical stylus. An 18µm spherical stylus or, even better, an elliptical or line contact stylus can be used. These diamond profiles greatly enhance the stylus's ability to accurately reproduce the record's inscription with more detail.

    It is worth noting that when a properly aligned stereo cutterhead is used to cut a mono record, there is no difference compared to using a mono head as long as the signal supplied is identical for both channels. The choice of cutting stylus should also ensure the creation of sufficiently deep and wide grooves to accommodate users who prefer to replay mono records with a traditional spherical 25µm stylus.

    For instance, the 2M Mono model incorporates an 18µm spherical stylus for optimal mono playback.

  • The LPs in The Beatles in Mono box has, according to GRAMMY®-winning engineer Sean Magee from Abbey Road Studios, been cut with a minimum groove width of 60 µm. This kind of groove will make it possible to use most modern mono cartridges without any problems. However, to get the most out of the grooves, a line contact type like the Fine Line on the MC Cadenza Mono or the Shibata on the specially developed 2M Mono SE will be perfect. Line contact stylus used in MC Quintet Mono, MC Cadenza Mono, and 2M Mono SE.