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Uncommon Media (December 2018, updated June 2022)


The discussion of Mini-Cassettes and Microcassettes has been expanded in the June 2022 update.

As I was developing the operations concept for my audio conversion business, I envisioned addressing media that historically had been in the mainstream:  78s, 45 and 33 1/3 rpm microgroove records, and Compact Cassettes (the formal name for what is generally referred to simply as “cassette”).  I added reel-to-reel tapes simply because I had a tape deck.  With these media in mind, I purchased, upgraded, or reconditioned equipment to handle these needs. 


While most of my projects have been what I expected, customers sometimes surprise me with recordings on media I hadn’t planned on.  These are presented below, and I will update this article as I encounter more uncommon sources.


Uncommon Media I Have Converted


Nitrocellulose Lacquer (“Acetate”) Records

While most commercial 78s were made of shellac resin, these 10” or 12” records were made from lacquer, plasticized with castor oil and applied to an aluminum, glass, or cardboard core.  Introduced in 1934, they were designed for direct-to-disc recording where sound was cut onto a blank record that would become the finished product (see Figures 1 and 2; the additional holes were to anchor blanks on the recorder so they wouldn’t slip during cutting).  One of their intended uses was for personal recordings, and their popularity increased through the 1940s and 1950s, at which point the medium was overtaken by tape recorders.  Lacquer recordings were typically made at home, in auditoria, or in coin-operated recording booths, and the medium became popular during World War II for sending spoken messages between troops overseas and their families back home.  Though popular for personal recording, the sound quality of lacquer records was limited by the technology of the time, comparable to that of shellac 78s.  Physically, they were subject to chipping, and they were more vulnerable than shellacs because the castor oil could leach out of the record (notably by using Saran Wrap to protect the record), rendering the records unplayable.

Audiodisc Recording Blank Label.JPG

Figure 1.  Audiodisc lacquer record label.

RCA Victor lacquer record label.jpg

Figure 2.  RCA Victor souvenir lacquer record label from the 1940 New York Worlds [sic] Fair.


Lacquer records are frequently referred to as “acetate” records, but there is no acetate in their composition.  The term appears to be attributable to a warning on some labels to “Use only acetate needles” to play these records, which refers to high-grade steel needles that wouldn’t degrade the lacquer as rapidly as inferior needles.


Most lacquer recordings in the 1940s were made at 78 rpm and would capture approximately five minutes per side.  The use of 33 1/3 rpm was more prevalent in the 1950s, allowing about 11 minutes per side.  Playing them on a modern turntable requires a 78 stylus, regardless of the recording speed.


Though obsolete as finished products, nitrocellulose lacquer records with aluminum cores have been and are still used in the first step of a multi-stage process in the production of vinyl records.  Using a lathe, the audio recording is cut onto a lacquer blank.  The cut blank is sprayed with tin chloride and liquid silver and electroplated with nickel.  The fused metal layer is then removed and serves as a stamper for pressing the vinyl records.


I have so far had one project involving lacquer records, recorded at both 78 and 33 1/3 rpm.  Like shellac 78s, they require RIAA equalization pre-emphasis to undo de-emphasis performed by modern pre-amps (see Equalization) and extensive noise reduction.



Mini-Cassettes (2.2” x 1.32” x .33”) were introduced by Philips in 1967, four years after they had introduced Compact Cassettes.  The primary function was for dictation and transcription using a hand-held voice recorder (see Figure 3).  Less prevalent purposes included early answering machines and data storage for a Philips home computer.  The cassettes could hold 30 minutes of recording, 15 minutes on each side.


Unlike most other tape formats, the take-up reel transports the tape across the heads rather than a capstan and pinch roller.  The disadvantage of this approach is that the tape speed varies, not only with how much tape has been wound onto the take-up reel, but also with the tightness and evenness of the wind.  While adequate for voice recording, this technology is ill-suited for music.  It does offer a distinct advantage, though.  While playing a tape, the user can easily move the recorder’s slider switch from play or stop to fast-forward or rewind without disengaging the tape from the playback head.  When dictating, the speaker can quickly rewind or fast-forward while listening to what was recorded (at a much higher speed, of course) and target a spot to begin recording over what isn’t wanted.  The same capability aids those who are transcribing recordings to a hardcopy medium.


Mini-Cassette recorders have two other weaknesses.  One is that there is no erase head.  Recording over a previously used tape relies on the record head to write enough signal to mask what was already on the tape.  This approach is less than perfect, and repeated re-recordings will accumulate background noise, rendering the new recording less comprehensible.  The other weakness is that built-in microphones will often capture noise from the device’s tape transport mechanism.


Despite the technological limitations, there continues to be a market for Mini-Cassette recorders and their cassettes.  Though expensive, both remain in production today, even in the face of competition from hand-held digital recorders (perhaps because of the easy-to-use shuttling capability, or the ease of handing a cassette to a transcriptionist rather than coordinating the transfer of an audio file).

Mini- & microcassetts and their recorders.jpg

Figure 3.  Mini-Cassette (left) and Microcassette recorders with their cassettes.



Microcassettes (1.97” x 1.3” x .33”) were introduced by Olympus in 1969, intended for dictation and transcription using a hand-held voice recorder (Figure 3), for answering machines (where they became dominant), and for computer storage.  Microcassettes come in 10-, 15-, 30-, 60-, and 90-minute lengths (half on each side).  The Microcassette recorder’s standard tape speed is 15/16” per second, half that used with Compact Cassettes.  Some models offer the option of recording at 15/32” per second, which doubles the recording time—and worsens the audio fidelity.  (I recently converted a 90-minute Microcassette recorded at half speed, which yielded three hours of noisy audio content.)


Olympus introduced a “high fidelity” Microcassette model in 1982 that could satisfactorily record music in stereo.  This model was discontinued after only two years due to limited availability, the model’s cost, the recommended use of the more expensive Type IV (“metal”) tape, and shortened battery life (as low as two hours) because of the current necessary for the Type IV tape bias (see What Are Those Codes on Cassettes?).


Like Compact Cassettes, the transport mechanism involves a constant-speed capstan and pinch-roller, so the speed of the tape across the recording and playback heads is the same regardless of whether the tape is near its start or its end.  Unlike the Mini-Cassette, the tape is disengaged from the heads when playback is stopped, and one cannot listen to the audio in fast-forward or rewind modes.  As a result, shuttling forward or backward to a particular spot involves guesswork.  Like Mini-Cassette recorders, Microcassette devices lack erase heads, so repeated recordings on the same tape will progressively worsen the audio quality.  And the built-in microphone may capture the recorder’s tape transport noise.


Microcassette devices and cassettes are still in production and are more reasonably priced than Mini-Cassette items.  I receive one or two Microcassette conversion requests per year.


Confusion Between Mini-Cassettes and Microcassettes

In my research, I’ve encountered inconsistent and often erroneous application of the terms “Mini-Cassette” and “Microcassette.”  While “mini” and “micro” both imply “small,” and while both cassette types are noticeably smaller than Compact Cassettes (see Figure 4), the devices and their cassettes are not interchangeable.  Mini-Cassettes are slightly larger than Microcassettes, and you’ll note in Figure 4 that the tape transport sprockets are very different.​​​​​​​​​​​​​​​​​​​​

Compact, mini- & microcassettes.jpg

Figure 4.  Compact, Mini- and Micro Cassettes.


You would think that users and, especially, vendors would be aware of and respect the difference.  Alas, this is not the case.  Here are some examples of using inappropriate terms and their consequences.


  • While sellers on eBay in large part describe their Mini-Cassette devices accurately, the Item Specifics section of the posting typically lists the media as “cassettes” or “microcassettes.”It’s not clear to me that “mini-cassette” is among the choices available for that field.This can lead buyers toward making a wrong purchase decision.

  • Several one-star buyers’ reviews on eBay state that they were unable to play their own cassettes in the devices they purchased, sometimes blaming the manufacturer for a design requiring a proprietary cassette size.It’s likely that these buyers were unaware that Mini-Cassettes and Microcassettes are different, or they may have been misled as described above.

  • GE and Panasonic are selling Walkman-type devices on Amazon labeled by the companies as “Mini Cassette Recorders,” none of which specify the type of cassette used.One must read the Customer Questions & Answers section in the hopes that someone has mentioned that they use only Compact Cassettes.The likelihood that potential buyers will be misled is high, and the collection of scathing one-star reviews is richly deserved.Both companies, especially Panasonic, should know better.

  • A 2022 review of the “10 Best Mini Cassette Recorder[s]” listed seven Microcassette and three Compact Cassette devices (the GE and Panasonic models noted above), but no Mini-Cassette recorders.I find it hard to believe that the hands-on evaluation failed to reveal the two different cassette types used by these products.Given this methodological lapse, it’s fair to conclude that the self-proclaimed expert reviewers were unaware that Mini-Cassette recorders exist and that they use a third type of cassette.It’s conceivable that they may have stumbled upon the Philips Mini-Cassette recorder but dismissed it because of its price.


Instead of “let the buyer beware,” the motto to strive for should be “let the buyer be educated.”


Digital Audio Tape

Digital Audio Tape (DAT) is discussed in a separate article.




Other Uncommon Media


Aluminum Records

Aluminum discs were introduced in the late 1920s to record radio broadcasts or provide archival copies for performers or sponsors, and they were occasionally used to make recordings at home or in coin-operated booths at fairs.  The use of bare aluminum discs was short-lived, being overtaken by the introduction of lacquer records, described above.  Most aluminum recordings fell victim to scrap metal drives during World War II.


The grooves on aluminum records weren’t cut, but rather indented by a heavy recording head.  The net result was very wide grooves in a soft medium that would be damaged by any hard stylus, including steel needles in use at the time or modern crystal styli.  Owners were advised to use organic needles instead, typically a thorn or sharpened bamboo (which can still be found for sale on the Internet).


8-Track Tapes

8-track tapes appeared in 1964, offering two advantages over the then current reel-to-reel tape recorders.  Users no longer had to fumble with threading the tape, and due to their looped continuous play capability, one didn’t have to remove, flip, and rethread the tape to play the rest of it.  Enjoying a strong market in car stereos, 8-tracks were very successful from the mid-1960s to the late 1970s.


8-track tapes played at 3.75” per second, and like reel-to-reel, they used 1/4“ tape—though with eight tracks instead of the four on reel-to-reel tapes.  Rather than having feed and take-up reels like reel-to-reel, Compact Cassette, Microcassette, and Mini-Cassette recorders, 8-tracks had a single reel.  To create a continuous loop, tape was pulled from the inside of the reel at its hub, transported across the read head by a capstan and pinch roller, and then wound onto the outside of the reel at its rim.  The angular velocity of the reel was dictated by the speed of the tape being played and then wound onto the reel.  As each layer of tape shifted position away from the reel’s rim and toward the hub, the layer’s circumference became less and less, and the tape’s linear speed (which had to remain constant in order for the tape to be played) drifted further and further away from the reel’s angular speed.  Consequently, the tape was always slipping against its neighboring layers.  To prevent abrasion of the tape’s oxide layer, it was coated with a lubricant.  Unfortunately, the lubricant—and eventually the oxide—could be scraped off the tape, and the residue could collect on the capstan, which would cause an uneven and increased playing speed.  Because of this and several other difficulties inherent in their design, 8-tracks eventually lost popularity to Compact Cassettes, which had fewer inherent problems.


Wire Recordings

Wire recorders were introduced in 1930 for uses such as dictation, and they were used extensively by the military during World War II.  They were popular for home recording from 1947 to 1952, at which time they were overtaken by tape recorders.  (A wire recorder was featured in the movie Dick Tracy.)


Recordings were made by magnetizing a steel wire that was .004-.006” in diameter (a bit wider than a human hair).  The best wire was made of stainless steel; lesser quality wire that didn’t use stainless steel was marketed but was subject to corrosion.  Typical spools contained 7200’ of wire, and a spool was capable of recording about one hour at 24” per second.  Like Mini-Cassettes, the wire was transported by the take-up spool, so the actual speed was slower at the start of the wire and faster at its end.  The sound quality was decent for its intended use of capturing speech, but with a frequency range of only 200 Hz to 5 or 6 KHz, wire was inadequate for music (the normal range of human hearing is 20 Hz – 20 KHz).  Unlike magnetic tape, stainless steel wire recordings have not degenerated over time.  Functional wire recorders are still available, but they’re vanishing.  Wire recordings will likely outlast machinery that can play them.


Like a Kid in a Candy Store

There’s a certain risk associated with encountering uncommon media, and that is a sudden desire to acquire the capability to play them.  Hypothetically, my audio equipment wish list would include an 8-track tape deck, a wire recorder, and a gramophone or custom-built wide stylus to play aluminum records.  While the first typically has a headphone jack or line out jacks, and while a wire recorder’s speaker wire could be routed through an attenuator to create a line level output signal, recording from a gramophone would require a microphone or some other kind of transducer to convert mechanical vibrations into an electronic signal.  Though I’m unlikely to pursue any of these technologies in the near future, I can still fantasize about acquiring them!

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