Recording the Masters FOX C-60: The New Audio Cassette Standard

by Carlos Guzman

Technics RS M63. That was the first cassette deck recorder I bought with my own money. On monthly installments, I paid $21.50 for 24 months with my funeral home’s attendant part-time job. I would prefer the RS M85, but I couldn’t afford the payments so, I was very happy with my new acquisition. A 3-head machine with a decent sound and beautiful digital meters. By those days, TDK was my preferred tape and I bought it by boxes of 10. I recorded hundreds of tapes on that machine and used it until the main motor passed away! Ha! I still conserve those tapes, even the first one I recorded on the M 63 in 1979.

As time went by, the 80’s became the heydays of the audio cassette technology and the development of extraordinaire tape formulas elevated that media to higher standards and excellent sound. Then, with the arrival of advanced cassette decks by Nakamichi, Revox, Tandberg, Teac, etc , the cassette tape obtained the recognition it deserved among the high-end circle for the very first time in its 30+ years of existence. The Nakamichi “Dragon” was elevated to a cult status and the race for “the best” was on. Unfortunately, when the cassette media was on its peak, the CD took over and little by little the tape faded away into history. This was very sad for me because I used to have an audio cassette duplication plant and the switch to CD pressing was not fun, neither cheap! Who would imagine that many years later the tape revival would take place again? I never stopped using tapes in my life, but a serious come back was never on my mind!

Tape Revival

On the pro arena, the tape kept going longer than for domestic applications. The used of 24 ch, 2” tapes were still in vogue during the 90’s and the masters I received for Mastering at my business, arrived on ½” tapes, running at 30 ips or 15 ips with Dolby SR. Suddenly, more and more DAT’s and CDR’s started to show up, replacing the better sounding, but more expensive tape. Quantegy and EMTEC were the last incarnations of Ampex and BASF respectively when both companies decided to divesture their tape businesses into independent entities and since then both companies has gone through a lot of changes, and with all honesty it’s a miracle that both still alive because 3M, the first of the 3 who abandoned the tape arena, never came back.

Couple of years ago, the people from Mulann Industries of France bought the machinery and formulas of the BASF tapes from RMGI. Since then, they have been manufacturing the legendary BASF formulas under the Recording the Masters (RTM) brand, but not only that; they have also been developing new tapes, like the new LPR 90 open reel tape, for example. Surprisingly, not only the open reel tape has become the new kid on the block for the audiophiles, but the audio cassette has become the main media of the independent artists who release their music on cassettes as well! Who could have envisioned that? The remaining living techs has been frantically restoring and refurbishing Walkman’s and classic cassette decks lately. At least a new open reel deck has been developed (Ballfinger) but the latest cassette decks are not what you can call a quality product. That’s the main reason why the serious recordist has been forced to restore old gems.

Since many inquiries were made concerning a new cassette tape, RTM was finally convinced to experiment with a new audio cassette basing its formula on the fabled SM 900. Just imagine the process of developing and slitting a tape that has not been created for over 20 years now! It was not easy. I asked Theo Gardin, a young and feisty French guy who’s in charge of the sales for RTM and he confirmed that it was not easy indeed. A lot of experimenting, trial and error went through. Finally, and just recently, they were able to create the first new and fresh formula of an audio cassette in decades: the new FOX C-60.

What’s in the name?

FOX=Ferric Oxide. But don’t be deterred by the “ferric” on it because this is not a common “ferric”. This is what we can call a “Super Ferric” formula as it was based on their fabled SM 900, their best professional open reel tape formula. As soon as they came out with prototypes, they were kind enough as to send me 3 samples. All are C-60 and will continued to be by now because the thickness of the C-90 film is no longer produced and they must experiment with new options. Anyway, I already recommended to load the tape in non-standard lengths, like for example a C-64. After all, this is the first cassette tape formula developed in 20 years, so, who cares about any standard?

The Fox: tape and shell

First, let me clear out that the pictures you see here might not be the final product as these are prototypes only. I received 3 tapes, C-60, ferric or “normal” loaded in a clear C-0 (shell). The shell looks simple but when I winded the tape on any of my decks, it runs extremely smooth! To be honest, I was surprised. The shell is a 5 screw on with no graphite sleeve inside. A normal looking tape pad. I mean, nothing special…until you run it!

The basic parts which constitute a precision cassette are:

  • 2 shell halves plus their windows
  • 2 lubricated foil sheets, often called slip sheets”
  • 2 hubs, each with an interlocking piece to attach the tape leader
  • 2 roller guides on lubricated stainless-steel axle pins
  • 1 metal shield
  • 1 pressure pad
  • tape and 2 leaders

At least that’s how a good quality shell must be. This one has no slip sheets, neither the steel axle pins, but as I have said: this is just a prototype and besides that, I’m afraid that we wouldn’t be able to obtain the higher standards of C0’s manufacturing with today’s available tooling.

The slip sheets, made of a variety of plastic films with Teflon, silicone, or graphite lubrication, act as bearing surfaces for the hubs and as gentle guides for the tape packs. Without them, a cassette housing cannot provide uniform tape travel and cannot reduce tape edge damage. Although these sheets are often overlooked components of a cassette housing, they are critical in keeping wow and flutter to low levels because of the contact with the moving tape and hub.

The guides are very critical for proper alignment, especially in double-capstan drive systems. Their axle pins must be wobble-free and aligned 90° to the plane of tape travel to avoid shifting the tape across the heads. The guide itself should be perfectly concentric. Its shaft should have a slight bulge to it with the widest part exactly in the middle of the tape path. The molding technique must be such that no seam or burr exists anywhere on the guide. The ends of the guide have flanges with very sharp delineation for the best tape contact. The roller is usually low- friction Delrin® -type plastic to allow the smoothest rotation on the axle pins.


I interviewed their research and developing director, Monsieur Guillaume Enguehard, a nice young guy that is also an audiophile like many of us, and he was very informative:

Since my French is limited, I decided to call him Guil. It happened to be that I correctly guessed what the name FOX was all about:

Regarding the name you’re right: FOX means Ferric Oxide.

What made you decide to go ahead with a new cassette tape?

The first step was to decide to do it. R&D cost money, Mulann is a small company and we haven’t got a lot of human resources. We had to know if a market will exist and if we will not waste our time.

Yep! You are right about that and I remember have discussing this issue with your boss Jean-Luc Renou and with Theo as well.

Technically speaking, we begun by a benchmark. We bought several brands and type of cassettes and we measured them (Thickness, Mol, Sol, Bias Noise, Frequency response etc.). Results allowed us to determine a target to achieve in terms of audio performances.

Having some high-quality open reel tape formulas already developed, did you adapt anything form it?

Yes. As we had two formulations for our reel to reel tape we tried both with adapted parameters on our coating machine. With these tests, we’ve chosen the most adapted formulation for our cassette. Then we performed two trials: The first was ok but the tape was too thick for a cassette format and some settings on our coating machine had to be adjusted: Profile of the knife coater, speed of the machine, tension etc…

The second trial is the one you have in your hands.

I see. What was your main obstacle?

The main difficulty was to coat a very thin and homogeneous magnetic layer on many kilometers of base film. The slitting step is also difficult because winding a 3,81mm tape into pancakes is more easily said than done.

I know Mulann manufactures other kinds of tapes for other applications. How did that help?

Added to R2R tapes, Mulann produces instrumentation tapes for military application. These tapes are very demanding to manufacture. Thanks to that, we have a strong experience and knowledge in term of precise coating. We have used this experience to coat the FOX cassette.

Well folks, there you have it! A short story of how the people of Mulann and their RTM division decided to risk their resources developing a new cassette tape formula in years! Now, the main question is always the same: are you planning to develop a Chrome version?

As Guil says: it’s easier said than done. Regarding the CRO2 question, this is what Theo Gardin has to say about it:

For the moment, we are focused on the Ferro version. The Koreans are our current source for a type of (chrome) pigment, but it is not a reliable source as they are not sure to keep providing it. Same case regarding China.

Why does the serious cassette tape recordist keep asking for Chrome? Well, according to BASF, RTM predecessor, this is what happens with the CRO2 tape:

The greatest single advantage of chromium dioxide lies in the shape of its particles. E.l. DuPont, an American company, discovered the process by which chromium trioxide decomposed in the presence of water at a temperature of 900° F and under a pressure of 30,000 psi to yield a synthetic mono-crystal of chromium dioxide. These particles are very small, very long and thin, and very similar to each other in size and shape. They are also totally free of the physical deformities that plague gamma ferric oxides. Gamma ferric particles not only vary a great deal from each other in both shape and size, they also suffer from physical flaws such as dendrites and holes. Dendrites are branch-like imperfections that stick out from the trunk of the ferric particle. The holes are created when gasses escape from the particle in refining stages. Under a microscope the ferric particle looks like a spongy rod; a CrO2, particle looks like a smooth glass rod because it has no deformities. (BASF Technical Bulletin)

The most important characteristics of Chrome are: Lower noise, better dynamic range, better MOL handling, last longer and has a greater pressure stability (head against tape pressure).

So, sorry folks. No new chrome tape by now. We’ll have to exploit the FOX till’ its full limits and that’s exactly what I’ve done. I guess that if the sales numbers for the FOX are encouraging, perhaps RTM could be inspired to manufacture a CRO2 formula. Who knows?

Audio Tests

The cassettes arrived in what we professionally call an “O-Card”. A nice looking one with the Recording the Masters logo all over it. Again, this is not the final product, but it looks good anyway! Since I have no laboratories or specialized equipment to measure the physical and technical properties of any tape, I just conducted what any advocated recordist would do. I tried the tapes on 3 different decks from my collection: Nakamichi Dragon, Nakamichi CR 7 and Revox B 215S. I also did another test duplicating an open reel tape from an Otari MTR 12 to a Nakamichi ZX 7. All tests were passed with flying colors.

We have already mentioned that ferric formulas have limitations with the high frequencies and tend to produce more hiss. This has been historically correct since the beginning. We know and have used “super ferrics” from the 80’s and 90’s but most of the time the serious recording hobbyist preferred the CHROME or METAL formulas. Unfortunately, it seems to me that we’ll have to adapt and learn how to exploit the FOX properties to the maximum and get the best out of it.

I tried several recordings with Dolby B, Dolby C and no Dolby at all, with and without HX PRO. I pushed the FOX to +6db on the Naks and the tape handled it very good. Definitely, once we recorded the same section on the Revox with Dolby C and HX PRO, the game was over! The sound was so good that we decided to broadcast one of my Eclectomatik shows (on the air every Saturday at 11:00 AM EST by Frission Radio . Com) recorded on a Fox C-60. Over 3,000 persons heard the historical moment and everybody seemed highly impressed with the results.

As a final trial, I decided to try a dubbing from open reel to cassette tape like it used to be when duplicating real time cassette tapes in the 80’s, just like Nakamichi used to do in Torrance, CA, to get the feeling of the cassette heydays. I got this copy from a soundtrack music producer friend of mine in California. The tape was recorded @30 ips, no NR and hot level. I believe it was a production copy of a big band jazz orchestra from GRP. How he got it? I never asked such questions…Ha! Anyway, I played the tape from the Otari MTR 12 to a Nakamichi ZX 7… HOLY SHIT! This is the closest you could ever get to a live concert and I’m deeply serious!

Well, again, I choose Dolby C on the ZX 7 and a level of +4 with occasional peaks at +6 db on the VU’s. You must listen to this. Many times, I had to realize that this was a ferric tape and not a super-duper Metal from the 90’s. Amazing.


It’s obvious that we have already seen the best days of the tape era and realistically speaking, we would never see this format occupying a main position on our everyday lives again. The modest revival we have noticed is more like a new fever en vogue comparable to the Cigar boom of the 90’s which slowly faded away but continue to live by this day on limited numbers and with the support of the “real cigar aficionados”. For the “hipsters”, the cassette is a nostalgic media and a convenient format to introduce new music for their niche public. but for other tape lovers like me, it’s still a serious music reproduction vehicle.

The problem the cassette had during its better days was the same as Vinyl: it takes knowledge, time and money to properly play an LP or a cassette. Most of what John Q Public knew about playing a cassette tape was one of those green colored, low quality duplicated tapes played on a cheap car stereo after been bombarded with high temperatures and UV rays all day long! The more fortunate had access to a nice Sony Walkman, but tell me: how many could experience a nice recorded Metal tape and played back on a decent deck? Not many. Unfortunately. Every time I tell my guests that the music they were hearing comes from a cassette tape, they simply couldn’t believe it! A properly played cassette could rival many old ¼ tk open reel tapes, even to this day.

Today, it’s almost a miracle that companies like RTM has taken the initiative to invest and develop new tapes and even more critical when we talk about cassette tape. It’s more difficult and costly to do this than an open reel tape. What we took for granted 3 decades ago, now is a needle in a haystack, like the pigments, films, and slitters used to produce such a minuscule tape.

As much as I love this format, we can’t play the naïve and expect a total resurgence selling millions of units a year like it used to be, but the fact that thousands of high-quality cassette decks are been restored every day, the launch of new productions on cassettes and the audacity of people like Mulann producing new tape formulas give us a light of hope among the digital stream “darkness”. It would never be the “new kid on the block” again or even represent significant figures for the big labels, but who cares?

About the Author

In 1994 I established the best cassette duplication plant in the Caribbean: Copytech Corporation. A year later we opened one of the best mastering suites in the whole USA with over $100,000.00 investment in acoustics and audio systems. I did over 1,000 projects earning several gold and platinum records, 2 Grammy nominations and finally a Grammy in 2002.

During one time or another, I used to have over 85 pieces of audio at home with over 30 cassette decks and open reel recorders. From a Nakamichi 500 to a Studer A 80 1/2″ machine! My collection is smaller now, but still one of the biggest in Puerto Rico and perhaps the biggest of cassette decks anyway. At the moment, I’m concentrating in quality instead of quantity and I’m only looking for the best cassette decks ever made, specifically Nakamichi & Revox. I do have other brands, but these 2 are my longtime favorites. I also own a Crown Open Reel Deck CX 822, Revox B 77, Revox PR 99 MKiii and an Otari MTR 12 with Dolby SR 361 and other toys.


  1. I still use a Tascam 414 with dbx compansion and the result is that I prefer this over anything else and it bears no resemblance to Protools. There is the new tape being manufactured by National Audio and now this FOX tape. Although not Chrome, what results would I expect? I am still running Type II old stock but eventually this will run out.

Comments are closed.