(Advent on Tape.) Why We Believe That Chromium-Dioxide Is The Tape To Buy For Highest-Quality Cassette Recording.
When we at Advent were developing the first high-performance cassette recording
equipment, we applied two innovations that were crucial for making cassettes
that could equal or surpass the quality of the best stereo records. One was
the Dolby System of noise reduction.
The other was DuPont's chromium-dioxide (CrO2) tape formulation.
At the time, chromium-dioxide was being used (as it still is) for video recordings, for which its high-frequency performance was unparalleled. But no one was marketing it for audio cassettes. Since we felt it was a must for highest quality, we decided to market it ourselves although we had never thought we would be in the tape business.
Since that time, other manufacturers have followed suit (as they have in making high-performance cassette equipment). And other tape formulations have appeared on the market, with claims of performance surpassing that of chromium-dioxide. Some claims have been, to put it kindly, very questionable. So it feels like the time for us to be very explicit on what chromium-dioxide has to offer. We think no other tape offers its combination of advantages.
Here are those advantages:
High Coercivity and Excellent High-Frequency Response.
Chromium-dioxide is a man-made oxide, "grown" very much as crystals are: Unlike iron (ferric) oxide, which has to be ground and milled to achieve an appropriate particle size for tape, CrO2 particles can be grown to near-perfect size and shape for cassette recording.
One of their advantages is high coercivity. That is, it takes a very strong force to magnetize and demagnetize chromium-dioxide tape. One thing this means is that the bias current necessary for tape recording, which has a tendency to erase high frequencies during the recording process (especially at low speed), has far less of this effect on CrO2 than on standard ferric oxides.
Chromium-dioxide holds onto high-frequency signals that would be "self-erased" on standard ferric oxide tapes. More important, it can put onto the tape an unprecedented total amount of high-frequency energy--a function of both its coercivity and the near-ideal size and orientation of its particles. No tape we know of surpasses it in this crucial consideration, and few approach it. (Probably the best indication of CrO2's high-frequency abilities is that it is considered a prime tape for video cassette recording, in which it must deal at relatively low speed with a video bandwidth in the millions of Hz.) Low Noise and High Output.
The unique advantage of CrO2's total high-frequency capability for cassettes is the way it lends itself to the objective of a low-noise, wide-frequency-and-dynamic-range medium.
As we indicate in the diagram, chromium-dioxide's high-frequency response begins to rise at 1,000 Hz, and is up by 6-7 dB at 10,000 Hz. This rising characteristic allows an unusually steep equalization of the signal during playback (the "CrO2" equalization now found on all good cassette decks for home use) to level out the overall frequency response. And in this equalization process, the tape noise under the high frequencies automatically comes down along with the signal by 4-6 dB. (That means 4-6 dB greater noise reduction than would be possible with standard equalization of standard tape.) That is a tremendous advantage, and in conjunction with the Dolby System was, and is, the key to cassettes with sound that is at least as good as that of the best records. And CrO2's noise-reduction benefits for cassettes are automatic-built into the playback process.
6-7dB TAPE NOISE
Frequency in Hz (cycles per second Frequency in Hz (cycles per second) A. Chromium dioxide's rising high-frequency response (up by 6-7 dB at 10,000 Hz).
B. When this response is equalized downward in play back for flat response, tape noise is automatically reduced by the same amount.
It's also possible to increase potential signal-to-noise ratio in another way, as conventional cassette tapes have done, by raising the total amount of signal that can be put onto tape. But to realize that potential in everyday use, the recordist at home has to be able to set levels critically for maximum signal on each recording. In practice, most people can't manage this and don't get anything like the maximum benefit from this approach.
Which is why we introduced not only CrO2 itself but the special equalization characteristic that makes its low-noise potential automatic in everyday use.
While other tapes have since claimed to have added still more dynamic range, their maximum increase is actually small (2dB) and realizable only with the highest possible setting of recording levels.
In practice, we know of no tape with significantly, audibly greater signal-to-noise capabilities than CrO2.
Low Print-Through.
Another advantage of CrO2's high coercivity is that it not only magnetizes exceptionally to begin with but stays magnetized to an unprecedented degree, storing the signal with an absolute minimum of signal leakage ("print-through") from one layer of tape to the next.
Print-through can be a none-too-subtle form of noise, and can contribute to a murky overall recording quality.
CrO2 has the lowest print-through we know of in cassette recording, and this, along with its very low modulation noise, makes it an even more impressively low-noise recording medium overall.
Low Drop-Out.
CrO2's long, thin particles disperse very evenly over the surface of the tape (see photo), without the tendency to clump or leave bare spots. Their small and consistent size also allows them to be easily oriented the right (longitudinal) way on tape.
These two factors add up to a highly uniform, consistent tape coating that avoids drop-out problems either at first or after repeated playings.
1 1/2ยต : A 5,000-time magnification of a very small section (less than half a cassette tape width) of Advent CrO2 tape.
The 1 1/2-micron marker under the photo indicates the width of a standard head gap in cassette recorders.
The extremely even and almost perfectly longitudinal dispersement of the oxide particles makes for uniform response and freedom from drop-outs.
Low Head Wear.
Chromium-dioxide's head-wear characteristics are satisfyingly low not only for audio cassette recorders but for operation (with heads of critically narrow gaps) in video cassette recorders. A home recordist can expect excellent head life with CrO2. Compatibility.
The CrO2 playback standard pioneered by Advent is now provided in all high-quality stereo cassette decks for home use. You can enjoy chromium-dioxide's full capabilities on all of them.
Among premium tapes other than CrO2, however, are some that require equalization and/or biasing that isn't provided by today's cassette machines. Whatever the theoretical advantages of these tapes (and we know of none that exceeds CrO2's sonic capabilities), you can't realize them in the right proportions in actual use. Using them on today's cassette recorders is like using a film with a camera that doesn't supply the right ASA number.
Most auto stereo recorders don't supply the right pro visions for either CrO2 or other premium tapes, and we know of no way you can enjoy their full advantages on the road. What you do get from CrO2 on car cassette machines, however, is a high-frequency boost that in the usual circumstances (with equipment that isn't the ultimate in high-frequency response) is pretty welcome.
Uniformity.
The unique nature of CrO2 particles makes for excellent coating uniformity from batch to batch in the manufacturing process. Overall results with any tape also depend on keeping other factors consistent, including the manufacture of the cassette housing. We at Advent take considerable pains to make sure of product consistency in tape as well as on other products. and we know that several other marketers of CrO2 take similar pains. Not all brands of CrO2 are the same in final quality, but the consistency that's made possible by CrO2's basic properties is at least as good as that of any other tape.
Price-Performance Ratio.
You can enjoy all of chromium-dioxide's advantages for a cost that is generally less- sometimes by a very wide margin-than that of other "premium" tapes.
(Prices vary, so we can't do a brand-by-brand break down here. But you can generally expect to pay between $3.00 and $4.00 for a C-90 cassette of Advent chromium-dioxide. And we think any check you care to make will quickly support Advent chromium-dioxide's price advantage relative to other "premium" formulations.) CrO2 also doesn't cost more than standard lower-performance ferric oxides. It does cost a good bit more than so-called "bargain" tapes, but those tapes are generally no bargain in performance, durability, and kindness to tape machines.
We at Advent aren't primarily in the tape business.
We introduced, and continue to market, DuPont's chromium-dioxide formulation because we feel it is an unparalleled overall combination of the things that are important to people who are seriously interested in cassette recording. Chromium-dioxide isn't the only excellent tape on the market, but it is the best combination we know of all the factors- including price-that determine the real enjoyment of real people in real situations. We know of no tape that's better for cassette recording.
Advent Corporation, 195 Albany Street, Cambridge, Massachusetts 02139.
*Back in the days when CrO2 was first coming into use, a whispering campaign- begun, we suspect, by someone with a lot to lose if CrO2 became important (as it did)-began to spread the story that chromium dioxide wore heads excessively. This has never been true, and at least one manufacturer who recently asserted that claim in print has since retracted it. In six years of selling CrO2 and cassette equipment, we haven't received a single complaint of excessive headwear from CrO2.
Advent Corporation, 1976
-----------(High Fidelity, Jan. 1977)
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