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With the continuing introduction and updating of cassette tape formulations, it was just about inevitable that some manufacturer would deliver samples after the deadline for our "Mass Tape Test" (September 1983). Konica and TDK had that distinction, but the omission is being corrected here. There are two Konica Type I formulations, designated ML and GM-I, a Type II tape called GM-II and a Type IV, Metal. TDK introduced a new metal particle formulation, designated HX-S, which is unique in that it is designed to use Type II bias. The manufacturer claims greatly improved high-frequency MOLs, which normally aren't very good for Type II tapes.
This follow-up will also cover retesting of Radio Shack (Realistic) and Swire formulations. Radio Shack specifically questioned the results presented for their Supertape Hi-Bias tape, but provided samples for their entire cassette line. Retesting was conducted on the three formulations covered before, and the same tests were run on Realistic Low Noise, which had not been evaluated. Swire also felt that the results indicated the samples of their tapes were not representative and provided new samples for retest.
A brief word is in order to describe the evaluation leading to the results in the Table, response plots, and commentary that follow. All of the tests were made on a Nakamichi 582 deck.
The bias for each tape was adjusted for best response at 20 dB below Dolby level, after adjusting the record head for alignment with the playback head for that particular sample. The bias level was metered and referenced to the bias that secured best response with the IEC reference tape for the tape type under consideration. The record sensitivity was checked against the same reference tape. Because the frequency responses at -20 dB were so similar, they were not plotted. Those at 0 dB, or Dolby level, were, however, as they showed the limitations from high frequency saturation.
The MRLs (maximum record levels) at a limit of 3% third-harmonic distortion were measured at 100 and 400 Hz and at 1 and 2 kHz. The 3% THD limit for higher frequencies was established using twin-tone IM techniques. The signal-to-noise ratio was measured with both IEC A and CCIR/ARM weightings, using the level for 3% distortion at 400 Hz as the reference. (The Table of results does not list the CCIR/ARM figures, as they were consistently just about 2.6 dB less than the dBA results.) Modulation noise was measured by recording a 1-kHz tone at +3 dB, notching out the tone in playback with a very narrow filter, and measuring the output noise after a bandpass filter of 500 to 1,500 Hz was inserted.
The output-level stability, dropouts and flutter were all measured on the playback of a recorded 3-kHz tone.
The stability was examined with a 2-S/division sweep on a spectrum analyzer tuned to 3 kHz, while the dropout check used a sweep rate of 0.05 S per division.
Table I lists the results of the evaluation of the 12 formulations. The arrangement is exactly the same as used in the earlier article, facilitating any comparisons that might be desired.
Each of the 0-dB response plots has a 3% MRL curve added to help visualize the significance of the figures in the Table.
The brief comments below on each of the formulations are arranged alphabetically by brand within tape type.
Most of the tapes showed little or no skew and had consistent sensitivity and bias. The output-level stability was usually quite good, and most of the samples showed average flutter.
Type I Tapes
Konica ML: Overall, the results would be classified as typical for a Type I tape. The analyzer display in the dropout test showed some roughness, but dropouts close to audibility were quite infrequent.
Konica GM-l: This is one of the better tapes in this category, with good MRLs, nice responses, high consistency, no skew, low noise, very good output-level stability and no dropouts, even of a minor nature.
Realistic Low Noise: This is a non-premium tape with low MRLs and higher noise than most Type I tapes. The consistency was quite good in most respects, but one of the samples which showed a little skew also had some output-level wandering (0.35 dB) and higher than average flutter.
Realistic Supertape Gold: Tests of the newer samples revealed that a good Type I tape had become better, with higher MRLs, lower noise, and improved output-level stability. Flutter was slightly better than average.
Swire Laser XL: The new samples evidenced general improvements. Especially worthwhile was the over 5-dB increase in MRLs from 100 to 2,000 Hz.
Bias and sensitivity were much closer to the IEC reference tape. The samples had noticeable skew, however, and the output-level stability was just fair.
Swire Laser UHDI: The earlier tests of this formulation had shown an unusual distortion spectrum under some conditions, but the new samples did not have any such characteristic. The MRLs were fairly good across the band, and there was a slight improvement in the signal-to-noise ratio. The samples were very consistent, including their lack of skew.
Type II Tapes
Konica GM-/I: This is a good Type II tape, with good MRLs, low noise, no dropouts and excellent output-level stability. The samples had excellent consistency of sensitivity, bias needs and lack of skew.
Realistic Supertape Hi-Bias: It was quickly apparent that results with the new samples were better than first reported. A reassessment of the earlier samples revealed that a reference-level error of 2 dB had been introduced inadvertently while doing low- and mid frequency MRL tests with this formulation only. The new samples provided even better results, with good MRLs and low noise, as shown in Table I. There was little measured skew, also an improvement over the earlier report.
Swire Laser UHDII: The new samples of this tape were somewhat different from those tested before: Poorer low frequency MRLs, better high-frequency MRLs, a lower signal-to-noise ratio and lower modulation noise. Overall, it remained one of the poorer Type II tapes.
TDK HX-S: The test results listed in the Table demonstrate that this formulation takes its place as the highest performing of all Type IIs, with the most extended responses at both 0 and -20 dB and the highest MRLs overall. The signal-to-noise ratio is very good, but not outstanding, and the modulation noise is a little high. The required bias was to the IEC reference, but the sensitivity was at +3.5 dB-not a problem if one compensates for it. There was outstanding consistency among all samples, including both sides.
Type IV Tapes Konica Metal: This is a typical metal tape, showing extended responses, high MRLs and low noise. The consistency from sample to sample was very good, including no skew. The dropout display was a bit rough, but none of them got to the audibility threshold.
Realistic Supertape Metal: These new samples were in improved boxes with shrink-wrap, a change from the Radio Shack practice of using simple label seals. More important, however, was the increase in MRLs across the band, making this one of the better metal tapes. Its consistency remained one of the best for this tape type, and the low price adds to its appeal.
The evaluation of these 12 formulations demonstrated that the user can expect to see continuing improvements in products from tape manufacturers. TDK HX-S is an unusual addition to the tapes available, and for some decks, the lower bias requirements of this excellent formulation will be beneficial. And there will be new names appearing on those boxes as other firms hope for success in this competitive market. Perhaps this will increase confusion about what choice to make, but isn't it nice to have a number of quality formulations to choose from?
(Audio magazine, Sept. 1984; by Howard A. Roberson)
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