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Three samples were considered the minimum number to make any determination of cassette consistency. Information was requested on each formulation's magnetic properties, features worthy of note, and prices. Unfortunately, technical information was not obtained on the majority of samples, and much of the data actually received was incomplete in one way or another. It was not possible, therefore, to correlate the test results with magnetic properties. Prices were obtained for most of the cassettes, but they were most confusing, what with list price, dealer price, audiophile net, maximum retail price, direct mail order, etc.
The requested samples were received from most of the makers, although fewer than three samples were provided in some cases. A few of the brands were obtained by direct purchase, including the bargain store labels, K-Mart and Zayre. All sources were contacted shortly before the testing started to ensure that the samples being used were representative of current production. The bargain-priced tapes were included so that their actual limitations would be defined and to supply additional information on how improvements in formulations benefit the purchaser.
A total of 58 formulations were tested, and technical data was secured on less than half of these. The table lists the majority of the C-90 magnetic specifications given, but some characteristics of lesser interest are not shown. The Tape Type entries were limited to "Fe" for many varieties of ferrics, "FeCr" for ferrichrome, "FeCo" for ferricobalt, and CrO2. As most of the manufacturers say very little about the exact make-up of the formulations, the listing is undetailed, and there could be some error.
The magnetization curve figure has points of interest labeled for reference.
The coercivity, ft., is the demagnetizing force needed to bring the induced flux to zero, and is expressed in oersteds. The retentivity, Br, is the number of flux lines per cm' (gauss) of the tape coating cross-section, the width of the tape, and the coating thickness. It is indicative of high-frequency sensitivity. Remanence, is the actual magnetic signal retention in lines of flux (Maxwells) applied to the specific tape. It is the total flux, not the flux density (gauss). Most manufacturers give values for the 0.150-inch width of the cassettes tapes. Some, however, give values for '/a-inch widths, and their figures must be multiplied by 0.6 for the smaller width. Remanence affects distortion, sensitivity, and output at the lower frequencies. Squareness ratio is the decimal fraction of the flux remaining relative to the maximum possible at saturation. It is a measure of the "efficiency" of the magnetization process.
Although DIN standards are not true international standards, some of them are used throughout the world. Test tapes made by BASF include a blank section of tape which is used to establish reference levels for sensitivity at 333 Hz and for bias. The manufacturer's figures for sensitivity and bias give his values in dB relative to the reference tape levels.
Sometimes confusion may arise because the bias for CrO2 tape may be referred to either the standard ferric tape or to the standard CrO2 tape. If the values are close to zero, the reference is to the standard CrO2 tape.
A basic guideline for the testing of each tape type was that each one would be presented at its best, with bias and EQ adjusted for best results. There was no "standard" fixed bias used to match one particular tape, causing other tapes to appear less satisfactory. An important part of the evaluation gear was a Technics RS-990005 3-head cassette deck.
This unit has front-panel continually variable bias and EQ pots, greatly facilitating the test process.
The first step for each tape was examination of the C-90 record playback response with the 1/3-octave RTA with pink noise being recorded at a low level. (A few tapes were available only in C-60.) The record head was adjusted for alignment with the play head, for the skew of the cassette in use. EQ was always started in detent (zero reference), and bias was adjusted for the best response between 1 and 10 kHz, with limits of +1 .5/-0.0 dB. EQ was used, if needed, to meet these amplitude limits. Bias was measured on the dB scale of a Heath SM-5238, referenced to standard bias, with a scope monitor. The EQ change was measured by noting the shift in dB at 10 kHz.
Notes on Headings: "COER" and "Oer" are "coercivity" and "oersteds" respectively.
"RET" and "Gau" are "retentivity" and "Gauss" respectively.
"REM" and "Max" are "remanence" and "Maxwells" respectively.
"SOU" and "RAT" are "squareness ratio." "SENS" is sensitivity, at 333 Hz.
Prices for C-90s are given as supplied and include all varieties of list, suggested net, direct mail order, suggested retail, etc.
The reference record level was established at 400 Hz for Dolby-level indication (200 nWb/m) in playback. Playback of the internal 400-Hz tone gave the data on tape sensitivity. Record/playback responses were run at the reference record level and 20 dB below that.
The maximum record level was measured at 100 and 400 Hz, and 3 kHz with an HDL3= 3 percent guideline and at 10 kHz for tape saturation. The signal-to-noise ratio used IEC "A" weighting with the 400-Hz 3 percent distortion point as the signal reference level. The Nakamichi T-100 audio analyzer was used to measure levels, signal and noise, and the distortion at 400 Hz. A Tektronix 5L4N spectrum analyzer was used for the 100 Hz and 3 kHz tests.
Swept responses utilized an Exact 128 generator with an 80-second sweep, a Gen Rad 1933 SLM as the a.c./d.c. log converter and an MFE 715 X-Y recorder. A Morrey-modified Heath IG-18 generator was the low-distortion source.
Modulation noise was measured with a 1-kHz tone recorded at 0 dB. The 500-to-1500 Hz bandpass was set with a Gen Rad 1952 filter, and the tone was notched out on playback with a UREI 560, with all suppressor filters at 1 kHz.
Flutter data was gathered with the Nakamichi T-100. Earlier data had also been taken with a Tandberg TCD-330 feeding a Ferrograph RTS-1. Amplitude stability and drop-outs were measured, to some extent, with the slow swept-frequency responses. Additional data was gained with a 3-kHz tone feeding the SLM on playback with Fast response, with its output feeding a storage scope.
Consistency of bias and EQ requirements, frequency response, sensitivity, and skew were checked for all samples of each length. Variations in C-60s or C 120s compared to C-90s were also determined, and their record/playback response plotted.
The 58 formulations were distributed in five categories as follows: 8 low-bias ferric tapes, 34 normal-bias ferric tapes, 3 ferrichrome tapes, 8 CrO2 tapes, and 5 high-bias non-CrO2 tapes. The need for the first category was revealed in the testing as these tapes exhibited common properties. The table shows the results with all of the C-90 tapes, grouped in the categories mentioned. (C-60 results are shown when that was the only length available.) Listed are the high-frequency 3-dB down points at 0 and-20 dB, the MRL at four frequencies, the S/N ratio in dBA, the modulation noise in (-) dB, and the relative 400-Hz sensitivity and bias, both in dB. The EQ is given in dB change introduced at 10 kHz. The flutter is weighted peak in percent. Frequency response plots are shown for each of the cassettes, including C-60 and C-120 lengths. Additional comments on each formulation appear with the discussion of the plots below. Cassettes were screw-assembled with regular hard-plastic boxes, unless noted otherwise.
As mentioned earlier, the bias and EQ were adjusted for the best response with each tape, with particular attention to the region between 1 and 10 kHz. Data taken on many tapes showed that a rough guideline could be drawn that for every dB change in bias with a particular tape, there would be a 2-dB change in response at 10 kHz. Increasing the bias would cause a drop in response, and decreasing it would have the reverse effect. With a particular recorder, changing to a tape requiring less bias could cause an unacceptable loss in highs, or perhaps reduce excessive highs in another case. A tape calling for more bias, of course, would add more response at the high end. From the bias listing in the table, you can tell what to expect in this regard if you do mage a change.
Consistency of bias requirements from one length to the other is reported for each formulation so that you will know what to expect. Perhaps you will want to choose a tape which shows the same bias for all lengths. Consistency of sensitivity for the various lengths of one tape, and differences in sensitivity from one tape to the other, is important for best Dolby tracking, particularly if your deck does not have provision for adjusting the record sensitivity. Variations in tape skew as shown by the need to adjust the record head of the Technics RS 99000S are indicative of changing mechanical alignment of the tape itself. If the tape were made and guided perfectly, the skew problem would disappear.
The relative skew from sample to sample for a tape, expressed in dB loss at 10 kHz, is indicative of the mechanical consistency resulting from design, manufacture and assembly.
Low-Bias Ferric Tapes
The eight tapes in this category all had the best responses with bias 3.0 dB or more below the ferric bias reference.
Some of the responses at -20 dB did not seem bad, but most were somewhat poorer at 0 dB. At the bottom of each column for the eight tapes are the average values. Note that the MRLs are below zero at all frequencies; measurable compression had taken place by the time these tapes had been driven hard enough to get to the reference playback level. All S/N ratios are less than 50 dBA, and the average modulation noise is less than 43 dB down. Most of the tapes had typical flutter figures, but the K-Mart and Zayre tapes were 50 percent higher than most. It had been expected that these two tapes would not be particularly great, but more had been expected from some of the others. No tapes in this category can be recommended for true high fidelity recording, though they can prove adequate for other purposes.
Normal-Bias Ferric Tapes
This category includes 34 tapes, more than half the total. Bias requirements ranged from -1.8 to +0.9 dB, with most figures between -1.0 and +0.4. Discrepancies between the bias specifications and the test settings kept appearing, but these differences were small in many cases. The average results for this large group were markedly better than those for the low-bias tapes high fidelity had been reached. It should be noted, however, that those formulations with bias values from -1 .8 to-0.7 were generally not the equal of tapes with higher bias requirements.
Once again, keep in mind that a lower bias tape (say -1.5 dB) would have a high-frequency loss (2 dB at 10 kHz) for more normal bias (say-0.5 dB). There are improvements in every single area over the low-bias (-3 dB) tapes, but some formulations in this category are little better. DAK HEC-SL, for example, has MRLs all below 0 dB and a S/N ratio of less than 50 dBA. There are other tapes with all MRLs below zero dB, and all of these have bias values on the minus side.
On the other hand, Ampex 20-20+ and Grand Master, BASF Professional I, Maxell UD and UDXLI, Memorex MRX3, Realistic Supertape Gold, Nakamichi EXIT, Scotch Master I, and TDK AD all deliver very good frequency response, excellent MRLs, very good S/N ratios, and low modulation noise. The average bias for these tapes was +0.1 dB. Review of the table will allow comparing a tape with any other, and with the averages for the category. Do not put too much weight on minor differences in frequency response. The difference in sound between roll-off at 1 5.5 and 16.5 kHz is very subtle, and such a difference can be caused by a small change in the bias.
More important is the smoothness from 1 to 10 kHz shown in the plots.
This group of just three tapes showed the best performance in response at-20 dB, MRLs at 100 and 400 Hz, and S/N ratio. Modulation noise was very close to that for the ferric tapes. The MRL at 10 kHz was somewhat better than the average of the better ferric tapes. The responses at 0 dB and the MRLs at 3 kHz were not quite as good, however, and the cause is unclear.
The eight tapes in this group showed response limitations similar to the FeCr cassettes at 0 dB, but the rolloff was at a higher frequency. At-20 dB, the high end limit averaged 18.2 kHz, better than any of the ferrics, although not equal to any of the FeCr tapes. The high-end-3dB point could have been shifted out very easily with a reduction in bias, but with an increase in a broad peak around 10 kHz, putting it above the +1.5 dB test limit. The S/N ratios were very good, although not up to those of the FeCr cassettes. The average modulation noise was lower than the ferric or FeCr tape averages. With the exception of BASF Professional II and Realistic CrO2, the test bias range was +0.5 dB, a small change in requirements from one tape to the other.
High-Bias Non-CrO2 Tapes
The five tapes in this group had performance that, on the average, was superior in each area compared to the CrO2 samples. There was some variation within each group, however, and any prospective choice should be compared to the other 12 tapes in the two categories, to say nothing about the FeCr formulations or one of the better ferrics. The flutter was very slightly higher than in any of the other categories.
Low-Bias Ferric Tapes
DAK HE: Generally smooth responses, but limited in extent. Compression across frequency range at zero dB level with roll-off of lows. Continual, rapid variations in sensitivity of 0.5 dB. Skew consistent within 1 .5 dB at 10 kHz for C 90s. Skew and bias of C-60s consistent with C-90s. Many medium drop-outs.
Sonic-weld cassette, a bit rough.
K-Mart: Generally smooth responses, but limited in extent. Compression across frequency range at 0 dB level.
Continual, rapid variations in sensitivity of 0.5 dB or so. Consistent skew and bias. Three medium and nine minor dropouts. Sonic-weld cassette, a bit rough, one of which jammed. Plastic bag.
Lafayette LN: Generally smooth response, but limited in extent, particularly at 0 dB where compression occurred. Continual variations in sensitivity of 0.5 dB or more. Spread in sensitivity of 2 dB from cassette to cassette.
Consistent skew and bias within C-90s.
Bias 2.4 dB higher (-0.9 dB) for C-60s.
Skew change caused 1 .5 dB drop at 10 kHz re C-90s. One C-60 jammed. Five medium drop-outs. Sonic-weld cassette.
Soft plastic box.
Lafayette Criterion: Generally smooth response. Overall the best performer in this category. Sensitivity spread of 1 dB. Consistent bias, but one C-90 had change in skew causing 3.5 dB drop at 10 kHz (on the three-head test deck). The C-60s had skew resulting in more than 10 dB drop with C-90 setting. C 60s showed compression at 0 dB. Nine major drop-outs.
Realistic Concertape: Limited frequency response. Compression at 0 dB. Continual, small variations in sensitivity. Consistent bias and skew. Eleven minor drop-outs. Sonic-weld cassette. Plastic bag.
Realistic LN: Limited frequency response. Compression at 0 dB. Amplitude variations generally less than 1/4 dB. One C-90 much different in skew. Skew effects for C-60s showed 3 dB spread at 10 kHz. Three medium and nine minor drop-outs. Sonic-weld cassette.
Royal APC/LN: Very limited frequency response. Heavy compression at 0 dB. Continual, rapid sensitivity variations up to 1 dB. Many major drop-outs. Excessive drag tripped end-of-tape sensor, preventing some tests. Sonic-weld cassette.
Zayre Pro Range: Mediocre response with continual, rapid sensitivity variations up to 1 dB and heavy compression at 0 dB. Sensitivity variations prevented getting data on bias and skew consistency.
Seven minor drop-outs. Sonic-weld cassette. Plastic bag.
Normal-Bias Ferric Tapes
Ampex Plus. Good frequency responses, average for this category.
One sample showed periodic sensitivity variations of 0.5 dB. Consistent bias and skew for C-90s, and for C-60s, but C 60s 0.7 dB less bias (-0.6 dB) and had different skew. Six minor drop-outs.
Ampex 20-20+: Good, smooth frequency response. Periodic sensitivity variations of 0.3 dB. Bias requirements consistent for both lengths. C-60s skewed slightly relative to C-90s. Four very minor drop-outs.
Ampex Grand Master: Very good, smooth frequency response with excellent headroom across the band. Excellent consistency in sensitivity, skew and bias requirements for all samples of both lengths. Two medium drop-outs. One of the best ferric tapes.
AudioMagnetics High Performance: Above average frequency responses with good headroom across the band.
Sensitivity spread over 1.5 dB plus continual small variations. Skew quite consistent from cassette to cassette, but varied some with time. Ten minor dropouts.
BASF Performance: About average frequency responses with lower than average headroom across the band. Sensitivity spread 1 .2 dB with very minor variations with time. Skew very consistent for all samples. C-60s required 0.3 dB more bias (to -1.3 dB). One medium drop-out.
BASF Studio: Frequency responses, headroom, etc. generally average for this category. Excellent consistency in bias and skew for all samples and all three lengths. Sensitivity consistent for all C-90s and C-60s, but 2.6 dB lower for C-120s. One major drop-out.
BASF Professional I; Very smooth frequency responses, although not particularly extended at-20 dB. Excellent headroom and S/N ratio. Sensitivity spread 1.6 dB, with very little variation with time. Bias requirement consistent, although shift in skew with one sample was evidenced with 1.5 dB drop at 10 kHz. One medium drop-out.
Capitol 1: Frequency responses generally smooth, but below average, as was the MRL at most points. Sensitivity, bias, and skew were consistent most of the time and for most samples, but a slow amplitude "breathing" in the higher frequencies made assessment difficult. C 60s required 1.8 dB lower bias (to-2.7 dB). One major drop-out. Sonic-welded.
Capitol Music: Smooth frequency responses, but below average, as was the MRL at most points. Consistent sensitivity, bias, and skew among C-90s and among C-60s, but C-60s were 1-dB more sensitive, required 0.4dB less bias (-1.0 dB) and showed 2-dB droop before correcting the record head. Three very minor drop-outs.
Certron HE: Average frequency responses. Below average for MRLs and other entries in table. Generally consistent sensitivity, skew, and bias requirements. Periodic small sensitivity variations. Five minor drop-outs.
Columbia Low Noise: Below average in frequency response and other respects.
Sensitivity spread of 1 .6 dB with minor variations with time. Skew inconsistency, with some samples down 6 dB at 10 kHz compared to most. C-60s required 0.9 dB less bias (-2.0 dB). Five very minor drop-outs. Sonic-welded.
Comsette Low Noise: This formulation provides average performance in all respects, with the exception of higher modulation noise, for a lower-than-average price. Variations in sensitivity of up to 2.5 dB at a 2 Hz rate appeared at one point. Some samples had noticeably different skew than others. Bias requirements for C-120s matched the C-90s, but the C-60s required 0.7 dB more (-0.3 dB). Seven minor drop-outs. Sonic welded.
DAK HEC-SL: Low-priced, direct-mail-order cassette was one of the poorest performers in this category, as examination of the table entries will show. Sensitivity was fairly consistent from cassette to cassette, but varied with time. Relative skew reached 1.5 dB at 10 kHz. Six minor drop-outs.
Fuji FL: Frequency responses and other characteristics were average. Sensitivity was very consistent and did not vary with time. Too few samples were received to check C-60 and C-120 consistency.
Four very minor drop-outs.
Fuji FX-I: Frequency responses and other results were, in general, above average. This cassette tape was outstanding in its consistency of sensitivity, skew, and bias requirements for all samples of both lengths. There were minor wiggles in amplitude in the plotting, but there were zero drop-outs.
Lafayette XHE: Average performances were obtained with this tape. Sensitivity, skew, and bias requirements were consistent among all samples of both lengths, with the exception of minor sensitivity differences. Variations with time were very small, and there were six minor drop-outs.
Maxell LN: Frequency responses and other results with this tape were average.
Skew was consistent among all of the samples, and bias and sensitivity were consistent for each length. C-60s required 0.9 dB more bias (+0.1 dB) and had the same sensitivity as the C-90s.
C-120s required 0.3 dB more bias (-0.5 dB) and were 1 .4 dB less sensitive than C-90s. Sensitivity variations with time were very small except for the C-120s, which had a slow, periodic shifting. Two medium drop-outs.
Maxell UD: Very smooth, above average frequency responses with other areas of high performance to match. Excellent consistency of sensitivity, skew, and bias requirements among all samples of both lengths. Small sensitivity variations with 3-second period. Zero drop-outs.
Lowest flutter of all tapes.
Maxell UDXLI: Generally smooth, above average frequency responses, but showing periodic sensitivity variations, of perhaps 0.5 dB. A high-performance tape in other areas, listed in the table, and with one exception, all samples consistent in sensitivity, skew, and bias requirements. Zero drop-outs.
Memorex MRX3: This tape formulation can provide performance that is above average in all areas. Bias and skew consistency could not be pinpointed as frequent, random level variations with most samples prevented ascertaining the best settings of the bias pot and the record head. With the best C-90 sample, used for the plotting, there were 1-dB variations about every two seconds. Four minor drop-outs. Sonic-welded. Memorex box.
Nakamichi EX: The results were above average and quite similar to Maxell UD. Sensitivity, skew, and bias requirements were consistent among all samples. Amplitude variations were very small, and there were zero dropouts.
Nakamichi EXIT: The response plots are above average, similar to Maxell UDXLI, but smoother. Outstanding consistency in sensitivity, skew, and bias requirements. Two medium and four minor drop-outs.
Realistic Supertape Gold: This tape, recently introduced by Radio Shack, had the widest frequency response at-20 dB for the ferrics. It was also one of the best in other areas, particularly MRL and S/N ratio. Sensitivity, skew, and bias requirements were very consistent for all samples of both lengths. There were some long-period variations in sensitivity of 0.8 dB. There were four medium and 7 minor drop-outs.
Royal Ultra Linear: This formulation had frequency responses and other characteristics that were average, in general.
Skew was fairly close among all samples. C-60s were 2 dB more sensitive than C-90s with 1 .5 dB less bias (-1.4 dB). Sensitivity variations occurred at times with a shift in level up to 2 dB. Drop-outs were minor.
Scotch Highlander: The frequency responses were below the group average, and the MRLs and the S/N ratios were low. Amplitude "breathing" at the higher frequencies prevented getting valid data on consistency. It appeared that the C-60s were quite close to the C-90s, but the C-120s required 1.6 dB less bias (-3.4 dB) and the sensitivity was 1 dB lower. Six minor drop-outs. Sonic-welded. Slide-in plastic box.
Scotch Dynarange: This tape delivers above average performance in every area, with the best response at 0 dB in this category. The MRLs were very good, with that at 10 kHz the best of all ferrics. Consistency was excellent among all samples and all three lengths.
C-120s were exceptions in that they needed 0.5 dB less bias (-0.2 dB) and were 2 dB less sensitive. A few very minor drop-outs. Sonic-welded.
Scotch Master I: One of the best of the ferrics with smooth, wide frequency responses, high MRLs, and S/N ratios.
C-90s consistent in all respects, but C 60s exhibited random and cyclic sensitivity variations which made adjustment difficult and interfered with the plotting.
Fourteen minor drop-outs.
Sony LN: Average frequency responses, and close to average in other areas.
Some variations in sensitivity, skew, and bias needs. Occasional 0.3 dB variations in sensitivity. One medium and four minor drop-outs.
Sony UHF: Overall, close to average in performance for the normal-bias ferrics.
Very good consistency of sensitivity, skew, and bias requirements for all samples. Occasional shifts in sensitivity of 0.8 dB. Ten minor drop-outs.
Superscope HF: Frequency responses were smooth at-20 dB, a bit limited at the high end, more so at 0 dB. Other results were also about average for the group. Skew and bias requirements were consistent for most samples. C-60s were 1 .4 dB more sensitive than C-90s.
Sensitivity varied 0.3 dB quite continually. One medium and 10 minor drop-outs.
One C-90 jammed. Sonic-welded.
Superscope SHF: Frequency responses were quite similar to HF, but this tape does provide the benefits of higher MRLs and lower noise. About average in performance, overall. Very good consistency in all respects, with the exception of one C-90 which had a somewhat different skew. Random shifts in sensitivity of 0.5 dB. One medium and 11 minor drop-outs.
TDK Maverick: Average frequency responses, but poorer than average in the other areas, except for modulation noise which was lower than most. Excellent consistency of sensitivity, skew, and bias needs for all samples. Zero dropouts. Cardboard box.
TDK D: The comments on TDK Maverick apply, in general, although modulation noise was average. The C-120 length required 0.9 dB less bias (-1 .9 dB) and was 1.7 dB less sensitive. C-180 samples could not be matched for performance and were dropped from the testing.
Sensitivity shifts of 0.5 dB appeared randomly. One medium and eight minor drop-outs.
TDK AD: Wide, smooth frequency responses, high MRLs and low noise make this one of the best ferrics. Consistency was outstanding with substantially no variation in sensitivity, skew, or bias requirements among all samples.
BASF Professional III: Wide frequency response at-20 dB, characteristic of the FeCr tapes. High MRLs, in general, and highest S/N ratio of all tapes tested, but also highest modulation noise in category. Excellent consistency among the three C-90 samples. Two minor dropouts.
Scotch Master III: Wide frequency response at-20 dB, best response of group at 0 dB. Other excellent results including high MRLs and best modulation noise in group. Sensitivity variations and high-frequency amplitude "breathing" with some samples prevented a complete assessment of consistency. C 60s appeared to need 1.1 dB less bias (1.6 dB) and to have 0.7 dB less sensitivity. Three minor drop-outs.
Sony FeCr: This tape had the widest frequency response of all tapes at-20 dB, but only a little greater than the other FeCr tapes. Sensitivity was quite consistent for all samples. C-60s required 0.8 dB less bias (-0.2 dB), and there were variations in skew. Two medium and two minor drop-outs.
BASF: Fairly wide response at-20 dB, but poorest of the group at this level and at 0 dB. Overall, the poorest of the CrO2 formulations. Most samples consistent in skew and bias needs. Some samples required change in bias of 0.5 dB. C-60 sensitivity 0.9 dB lower. Two medium drop-outs.
BASF Professional II: One of the best of the CrO2 tapes in response, with high MRLs and S/N ratio, along with low modulation noise. Consistency very good in all respects, except that one sample required more bias. Minor continual amplitude variations. One medium and three minor drop-outs.
Capitol Music: Frequency responses below average for group. Other characteristics were generally about average.
Considerable variations were evident in skew and sensitivity. C-60s required 1 .1 dB less bias (-1.1 dB) and were about 1 dB more sensitive. There were random shifts in sensitivity up to 1 dB. Two major and 10 minor drop-outs. No auto-switch sensing holgs.
Memorex: Frequency responses and modulation noise were better than average, while other characteristics were average for this category. Skew and bias requirements were very consistent for all samples. Sensitivity of the C-90s had a spread of 1.0 dB, but the average was close to that for the more consistent C 60s. Sensitivity shifts of about 1 dB appeared every several seconds. Three minor drop-outs. Sonic-welded. Memorex box.
Realistic: This was one of the better tapes in the group, with the best frequency response at-20 dB and better than average MRLs and S/N ratio. Modulation noise, however, was the poorest. The majority of the samples were consistent, but some had different skew.
C-60 bias was 0.6 dB higher (-0.1 dB) than the C-90s which had a large spread in sensitivity. Sensitivity varied 0.7 dB with some regularity. Four minor dropouts. Sonic-welded.
Royal: This formulation produced above average results in most areas listed in the table. Consistency was poor, however, not aided by the fact that mis-labeled C-60 samples were really Royal APC/ LN. Two C-90s tripped the end-of-tape sensor because of excessive drag, and two C-60s jammed. The samples that continued to work had minor sensitivity variations. Two minor drop-outs. No auto-switch sensing holes.
Sony: The-20-dB response and most other results were average for CrO2 tapes. The 0-dB response and the modulation noise were the best in this group. Excellent consistency in skew and bias requirements and in C-90 sensitivity. C-60 sensitivity had a 1.5 dB spread and was 0.8 dB lower, on the average. Two minor drop-outs.
Superscope: The-20-dB response was quite smooth and above average in extent, while the sensitivity, skew, and bias needs were all very consistent for the C-90s tested. Minor sensitivity variations with time. Three minor drop-outs.
No sensing holes.
High-Bias non-CrO2 Tapes
Fuji FX-1I; The frequency responses were the poorest in this category, but not at all far below others, and better than the average for the CrO2 tapes. Other results were slightly below average in most cases. Just two samples each of C-90 and C-60 had been obtained, but since the consistency of skew, sensitivity, and bias was so outstanding among those four, other samples should be expected to show similar excellence. The sensitivity was very stable with time, with 0.2 dB wiggles at the most. Zero drop-outs.
Maxell UDXLII: One of the best tapes in this group and in all categories with extended frequency response, especially at 0 dB, high MRLs and low noise. Consistency was excellent with insignificant variations in sensitivity, skew, or bias among all of the samples. One medium and six minor drop-outs.
Nakamichi SX: Perhaps the poorest tape in this group overall, but superior to the average CrO2 tape. Not quite equal to the same-source TDK SA reported below.
(Being earlier samples might be a cause.) Outstanding consistency with constant sensitivity, skew, and bias for all samples. Three minor drop-outs.
Scotch Master II: This formulation was one of the best performers in most areas of interest, with wide frequency response, high MRLs and the best S/N ratio in the group. On the other hand, sensitivity and skew variations with half the samples caused amplitude changes up to five dB in both cyclic and random fashion. Four major and 12 medium drop-outs.
TDK SA: Average performance for this category, but superior to most CrO2 tapes. Excellent consistency of sensitivity and skew. C-60s required 0.5 dB less bias (-0.4 dB).. Sensitivity variation of 0.3 dB every 2.5 seconds. One major and eight minor drop-outs.
Is there one best tape to buy? No.
There are really a fair number of well performing tapes to choose from, with various trade-offs to be weighed according to your own particular needs. We can say that the low-bias ferrics are unacceptable, but in the normal bias range there are a number to choose from. Most of the really good ones have bias quite close to zero, so that will not be a major factor in switching from one to another.
Do keep in mind, however, what the effects of bias differences are. The FeCr tapes provide better performance for more money. Are they worth it to you? The non-CrO2 high-bias tapes gave superior results to the averages for the CrO2 tapes, but not necessarily when compared to the better ones in that category. The non-CrO2 tapes had slightly higher flutter, but these differences were very small. The flutter readings varied more from time to time with the same cassette than they did from one type to the other. Your final choice could very well depend upon local availability, best price/performance ratio, or even the ease of writing on the labels.
The general recommendation is to use a tape that offers the combination of performance at least as good as you need, consistency in all respects, and acceptable cost.
(Source: Audio magazine, Sept. 1978; by Howard A. Roberson)
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