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Can chrome tape sound as good as CDs? Taking the BASF CD challenge Over the next few months in shopping malls, record bars and at major sporting events, Australians will be challenged to identify whether music is coming from a BASF chromium dioxide audio tape or a CD. BASF reckon you won't be able to hear the difference. By LEO SIMPSON Not only do BASF reckon that their chrome tape is "damn close to CD" but they also state that their chrome tape is "99.9% noise-free". Such claims seem outrageous, don't they? After all, everyone knows that CDs and CD players have a much greater signal to noise ratio and available dynamic range than cassette players. CDs also have lower distortion, better frequency response and much lower wow and flutter. BASF still reckon that few people will be able to tell the difference when they listen to the set-up they will have in shopping malls and record bars. Essentially, the equipment rack you will see uses standard Pioneer hifi equipment - a CD player, a 3-head stereo cassette deck with Dolby C noise reduction and a stereo amplifier which drives several sets of headphones. At the top of the rack is a unit made by BASF which switches the · output signals from the CD player and the tape deck to the inputs of the stereo amplifier. It does this in a random fashion so that you listen to 10 12-second segments of music. You then have to identify, as you listen, whether the music is coming from the CD player or the tape deck. The tape deck is recording the signal from the CD player and the output is taken from its playback head. Thus it is quite easy to pick when the music is switched because there is a time delay of abuut 0.3 seconds between the CD signal and the tape playback signal. Picking the moment when the signal is switched is no problem at all; picking which is which is a lot harder. Most people, after they 've marked the score sheet, get less than five out of 10 right. Dolby C noise reduction When these two Sydney Kings basketballers took the BASF CD Challenge, they could not tell the difference. Depending on the type of music being played and the noise level of the surroundings, it can be very difficult. Few people achieve a score of better than 5 out of 10. 68 SILICON CHIP The tricky part is the use of Dolby C noise reduction in the tape deck. BASF make the point that compact discs are rarely recorded with a dynamic range of more than 70dB and that most hifi cassette decks with Dolby C can achieve a signalto-noise ratio of 70dB or better. Hence, as far as signal-to-noise ratios are concerned, there is less difference between CDs and cassettes than you might think. The other trick is in the selection of the music used for the test. If the program is classical music, it tends to be easier to pick the difference than with most popular vocal recordings which have relatively little 40 . 1 -,~ 30 .,.,r - ·- _,. f ., ~ f -" L V I I I' . ~ 10 ,,IIT _J\ ,, - -., -- - I ~, ~ ." " .. -""LI. " . ,. -,-,. \ ~ 'I.Tllo . - - I \ -•• ,n "' ,.,. _,. , . ' - Hz 50 100 200 dynamic range. The other point to be noted is that the venue where these "CD challenges" are taken is not the best for serious music listening. Shopping malls are notoriously noisy places so, even when listening on headphones, trying to pick differences in sound quality is very difficult. Most people are likely to conclude that the differences are non-existent, which is just what BASF wants them to think. Is it valid though? With a lot of recorded music on CDs, the answer is yes - because it has not been critically recorded with the very best sound quality in mind. However, if the same comparison is carried out in a quiet room with good loudspeakers and the very best that CDs can offer, few hifi enthusiasts with keen hearing will have any problems picking the difference between CDs and BASF chrome cassettes simultaneously recording with Dolby C. If the test was done using dbx noise reduction, it would be quite a lot more difficult. Incidentally, while most hifi cassette decks these days have both Dolby B and C noise reduction, most car players, Walkman-style players and "ghetto blasters" don't even have Dolby B. 500 ,,,..,. I I - & .,, • l;ll 2000 l'ln y ' lo T I \ IN Ill ..I 'Y .. ., T T I ~ .. I . " .... L -T -r,, I \ \ \ I l. ' \ \ I ~-'l. 1000 - - -- "' I •- 0 20 JY I - •• I .. . "' "\ \ I I.I I , .. I I ~ ,- ~ ft -,, ,, ,,.... ,, . -. lr'I J ,. "' T [7 V ,,_. /\ I ,,. r IW ,J V ,. .,r ,r, 20 - _. . & .,, f 5000 10000 ' 20000 The cornerstone of the BASF CD Challenge is the use of Dolby C noise reduction. These curves show the difference in high frequency noise attenuation between Dolby B and C. Dolby C can give a signal/noise ratio of 70dB or better. What is the point? Why has BASF gone to the trouble of running the CD challenge? Well, as you might expect, it is a marketing exercise designed to draw attention to its new Chrome Maxima II cassette. This has a redesigned housing which is claimed to be more rigid and to give better tape azimuth for minimum high frequency losses. The housing is also claimed to be less likely to distort when subjected to the high temperatures in cars. At the same time, the tape formulation has been improved to give a greater dynamic range, which is where the statement " 99.9% noise free" comes from. BASF quote a signal to noise ratio of 60. 5dB without noise reduction. When you convert this to a straight ratio, it gives a figure of .0009441 or as BASF states, better than 99. 9% noise free. What do you think? ~ BASF's new Chrome Maxima II uses a high precision shell which gives better tape azimuth and is less likely to distort at high temperatures. The tape is a double layer type with high coercivity for greater signal range. APRIL 1990 69