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Q. I have a B.I.C. T-4M cassette deck, whose line input is rated at 200 millivolts, and a Yamaha C-6 preamp, whose line inputs are rated at 150 millivolts. Can the preamp drive the tape deck to an adequate level, or do these ratings not matter? -Wayne Noel, address unspecified. A. The Yamaha does not amplify line-level input signals going to its tape output, so the tape deck sees exactly the same source signal as the preamp does and at exactly the same level. In short, don't worry about it: The two specifications have nothing to do with each other. Q. I want to get more of a "concert hall" sound from my system, which now consists of a Yamaha CR-1020 receiver and TC-1000 cassette deck, a Dual 626 turntable with an Ortofon cartridge, and Infinity RS-1.5 speakers. Can I achieve the "surround" effect I'm looking for without going quadriphonic, and if so, what additional equipment will I need? - John Wright, New York, N.Y. A. These days you won't get much of the effect you're looking for even if you go quadriphonic because so few quad recordings are being made and so few really good ones ever were made. You can, of course, use the matrix systems (like SQ) to "enhance" ordinary stereo recordings. Used either way, they require an additional amp and a second set of speakers, preferably very similar or identical to the main pair. Delay lines, which at present are the most popular means of ambience enhancement, also require at least one other amplifier (though some include the second amp on the same chassis). Newest on the scene are image-enhancement devices, such as the Carver C-4000 Sonic Holography preamp (test report, January 1980), but while they give you a more realistically three-dimensional stereo image, with greater depth and localization, they create no hall-sound effect as such. My deck, a Technics RS-M 11 Mk. 2, is metal-compatible, though I don't intend to use metal tape for now. A friend has a DBX 122 noise-reduction unit, which increases signal-to-noise ratio by 30 dB and headroom by 10 dB; but in order to maintain wide frequency response, he must record at about-20 VU, peaking at-10 VU. Is there any other unit that reduces noise as much but will allow recording at higher levels? - David Leason, New York, N.Y. A. It sounds as though you missed our coverage of noise-reduction systems in our August issue. The answer is a qualified no; but the question is why you would want to get still more noise reduction by recording at a higher level. To use your figures (which, basically, we agree with), 30 dB of noise reduction in a 2:1:2 compander system like DBX's presumes a 60-dB dynamic range in the original program content. (If it were more, the noise reduction would be more, too.) With inherent tape noise somewhere around 50 dB below "0 VU" and maximum recorded level at-10 VU, minimum compressed program level would be at-40 VU, some 10 dB above the noise and therefore some 20 dB above it after playback expansion. So total signal-to-noise ratio, from maximum reproduced program level to reproduced tape hiss, would be 80 dB. Your other equipment may well have that much dynamic range, but relatively few listening rooms do. Q. I own a good turntable, but when I play records, the woofer cones in my speakers start to bounce madly back and forth. This does not happen when I play tapes or FM broadcasts. What causes this, and will it hurt the woofers? -Nephtali Vasquez, Los Angeles, Calif. It sounds as though the low-frequency resonance of your arm/ cartridge combination is occurring down in the record-warp region below about 8 Hz. The resonance boosts the warp signals, which your amplifier then dutifully passes on to your speakers, causing excessive cone excursions and wasting amplifier power. Muddy sound is a more likely result than permanent woofer damage. You can cure this problem at the source by using a lower mass tonearm, a lighter cartridge, a pickup of a lower compliance, or some combination of these to raise the resonance frequency into the safe region between 8 and 12 Hz. My record collection spans twelve years and a succession of turntables, most incorporating inexpensive cartridges. Now I have a B.I.C. 80-Z turntable with an Audio-Technica AT12Sa cartridge, and most of my records sound like they're being played on a Victrola, with lots of surface noise. Is there anything I can do to get rid of the noise? -Douglas Rowe, Livonia, Mich. The first step is to try cleaning the records. Many fine products are available for this purpose (see "Record Cleaners and the Real World," July 1980). If that fails, and if the noise consists mostly of ticks and pops, a dynamic noise filter such as the SAE-5000 might help. You should arrange for a home trial before buying, however; such units can literally be overwhelmed if there is too much noise. In that case, the only way out is a good high-cut filter (which will lop off some of the music with the noise) or new records-which may not be as bad as it sounds. Remember that you can buy 35 or 40 LPs for the price of a tick-and-pop suppressor. The most capable noise-suppression device we've worked with, from Packburn Electronics, costs a cool $3,000 or so. I've bought a few of the new digitally mastered records and have been duly impressed with their bass impact and overall clarity. To me, however, they sound somewhat antiseptic in the treble. Is there some technical tradeoff that makes digital better on the lows and analog better on the highs? -Phil Bucoli, East Orange, N.J. The sound of recordings made at the same time from the same source with a properly adjusted analog recorder plus good noise reduction and with a digital recorder should differ very little if at all. What you are hearing is probably the result of microphone technique and placement, rather than recording technology. Microphones sound quite different from model to model, even when they are of the same basic type and pickup pattern, and just moving a mike a few feet can make a significant audible change. Remember also that, whether by necessary compromise or sloppy cutting and manufacturing, few records sound exactly like their master tapes. HF (High Fidelity, May 1981) Also see:
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