Put a new count on the old adage: Three heads are better than two. That, at any rate, applies to tape recorders, where three-headed models are gaining prominence.
One reason for this trend is that triple-header tape decks have come down in price.
Formerly found only in the highest price brackets, these designs are now appearing in less expensive models.
But at a typical price of about $400, they still cost more than many conventional two-head designs.
A "head" is the crucial part of a tape deck that performs the basic recording and playback functions. It magnetizes the tape as it rolls by, imprinting upon it the sound in the form of magnetic patterns.
In playback, the process is reversed, and the magnetic pulses carried by the recorded tape induce an electrical signal in the head as the tape travels past.
This signal is then amplified and fed to the loudspeakers.
In less elaborate recorders -- the two-head designs -- the same head is used for both recording and playback.
Depending on how the head is switched into the electronic circuit, it can either print the signal onto the tape or "read out" the signal from a tape already recorded.
The second head of such recorders is the so-called erase head. As the name implies, it acts as a magnetic eraser that automatically removes any previously recorded signal from the tape whenever you hit the "record" button.
This allows the same tape to be used over and over again for different recordings.
Triple-head models offer advantages that account for their rising popularity.
In these machines, the record and playback functions are not combined in a single head but divided between two separate ones (with the third head performing the erase function).
Because each function employs its own head, the playback head can be used to listen to the tape during the recording process, monitoring the signal that has just been recorded.
Any fault in the recording can thus be detected instantly and rectified immediately.
This monitoring capability accounts for the rising interest in such cassette decks. Cassette decks are increasingly used for copying CDs, and the character of digital sound makes close monitoring essential.
For example, if you hear marginal distortion at loudness peaks, you know that the recording level has been set too high.
When monitoring the tape on a three-head deck, the distortion becomes evident at once and any adjustment can be made promptly.
The need to check the tape while the recording is being made is even more important when a live performance is taped, especially if the occasion is a one-time event, with no chance for recording it again to eliminate flaws.
Instant correction of any problems becomes imperative, and besides, real-time confirmation that all is well is reassuring.
There are also technical advantages. The combined playback head used in two-head decks is, at best, a compromise because contradictory requirements apply to the design of recording and playback heads.
These have to do mainly with the width of the gap in the head that directs the flow of magnetic force.
In combination heads, either the recording or the playback function will be hampered in terms of frequency response -- not appreciably, but to an extent that may bother perfectionist. Using separate heads for recording and playback sidesteps this problem.
Among recent three-head designs that have descended to the middle price brackets, Panasonic's RS-B755 ($439) also boasts another important refinement.
The tape is driven directly by the motor shaft, without intervening belts and gears. This arrangement assures evenness of the tape motion.
Similar performance and thoughtful design mark Denon's DRM-700 cassette deck ($400).
Other fine triple-headers in this price class include Sony's TC-K650ES ($400) and Yamaha's KX-630Ti ($469).