by HERMAN BURSTEIN. If you have a problem or question on tape recording write to Mr. Herman Burstein at AUDIO, 134 North Thirteenth Street, Philadelphia, Pa.19107. Please enclose a stamped, self-addressed envelope. All letters are answered.
From time to time readers ask why there are surprisingly large price differences among tape machines with similar performance specifications and similar surface appearance. To the layman, and particularly to the novice, there is a substantial tendency for two machines of the same dimensions, one glittering with knobs and costing $150, and the second, glittering with about the same number of knobs but differently arrayed, and costing $300, to look much alike. The general answer is that differences in price tend to be due to differences in how well a machine performs and in how long a machine continues to perform well.
Play Records through a Recorder
Q. I intend to use my stereo record player with other stereo equipment.
If I should purchase a ___ tape recorder, what would be a good way to hook it up? Also, can I use this tape recorder as an amplifier? If I cannot, can I purchase an amplifier to be used with the turntable and tape recorder? Please advise as to the speaker system.
-G. F. Ingram, address withheld.
A. The tape machine to which you refer has a power amplifier, so that you can hook up an external speaker to it, if you wish. If your record player has a ceramic cartridge, rather than a magnetic one, you can probably find some way of operating your record player through the tape machine. But if the record player has a magnetic pickup, I doubt that you can feed the pickup signal directly into the tape machine. However, some relatively inexpensive phono preamps are available from the audio stores and catalog houses; these can pre-amplify and equalize the signal from your magnetic preamp, so that the resulting signal can be satisfactorily fed into the tape machine's high-level input.
Stereo Mixer
Q. I have been searching for plans for a high-quality solid-state microphone mixer (stereo). Could you make suggestions for such a mixer or guide me to a source of plans for such a mixer?
-John Richardson, Pauls Valley, Okla.
A. You may find parts or all of what you are seeking in: (1) William G. Dilley, "A Condenser-Microphone Mixer," AUDIO, October 1962; (2) Peter A. Satrk, "Transistorized Stereo Microphone Mixer," AUDIO, October 1963; (3) William A. Rheinfelder, "High-Quality Phono Preamp with FET's," Ammo, November 1966.
Cross-Field Heads
Q. I am interested in finding a tape recorder that is capable of recording the whole audio spectrum from 20 to 20,000 Hz with good fidelity. I notice that many preamps and power amps are capable of this wide-range response. Thus I have come to the conclusion that the tape head is the part of the tape recorder that limits frequency response and uniformity of response. Is this conclusion correct? If so, what type of head is best for wide-range frequency response? I have heard about cross-field heads and have noticed that they are held to be capable of wider response, but do they also exhibit uniformity of response? Also, do they affect fidelity in any other way? Can I obtain information about cross-field heads?
Jim Rasmussen, Cicero, Ill.
A. The limitation on frequency response, particularly treble response, is basically tape speed. The art of making tape heads has reached the point where at speeds of 3.75 ips and higher the heads present very little problem. An important factor in treble loss is bias current applied to the tape (bias is employed to minimize distortion and maximize the amount of signal recorded on the tape). Bias loss varies inversely with wavelength; thus, the slower the tape speed, the shorter is the recorded wavelength at a given frequency, and the greater is the loss at that frequency. In most machines, bias current is applied to the tape via the record head. Using the cross-field principle, however, bias current is applied via a separate head. Usually this head is placed opposite the record head, so that the bias head contacts the base of the tape rather than the oxide (as do the record, play, and erase heads) . The cross-field principle was developed by the Illinois Institute of Technology, Chicago, Illinois.
More information may be obtained from the January 1969 issue of Aunro.
Red and Black Oxides
Q. I have some questions pertaining to magnetic tape: (1) Why is practically all pre-recorded tape red oxide? (2) Why is black-oxide tape used so much in blank white box and bargain-tape sales outlets? (3) Is black oxide any more severe on tape recorder parts than red oxide? Let us assume both are a good-quality product. (4) Is there any major difference in print-through, output, or frequency response when both red- and black-oxide tapes are quality tapes? (5) Is there any specific reason why black-oxide tapes are often lower priced?
Glen Blair, Idaho Falls, Idaho.
A. (1) I would guess because the oxide formulation in question best meets audio needs. (2) This may be because the tape was originally made for other than top-quality audio purposes, or because the formulation is a cheaper one. (3) I don't know. The important thing is the amount of lubricant in the tape and the smoothness of the oxide formulation so that there is minimum friction between head and tape. (4) There may be. So-called high-output tapes, which achieve this higher output partly through a different oxide formulation, tend to have higher print-through. Different oxides also have different frequency-response characteristics. To the extent that differences in color correspond to differences in oxide formulation, differences in color correspond to differences in output, frequency response, and print-through. (5) This question really relates to question 2.
--------
(Audio magazine, 11/1969)
Also see:
= = = =