We need a selection to control where in the signal flow to monitor back from. Usually, there are three points in the signal flow. Choosing the input option monitors the audio at the input point- the signal before it reaches the record head, listening to the audio before it reaches the tape. Simple enough so far…. What is heard depends on the record status safe or armed and whether the tape machine is playing, stopped, or recording. If record is armed but playback is stopped, the audio heard is actually the same signal as if in input mode.
But if record is armed and the tape is playing, the audio heard is the playback audio picked up by the sync head. And if recording, record safe channels monitor playback audio via the sync head and record ready channels monitor at the input point. This is why there is a separate repro head — it allows one to monitor what has been recorded to tape instead of the audio entering the machine at the input point. This is especially helpful while laying down initial tracks. Repro monitoring is designed exclusively for playback.
The repro and record heads have different physical and electronic properties which affect the sound quality of the playback. The record head is optimized and designed for recording, not playback. It also has a limited response to lessen the crosstalk between channels when overdubbing. If in record ready and stopped, the signal is monitored at the input point. There are switches to select these three modes for each individual channel.
There are also master selection switches that override the individual channel selections to choose the monitoring for all channels simultaneously. This rectangular aluminum or steel block, usually mounted over the tape heads, is in the shape of one concave groove that holds the tape in place.
The thin, deeper grooves across the large flat groove are for splicing. Different angles can be offered on different blocks. Some editing blocks have an additional line groove for even softer cuts such as 30 or 45 degrees for soft cuts which are used for non-musical edits. Some tape machines have a remote auto-locator box.
The counters can be electronic or mechanical — both give numerical readouts to keep track of relative locations on the tape. If the machine has a separate counter for the tape time and the locate time, most likely they have separate buttons that will reset the current tape time as the designated zero starting time, as well as a button that resets both to zero. There are also often ways to reset the locate readout to be the same as the tape readout.
A locate time function can quickly wind the tape back to a user-specified point on the tape. Many tape machines have a rehearse feature that enables practice punch-ins without destructively recording. Varispeed, or variable speed, is exactly what it sounds like, varying the tape speed during playback. Slower speed means audio plays back at a lower pitch, and higher speed plays back at a higher pitch. You can also play with the varispeed for creative effects.
Ween and Beck made extensive use of this technique in the 90s, recording their voices at vastly different speeds for a bizarre effect. This means nonlinear frequency response changes , tape compression, and saturation of 3rd order harmonics. In a normal cassette player, there are actually two of these small electromagnets that together are about as wide as one half of the tape's width. The two heads record the two channels of a stereo program, like this:. At the top of this picture are the two sprockets that engage the spools inside the cassette.
These sprockets spin one of the spools to take up the tape during recording, playback, fast forward and reverse. Below the two sprockets are two heads. The head on the left is a bulk erase head to wipe the tape clean of signals before recording.
The head in the center is the record and playback head containing the two tiny electromagnets. On the right are the capstan and the pinch roller , as seen below:.
The capstan revolves at a very precise rate to pull the tape across the head at exactly the right speed. The standard speed is 1. The roller simply applies pressure so that the tape is tight against the capstan. Most higher-end tape decks have controls like those below for different tape formulations and bias.
Most higher-quality tapes tell you their formulation by stating a type. There are four types of tape in common use today:. Sound quality improves as you go from one type to the next, with metal tapes having the best sound quality. A normal tape deck cannot record onto a metal tape -- the deck must have a setting for metal tapes in order to record onto them. Any tape player can play a metal tape, however. The controls on the tape deck let you match the recording bias and signal strength to the type of tape you are using so that you get the best sound possible.
Bias is a special signal that is applied during recording. The first tape recorders simply applied the raw audio signal to the electromagnet in the head. This works, but produces a lot of distortion on low-frequency sounds. A bias signal is a kilohertz signal that is added to the audio signal. The bias moves the signal being recorded up into the "linear portion" of the tape's magnetization curve. This movement means that the tape reproduces the sound recorded on it more faithfully.
Several of the links on the next page go into this topic in detail, and also cover Dolby noise-reduction systems. For more information on tape recorders, cassettes, magnetic recording and related topics, check out the links on the next page.
Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Tape recording relies on a plastic film coated with tiny magnetic particles on one side the tape moving at a consistent speed through a tape machine. This is accomplished by unwinding the tape from one reel, passing it through a series of stabilizing rollers and guides, and spooling it onto a second takeup reel to be stored.
If the speed is changed during playback or recording due to improper settings or faulty motors, the pitch will be distorted. Between the reels, the tape passes over a series of magnetic heads that convert audio signals into magnetic energy and back again. First the tape passes over the erase head, which if the track is armed scrambles anything stored on that track. Next comes the record or sync head, which is essentially a stack of magnets one per track , each wound with a coil of wire.
Between the positive and negative poles of each magnet is a tiny gap where an electromagnetic field is created that fluctuates in response to the changing signal. As the tape passes by, these pulses align the tiny magnetic particles into patterns, leaving a record of the sound. The physics behind magnetic tape give the medium an idiosyncratic sound, which is coveted for its unique saturation properties. The tape can only absorb so much magnetic energy, but instead of distorting like an amplifier when overloaded with signal, it compresses the sound in a soft, flattering way.
This saturation effect, combined with all the analog circuitry on the inputs and outputs, gives tape an unmistakable sonic signature that can be subtly pleasing or intentionally exaggerated for an effect.
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