CLASSIC HI-FI EQUIPMENT

The remembered fever of voluminous and heavy Hi-Fi equipment seems to be back. The suspected reason is its special quality of electronic design and high quality materials, in contrast to the present equipment where plastic and other similar materials are not as resistant to the test of time. The golden age of Hi-Fi equipment is particularly remembered in the 70's and 80's. Automation in electronic design took its first steps and designers...

Functions as important as recording require for their perfect execution, some kind of indication more precise than the operator's own ear, so almost all the devices on the market incorporate some kind of modulation indicator. The most common are: A) The meter This is simply a galvanometer equipped with a bridge rectifier; Therefore its indication is only valid for average signal values. They are usually provided with graduated scales. One from 0 to 100 and the other from -20 to +3 VU. The zero of the VU scale corresponds to...

Noise reduction systems.  Most high fidelity cassette decks incorporate a noise reduction system, of which the most common is the Dolby B version that uses a huge percentage of devices on the market. This electronic noise reduction system appreciates the level of signal reaching the recording head; If it is very high, it does not act; If on the other hand its value is weak, it increases its amplitude and later allows the recording to take place.  When reproducing this signal along with the tape noise is reduced its value...

A) Heads and number of tracks.  The width of the standard cassette tape is 3.8 mm instead of the 6.35 mm of the reel to reel tape or open reel tape; therefore, the recorded tape width is also smaller. As a direct consequence of the reduced track width, it is possible to deduce that the achievement of authentic high-fidelity decks to the cassette is a goal that has been widely achieved today and has always been a task that required time and enormous research effort.  One of the topics that has occupied the laboratories of the main manufacturers...

To obtain maximum performance in its function, the magnetic head must be correctly positioned with respect to the magnetic tape in both height and azimuth. It is called azimuth to the angle that the air gap forms with the perpendicular to the direction of advance of the tape. The position of the head must be so precise that the azimuth is zero...

The demands of this head are much less critical than the others of recording or reproduction, since its function is to record on tape a high fixed frequency. The magnetic circuit is made in two similar halves.  As magnetic material is generally used ferroxcube, the air gap usually has a length of 0.3 mm while the winding is manufactured in a single winding. ...

It must have medium characteristics between the requirements of recording and reproduction, although more importance is given to the reproduction function, therefore, air gap length, winding impedance and shielding must be approximated to those required for reproduction.  The mixed recording-reproduction head is used in most of the equipment on the market and its latest quality levels ensure a completely satisfactory result...

The length of the air gap acquires in this type of heads a paramount importance, since it must be very small to be able to "read" the high frequencies contained in the tape.  On the other hand, in order to obtain a good signal-to-noise ratio it is necessary to increase the surface of the air gap and therefore its length. A middle ground must therefore be adopted.  Usually a reproduction head has air gaps between 3 and 5 μm. The winding is of low impedance and the shielding system must offer a very effective protection...

The magnetic heads of recording, reproduction or erasure it is possible to distinguish two main components:  A) Magnetic nucleus.  B) Winding.  The magnetic circuit is usually composed with very small remnant induction. Hysteresis losses should be minimal as well as those produced by eddy currents.  The winding is distributed in two windings each located in a seminore. This arrangement is preferable because it reduces the sensitivity of the head to disturbing external fields.   The entire core-coil assembly is encapsulated...

>The device which performs the function of recording and reproducing the audio signal on a magnetic tape is commonly called a tape deck. The elements related to the recording-reproduction process common to any tape deck are as follows: 1) Magnetic heads. 2) Recording-reproduction amplifiers 3) Polarization current generator. ...

As much as greater be the surface of the engraved trail will also be greater the quantity of particles of flux-producing and therefore the output voltage will be increased at the terminals of the reproduction head. Increasing the air gap length increases the output voltage, but, in return, the response at high frequencies will be reduced. In practice, the design of the reproduction heads will always be made taking into account the compromise between the signal level and the frequency response. ...

This factor of great importance in all the systems of transmission of information is of singular importance in the case of the recording tape, since unfortunately there are always some noises that inevitably are inherent to the magnetic heads or the magnetic support (tape).  Because the magnetic head of reproduction is sensitive to variations in magnetic flux, it is necessary to take into account that there is no magnetic field around the stereo deck, as well as insulate (with good shielding) power transformers and the motors...

The main elements of a magnetic head are the coils and the gaps (two sets, each one corresponding to a stereo channel). These gaps end up on the surface of the head, on which the tape passes at a certain speed, and are separated by a space of very small size filled with non-magnetic material that separates both poles; the dimensions of the gap are expressed in microns and their definitive value depends on the type of application of the head and the investment (time and money) that the manufacturer has destined for its production.  The...

We imagine a magnetic tape of them utilized currently in the stereo decks. Basically it consists of a plastic film on which a fine layer of magnetic material is deposited. Even when the plastic support and the agglutinating elements are very important for the smooth operation of the tape, the magnetic layer is the medium that allows recording, and therefore must be a ferromagnetic material.  In most cases different varieties of iron oxide are used although in recent years new materials have appeared suitable for that purpose. The...

The location of the turntable with respect to the loudspeakers should be carefully studied, as they often appear coupling or feedbacks that appear in the form of annoying hum that come to completely prevent hearing. This phenomenon is called Larsen effect and is caused when the sound waves generated by the loudspeakers affect the turntable whether traveling through the air or more frequently when propagating the furniture, walls and roofs. When vibrating the entire turntable, the cartridge detects these vibrations and injects them again in...