Willi Studer Ag

Other

Studer Revox Ag

Willi Studer A.g. Fabric Fur Elektronische Apparate

Paul Zwicky

Eduard Marthaler

Roger Schultheiss

Matthias Zbinden

In order to obtain for electrodynamic loudspeakers, on the one hand, the energy-favorable acoustical enhancement by the bass reflex principle and, on the other hand, to be able to use the motional control of the diaphragm of the electrodynamic loudspeaker by controlling such by means of an amplifier exhibiting negative output impedance, it is proposed to compensate the thus resulting unfavorable frequency characteristic by a forwardly connected circuit which generates an inverse characteristic with respect to the unfavorable frequency characteristic.

Amplifier unit

In order to be able to improve the level or the dynamic ratio and the signal-to-noise ratio of a magnetic storage medium for analog signal recording, with the distortion factor remaining the same, certain rules are formulated for the quality of the magnetic particles in the storage medium. According to these rules the particles shall be of at least two kinds, all particles of one kind having the same structure. Furthermore, the distribution curve (9) which specifies how many particles possess a certain coercive field strength shall be broadened in the range (20) of the most frequent coercive field strength (H.sub.c9), as compared to a Gaussian distribution.

Magnetic storage medium containing at least two different populations of

In a loudspeaker with a number of speaker units, each connected across one power amplifier to a diplexer, the power amplifiers having negative source impedance (-R.sub.1) are utilized. The diplexer includes an adder circuit and a filter connected thereto. The power amplifiers with negative source impedance reduce the linear distortions to such an extent that the use of modern diplexers is possible and further measures for reducing nonlinear distortions are appropriate.

Electrodynamic loudspeaker

A simple technique permits improving the distortion of a loudspeaker with a magnetic system. The magnetic system incorporates measures for operation thereof within the saturated region of the magnetic characteristic of the magnetic system. These measures comprise a division of the magnetic circuit into a section with magnetic saturation, and sections without magnetic saturation, which are adjacent to an air gap.

Magnetic system for dynamic loudspeaker

In order to record audio signals on a magnetic record carrier, there is produced a high frequency pulsed signal which contains the low frequency information pertinent to the audio signal. This high frequency pulsed signal is produced in a manner such as to be substantially free of any signal component which has a frequency lying in the frequency range of the low frequency audio signal. As a result, cross-talk produced during recording on a plurality of tracks can be substantially reduced.

Method of, and apparatus for, recording audio signals using recording

A transducer for converting electrical input signals into an electrical or mechanical output. The transducer employs a circuit for producing a negative source impedance and a winding cooperating with the circuit. The winding has first and second parts connected end to end. The ratio of the induced electromotive forces developed across the first part relative to that of the second part differs from the ratio of the ohmic resistance of the first part relative to that of the second part.

Signal transducer

In amplifier circuit arrangements for low-distortion transmission of audio signals a transformer is provided in order to isolate a source circuit from an amplifier of the amplifier circuit arrangement. Good transmission characteristics, however, can only be obtained in such circuit arrangements by using transformers of comparatively great dimensions. In order to achieve improved transmission characteristics and yet design the transformer in such a manner as to have small size, to be of low weight and inexpensive, the amplifier of the amplifier circuit arrangement is provided with a negative feedback circuit. This negative feedback circuit is connected to the source circuit by using a transformer connected in series with the current-voltage source of such source circuit.

Low-distortion audio amplifier circuit arrangement

The disclosed arrangement is for a short pickup arm used with a tangential scanning system. The arm is supported on a single jewel thrust bearing and held against sideways tilting by a pair of attracting magnets, one mounted on the arm above the bearing and the other fixed above the first. This permits the arm to move freely in a plane parallel to the record and in a plane perpendicular to the record and tangent to the grooves. The center of gravity of the arm is chosen to be on a line between the bearing point and the stylus point in order to minimize the effects of outside disturbances.

Bearing arrangement for a record player tonearm

The disclosed arrangement is of the type for a short tonearm which is guided over the record so that the tonearm remains tangential to the grooves of the record. The tonearm is balanced mechanically on a single point bearing, with the phono cartridge to one side and a counterweight to the other side of the bearing. A permanent magnet fixed to the top of the tonearm interacts with a stationary magnet closely spaced from it to hold the tonearm vertically. The tonearm magnet is a vertical, round, solid cylinder section, while the stationary magnet is a parallelepiped with facing width equal to the diameter of the facing tonearm magnet. This constrains the tonearm to prevent it from tipping to the side, while permitting rotation about the vertical axis and about a horizontal axis through the point bearing and perpendicular to the tangent to the record groove. The improvement comprises that the stationary magnet is provided with a winding. By control of a direct current in the winding, the tonearm can be raised and lowered and the stylus pressure controlled, even while the stylus is tracking in a groove. Futhermore, the tonearm can be magnetically preloaded, so that in the absence of current in the control winding, the tonearm raises to its rest position, thus preventing damage to the record. Various designs are described for determining the interaction of the movable and stationary magnets and the superimposed magnetic field of the control winding.

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Dielsdorf, Switzerland

Paul Zwicky