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Various measurements on audio equipment. by jimmy67music. A classic reprint of the famous Norman Crowhurst book that is a complete compendium of measurement and testing techniques for audio equipment including. AUDIO MEASUREMENTS. by Crowhurst, Norman H. Edition: First Edition; First Printing. Book Description. New York: Gernsback Library, Inc.. First Edition .

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The nnorman resistor is not quite all that is needed for providing bias in some instances. For this reason, much more attention is given to the prevention of induction by magnetic fields.

Although this two-stage arrangement can never get as far as causing oscillation, it can cause a peak in the frequency response.

AUDIO MEASUREMENTS by Crowhurst, Norman H –

The reactance of a capacitance is inversely proportional to its capac- itance value, hence the feedback divides the effective capacitance by This is very detailed, covering a lot of angles and well-documented. As far as the tube is concerned, the effect is the same. For this reason, two ground points must be provided.

A 1-volt audio signal between grid and cathode will produce 50 volts audio at the plate.


This is true whether the sharp rolloff is produced by this kind of synthesis or, even more important, by feedback adjustments. Crowhyrst heater voltage became standard, because it was then possible to operate the tubes alternately from a battery or a 6. Resistors are considerably cheaper than chokes, and modern electrolytic-type capacitors crowhjrst get very large values of capacitance into quite a small space at low cost. High- impedance output – – – – Amplifier Long, high-lmpedance lines give excessive loss of high frequencies, susceptibility to electric pickup.


In a smaller room, where reverberation is almost absent and by the very size of the room, intensity must equalize somewhatthe hearing faculty gets extra critical about time differences. This potential is usually 6. In the case of high fidelity, this audio waveform sequence may be a com- plete musical performance. This also applies to the reactance of ar y capacitance between grid and cathode of the tube. In this case, the output is rectified in the same way as before to produce a negative bias.

The convenience of this method is that the distance between any other point on the locus and this position, measured 1 unit from O, also represents crkwhurst the normam and phase angle of the feedback factor. We are principally concerned with volt cycle a-c sources.

Audio Measurements by Norman Crowhurst dwnld

This overshoot move- ment will generate a further voltage. It means that the gain of the amplifier becomes infinite at this frequency, and will go on amplifying its own output indefinitely, without the need for any input.

Looking at it as a simple geometrical diagram, however, can give us a good picture of what happens without knowing all the mathematics. Bearing this in mind, if we take a 9-millivolt sample of the output and subtract this from the original input of 10 millivolts, we shall have the re- quired 1-millivolt input.

For this reason, there must be a change at some frowhurst to constant-amplitude recording. Which give the best wave- form? The fluctuation at the cathode of the second tube is much bigger than that at the first stage.

The measurement circuit is here and the measurements are here. We can look at this on the graphs of db response and phase shift caused by each coupling network. If we add a second arrangement with the 3-db point at the same frequency, we would double these values.



The quantity A X p or Ap jorman called the loop gain. It repre- sents the amount by which the gain is divided by connecting the feedback. It is better to allow the sound pattern to be slightly different from the original, but still a credible reproduction of it, than to try to reproduce the original sound exactly and fail in some more important aspect.

The conven- ience of a-c as a source of supply is that the voltage can auudio be stepped up or down by means of a power transformer.

Suppose that the magnetic field induces 6 microvolts in a given circuit loop. This would require special equalization on playback. This peak may not show in the overall response of the amplifier, because the output transformer may produce sufficient loss crowhurrst offset it.

All kinds of power components and circuits radiate at power frequencies mostly 60 and cycles. This can cause instability if not properly controlled.

This d-c is then used as a bias for the variable gain stage with the result that louder program material produces a bigger negative bias reducing the amplification. Electrostatic induction is really a misnomer; this induction is better called electric induction, because it de- pends crowhurat the continuous fluctuation of the charges induced.

This corresponds to the loop gain ratio of 9. There are two main approaches to this objective.