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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With either the solid or the open back, electrical damping from the amplifier makes a considerable difference to the response of the loudspeaker, but neither performance is as good as that with the acoustic re- sistance.

Audio Measurements by N.H. Crowhurst – code | Hifi Collective

In audio work, the exact waveform of the oscillation is important. When it gets as big as this, the response indicated is one with a peak.

Without feedback, a 2-millivolt input would produce the volt output. This corresponds to the loop gain ratio of 9. Because of these complexities, only playback re- sponse is specified. Thus a positive fluctuation from grid to cathode will be accompanied by a positive fluctuation from cathode to ground.

First we draw a line in one direction from O, representing Ap. For this reason, the positive-feedback oscillator produces considerably more harmonic distortion than either of the other types.

This means that the total input need only be 9 volts instead of 10 volts, and that the positive feedback has reduced the amount of gain lost by Tube development has made it easily possible to get more gain from an am- plifier. What limitations are there to this method of damping? If there were only a resistor between the supply voltage and the screen, screen current fluctuations would also be accompanied by some screen voltage fluctuations, and the plate voltage fluctuation would be affected by the screen voltage fluctuation.


There are three kinds of unwanted induction: If the microphone impedance is 50 ohms and the resistance of the connecting wire is ohms, the total input resistance to the amplifier will be ohms. For radio there are several possibilities: If an inductance is large, a very large voltage is necessary to pro- duce only a small change in current.

Explain the advantages and limitations of coaxial lines. Similarly, a negative fluctuation appears at the cathode of the second tube. Why is equalization necessary? Without feedback, an amplifier has an output source resistance that is 3 times its nominal load resistance.

Indicate which ones use velocity and which the amplitude principle. AmazonGlobal Ship Orders Internationally. This means that the advantages, too, are split. What kinds of transducer element can be used for a phonograph pickup?

The twisted line may also be shielded by a separate ground sleeve to minimize any electric pickup. An amplifier can become unstable because high-level audio electrical power at the output is fed back to the low-level input circuits.


Two kinds of rectifier are used for audio amplifier crowhjrst This peak may not show in the overall response of the amplifier, because the output transformer may produce sufficient loss to offset it. The outside conductor sleeve would be connected to ground, so that any electric field reaching it would be conducted along this outer sleeve and go to ground at the am- plifier without inducing any voltage on the inside wire.


Explain this possibility noeman reference to xrowhurst low- and high-frequency near-instability. At low load currents, the core is not saturated, but for higher current it progressively approaches saturation, which makes the circuit act as a ca- pacitor-input filter.

We can now find the operating point of this value of cathode resistor by plotting a curve on the tube characteristics.

If the transient pattern is a realistic recreation of the original, the reverbera- tion effects will be relatively unimportant. Sometimes equalizers may also be re- quired to remove undesired resonances, which requires another kind of circuit. What particular precautions are necessary in this kind of equipment?

Joining the outer ends of these lines produces a curve that represents all possible positions for the tip of the Ap vector and shows how Ap varies in phase and magnitude due to frequency changes.