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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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If the cur- rent should drop to 0. One uses an inductor and capaci- tor in parallel to produce a tuned or resonant circuit in which energy passes between the inductor and capacitor at the resonant frequency of the circuit.

Here, however, the voltage divider is fixed rather than variable. Amazon Drive Cloud storage from Amazon. Besides the well-known case of a loud- speaker feeding back to a microphone in a public address system, where else can this phenomenon cause trouble?

This peak may not show in the overall response of the amplifier, because the output transformer may produce sufficient loss to offset it. The effective input resistance of the am- plifier is affected normaan the method of injection. We may conclude that series injection causes the input re- sistance to be multiplied by the feedback factor — in this case, Corwhurst this reason the only way to accentuate some frequencies is to cut down frequencies in the rest of the range.

One push-pull primary connects to the cathodes of the tubes, with its center tap to the ground. Consequently, the mismatch problems met in making the diaphragm of the microphone or loudspeaker act crowhrst over a wide range of frequencies are not present.

Stylus moves side-to-side and causes armature to vibrate between magnets and induce crowgurst in coil. What two basic ways are there of recording on discs? Not only does the loudspeaker impedance have to be matched to the amplifier output impedance, but the output impedance of the amplifier affects the operation of the speaker.



Diaphragm motion causes the loudspeaker to operate as a microphone, generating voltages in its voice coil. If we connect a capacitor in parallel with the resistance load that represents the amplifier, the rectifier will charge this capacitor up to the measureemnts value of the alternating voltage.

Resistors are considerably cheaper than chokes, and modern electrolytic-type capacitors can get very large values of capacitance into quite a small space at low cost. As the complete circuit from ground to the live side of the input at the amplifier consists of the entire line out to the microphone and back, the total voltage induced by the magnetic field will cancel out giving zero resultant induction. This is not sufficient to change its trans- conductance, so the amplifier works at full gain — in this case, 10, The sound reproduced through a loudspeaker seems quite confused because our hearing cannot sep- arate direct and reflected sound now that they both come from one source.

As far as the tube is concerned, the effect is the same. Suppose that the plate load resistor is 50, ohms and that, qudio this value of load line, measuremenst tube gives a gain of This led to two basic variations in output circuits, although many further minor variations have developed.

This means that relatively large-value resistors and capacitors normman provide a high degree of ripple reduction can be used without dropping the plate potential appreciably. Assuming that we still apply the original 10 millivolts of input, the output current will then be 0. It can be injected either in series or in parallel shunt crowhurrst the input re- sistance of the amplifier itself.


Explain this possibility with reference to both low- and high-frequency near-instability. An alternative system of tone control uses feedback. In addition, crowhursh supply control frequencies ccrowhurst for some kinds of automatic operation. At higher frequencies, it becomes less and less effective because the magnetism takes time to be induced in the material of the shield.

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

What kinds of transducer element can be used for a phonograph pickup? Each of these receptors, however, does not transmit its individual frequency to the brain. For low-current supplies, or even moderately larger current supplies up to or milliamps in modern amplifiersa resistor is sometimes used to replace the choke; this is an economy measure.

This occurs in public address systems where the complete system consists of a microphone, an amplifier, and loudspeakers to reinforce the sound of the speaker on the platform, or the orchestra on stage.

At small load currents, the inductance of the choke is sufficient to make the filter behave as a choke-input arrangement, and the output voltage is not more than 0. What two principal methods measurekents connection are used for tube heaters? With a 1-volt audio input from grid to cathode at 50 cyclesthere will be 50 volts audio output at the plate and about 60 millivolts at the cathode, which is not sufficient to make crohwurst appreciable dif- ference in the gain of the stage.