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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It is called a potentiometer, because it is a device that allows the potential at the slider to be varied. Amazon Advertising Find, attract, and engage customers. A sudden burst of audio usually causes the current demand from the high-voltage measuremebts to change, and with it the grid bias for the output stage and possibly the voltage supplied to the screens of any pentode tubes.

normman When the speaker dia- phragm starts moving due to an input signal from the amplifierthe mo- mentum of the diaphragm will tend to keep it in motion even after the drive current has ceased. Audioo locus vector curve itself is called a Nyquist diagram. Any transformer will radiate some magnetic field.

The louder the sound component of the particular frequency, the more frequently this nerve carries pulses to the brain. Chokes can also radiate at these frequencies. These tubes do not have uniform spacing of the wires that make up the control-grid.

Thus, when listening to orchestral music, the sound of the violin can be distinguished from all the other musical sounds going on at the same time. Magnetic shielding prevents the magnetic field that causes the induction from audil the low-level circuit. Finally the hearing faculty notices the frequency content reported by both ears.

Tube DIY Asylum

For this reason, this method of biasing is called automatic or self measurdments. How does the problem of making a cutter and pickup for disc recording compare with that of making a loudspeaker and microphone?


Withoutabox Submit to Film Festivals. Explain how ultrasonic bias works to improve the quality of magnetic recording. Amazon Restaurants Food delivery from local restaurants.

It is clear that compara- tively small changes in screen current result in quite large changes in screen potential, which means that the operating conditions of the tube are not very steady.

This is accomplished by shunting the cathode resistor by a large-value low-voltage electrolytic capacitor that bypasses the audio voltages. This occurs in public address systems where the complete meashrements consists of a microphone, an amplifier, and loudspeakers to reinforce the sound of the speaker on the platform, or the orchestra on stage.

Product details Paperback Publisher: They are, for example, likely to pick up magnetic induction, which can cause hum, or to pick up unwanted audio. At some frequencies, the fed-back audio is neither precisely in phase nor precisely out of phase with the original input, but somewhere in between.

The simplest way to eliminate this distortion is to use ultrasonic bias. At a live performance of a symphony, for example, we can concentrate on the crowburst coming to us from the orchestra and ignore the effects of re- verberation. This curve is called a Nyquist diagram.

Most modern tone control circuits combine the two arrange- ments with two controls, one for the treble boost and cut, the other for bass boost and cut.

Audio Measurements by Norman Crowhurst dwnld

Although electric pickup is not important to the low-impedance circuit itself, it can be transferred from the primary to the secondary of the trans- former by the capacitance between windings. The twisted line may also be shielded by a separate ground sleeve to minimize any electric pickup. The original normzn almost cancels itself by the feedback — for the 1 milli- volt actually fed into the amplifier, 9 millivolts are fed back to offset the 10 millivolts of audio fed into the complete arrangement.


So the ratio of the distances of any point on the measurementz from these two points gives us the frequency-varying part of the formula for amplification with feed- back.


Overall negative feedback that re- duces gain by 14 db when the positive feedback is not connected is also used. For negative feedback, the bigger the loop gain, the nearer the two figures come to coinciding. Suppose, for example, that the plate po- tential drops from volts to volts. What this circuit does is to reduce the dynamic range of the program. This capacitor has to have a very high breakdown rating if the metal parts are to remain isolated from the line voltage. For this reason, care has to be taken to insure that high-level vibra- tion cannot reach the turntable, the pickup, or any of the amplifying tubes that handle low-level audio if they are at all microphonic.

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.

What two principal methods of connection are used for tube heaters?

Written by Mark Lovell and Morgan Jones. This place is where I talk about my personal projects, interests and whatnot. As a result, the magnetization cancels out as the tape leaves the gap, ultimately demagnetizing it. Unfortunately, we cannot solve this problem by using a smaller cathode re- sistor because it would result in too high a current in the tubes when no signal was passing. Both the volume compressor and the volume limiter really use a kind of feedback.