Audio Measurements by N. Crowhurst - code Audio Measurements by N. Crowhurst - code Norman Crowhurst is the nearest thing to a legendary author on audio topics as we are likely to have. He was prolific in a way that few writers are, but more importandy he explained his subjects in a way that almost anyone, novice or expert, could understand. Audio Measurements, first published in , is a complete compendium of measurement and testing techniques for audio reproduction equipment, with discussions of all the instruments needed to use them. He begins with measurement techniques and follows with a full discussion of all manner of test equipment.

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Mauzahn Audio Measurements by N. Crowhurst — code Hifi Collective It minimizes the possible effect of magnetic and electric induction, and avoids high-frequency losses that occur at high impedance and the atten- uation due to line resistance that occurs in using low impedance. This overshoot move- ment will generate a further voltage. 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 both the magnitude and phase angle of the feedback factor.

It is a line drawn at an angle to correspond with the phase angle from a starting point representing zero. If the transient pattern is a realistic recreation of the original, the reverbera- tion effects will be relatively unimportant. This same two-channel sound could be re- produced over two loudspeakers, but the effect would not be as good. A complete Nyquist diagram starts from O and finishes af O, representing frequencies zero and infinity.

If the amplification is too great, the amplifier will distort the signal, and turning down the control will merely adjust the loudness of measyrements distorted program. This curve is called a Nyquist diagram. This is where the choke-input filter has an advantage. Why is equalization necessary? 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 another reason why the phase margin is not a very prac- tical criterion: Variations in speed at a greater speed than once per revolution are called Butter because of the effect they produce on the reproduction.

It cannot completely achieve the desired result because the acoustic characteristics of the listening room as well as those of the studio are present. Because the plate resistor is 50, ohms and the cathode resistor is ohms, a volt fluctuation at the plate will be accompanied by a 2-volt fluc- tuation at the cathode.

The series-resistor method has the advantage of economy on supply current, because it passes only the current necessary to feed the screen. This means that the advantages, too, are split. This name is used to describe an arrangement that will continuously adjust frequency response, increasing or reducing the high- and the low-frequency output.

The first idea for a volume control was to put this potentiometer across the output of the amplifier and take the connection to the loudspeaker from the slider and one end.

Copies of The Audio Crtitic can still be found online. Usually, with a-c-operated amplifiers, all of the heaters are connected in parallel to a winding on the power transformer. However this gets divided by the feedback factor in this case 51 to give an effective resistance of less than ohms.

Miscellaneous This particular response is impossible with any practical amplifier. Using an acoustic re- sistance consisting of a large number of holes that allow the air to pass through but offer resistance to its passage achieves an intermediate condi- tion that damps the diaphragm properly.

Inevitably such a change of approach will mean a change of stress. This peak may not show in the overall response of the amplifier, because the output transformer may produce sufficient loss to offset it. A foot length would have a resistance of ohms. Suppose that an amplifier has to work with a ohm resistance as its output load. However, the most commonly used method works by making the cathode positive rather than the grid negative. The other element of a smoothing arrangement is a capacitor.

The other special output circuit is called ultra-linear. This heater voltage became standard, because it was then possible to operate the tubes alternately from a battery or a 6. In considering feedback, do not forget that supplying the differ- ent stages from a common power supply can result in output circuit audio fluctuations being fed back to input stages, which are more sensitive.

Let us work out a ajdio example, using voltage feedback. Because the signal is at a very low level, we have to take precautions against possible unwanted pickup due to induction from magnetic or electric audip. Explore the Home Gift Guide. All amplifiers possess some reactance, such as coupling capacitors, which aiFFect the low-frequency response, and stray capacitances, which affect the high-frequency response.

We may conclude that series injection causes the input re- measure,ents to be multiplied by the feedback factor — in this case, This current in the shield sets up its own magnetic field that opposes the original inducing magnetism, and the two fields tend to cancel inside the shield.

The effective resistance now is 10, ohms instead ofohms, and shunt injection has divided the input resistance by the feedback factor. TOP 10 Related.


Audio Measurements by N.H. Crowhurst - code 7003

Daikora Because the signal is at a very low level, we have to take precautions against possible unwanted ctowhurst due to induction from magnetic or electric fields. This is very detailed, covering a lot of angles and well-documented. Assume that we have an amplifier that without any load connected gives 12 volts output for an input of 2 millivolts. Using this bias system, however, the shift in load line corresponding with the drop in plate supply voltage produces a new operating point, which msasurements still be optimum.



Welcome to my place! Written by Mark Lovell and Morgan Jones. Another year passed, another year older, another year wiser One is an excerpt from his bookWideband Amplifiersthe other measrements from an ancient article in the previous incarnation of Electronics World. So, take a look around, explore the various areas and let me know what you think!

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Tygolar Crowhjrst great to have you here! A study on the acoustic emissions due to mechanical vibrations in capacitors caused by magneto- and electrostriction. The measurement circuit is here and the measurements are here. Copies of The Audio Crtitic can still be found online. Oct always sees me in the US to meet lost of old friends, authors and make new ones! My projects however is audio stuff — things I designed, wrote articles about, and my personal system.

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