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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One is an excerpt from his bookWideband Amplifiersthe other is from an ancient article in the previous incarnation of Electronics World. This is accomplished by shunting the cathode resistor by a large-value low-voltage electrolytic akdio that bypasses the audio voltages.

This particular response is impossible with any practical amplifier. Crowhurst – code Audio Measurements by N. Thus, from the viewpoint of the millivolt total input, the resistance appears to be notohms, but 1, ohms, or 1 megohm.

The negative bias is compared to another d-c voltage that corresponds to a noeman below the maximum output that can be allowed.

Audio Measurements – Norman H. Crowhurst – Google Books

Motional impedance is the impedance reflected back to the loudspeaker terminals due to the movement of the diaphragm. Care must be taken to see that the beneficial effects of the negative feedback — reduced distortion — are not cancelled in the pro- cess.

From there, curves are drawn at 0. If the rise produced by the swinging choke just offsets the losses produced by increased current through the rectifier, the power transformer, and possibly a further smoothing choke, the output voltage of this kind of filter will be almost meadurements constant as the load current is changed. This can be illustrated quite effectively by mounting a loudspeaker in a simple enclosure with three alternatives for the back of the enclosure.

It has an internal resist- ance of 5 ohms. However this gets divided by the feedback factor in this case 51 to give an effective resistance of less than ohms.


This does not allow for losses in the head, however, which complicate measuremenys response somewhat. Last but surely not least, let me mention my publication Linear Audio. Name various locations where an equalizer is required. The voltage across the capacitor drops by some amount, however small, between charges, before the next pulse comes along to restore the charge.

The measurement circuit is here and the measurements are here.

Both the volume compressor and the volume limiter really use a kind of feedback. English Choose a language for shopping. Explain how a a choke and b a capacitor may be used to smooth out the large fluctuations in rectified a-c.

Thus ultra- linear can be regarded as using less negative feedback from plate to screen than occurs to convert the pentode to triode operation. The dangerous thing now is that, with positive feedback, the amplifier will oscillate because the output voltage will equal the input voltage; conse- quently, no external input voltage is needed — the amplifier will continue to amplify its own output at this particular frequency.

This means that the advantages, too, are split.


A very small capacitor is connected between this high-voltage negative line and the metal parts that are accessible and thus liable to be touched. This type of line also protects against magnetic pickup, because any mag- netic field will induce exactly the same voltages in both the inside wire and the outer sleeve.

Inevitably such a change of approach will mean a crodhurst of stress. Even if one million astronomers believe something, that doesn’t nofman it true – a remarkable story about the human condition. An early attempt to apply it to discs used two separate grooves, spaced apart by a fixed distance.

In addition, we must transfer to the am- plifier as much as possible normaj the audio voltage picked up by the microphone, to maintain the signal well above the noise level. If a screen is to be operated at volts from a volt supply, what resistors should be used so that change of screen current from 0.


As soon as the output exceeds the delay voltage, the grid of the gain-control tube goes negative quite rapidly, turning the volume back, and insuring that no distortion occurs.

By continuing to use our website you are agreeing to our use of cookies. Nroman is gain margin? Increasing the value of Ap at all frequencies uniformly multiplies up the whole size of the curve in proportion. These additional components are necessary for an- other reason. The series-resistor method has the advantage of morman on supply current, because it passes only the current necessary to feed the screen.

For this reason, there must be a change at some point to constant-amplitude recording. For this reason we need to do some- thing to smooth out the ripple component. It can also become unstable because high-level acoustic energy radiated from the croowhurst is fed back to a microphone. According to each half-wave of the rectifier waveform, the output of a choke input filter is always 0. A single choke or a single capacitor does not smooth out the ripple com- pletely.

To make this work, it has two requirements: This is a considerable help in the con- struction of a complete amplifier, because it allows the cathode to be biased to any suitable voltage, while permitting all of the heaters in crwohurst different tubes to run from the same supply in any convenient manner.