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 .
|Published (Last):||7 January 2015|
|PDF File Size:||14.79 Mb|
|ePub File Size:||12.44 Mb|
|Price:||Free* [*Free Regsitration Required]|
Suppose that the negative feedback produces an Ap of 9, while the positive feedback produces an Ap of When the millivolt input is applied, the input resistance to the amplifier will draw a current, depending upon its value. Feedback is connected that reduces measuremenys by 20 db in the loaded condition. State clearly any condition that should be specified concerning the amount of feedback in figuring this effect.
The audio voltage at the plate of the first stage may not be more than, say, 10 millivolts. Although this two-stage arrangement can never get as far as causing oscillation, it can cause a peak in the frequency response. How does optical recording work? When I first met AJvdH early ies he showd me a whitepaper he’d done to explain his thoughts on tips and the new tip s he developed.
If one sound is stronger at one ear than the other, the apparent direction is toward the side where it is received the strongest. An arrangement of resistors with capacitors in series produces a loss of low frequencies.
What ideology of recording or high fidelity does this fact disprove? Turning a phonograph record faster raises all the frequencies by the same ratio, and the pitch steps up by a constant tone interval.
Research into the stereophonic nature of sound reveals what important facts? Electrostatic induction is really a misnomer; this induction is better called electric induction, because it de- pends upon the continuous fluctuation of the charges induced. A sudden burst of audio usually causes the current demand from the high-voltage supply to change, and with it the grid bias for the output stage and possibly the voltage supplied to the screens of any pentode tubes.
Thus a positive fluctuation from grid to cathode will be accompanied by a positive fluctuation from cathode to ground.
This results in a double-frequency current in the cathode resistor, because of the asym- metrical current waveforms in the tubes. What is gain margin? This insures that the audio voltage on the screen is the same as that on the cathode. Assume that we have an amplifier that without any load connected gives 12 volts output for an input of 2 millivolts.
Audio Asylum Thread Printer
For this reason, the best place to connect a gain control is somewhere in the middle of the amplifier. An important measurementts to notice not stated in many textbooks on the subject is that we must use the gain without the load connected in this formula. By means of a pair of headphones, one of these channels is de- livered to each ear of the listener when the record is played. Describe an experiment that demonstrates this.
This particular response is impossible with any practical amplifier. In the formula for positive feed- back, the feedback factor by which the gain is divided is 1 — AP.
If the loop gain were 99 This also applies to the reactance of ar y capacitance between grid and cathode of the tube. At low load currents, the core is not saturated, but for higher crowhurwt it progressively approaches saturation, which makes the circuit act as a ca- pacitor-input filter. As the current drain in- creases, the choke begins to saturate, and the rectifier starts pulse-feeding the capacitor at the output end of the choke.
With it connected, the reduction is 26 db. This means that, in a large room, wide-spaced speakers fed with audio in which the intensity corresponding to different locations is emphasized will give the best stereo. The usual cause of distortion to square waves is the way in which amplifica- tion varies at high frequencies. Crowhurst – code Audio Measurements by N. Amazon Advertising Find, attract, and engage customers. Share your thoughts with other customers. Distinguish between the inherent characteristics of smoothing vrowhurst utilizing a capacitor input and b choke input.
Without feedback, the internal resistance was 5 ohms; meaeurements feedback it is 1 ohm. At higher frequencies, it becomes less and crowhurxt effective because the magnetism takes time to be induced in the material of the shield.
AUDIO MEASUREMENTS by Crowhurst, Norman H –
Which give the best wave- form? Give the deficiencies associated with using lines at high and low im- pedance that xrowhurst to choice of a medium line impedance. The use of any middle-value impedance,or ohms merely minimizes the defects of either high or low impedances.
Variations in speed at a greater speed than once per revolution are called Butter because of the effect they produce on the reproduction.
Suppose that an amplifier has to work with a ohm resistance as its output load. To get the full gain of the tube we must avoid this feedback effect. The other special output circuit is called ultra-linear. This makes the cathode positive with respect to ground by an amount that varies with the plate current.
Acoustic feedback is not limited to systems possessing microphones; it can also occur in a home reproducing system due to a tube, or the phono- graph pickup, acting as a microphone.
Connecting the resistor between the cathodes will allow some of the fluctua- tion from the cathode of crowhhrst second stage to mmeasurements the fluctuation at the cathode of the first stage.
This was first discussed by Norman Crowhurst and D. In addition, we must transfer to the am- plifier as much as possible of the audio voltage picked up by the microphone, to maintain the signal well above the noise level. How could you evaluate the source resistance without feedback connected?
This impedance is only a small fraction of the total impedance of the loudspeaker, most of which is due to the resistance and inductance of the voice coil.