There are two questions about the frequency division circuit, as shown in the figure

QWE4562009

There are two questions about the frequency division circuit, as shown in the figure [Copy link]

 

There are two questions about the frequency division circuit, as shown in the figure

maychang

How is the attenuation slope calculated? It is calculated based on the voltage division of resistance and capacitance. This is the case for both high-pass and low-pass in the figure.

maychang

What is the impact of the notch? The input signal includes signals of various frequencies. This notch will reduce the amplitude of the signal of this frequency relative to other frequency signals.

QWE4562009

maychang posted on 2018-12-11 12:00 How is the attenuation slope calculated? It is calculated based on the voltage division of the resistor and capacitor. This is the case for both the high-pass and low-pass circuits in the figure.

Let me give you an example

QWE4562009

maychang posted on 2018-12-11 12:02 What is the effect of the concave? The input signal includes signals of various frequencies. This concave will reduce the amplitude of the signal of this frequency relative to other frequency signals.

The amplitude of the signal of other frequencies is reduced. -----------------If it is not reduced, it will be better? Why not directly------This concave will reduce the amplitude of the signal of this frequency

maychang

QWE4562009 posted on 2018-12-11 16:59 Give an example

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Chapter 9 begins.

maychang

QWE4562009 Published on 2018-12-11 17:01 The amplitude of the signal relative to other frequencies is reduced. -----------------If it is not reduced, it is better? Why not directly------This concave will make the frequency...

The amplitude of the signal relative to other frequencies is reduced. -----------------If it is not reduced, it is better? Yes. It is usually always hoped that the gain does not change with frequency within the passband.

maychang

QWE4562009 Published on 2018-12-11 17:01 The amplitude of the signal is reduced relative to other frequencies. -----------------If it is not reduced, it is better? Why not directly------this concave will reduce the amplitude of the signal at this frequency...

"Why not directly------this concave will reduce the amplitude of the signal at this frequency" Because this concave does not reduce the amplitude of the signal, and we do not know the amplitude of the signal.

QWE4562009

maychang posted on 2018-12-11 18:25 The amplitude of the signal is reduced relative to other frequencies. ----------------- Is it better if it is not reduced? Yes. Usually we always hope that the gain in the passband is not...

What does this mean?  

maychang

QWE4562009 posted on 2018-12-13 08:53 What does this mean?

The first post circuit is the frequency division circuit of the audio amplifier. Its function is to divide the audio signal containing many frequency components into two paths (one is a relatively high frequency component, and the other is a relatively low frequency component), amplify the two paths separately, and then drive the tweeter and woofer respectively. We always hope that the original sound signal can be fully reproduced, and we don’t want the original sound signal to be missing or lacking certain components. For example, the sound frequency of the triangle in the orchestra is quite high, and the sound frequency of the timpani is relatively low. We hope that the sound of both instruments can be heard, and we don’t want the sound of the timpani to be strong and the sound of the triangle to be weak. This requires that the audio amplifier, including the frequency division circuit in the first post, has the same amplification factor for any audio signal, and cannot have a high amplification factor at some frequencies and a low amplification factor at other frequencies. Therefore, we do not want the "sag" mentioned in the first post to appear on the amplitude-frequency curve. This "sag" means that at this frequency, the total amplification factor of the circuit is small, and the sound of this frequency sounds relatively weaker than the original sound.

QWE4562009

maychang published on 2018-12-13 09:29 The first post circuit is the frequency division circuit of the audio amplifier. Its function is to divide the audio signal containing many frequency components into two paths (one is a relatively high frequency...

Any audio signal has the same amplification factor? Can this be done?

QWE4562009

maychang published on 2018-12-13 09:29 The first post circuit is the frequency division circuit of the audio amplifier. Its function is to divide the audio signal containing many frequency components into two paths (one path is a relatively high frequency...

The amplification factor of any audio signal is the same ----- does it mean all the frequency range of the audio? Shouldn't this range be very narrow?

QWE4562009

maychang published on 2018-12-11 18:27 "Why not directly------this notch will reduce the signal amplitude at that frequency" Because this notch does not reduce the signal amplitude, the signal amplitude I...

-6dB/octave means 6dB attenuation per octave. Taking the first-order RC low-pass as an example, when the frequency is greater than the corner frequency 1/(2π*RC), the gain is proportional to 1/f (f: frequency), and the attenuation value of frequency f1 and 2*f1 = 20*log(1/2f1)-20*log(1/f1) = 20*log(0.5) = -6dB (2) The notch means that the signal at that frequency has additional loss. ------------------Is this correct?  

maychang

QWE4562009 posted on 2018-12-13 13:51 The amplification factor of any audio signal is the same - does it mean that all the frequency ranges of the audio? Shouldn't this range be very narrow?

The frequency range of sound audible to the human ear is 20Hz~20kHz, and the ratio of the highest to the lowest frequency is 1000 times, which is not a small range.

maychang

QWE4562009 Published on 2018-12-13 13:50 Can any audio signal be amplified to the same multiple? Is this possible?

Can any audio signal be amplified to the same multiple? Is this possible? Yes. For ordinary oscilloscopes, the frequency range of the Y-axis amplifier is usually required to be from zero (in fact, there is no zero frequency, usually the zero frequency is just arbitrarily low, such as 0.0001Hz) to tens of MHz, far beyond the audio range (20Hz ~ 20kHz).

maychang

QWE4562009 posted on 2018-12-13 13:55 -6dB/octave means 6dB attenuation per octave. Taking the first-order RC low-pass as an example, when the frequency is greater than the corner frequency 1/(2π*RC), the gain is proportional to 1/f (f: ...

Is this correct? Yes. But to be clear: the amplitude-frequency characteristic of the first-order RC low-pass is 3db attenuation at the "corner frequency". The picture in your first post shows two filter circuits, a high-pass and a low-pass. Both filter circuits are second-order (two first-order in series).

zhuyebb

No reply, no forum

QWE4562009

maychang posted on 2018-12-13 15:33 Is this correct? Yes. But to be clear: the amplitude-frequency characteristic of the first-order RC low-pass is 3db attenuation at the "corner frequency". The picture in your first post is...

Do you use this 1/2π*RC or 159/RC to calculate the frequency?

QWE4562009

maychang posted on 2018-12-13 15:28 Is it possible to make any audio signal have the same amplification factor? Yes. For ordinary oscilloscopes, the frequency range of the Y-axis amplifier is usually required to be from zero (real...

The X-axis is time, right? ???????

maychang

QWE4562009 posted on 2018-12-14 11:02 Should I use this 1/2π*RC or 159/RC to calculate the frequency?

"Should I use this 1/2π*RC or 159/RC to calculate the frequency?" 1/2π is equal to 0.159. Why do you need to memorize those formulas?