# How to attenuate an already amplified output?

• chebyshevF
In summary, the speaker has a high pass filter circuit with amplification that they don't want. They are considering introducing another capacitor in series or using a voltage follower, but someone suggests using an inverting opamp with a gain of -1/2 to achieve the desired input=output at the frequency where amplification starts, without affecting the poles or zeros of the total transfer function.
chebyshevF
I have a high pass filter circuit, which I've designed from a transfer function, and from the Bode Plot, I'm getting some amplification, yet I don't want that. I just want my input=ouput at the frequency where amplification starts. How can i go about to do this?

Should i introduce another capacitor in series? A voltage follower perhaps?

chebyshevF said:
I have a high pass filter circuit, which I've designed from a transfer function, and from the Bode Plot, I'm getting some amplification, yet I don't want that. I just want my input=ouput at the frequency where amplification starts. How can i go about to do this?

Should i introduce another capacitor in series? A voltage follower perhaps?

If you can accommodate the inversion, use an inverting opamp circuit and set the gain to 1/ the gain of the HPF circuit's gain.

^^Actually I tried an inverting opamp, yet didn't think of setting the gain to the inverse of my HPF circuit's gain. I don't understand why though? So it swaps the pole and zero that i have, hence i get new capacitor values..i can't quite put my 'finger' on it but it kinda makes sense.

chebyshevF said:
^^Actually I tried an inverting opamp, yet didn't think of setting the gain to the inverse of my HPF circuit's gain. I don't understand why though? So it swaps the pole and zero that i have, hence i get new capacitor values..i can't quite put my 'finger' on it but it kinda makes sense.

A simple inverting amp stage after the output of your filter should not affect any poles or zeros of the total transfer function. If the gain of your filter is x2, just make the gain of your inverting amp stage -1/2.

## 1. How can I attenuate an already amplified output?

There are a few different methods for attenuating an already amplified output, depending on the type of amplifier you are using. One option is to use a volume control or attenuator knob on the amplifier itself. Another option is to use a passive attenuator, which can be inserted between the amplifier and the speaker. Finally, you can also use an active attenuator, which uses electronic components to reduce the output level.

## 2. Will attenuating an already amplified output affect the sound quality?

In most cases, attenuating an already amplified output should not significantly affect the sound quality. However, using a passive or active attenuator may introduce some slight changes in the frequency response or dynamics of the sound. It is important to choose a high-quality attenuator and to adjust it carefully to minimize any potential impact on sound quality.

## 3. What is the difference between a passive and an active attenuator?

A passive attenuator simply uses resistors to reduce the signal level and does not require any external power source. An active attenuator, on the other hand, uses electronic components such as transistors or op-amps to actively reduce the signal level. Active attenuators are typically more expensive but may offer more precise control and less impact on sound quality.

## 4. Can I use a resistor to attenuate an already amplified output?

Yes, a resistor can be used as a simple passive attenuator to reduce the signal level. However, the exact value of the resistor needed will depend on the output impedance of your amplifier and the input impedance of your speaker. It is important to choose the right value to avoid damaging your equipment or affecting the sound quality.

## 5. Is it possible to attenuate an already amplified output without using any additional equipment?

If your amplifier has a dedicated volume control or attenuator knob, then you can use that to adjust the output level without needing any additional equipment. However, if your amplifier does not have this feature, then you will need to use a passive or active attenuator to reduce the signal level. Alternatively, you could also use an external mixer or preamp to control the output level before it reaches your amplifier.

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