DSP Settings
Compressor Settings
What is Compressor?
The time it takes for the compressor to respond to changes in input level is known as attack, and how quickly the compressor returns to no gain reduction once the input level falls below the threshold is known as release. In many compressors the attack and release times are adjustable by the user. Some compressors, however, have the attack and release times determined by the circuit design and they cannot be adjusted by the user. Sometimes the attack and release times are 'automatic' or 'program dependent', meaning that the times change depending on the input signal. Because the loudness pattern of the source material is modified by the compressor it may change the character of the signal in subtle to quite noticeable ways depending on the settings used.
Automatic Gain Control Settings
What is Automatic Gain Control?
An audio tape generates a certain amount of noise. If the level of the signal on the tape is low, the noise is more prominent, i.e., the signal-to-noise ratio is lower than it could be. To produce the least noisy recording, the recording volume should be set as high as possible without being so high as to clip or seriously distort the signal. In professional high-fidelity recording the level is set manually using a peak-reading meter.
If high fidelity is not a requirement, a suitable recording level can be set by an AGC circuit which reduces the gain as the average signal level increases. This allows a usable recording to be made even for speech some distance from the microphone of an audio recorder. Similar considerations apply with VCRs.
The disadvantage of AGC is that when recording, say, music with quiet and loud passages, the AGC will tend to make the quiet passages louder and the loud passages quieter, reducing the dynamic range and losing musical quality.
Most reel-to-reel tape recorders and cassette decks have AGC circuits. Those used for high-fidelity allow it to be overridden manually.
Most VCR circuits use the amplitude of the vertical blanking pulse to operate the AGC. Video copy control schemes such as Macrovision exploit this, inserting spikes in the pulse which will be ignored by most television sets, but cause a VCR's AGC to overcorrect and corrupt the recording.
Filters Settings
what is lowpass filter?
A low-pass filter is a filter that passes low-frequency signals but attenuates (reduces the amplitude of) signals with frequencies higher than the cutoff frequency. The actual amount of attenuation for each frequency varies from filter to filter. It is sometimes called a high-cut filter, or treble cut filter when used in audio applications.
What is highpass filter?
A high-pass filter is a filter that passes high frequencies well, but attenuates (reduces the amplitude of) frequencies lower than the cutoff frequency. The actual amount of attenuation for each frequency varies from filter to filter. It is sometimes called a low-cut filter; the terms bass-cut filter or rumble filter are also used in audio applications. A high-pass filter is the opposite of a low-pass filter, and a band-pass filter is a combination of a high-pass and a low-pass.
What is bandpass filter?
A band-pass filter is a device that passes frequencies within a certain range and rejects (attenuates) frequencies outside that range. An example of an analogue electronic band-pass filter is an RLC circuit (a resistor¨Cinductor¨Ccapacitor circuit). These filters can also be created by combining a low-pass filter with a high-pass filter.
What is Notchpass filter?
A Notch filter is a filter that passes all frequencies except those in a stop band centered on a center frequency. A closely related Knowledge base item discusses the concept of the Q of a filter. This Knowledge base item focuses on high Q notch filters - the type that eliminate a single frequency or narrow band of frequencies. A closely related type of filter - a band reject filter, is discussed in a separate knowledge base item. The amplitude response of a notch filter is flat at all frequencies except for the stop band on either side of the the center frequency. The standard reference points for the roll-offs on each side of the stop band are the points where the amplitude has decreased by 3 dB, to 70.7% of its original amplitude.
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