NQ_GA40P3_Amplifier_with_Line_IO-7
Author: Bogen
Description: Nyquist

Setting DSP Parameters

When you select DSP from the appliances web UI, the DSP page appears.

Figure 1. DSP Page

From this page, you can adjust settings in the DSP. The appliance uses traditional processors (for example, Compressor, Limiter) for audio signals in the digital domain.

The DSP page shows Mute and level selections for the input and output channels and allows you to adjust the channel input gain level.

Selecting the Menu button displays other parameters. DSP parameters and the Mute and level controls are described in the following table.

Table 11. DSP Page

Save Settings to Server | Backs up the DSP settings to the server. If this device is later replaced or reset to factory defaults, these DSP settings can be restored when the new device is “swapped” for the old on the Nyquist server. Note: This button appears on each DSP feature page.
Mute | Silences the audio.
DSP Features button | Presents a menu of DSP features that can be applied to the corresponding channel.
Channel Fader | Adjusts the channel volume level in 1-dB increments.
Signal LED | Illuminates when a signal is present.
Clip LED | Illuminates when a signal has exceeded the maximum threshold, indicating that the signal is “clipping.” Note: When Sound Masking is enabled, Clip LED is illuminated.
NET-IN LED | Illuminates when a signal is being received from the Network stream input. Note: When Sound Masking is enabled, NET-IN LED is illuminated.
LINE-IN LED | Illuminates when a signal is being received from the analog Line input.
IN VU meter (Line Input) | Indicates the strength of the analog input signal.
OUT VU meter (Line Input) | Indicates the strength of the output from the analog signal.
IN VU meter (Line & AMP Output) | Indicates the strength of the network input signal.
OUT VU meter (Line & AMP Output) | Indicates the strength of the channel output signal for both Line Output and Speaker Output.
Input Gain | Adjusts the strength of the analog line input signal.

The DSP features that can be applied to a channel, accessible through the DSP Features menu, are described in the following table.

Table 12. DSP Features

Compressor | Lessens the dynamic range between the loudest and quietest parts of an audio signal.
High/Low Pass | Sets the band of frequencies that will pass through the high pass and low pass filters and selects the type of filter that is used.
Limiter | Prevents a signal from exceeding an adjustable maximum level.
Outputs | Allows you to enable speaker or line outputs and to adjust the volume level for each output.
Parametric EQ | Uses a center/primary frequency to allow tailoring of the frequency content of an audio signal.
Settings | Allows you to provide names and colors for the input channel.
Signal Present | Illuminates green when audio is present in the channel input.
Reset button | Present on almost all DSP screens other than the main mixer, this button will reset the DSP settings to the displayed feature’s default setting.

Setting the Channel Level

The channel level control is a channel fader, which is adjusted in 1-dB increments and controls the output level for the channel. The channel levels can range from −60 to +12 dB. If you place the mouse over the fader, the numerical value of the level appears.

Adjusting Volume Levels

The channel fader control can be used to adjust the channel’s output level in 1-dB increments between −60 and +12 dB. The overall adjusted output level of the channel signal can be viewed on the OUT VU meter, marked in 2-dB increments between −60 and 0 dB.

Tip:​For best results, adjust input signal levels until you have a strong signal (i.e., within the green and yellow areas on the meter), then adjust the final output levels using the DSP Outputs controls.

To adjust the channel volume level:

1​On the appliance Web UI’s main page, select DSP.

2​Use the channel’s fader to adjust the volume level.

Knob Adjustments

Many DSP controls use knobs to adjust one or more settings. The value of a knob can be adjusted in one of two ways:

1​Click the knob control, hold the mouse button down, and drag the mouse up or down to increase or decrease the value.

2​Double-click the knob, type a value into the resulting popup, and click the Save button.

Signal Indicators

Each input channel has signal indicators and two vertical volume unit (VU) meters, labeled “IN” and “OUT”.

The green input signal LED(s) automatically illuminates when a signal is being received.

The red Clip LED automatically illuminates when the signal is clipping (i.e., exceeding a predefined threshold). Clipping can result in distortion and, for output signals, can even damage speakers. Note that the specific level and duration that a signal must reach in order to trigger the input signal LED can be configured via the Signal Present settings.

The “IN” VU meter indicates the strength of the channel’s input signal (after gain adjustments), while the “OUT” VU meter indicates the strength of the channel’s output signal. The VU meter not only illuminates green, yellow, or red (depending on the signal level), but also has a scale ranging from −60 to 0 dB to indicate the actual signal level.

Muting a Channel

You can mute a channel to cut off an audio signal and stop the input signal from being sent to the output channel. Note the input signal will still be visible on the IN meter, but the OUT meter will show that nothing is being forwarded to the output channel.

To mute a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Click the Mute button for the channel that you want to silence.
The Mute button will illuminate red. You can click the Mute button again to unmute the channel.

Compressor

A compressor reduces the dynamic range of a signal. This effect is perceived as quieting loud sounds and boosting quiet sounds.

Figure 10. Compressor Settings

To adjust the compressor settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Compressor.

4​Make desired adjustments using the controls described in Table 13, “Compressor Settings,” on page 25.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

5​Select Enable to apply the settings to the selected channel.

Table 13. Compressor Settings

Enable | Enables or disables the compressor DSP effect for this channel.
Threshold | Sets the threshold level, which is the point where the signal activates the compressor circuit. The range is −135 to +21 dB.
Attack | Sets how quickly or slowly compression will be applied to the signal once the audio signal goes above the threshold level. It specifies the length of time over which the compression ratio will gradually increase from no compression to full compression. The range is 1 to 500 ms.
Hold | Sets how long compression will be applied after the signal has fallen below the threshold. The range is 1 to 500 ms.
Decay | Sets how quickly or slowly compression will be removed from the signal after the signal has dropped below the threshold and the Hold interval has expired. It specifies the length of time over which the compression ratio will gradually decrease from full compression to no compression. The range is 0 to 2000 ms.
Knee | Sets how far below the threshold compression will begin to be gradually applied to the signal. A very low value, known as a hard knee, immediately applies full compression once the threshold is reached. A high value, known as a soft knee, will gradually start applying compression before the signal reaches the threshold, not reaching the full effect until the threshold is reached, thereby “rounding off” the compression effect. Increasing the knee level decreases the obvious transition from the uncompressed to the compressed sound. The range is 1 to 100 dB.
Ratio | Sets the compression ratio to be applied to the signal. For example, if the ratio is set for 6 (6:1), the input signal must increase by 6 dB for the output level to increase by 1 dB. The range is 1 to 100.
Input meter | Shows the strength of the input signal.
Output meter | Shows the strength of the output signal, providing a visual indicator of the effect of the compressor on the output signal.
Comp LED | Illuminates when compression is being applied to the signal.

High/Low Pass

High-pass filters allow signals that are higher than the specified frequency and attenuate signals that are lower. Low-pass filters allow signals that are lower than the specified frequency and attenuate signals that are higher. When combined, they are known as a band-pass filter. Band-pass filters can be used to tailor the frequency response of a microphone exclusively for vocals, which can be very useful in a noisy environment to filter out the higher and lower frequencies that could mask the human vocal range during announcements.

You can specify the range of frequencies that will pass through the high-pass and low-pass filters and select the type of filter that is used through the channel’s High/Low Pass drop-down menu option.

Figure 11. High/Low Pass Parameters

To adjust the high/low pass parameters for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select High/Low Pass.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Set the parameters described in the following table:

Table 14. High/Low Pass Parameters

High-Pass (Low Cut) This feature helps eliminate low-frequency noise (signals of 100 Hz and below, such as background rumble from ventilation systems, etc.) and is used primarily with microphone-level input. It is particularly effective when handheld microphones are used.
Enable | Enables or disables the High-Pass filter.
Frequency | Set the cutoff frequency. You can adjust the frequency by moving the knob (click and move up or down) or by double-clicking the knob and typing the frequency. When typing the frequency, only numeric values from 20 Hz to 20,000 Hz can be entered. The high-pass filter attenuates content below this frequency and lets frequencies above this cutoff frequency pass through the filter.
Type | Available filter types are: Linkwitz-Riley (12, 24, 36, and 48 dB per octave) Butterworth (6, 12, 18, 24, 30, 36, 42, and 48 dB per octave) Bessel (12, 18, and 24 dB per octave) Note: The term “dB per octave” describes how steeply frequencies below the selected cutoff frequency are attenuated. For example, if the cutoff frequency is 100 Hz and the filter type specifies 12 dB per octave, a 50-Hz signal (i.e., one octave lower) will be attenuated by 12 dB and a 25-Hz signal (i.e., two octaves lower) will be attenuated by an additional 12 dB.
Low-Pass (High Cut) This feature helps eliminate high-frequency noise (signals of 8000 Hz and above) such as background hiss and sibilance (excessive "S" in vocals, etc.) and is used primarily with microphone-level input. It is particularly effective when handheld microphones are used.
Enable | Enables or disables the Low-Pass filter.
Frequency | Set the cutoff frequency. You can adjust the frequencies by moving the knob (click and move up or down) or by double-clicking the knob and typing the frequency. When typing the frequency, only numeric values from 20 Hz to 20,000 Hz can be entered. The low-pass filter attenuates content above this frequency and lets frequencies below this cutoff frequency pass through the filter.
Type | Available filter types are: Linkwitz-Riley (12, 24, 36, and 48 dB per octave) Butterworth (6, 12, 18, 24, 30, 36, 42, and 48 dB per octave) Bessel (12, 18, and 24 dB per octave) Note: The term “dB per octave” describes how steeply frequencies above the selected cutoff frequency are attenuated. For example, if the cutoff frequency is 8,000 Hz and the filter type specifies 12 dB per octave, a 16,000-Hz signal (i.e., one octave higher) will be attenuated by 12 dB and a 32,000-Hz signal (i.e., two octaves higher) will be attenuated by an additional 12 dB.

Limiter

A limiter is a compressor with a high slope (i.e., attack) that is used to prevent a signal from exceeding a set decibel level. Limiters are used as safeguards against signal clipping.

Limiter parameters are set per channel.

Figure 12. Limiter Settings

To adjust the limiter settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel or select the Menu button for the Output.

3​From the drop-down menu, select Limiter.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Adjust the following settings as needed:

Table 15. Limiter Settings

Threshold | Sets the signal level at which the limiter is triggered. Any signal exceeding this threshold will be compressed to this level. The range is −24 to +24 dB.
Decay | Sets the rate for turn off of the limiter after the signal is below the threshold. Decay range is 5 to 2300 milliseconds.
RMSTC (Root Mean Square Time Constant) | Sets how fast the limiter reacts to a signal that has exceeded the threshold. RMSTC range is 50 to 10000 dB/sec.

Adjusting Outputs

Selecting Outputs allows you to enable and adjust the volume levels for speaker and line outputs.

Figure 2. Outputs

To adjust outputs for speaker or line:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button.

3​From the drop-down menu, select Outputs.

4​To enable outputs for a speaker or line, select Enable for the corresponding output.

5​Make desired Volume adjustments by adjusting the knob. Volume levels range from 0 to 15 dB for the Speaker Output and −15 to +15 dB for the Line Output.

Parametric EQ

A parametric equalizer is a multi-band variable equalizer that allows control of frequency amplitude (boost/cut), center frequency, and frequency bandwidth, or Q.

Figure 14. Parametric Equalizer Settings

The parametric equalizer settings for your device allows you to adjust the Q and gain for seven separate frequencies, which then become plot points on the screen’s graph.

To adjust the parametric equalizer settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Parametric EQ.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Adjust frequencies as desired, ensuring the Enable LEDs are green for each selected frequency. You can adjust the frequencies by moving the Freq knob or by double-clicking the knob and typing the frequency. When typing the frequency, only numeric values from 20 to 20,000 can be entered.

5​Make desired Q adjustments by adjusting knob (or double-clicking and typing the desired adjustment). Q can be from 0.1 to 20 and sets how wide to either side of the selected frequency the adjacent frequencies are affected.

Q is the Quality or Quality Factor, which refers to the bandwidth of one band of a parametric equalizer. Q is calculated by dividing the center frequency in Hz by the width of the boost or cut zone, +3 dB or −3 dB above or below 0 dB.

6​For each frequency, use the Gain knob or double-click the knob and type the gain to either boost (turn up) or cut (turn down).

Gain knobs can be moved between +12 or −12 dB. By default, each knob is set at 0 dB, which means that no frequencies are being boosted or cut.

7​Select Save Settings to Server.

Settings

You can set select a name and a color for the input channel.

Figure 15. Settings Parameters

To adjust the settings for the channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Settings.

4​Type the name that you want to display for the channel.

5​Select a color that will be used to highlight the channel.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

6​Select Save.

Signal Present

You can configure the threshold level that a signal must reach before the signal LED is lit, as well as how long the LED will remain lit. You can configure this for each channel.

Figure 16. Signal Present Parameters

To adjust the Signal Present settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Signal Present.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Adjust the following settings as needed.

Table 16. Signal Present Parameters

Threshold | Sets the minimum level the signal must reach before the signal LED is illuminated. Threshold range is −144 to +24 dB.
Hold | Sets the minimum number of milliseconds that the signal LED will remain illuminated. Hold range is 2 to 200 milliseconds.