Notch Filters

Stopping Feedback with Notch Filters



Eliminating Feedback with Notch Filters 

Feedback can sometimes occur when using the ToneWoodAmp, just like with other amplifiers or PA systems. However, there's a solution! Notch filters are a great tool to help isolate and reduce those feedback frequencies, resulting in better sound quality, especially at higher volume levels. While you can get creative and use the notch filters as an EQ, their main purpose is to specifically target and reduce the frequencies that cause feedback.

The ToneWoodAmp offers two programmable Notch Filters:

- Notch 1: Range of 50 Hz – 1049 Hz

- Notch 2: Range of 50 Hz – 2090 Hz

Note: The Notch Filters do not affect the DI signal out of the ToneWoodAmp.


Using the Notch Filters:

  1. Access the Notch Filter menu by pressing and holding the Amplitude knob for two seconds. "Filters>" will appear on the display.
  2. Turn the Amplitude knob clockwise to select Notch 1 or Notch 2.

Once selected, each ToneWoodAmp knob has a specific function for controlling the filter's parameters (refer to the diagram connected to the notch filters).

- The Effects knob cuts the selected frequency, increasing attenuation when turned clockwise from 0 to 20.

- The Parameters knob sets the notch filter frequency (FREQ), changing in either 40 Hz or 4 Hz increments.

- The Amplitude knob controls the relative volume of the selected filter, useful for identifying problematic feedback frequencies or adjusting feedback levels while setting the filters.


Eliminating Feedback using the Search and Destroy method:

  1. Enter the Notch Filter menu by clicking and holding the Amplitude knob for two seconds. "Filters>" will appear on the display.
  2. Turn the Amplitude knob clockwise to select Notch Low. The Amplitude knob now controls the filter's volume.
  3. Increase the Amplitude knob clockwise to allow the feedback to continue.
  4. Turn the Effects knob fully clockwise to apply the maximum amount of attenuation (cut value 20).
  5. Slowly turn the Parameters knob to scan through the frequency spectrum until the feedback starts to dissipate. Click the Parameters knob to toggle into fine-tuning (4 Hz increments) for precise adjustment.
  6. Once the problematic frequency is identified, gradually turn the Effects knob counterclockwise to reduce the amount of attenuation until the feedback becomes audible again.
  7. Turn the Effects knob clockwise a few notches until the feedback disappears again. This determines the minimum cut required to avoid feedback without altering the ToneWoodAmp's tonal balance.
  8. Click the Amplitude knob to save your changes. Notch Filter settings are automatically saved to individual Guitar presets.
  9. If you encounter another problematic frequency, select Notch High and repeat steps 3 to 8.

Note: The Notch High filter is set by default to cut 900 Hz, a commonly problematic frequency. However, feel free to adjust it as needed.


Once you effectively control these frequencies, you can increase the volume of the ToneWoodAmp without feedback issues and raise the Master Gain for more volume. Additionally, the Search and Destroy method learned here can be useful in many audio situations.