Setting the Input Sensitivity on RD Amplifiers is made simple thanks to their built-in clipping indicator. Following the steps below will ensure quick and consistent results providing a maximum, non-clipped output signal every time.
To set the input sensitivity, frequency appropriate sine waves (50 Hz for subwoofer channels and 1 kHz for full-range channels) recorded at a 0 dBfs reference level will be needed. They can be found on the FiX™ Calibration CD or downloaded from the Audio Files article. If the radio doesn’t have a CD player, digital versions of the sine waves can be played through USB or auxiliary inputs. Make sure to disable any equalization or DSP settings on the source unit and DSP (if one is present).
The Seven-Step Procedure
- Disconnect the speaker(s) from the amplifier.
- Turn off all processing on the source unit and the amplifier (bass/treble, loudness, EQ, etc.).
- Turn the input sensitivity control on the amplifier all the way down. If there is a sensitivity range switch, set it to the “low” position.
- Set the source unit volume to 3/4 of full volume. This will allow for reasonable gain overlap with moderate clipping at full volume.
- Verify that you have disconnected the speakers before proceeding. Play a track with an appropriate sine wave (within the frequency range to be amplified) at 3/4 source unit volume.
- Slowly increase the “Input Sensitivity” control until the “Clipping” Indicator is solidly lit, indicating maximum, non-clipped output. If the “Clipping” indicator is lit with the “Input Sensitivity” control turned all the way down, set the “Input Voltage” switch to the “High” position, then slowly increase the “Input Sensitivity” control until the “Clipping” Indicator is solidly lit
- Once you have adjusted each amp to its maximum unclipped output level, turn down the volume of the head unit and turn it off. Reconnect all the speakers, turn the head unit on and proceed to adjust the level balance between the subwoofer and satellite amplifiers. This is accomplished by listening to the system at a moderate level and turning down the input sensitivity controls of amplifiers that are playing too loudly. Do not increase the input sensitivity of any amplifier as this will defeat the purpose of this procedure by permitting excessive clipping (distortion).