Audiotec Fischer Tech Talk #2

What happens if you hook up a common amplifier or signal processor to an OE car radio instead of the loudspeakers?

Most of the OE car radios perform complex diagnosis procedures during start-up in order to detect a malfunction or whether speakers are connected. If the radio detects a malfunction, the following problems may occur:

  • Error messages stored in the car‘s CPU
  • Features are missing like the fader function
  • Speaker outputs will be switched off (= no more sound)


Conclusion: for proper operation the connected amplifier / signal processor has to behave on its highlevel input like a typical loudspeaker load!

An often proposed solution:
Take a couple of high-power resistors (min. 10 Watts load) and connect them in parallel to the highlevel speaker inputs of your amplifier / signal processor.


  • Expensive
  • Reduced sound quality due to higher signal distortion of the OE radio
  • Requires additional space
  • High installation effort
  • Additional heat dissipation
  • Unnecessary load for your radio and high current draw – bad if you like to use the original harness for powering your Plug & Play amplifier!


The intelligent solution: ADEP.3
The 3rd generation of our hard- and software based ADEP circuit generates a “dynamic” load for the OE radios and therefore avoids the previously mentioned issues. At low levels, the input impedance of our devices is low enough to "fool" the speaker diagnostics in today's car radios.
Depending on the radio volume, the ADEP.3 circuit adapts itself dynamically so that the radio is not unnecessarily loaded. Hence the reduced power consumption of the radio is a real benefit for our MATCH Plug & Play amplifiers if those are directly powered from the factory harness of the radio!

The ADEP.3 benefits at a glance:

  •  Avoids failure messages in the car´s error memory
  • Keeps features e.g. fader function
  • Ensures best possible sound quality
  • No unnecessary load of the OE radio´s speaker outputs
  • Perfect OEM integration without additional installation effort