I decided to extend a little bit the measurements of the MOD Duo I’d done here:
The additional measurements were performed with MATLAB and a RME Fireface sound card. 2 channels of the RME were used, one for the MOD Duo measurement and the other one as a loopback to get a reference value for the gain and delay. What was performed:
- Impulse Response
- Magnitude Response (Sprectrum)
- Harmonic Distortion
The pedalboard used was initially a simply bypass IN1 -> OUT1 and IN2 -> OUT2. Here are the results:
A few things can be noticed here. First of all the delay is indeed around 8ms, as already measured in the link above. Alos, as you can see, there is clearly a problem in the IN1->OUT1 path. A huge distortion is present in the high end (starting at 1kHz) and there is a unexpected gain of 7dB.
In contrast, the IN2->OUT2 path has a much cleaner spectrum. However, the -3dB gain is also unexpected.
The problem could be either in IN1, OUT1 or both. In order to mitigate that, I modified the pedalboard slightly and performed the same measurements for IN1->OUT2 and IN2 ->OUT2, still with only a wire connecting them.
The conclusion from this cross measurement is that there is a problem with IN1, which could be related to the hardware. It would be good to know whether:
Someone else also had a problem with IN1 or experienced some strange behavior there
Why is there a -3dB gain in the “clean path”
Currently as a workaround I can simply avoid IN1 and add a gain module to compensate for the 3dB difference.