Mooer Micro DI schematic

From the vendor

Mooer Micro DI schematic

Apr 24, 2023 2 min read

I've got my hands on an undersized Mooer Cabsim/Balanced driver pedal, and without even sparing any time actually trying how it sounds, I've opened ARTA to see how interesting the cab sim response what. This is what I found:

Not bad! The bass cut is a bit gentle, but the treble filter seems steep enough, and the mid range isn't completely flat either! This seems more than a minimum-effort low-pass filter, so without wasting any more time, I started tracing the circuit.

Pulling the ground lift switch cap out, which prevented the board from coming out, was suprisingly challenging, and then the two-tier design (top for the circuit, bottom for jacks and ground switch, held together by two rows of pins) needed some convincing coming apart.

After that, it was just a small SMT board with most of the connections on the top layer and it didn't take long to trace:

As usual, this is just my personal trace of the circuit, so I cannot guarantee exactness, but it's good enough to discuss the strengths or weaknesses of the design and for repair purposes. In this, I think I'm doing the pedal a service actually.

Since SMT resistors and polarized capacitors can be read but ceramic capacitors can't, I'm only giving values for the former, because I'm not going to desolder the latter to read meaningful values; still, the schematic is more than good enough because it shows the topology and is complemented by the frequency response measurement.

After the switchable-gain input stage, we have the bypassable cab sim, which consists of nothing more than two second-order low-pass filters of the most known Sallen-Key type, wrapped by two noninverting amplifiers and a shelving filter. These few elements effectively combine together to give the measured response. The balanced output is the usual inverter-based one, the ground lift puts a parallel RC in the ground path of all connectors.