There are many similarities, but looking on the inside, 2 totally different transformers. The AVR has about 8 lbs on the MXR. A giant transformer. I understand that the MXR, with the magnetic field amp, has Bob's technology that allows a smaller transformer. However, the AVR is also a MFA. All of the circuit boards look similar, but the AVR has an extra amp mounted in the rear for the surround speakers.