A MUSE operational amplifier is used in the RIAA equalization amplifier. Polypropylene capacitors have been used in the signal path and in the RIAA equalization circuits. There is selectable input loading for both resistance and capacitance along with two different gain settings located on the back panel making the Fono MC MK4 compatible with most low output MC cartridges. The new Fono MC MK4 circuit resulted from the development work carried out on the hugely successful Aria phono amplifier.
The aesthetic design of the Fono MC MK4 was as important as the quality of its electrical capabilities, so it benefits from the same new aluminium case as the Rega Neo MK2 PSU and Fono MM MK5 phono stage, giving it a design which offers a familiar feel and moreover brings it in line with its illustrious bigger brothers.