The upgrade is two separate modules that come together. The first module is a rather large PC board with several different functions. The first is a low voltage bridge rectifier that feeds two independent regulators set up to provide 6.3V DC to each 6V6. This portion of the board is wired in and tested first, and it takes out some 60Hz content (and harmonics) from the noise floor. The other half of the PC board takes the high voltage DC rail and uses a C4S and a stack of Zener diodes to create a regulated high voltage rail that's a bit quieter than the stock power supply, as well as keeping that last big 220uF/350V power supply cap out of the signal path. This regulated supply feeds two additional constant current sources that replace the stock plate loading resistors.
The second PC board is designed to hold the Alps Blue Velvet balance and volume potentiometers, and these replace the stock parts. This module is substantially easier to add to the Moreplay than our typical BeeQuiet attenuator, and it's more appropriate at the price point of the Moreplay. The BeeQuiet attenuator design also presents some additional design challenges that don't work all that well with the 6V6 circuit in comparison to our other products that use it.
