26/01/17 - New update on the project here
I was working on the version 3 of the power adapter for Commodore 64 in the last 2 month, a new model that should correct all of the problem the last versions have.
I had started by replacing the modified sine wave by a pure sine wave, everything was going great but when I started testing the prototype, I realized that a pure sine wave generator was not enought to remove the buzzing noise coming from the common mode filter, to remove completely the noise I needed to have a isolation between the +5V and the 12V (or 15V).
Using 2 isolated voltage is not difficult but it would increase the price significantly, especially if I solder and assemble myself.
I have modified the prototype using 2 power adapter and it work great but the retail price would be too high for me at the moment for this solution, maybe when I start to do SMD assembly.
But when I say too high I compare it to another project I had at the same time for the C64, at the start I wanted to propose a AC power supply to complement the other power adapter but as the price should be really similar, this one will replace it, I had chosen to use a classic 9V transformer and a +5V regulated power supply, it's a complete AC power supply, to replace completely the original power adapter. It will be available in 110V and 230V and (I hope) before 2017.