Tjjq44 on System.cfg has modded an original Amstrad CPC DDI-1 disk controller for 464 with a memory expansion by Zaxxon, see the photos below and a video on youtube of the Amstrad CPC 464 loading programs from the DDI-1.
It's necessary to unsolder the 50 pins connector in order to slide in the 512 Kb memory expansion by Zaxxon.
A micro switch let you activate or not the memory expansion.
A wire is used to bridge the +5v of the Amstrad CPC and +5v of the interface so you don't rely on FD-1's power supply anymore. Initially, there's a capacitor between those two pins, you can remove or leave it, it doesn't matter. (Amstrad had done this at the time so that when the user turned off his floppy drive the CPC behaved as if the extension was not present, it avoided having to disconnect the interface or type |TAPE as soon as he wanted to use a tape).
The pins 2,4,6 and 14 have been removed inside each 34 pin connector so that the +5v does not end up on the drive pins. (be careful when opening the connectors, the plastic can break easily).
The 2 small keyed lugs on each 34-pin connector have been filed down to allow connection of any type of drive: FD-1, 3.5 inches classic, gotek...
A switch makes swapping possible between drives, A becomes B and vice versa, practical if you have a gotek and a 3 inch connected simultaneously. For the drives to be recognized, it'll be necessary to ensure that the drive at the end of the ribbon cable has its "drive select" jumper set to 0 and the one in the middle to 1 (no need to do this on a FD-1 , it will respond in any case, its location on the ribbon cable determines whether it is A or B).
The original amsdos ROM has been replaced by a 32 kB amsdos/parados ROM (soldered without stand due to insufficient room). The choice is made by setting pin 27 to 0v (amsdos) or 5v (parados). Currently it is hardwired to 0v because I no longer have micro switch on hand. (However it's not very serious, parados was very useful in order to have 720k of storage per physical diskette, with gotek storage is almost unlimited so we don't care much).