Besides the "big" brands' disk drives for the Amstrad CPC, there were also user solutions and garage company made disk drives for the Amstrad CPC.
These usually came without their own DOS, or you had to replace the built-in AMSDOS with a DOS like ParaDOS or a patched AMSDOS.
But even without a special DOS taking use of the higher capacity of those drives, the use of such drives made sense, as media were much cheaper than 3" media.
Today, with supplies of 3" disks draining and company solutions no longer being produced, a self-made 3 1/2" disk drive is the perfect supplement for every CPC user.
Schematics
Amstrad/Schneider CPC664/CPC6128 (Not German CPC6128s!)
Drive has RDY-signal
Schematics for PC disk drives with own READY signal on an Amstrad/Schneider CPC664/CPC6128 (Non-German CPC6128 only)
Drive doesn't have RDY-signal =
Schematics for PC disk drives without own READY signal on an Amstrad/Schneider CPC664/CPC6128 (Non-German CPC6128 only)
Amstrad/Schneider CPC6128 (German models and grey imports from Germany only!)
Drive has RDY-signal
Schematics for PC disk drives with own READY signal on a Schneider CPC6128 or a German Amstrad CPC6128
Drive doesn't have RDY-signal =
Schematics for PC disk drives without own READY signal on a Schneider CPC6128 or a German Amstrad CPC6128
Amstrad CPC6128plus
Drive has RDY-signal
Schematics for PC disk drives with own READY signal on an Amstrad CPC6128plus
Drive doesn't have RDY-signal =
Schematics for PC disk drives without own READY signal on an Amstrad CPC6128plus