Let me say I am quite interrested in this topic. The hybrid on the 1571/1541C is a quite a black box, and yes, we do have schematics of the old 1541, but it doesn't mean that circuit is optimal. If someone wants to design new floppy drive controller boards without using old chips, the internals of the hybrids are quite interresting material.
Exactly the latter! And from this perspective, even if the old discrete circuitry may not be economically optimal, it may be good enough for now, as there seem to be zero compatibility issues between the discrete circuitry and the later versions using the hybrid.
The discrete version may be even better in terms of adaptability!
Because, if we summarize problems and possible goals, we get the following picture:
- There are zillions of drive carcasses rendered useless by broken Mitsumi Newtronics heads
- For every repair, we currently need a compatible ALPS mech, scavenged from another probably good drive
- Choice in media is limited
So, we need ways to accomodate other manufacturers' drive mechs to the 15xx drives. Being able to modify and enhance the R/W amp, I can think of the following:
- create one universal 15xx mainboard that fits all drives
Kinzi et al. have shown in the 1570-II project that this is perfectly possible. Even firmwares are available already.
- make accomodations for a big choice of PC SD/DD drives
- make accomodations to use HD diskettes (recording still no more than 170kB per side)
- seriously consider a 3.5'' drive using actual GCR
- also consider recording GCR to 3.5'' double sided and HD (still without changing capacity, just enhancing the choice of available media)
Biggest obstacle in terms of availability and adaptability, except for the modifications to the 3rd party drives, should really be the hybrid and/or the Sony etc R/W amp used in the 1541-II drives.