Quote
Nick - if the input filter/fuse/switch can be upgraded/redesigned then I can't see why the SMPS shouldn't be retained for the digital and control circuits.
Use the separate (and isolated) analogue linear PSU for the analogue circuits but you must be aware of the new grounding requirements, I guess you'd need a schematic
I was particularly keen to use linear supplies for everything, not just the analogue stages. Triple-output linear PSUs typically have the 5V and the +/-12V supplies isolated anyway - always with different secondaries, and often with separate boards. When I install them I keep the 5V and the +/-12V returns separate as well. I wouldn't consider using a switching supply just for the digital circuits.

Edit - indeed, if I ever get another HD621, I would certainly fit an FG 305 linear PSU. I'm confident it would improve the jitter performance.

One option I did consider was having TWO linear supplies: one for +5V and another for +/-12V. That might help isolation, and maybe optimise the volume / power capacity balence for smaller spaces. Where there is space though, like in the 861 and G68, I'd just go for a big single supply.
Originally Posted by Dpaws
Nick - Re the 905 http://www.produktinfo.conrad.com/d...0167-da-01-en-LINEARE_STROMV_NMC_902.pdf
Which regulators are used onboard - LM317?
All I know is what's on the datasheet - looks like LM7812/7912. I don't think there's anything special about the 905: the performance is par for the course, and no more. I suggested it because of the combination of 5V current capacity, and the form factor. Within the FG range, its the 105 that's the one to go for if you have the space (like the G68).

Nick