I've measured the voltage noise of the SR560's lead acid battery outputs; they're not so bad.
Steve ordered us some replacement lead-acid batteries for our battery powered pre-amps (SR560). In the unit he replaced, I measured the noise using the following setup:
SR560 Busby Box
(+12V/GND) -------------AC Input Out ---------------- SR785
The SR785 was DC coupled and auto-ranged. The input noise of the SR785 was measured via 50 Ohm term to be at least 10x less than the SR560's noise at all frequencies.
Its clear that this measurement was spoiled by the low frequency noise of the Busby box below 10 Hz. Needs a better pre-amp.