12VAC Common Reference
Your scheme will probably work. You should be aware that the AC ground and the DC ground are at very different and alternating potentials.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. The same circuit drawn three times but (b) and (c) have the reverse-biased diodes removed for clarity.

As shown in (b) and (c) the DC ground will vary in voltage between +0.7 V and -12√2 + 0.7 V with respect to the AC ground. You need to be sure that this won't upset your requirements.