The LM7812 handles a range of input voltages, the 6V doubled will give you enough to rectify and feed the regulator. I thought it was on the low side and went with a 12V transformer, which doubled is still well within the regulator range. Working in my case, thought about converting the doubler to just rectify but seemed like more work for no reason.
LM7812CT/NOPB data sheet shows input voltage range of 7 to 35 volts with 12v output. I've ordered the Modulous Doumbledor Transformer set and have selected 6.3 v for the aux to feed the PCB voltage doubler into the LM7812. Steve.
The LM7812 handles a range of input voltages, the 6V doubled will give you enough to rectify and feed the regulator. I thought it was on the low side and went with a 12V transformer, which doubled is still well within the regulator range. Working in my case, thought about converting the doubler to just rectify but seemed like more work for no reason.