First off, I am not an electrical engineer by trade, or even by education. Pretty much everything I know about EE is self-taught, and I know enough to make a hobby out of it, but may be missing basic, core concepts.
I have found an article on how to build an audio amplifier, linked here. I am confused by one of the calculations it presents, under the heading "Find the Maximum Supply Voltage Output By a Transformer" (the link takes you directly there). Here is an excerpt:
Keep in mind that a transformer’s voltage rating only tells you it’s AC voltage output. The DC voltage will be higher after the bridge rectifier diodes on your power supply convert the AC voltage to DC.
The article then goes on to include 1.41 in its calculations, which I recognize as how to deal with peak vs. RMS measurements, I understand where that's coming from, but my question is: is that at all necessary?
Is AC in general by-default expressed in RMS values? Is the "120VAC" here in the US actually closer to 170V peak-to-peak? I was under the impression that all AC expressions where peak-to-peak, and that if a transformer was outputting 25VAC on its secondary, then a full bridge rectifier (and capacitors for smoothing) was just going to output something close to 25V DC. Is that not correct?
Am I missing something else that would be blatantly obvious to an officially-educated engineer?