PROGRESS!
If you recall, I was suspect of my universal power block I had running my o-scope. Long story short, that was DEFINATELY introducing a lot of noise to my readings. This week I received a new 9v power supply and the BNC to RCA adapter for my o-scope. I had clean .wav test tones from Kicker. I headed onto the garage to try again.
First I tried playing the wav files from my MacBook to the AUX on the head unit. I had to CRANK the V/Div on the scope to see sine wave at all. Realized the volume on the computer was probably too low. Turned it up and it helped, but the readings still seemed low. I ditched the computer and switched back to using the test files on a USB stick.
For the first time since I started this process, I had the same smooth sine wave I see in all the videos I've been watching. Still a little glitching in the o-scope display (I'll wager the 9V battery connector would have yielded cleaner results), but what I had was workable!! The sine was clear, the settings were in the correct range, the frequency showing on screen was correct and the o-scope reacted appropriately to volume changes at the head! I found myself zooming in on the sine wave to really study the shape of the tips but in the end, I confirmed on the scope what I could hear with my ears. I now has a max volume for my head unit... ON TO THE AMP GAINS!
I switched back to the alligator clips, disconnected all the speakers and connected directly to the outputs on the 4ch amp. The same clear, positive results presented themselves and I was able to easily dial in the max gain for the front, and then the rear speakers. It was so easy I couldn't believe it had taken so long to get to this point. POWER SUPPLY MATTERS!!
I have a nagging suspicion that while I was setting amp gain, I wasn't at max, distortion free volume on the head unit, so I'm going to re-check that tomorrow. But it'll be a quick thing.
I ran out of time before being able to dive into the powered sub. What's the best way to measure the gain setting there?