Originally Posted by tesnevo

What are you using the phone for during this testing, the test tone?
If so DONT, you need to load the test tone on a USB stick and plug directly into the radio.
You can not use an volume adjustable signal source (phone-iPod-etc) to run a test tone unless you know what the optimal DNR/DB/voltage/signal out the signal source is producing in order to match it to the head unit/receiver at its optimal signal output DNR/DB/voltage/signal and volume.
Very ultra high end audio is done the above way with $45,000.00 test equipment designed for that.
The phone apps are good for testing output signal from source units (RTA-DB-SPL-FFT-etc) but should not be used for for the input signal for testing purposes.
So now to the simple way that's accurate;
When the test tone/signal is coming directly from the head unit (USB) , adjust volume at 4 bars from max and get your amp setting/reading that way only.

Originally Posted by WestTexasRanger

When I was tuning my amp, several forum members pointed me to various test-tones that I could play through my iPhone via USB cable. There was even some discussion as to what volume the phone should be set at, with the consensus being 3/4.

I used the Tone Generator from the Digital Designs Toolbox app to set my gains.

So do I need to reset the gains on my system using another test tone and a USB stick?

My system sounds great but it appears (from your post) that it's "Close...but no Cigar".

Originally Posted by tesnevo

It's all good brother. The volume that was said to be at 3/4 was to be your head unit.
Your ideal setup is the USB for the gains. For no harder than it is, easily said lol, I'd suggest doing it by USB.
If you leave it the way it is now you have a high probability of your rear fender falling off and both tires going flat.