bluetooth-specific gain settings?

I set my amp gains a while back with a SMD distortion detector and the included SMD tone CD. I ended up using 32 (out of 36) as my max headunit volume, and the gains were set to about 20-25 percent, give or take.

Then, I added a bluetooth adapter to my headunit, and have used my phone to stream music ever since.

Last weekend, my phone battery died, so I rummaged around and found an old CD and played it. The difference was remarkable - my system was about 25 percent louder at max (32) volume, and just sounded better all around. So, I'm wondering, since I use my phone as my music source, should I reset the amp gains with tones playing from my phone? After last weekend's accidental experiment, I feel like I'm leaving a lot of meat on the bone, so to speak, with my CD-based gain settings. Or, is there just something lost in the streaming process that can't be regained?

You should if BT is going to be primary. All gain settings are based on your source. Take the test CD and convert it digital and put it on your phone then retune with the DD-1.

The ideal scenario would be for the CD, radio and BT to all be the identical gain. That may be difficult. The problem is that most HU's do not have an adjustable Aux input level nor can you attenuate the CD level.
You can change to a BT module with higher gain, like a $39 JL Audio unit for example, or add a $59 adjustable JL Audio line driver to the BT unit you have now.
There is no guarantee that you can achieve enough BT gain to match the CD source gain without saturating the HU Aux input, as it's capacity is not unlimited and generally intended for a very low gain source such as a phone or MP3 player....a little different from an EQ with an adjustable Aux input. But you have the SMD DD in order to verify you are at a level that is okay. At minimum, you should get a lot closer match than you have now.
Another option is add an EQ and run the BT into the EQ versus the HU. Some won't like this because they give up functions, namely the existing remote controls.

Thanks for the responses guys. I really appreciate it. I checked the manual for my headunit (an Alpine CDA 9886M), and it doesn't appear that there is a gain setting for the aux input I'm using for the bluetooth adapter (a Milennia MIL-BTREC).

I'll probably end up getting the JL Audio line driver, but for now I guess I'll just retune using test tones played on my phone. One last question - when playing the test tones on my phone (a galaxy edge), what volume should my phone be at? I'm guessing about 80 percent of max, but thought I'd ask. I use a remote for my headunit to make volume adjustments when listening to music, so the phone is set to the same volume all day.

Some units, whether HU or phone, don't clip at all at 100% volume, while others may clip at 85%.
So 80 to 85% is a safe bet and leaves you a little extra gain in the case of weaker material.
If you still have access to the SMD you can measure with certainty.

I still have the DD-1, I just never thought to use it to check the phone. I guess all I need is a headphone jack to rca adapter. And thanks again for all your help!