I'm glad it worked for you ... and thanks for letting us know!
Actually, in my personal experience, a wired connection from the headphone jack is an ideal audio connection.
Any extra auxillary connection (like bluetooth or radio) must be powered, and so is typically dependant upon batteries- sometimes the ubiquious alkaline letter cells, but even worse are those horrible button cells.
Generally, a volume setting of 67% without effects or 53% with effects will produce a typical line level ouput that is compatible with audio equipment.
These percentages correspond to (in order) two steps above half way up and half way up the volume scale.
I am basing this on the typical volume system on Android, which is divided into 15 settings.
So 67% is 10 steps from 0, and 53% is 8 steps from 0.
This is what I have learned as a live sound engineer, where I sometimes have to hook up phones or such devices to mixing boards and the like that have VU-meters (or the modern equivalent).
Also, I have an older head unit in my car, and this is how I connect my device to it.
There is an LED VU-meter on the equalizer that controls three of the amps connected to the stereo. There is also an LED VU-meter on the amp that powers the front speakers. Both of these meters are in unison and correlate to meters on other audio equipment that I connect in the same way.
When I use the settings described above, the results are the same as if I connect any other line level device with an actual line out, such as a CD player or whatever.
