Hi Dance Host,
With my phone using Bluetooth, I get good sound from the unit.
When I wire from the phone to channel 3, not so good. My cable is Monster Balanced Out and Unbalanced In.
If your cable looks like this (below) with the Tip-Ring-Sleeve end plugged into the phone you are shorting the phone Left and Right outputs together. That can cause signal loss or distortion.
If you are connecting the Tip-Ring-Sleeve end plugged into the S1, then you are only getting the Left output from the phone. This might be okay if you convert the output of the phone from stereo to mono.
The S1 Pro Aux input is engineered to accept a stereo input.
From a phone to the S1 Pro Channel 3 Aux input, use a cable with 1/8 Tip-Ring-Sleeve connectors on both ends (below).
I use an unbalanced 1/4 inch jack into the S1.
If you are using a cable like this, you are shorting the phone Left and Right outputs together. That can cause signal loss or distortion.
The same cable gives good sound from Laptop to Channel 2.
Your laptop may be more tolerant about having the outputs shorted together than the phone.
The phone with this cable is not good into Channel 2, just like into Channel 3.
Please help with this.