May the 3.5mm audio output jacks of laptop computers and phones be "declared" as PS1?
More specifically you asked: In regards to 3.5mm audio output jacks from a laptop or phone. Some of these ports provide a bias voltage and are considered a power source. Bias voltage is in the area of 1.5-1.75 VDC. Could these ports / sources be "declared" PS1 for headphone, headset devices that plug into them?
In response, PS classifications per clause 6 are based on available energy to a circuit, measured in Watts, and are independent of the voltage, i.e., theoretically a 1.5-1.75 VDC circuit could be PS2 if greater than 15 W is available. Technically, Clause 6 requires measurement of the output from any port for connection of additional equipment in both Normal and Single Fault conditions to determine the PS level, and this requirement is provided without exception in either IEC 62368-1:2014 or IEC 62368-1:2018. Circuit analysis and engineering judgment may be able to provide enough evidence that PS1 is maintained. However, this can only be done on a case by case basis, i.e., all 3.5mm audio output jacks cannot be declared PS1.
The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review / analysis. Therefore, you are encouraged to contact UL for an in-depth consultation, either via your local account executive or via https://62368-ul-solutions.com/contact-ul.html.