Headphones are the simplest and most reliable way to prevent feedback when using FarPlay. As an alternative, you can use speakers if you use a directional mic and the following steps.
Turn hardware volume and gain knobs down.
Put the mic as close as possible to the musician.
Point the mic towards the musician. For a dynamic mic (like a Shure SM58), point the body of the mic towards the musician’s mouth. For a side-address condenser mic (like the Presnous Revelator condenser), orient the body of the mic vertically. Face the front of the mic toward the musician’s mouth (the front usually has a logo and, sometimes, a volume knob or indicator light).
Put the speakers behind the mic. Putting speakers off to the side also works. Don’t put any speaker in front of the mic.
Place the speakers far from the mic. If you’re using a dynamic vocal mic, start with 3 feet (1 meter) of distance between the mic and speakers. For a condenser, start with the mic and speakers several feet (a couple meters) apart.
When following the steps in QuickStart section 3. Configure and test your audio, adjust hardware volume/gain knobs gradually. This way, you can quickly reduce a volume/gain at the first sign of feedback.