Yamaha PSR-S670 - Manual (Page 16)

16 PSR-S670 Owner’s Manual
To adjust the volume of the entire keyboard sound, use the [MASTER VOLUME] dial while playing the keyboard.
You can adjust the contrast of the display by turning the [LCD CONTRAST] knob on the rear panel.
Connect a pair of headphones to the [PHONES] jack on the rear panel.
Adjusting the Master Volume
CAUTION
Do not use the instrument at high volume for long periods of time. Doing so may cause hearing loss.
Adjusting the Contrast of the Display
Using the Headphones
CAUTION
Do not listen with the headphones at high volume for long periods of time. Doing so may cause hearing loss.
Standard stereo
phone plug