PWM tone heard on ground plane of connected audio device

Status
Not open for further replies.

lqbert

New member
I'm using the PWM outs of the Teensy 2.0 to dim LEDs through a resistor. The Teensy's ground plane is connected to the ground plane of a Moog Werkstatt-01 synthesizer as I'm using the analog ouputs of a 16-bit DAC (being controlled by the Teensy via SPI) to send control voltage to the Werkstatt. I'm actually hearing the tone generated by the PWM controlled LEDs through my speakers when the LED is brightened. This tone is approximately 3.92KHz and I know it's coming across the ground plane, as it is heard when the volume on my audio mixer is all the way down, and it doesn't change in volume with a change of my audio mixer volume fader. I also took the tip of the TRS connecter going to my studio monitor speakers, and touched it to various ground points of my system (Werkstatt, Teensy components, mixer, etc) and the tone was heard in the speaker. Also, the tone disappears if Iuse my Ebtech Hum Eliminator (audio isolation transformer) to connect the Werkstatt to my mixer.

How can I alleviate this PWM noise/tone from my ground plane?

Thanks,
lqbert
 
Status
Not open for further replies.
Back
Top