[SOLVED] PWM only works with AUX IN

Hello community,

I'm having a some trouble with my little synthesizer project.
Currently I'm using PWM to generate an audio signal which seems to work fine. I'm able to produce sound as long as am plugging my synth into the aux port of some speaker (or just connect my headphones directly). This includes for example my guitar amp, which produces sound when I connect to its aux port, but not when I use its regular input port.
Eventually I want to be able to send my signal through some guitar pedals, however as it currently the stands this does not work. Even pedals that are true bypass do not allow any signal to go through, which seems rather odd to me.

Does anyone know what I'm doing wrong?

Kind regards

Something's probably connected wrong, and probably "shorting out". The guitar input is higher impedance and probably slightly-higher gain (also depending on the volume control) but if the signal is there it should work.

BTW - You shouldn't connect your headphones directly to an Arduino output because anything less than 125 Ohms will draw excessive current. So, put a resistor in series with the headphones.

Try connecting the headphones (with resistor) and guitar amp at the same time.

If the headphones work with both connected (and the guitar amp doesn't) you've got an open connection to the amp (or the amp is just bad or flaky). If plugging-into the amp kills the headphone signal, that's a short.

There is a very-slight chance that the "DC bias" on the Arduino's output is causing a problem. (The Arduino's output switches between zero an +5V, whereas a normal audio signal swings positive and negative and averages around zero.) If that's the problem, a series capacitor will block the DC, and a resistor to ground (after the capacitor) will hold the DC "average" at ground (zero volts). i.e. A basic [u]high-pass filter[/u].

Turns out a tiny bit of solder had made its way from the tip to the ring of my output jack. Seeing as the aux ports I was using are 3.5mm and the cable I was using for that is stereo, I got some sound. The large jack I was using to test the amp is mono and so, yeah, no sound. Silly :slight_smile:

Thanks for your help :slight_smile:

(btw no worries I've got a resistor in series)