Line-In jack on Sensor Expansion behaving strangely

Hi again. I was testing out the line-in jack on the sensor expansion by loading the “sound - spectrum analyser 1D/2D” pattern (and taking out the demo portion of that code). While the microphone reacts to sound, but it is very noisy, and reacts to the noise the PixelBlaze itself is emitting (see my other post).

When plugging a cable into the line-in jack - with nothing attached at the other end - the pattern is quiet and isn’t jumping around. However, if I then plug it into a low-volume speaker output on my computer all heck breaks loose. The pattern reacts to sound that isn’t playing and can’t “hear” anything that is playing.

I’m currently not able to use the sound input for anything due to the noise on either of these inputs. Please advise?

Hi @AreThree,
As mentioned on the other thread, you might be having power supply issues. Those can definitely manifest as artifacts on the audio input, either when idle, or when LEDs start drawing a lot of current.

Be sure you are using a line-level output, and not a powered speaker output. Amplified signals will have a lot more noise, and even the faintest of volumes will be too loud for the audio input.

Another thing that may be happening is a ground loop, causing the differences in the ground signal between your computer and the PB to show up as audio signal / noise. A ground loop isolator might help - but I would troubleshoot your power supply first!

Hi again @wizard - thanks for the quick response!

As I mentioned in the other post, I did move to a USB “wall-wart” which eliminated the capacitor noise from the PixelBlaze. However, the issues with the line-in jack and microphone remain. I’ve taken your suggestion and ordered the ground loop isolator you recommended which will be here in a few days.

As it has been some time since I first ordered and received my PixelBlaze and accessories, I’m trying to remember if this was an issue I was having before I moved. I believe there is a non-zero possibility that I might have ‘zapped’ the line-in jack with static electricity accidently when first experimenting with it. I’ve ordered another from Tindie to compare the two and see if that is the case…

Thanks again!

2 Likes