Microphone gain difference between 2 expansion boards

I’ve just started playing with two Pixelblazes and expansion boards, and they are amazing! However, I’m seeing a difference in microphone gain between the two boards.

With both Pixelblazes (V2) running v2.23 firmware, and running the same sound-reactive patterns, I definitely saw a visible difference in the sound “reactiveness” between the two boards.

So I played a 500Hz test tone and put a scope on pin 1 (output) of the LMV358 op-amp on each expansion board, and saw that one board had a peak-to-peak waveform that was almost half of the other one. Both units are connected to the same benchtop power supply, and the power looks clean.

Is there any reason this could be happening? Do I have two different “batches” of expansion boards?

Help & Thanks!

Hi @Irwin ,

There’s some difference between the older SB and the new one with the aux jack. Those are clearly different boards though, and I haven’t sold the old one for some time. Otherwise they should be the same.

Can you get high res as close as possible photos of the component side of both? I’m wondering if theres a QA issue.

If you need them to match, I can can you replacements (both, since I don’t know which one is right).

Thank you for the speedy reply!

I’ve attached pics of the 2 systems. I also measured all the resistors & capacitors in the audio circuit, and found that they were identical between the two boards. (Note that I removed and jumpered the aux jacks to make everything fit in my project.)

BTW, I do notice that the patterns with software AGC will compensate somewhat for the gain difference, but it’s still noticeable with most sound patterns.

I really appreciate the offer to send replacements! I think if you send me just one replacement I can compare it to my existing boards and figure out which one is “good”. I’d also be happy return the “bad” one if you want to investigate the possibility of a QA issue.

Files were too big to upload, so here’s a link: