Seed 1.2 Rev7 high frequency noise on audio out

Electrosmith Products Daisy Seed
1

As part of a product I got a newer seed (V1.2 rev 7) in comparison to the one I had been using so far (V1.1 rev 5). When probing the audio out with my scope there was a lot of noise which I first thought was due to my setup but after swapping the seeds and running the exact same code it is evident this noise is coming from the daisyseed itself.

It’s high frequency +150kHZ and has quite an amplitude of 750mV p-p but it doesn’t seem to have components that are in the audible range. The output signal being around 2.8V p-p max is 30% noise and although not influencing the audio this is ‘annoying’. The rev5 version just has a flat output when silent so this must be hardware related.

I’m wondering if anyone else is seeing this or if I might have a daisyseed with issues.

2

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3

This general similar topic has come up a number of times, and the answer seems to be to put a lowpass filter on the outputs (it can pass the full audio bandwidth (e.g have a corner freq. of e.g. 48Khz)). It seems to be a ‘feature’ of the new codec chip.

4

Thanks for your reply, I found some topics on the noise floor being higher for the newest codec but must have missed the ones that referenced this high frequency noise that’s just always there.

5

I think that part didn’t really get mentioned, as most people just focused on the audible part. I did notice it as well. I’m still not clear on how filtering out the out-of-audio-range signal can affect the in-band signal, but apparently there’s some non-linearities involved.