Seeking advice for microphone input

Hi everyone. So i got a daisy seed and want to build basically a looper pedal (i hope it will get additional features when the main function is done). The main usecase is for vocals, so i won’t get line-level input but microphone-level. The problem is that the seed has no microphone input, so i’ve looked around at mic preamps that i could integrate. As i’m quite new to hardware and specifically audio hardware, i’ve got a couple basic questions and would be happy for any opinion / advice on the components.

I don’t know much about microphones, but i know it will need to be a dynamic mic since i don’t want to deal with phantom power. Apparently SM58 is cheap and widespread?

For the preamp, i see two choices:

  • at first i was considering getting an additional I2S ADC, like the CS53L21 but (1) this seems to be complicated (i have to get both I2S and control right on the software side) and (2) i’m not too sure if they properly manage balanced input (as is usual with XLR mics): according to the diagram they sample first and then do the +/- subtracting for cancelling noise (i would have guessed it’s better doing the subtracting in the analog domain before the sampling machinery) and additionally it is supposed to be a two channel ADC, so using the two channels for balanced mics is weird (i’m sure i’ll have surprises in the I2S streams).
  • after some time i found analog mic preamps that look much simpler and more robust from analog devices (with “clean” balanced inputs): i’m guessing MAX4062. This means i’m using up an analog input from the seed, since this will sit in front, but that’s ok. There was also MAX4466 but it seems much more lo-fi and cannot control gain. SSM2019 would have been nice too, in a through-hole package easier to solder, but it runs on >5V, so i wouldn’t be able to connect it to the more stable “analog 3.3V” of the daisy. It seems even higher quality tho so perhaps it’s still worth (connecting its V+ to the “normal” 5.5V)?

Does MAX4062 seem like a reasonable choice or did i forget something important? Does anybody have other info on preamps with daisy? Thanks a lot! :slight_smile:

You might consider a ‘mic to line’ level converter - either completely external and pre-built, or an op-amp circuit if you want to build it. I recommend op-amp cookbook by Don Lancaster for ideas on how to do it.

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The Max chips seem much simpler than any op amp design, and they’re small and cheap.

4061 looks interesting - the 4062 has some extra stuff for adding a switched aux input. Read the datasheet, and the stuff about bias voltage can be ignored for a dynamic microphone, bias is for electret mic.

SM58 is a legendary professional microphone, but I don’t consider $100 to be cheap. There are SM58 clones for about 1/3 that price which are practically indistinguishable from SM58.


Update on my research: so SSM2019 spec says 5V is minimum voltage, but it seems it is intended to normally run with +/-15V. So it seems out of question.

About “mic-to-line” converters, i looked into that, but they aren’t that cheap (for what it should be) and pretty bulky. I’d rather not have some sort of dongle in my build, but rather a properly integrated preamp. Thanks for the link (btw i think the author is Walter G Jung right?).

Indeed the Max stuff seems to be the simplest solution. Yup i scanned through the datasheets, i was thinking about 4062 since there is so little price difference and perhaps i can upgrade it later to handle electret mics (yet bias seems low at 2.2V so not sure if it can handle common mics) or instrument input (on the aux input)… But maybe i should start simple and just use the 4061.

About the mic: ok, i’ll look around to find something equivalent.

2V ‘bias’ voltage is fine for an electret. Check out the Wikipedia page on electret microphones.

Shure SM48 and Behringer XM8500 are cheaper substitutes for SM58. $30-$40.

Correct - I conflated Walt Jung and Don Lancaster because of Lancaster’s other cookbooks - TTL, RTL, CMOS etc.

It also might be worthwhile to consider the Terrarium:

as the base for your project. The guitar inputs would be ‘OK’ as mic inputs, and you could choose components to make them better if you wish.

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