MAX98357 gain setting

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elembivos
 
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Joined: Fri Jan 13, 2023 9:00 pm

MAX98357 gain setting

Post by elembivos »

I do understand gain, and units of dB. It comes down to a ratio of input to output in either Volts or Watts depending on the situation. I get all that. I’ve searched here, sparkfun, and analog devices, but cannot find what they mean by the gain of this breakout board. Digital I2S in, to some voltage out?

It would make sense for the max output to be +/-Vcc, and the gain to be in -dBv from that reference, but all the dB numbers are quoted as positive. What is the reference for these numbers? Decibels doesn’t mean anything without a reference.

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elembivos
 
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Re: MAX98357 gain setting

Post by elembivos »

Ok, I found the reference in the data sheet, but it still doesn’t make sense to me. The output is:

Output (dBv) = Input (dBFS) +2.1dB + gain (dB)

Selectable gain varies from 3-15dB, so input + 5.1-17.1dB. Input is in dBFS (full scale reference) so can only be negative. So full signal digitally will be 0dBFS, so all gain settings are higher than this. Will this not guarantee full digital volume will be clipped by the supply rails? Unless the full scale DAC output is 17.1dBv lower than the power rails. But I can’t find the DAC output voltage. I just assumed it was referenced to the power rails.

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