I am working on the development of an auditory-based MobileEEG hardware in my research group. Our objective is to comprehend the perception of sound using an ear EEG setup (cEEGrid) in real-life scenarios. To achieve this, we are constructing hardware capable of measuring EEG signals and adding markers to the EEG data as different sounds are heard.

We use a microphone to capture the audio signal connected to the Bela Mini Starter Kit. However, the current issue is that the digital output from the Bela Mini is 3.3V, and the input range for my EEG amplifier is 400mV. To prevent damage to the amplifier, we are seeking ways to reduce the voltage. Although we currently employ some resistors, they do not significantly reduce it, and they should not introduce any temporal delay.

As someone with a background in Neuroscience and being relatively new to electronics, I would greatly appreciate any suggestions for a solution.

 

Welcome to AAC!

we currently employ some resistors, they do not significantly reduce it,

Then you are not using them correctly. Two resistors used as a potential divider would suffice.
However, you say the Bela Mini output is digital. Isn't your EEG amplifier expecting an analogue input signal?

 

Your description of your equipment and how it is hooked together is quite unclear.

Perhaps you could provide a diagram of what is connected to what.

 

Anything you do with active devices will introduce some time delay. That delay might be on the order of nanoseconds which might not be significant in your realm.