Which low cost high quality eeg device to choose to study localized gamma wave activity (part III) (Epoc Flex 32)?

We do not know of a function of proof for HackEEG32 or the Aliexpress 32 EEG board. After what we experienced with single board computers, we doubt about the function of these two devices. If these devices would work, and the seller is interested in selling it, whould he not make a demo and show …