Detailed review and measurements and modifications of the $10-15 Fever 6J1 Tube Preamplifier using the Audio Analyzer Suite together with the Analog Discovery. Taking it from "not so good" to "much better" with a few cheap modifications.

Note: I'm using a new version of the Audio Analyzer Suite that will be released shortly.

Download the pdf document with my notes here:
dropbox.com/scl/fi/hokdvv2t55oxwh8x6ygll/Fever-6j1-Preamp-Measurements.pdf?rlkey=bfa94t1p8yh9ofn526au9pjek&dl=0