It should give a high entropy result, even if the PRNG was seeded with a known seed which would then be used to reconstruct the randomness.
it gave Entropy = 4.053136 bits per byte.
that was for a file that had 125,000 hex private keys in it.
apparently it treat each character as 8 bits.
Well, the 'avalanche noise source' electronic method can actually be observed ('see what is going on'); you do need some lab equipment, though. Keep in mind that just visually inspecting the circuit can already give you some confidence that you received the circuit actually specified in the schematic. Inspecting the schematic tells you what the circuit does, so sneaking in some backdoor is going to be pretty hard on such a device.
i'd love to have one of those devices but i don't think i can get an oscilloscope and things to help build it. that's the problem i think you need that type of thing. building the thing while i guess its tedious would not be the hardest part the harder part would be figuring out how to interface it to something and do data collection. hence why you don't see people doing this all the time. and the people that do, they just show a short video of the output on their screen nothing to learn there.
All the information is laid out nicely here:
https://betrusted.io/avalanche-noise.html I just had a quick web search and seriously surprised that there's no ready-made PCB / DIY kit or similar, that you can plug in and get randomness e.g. through
cat /dev/tty.usbrandomdevice.