I wouldn't get hung up on the perception of audible volume, so much. That's the danger of hearing damage from the logarithmic scale of decibel measurement. It's not so much a perception issue as an energy issue. Doubling the energy inflicting the auditory nerve is deceptively harmful since it's not as easily perceived at high levels. So, the starting level being doubled is very significant! Doubling a 5-watt amp is not nearly as bad as doubling a 50-watt amp, but when you go doubling a 500-watt amp you're in dangerous territory. Then, too, length of exposure is a serious concern, since your perception decreases with more exposure. At high levels, every minute counts (hurts, sooner or later). Take it from a (nearly) deaf old frt.
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You speak the truth, I just can't hear you


rt.
That's like a manual forklift!

"There, that's 1 string." *guitarist starts noodling* *tuner: tries to tell me what the guitar is playing*
At that point I usually throw it somewhere and finish tuning by ear and remember why I hate these things. lol