Need to adjust the speed every time I turn on turntable

Agree, teo. We also tend to draw false relationships between a list of causes and a list of effects with no real data to support a connection of one to the other. But it makes us feel good to have a pat explanation in hand.

Just wanted to point out that many of the posts seem to confuse long term speed stability with instantaneous speed stability.  A turntable may measure out perfectly for speed over longer time intervals yet still create momentary episodes of pitch instability due to short interval speed errors.  There's a difference.

Sorry for a bit of nothing, but you wrote, "AC is not safer than DC - that was Edison’s argument...."  I interpreted that to mean that Edison argued that AC was safer than DC, which we both know was not the case.  I had a feeling you merely made an error in syntax, but I just wanted to get it straight. Now I see how you meant it.
Just think: If Edison had won the point, we wouldn't need rectification in our audio equipment, but on the other hand the DC voltages available for B+ would in many cases need boosting. Also, it would have been difficult to assure that everyone got the same DCV at home.

Cleeds, As I recall, from reading those very same history books, Edison promoted DC electrical transmission. It was Westinghouse and Tesla, who had left Edison, who promoted AC. Edison infamously electrocuted an elephant in order to demonstrate that AC was unsafe.