Lapslah
Super Member
I really do believe you're just trying to understand, so I'll give it a shot. I'll also say up front that I haven't read through all 6 pages of this thread, so apologies if I'm repeating what's already been said. FWIW, I agree with you to a point. Let's assume we're comparing two tables that both have accurate speed with zero fluctuation. I think what you're missing is that the table also acts as a platform for the arm and cart, and that matters for a couple different reasons. First, the platform must be a solid base that isolates the arm and cart from outside influences. Second, the platform must not introduce any influences of its own. That's not easy, since it must have a motor. These things seem small enough to be trivial until you understand that the amplitude of the waves being produced at the stylus level is microscopic. That's important, and I suspect this is where your logic is breaking down. At such small amplitudes, everything matters. Imagine trying to hit a golf ball during an earthquake. If your arm and cart don't have a solid base, that slop makes accurate reproduction difficult. And if your table introduces its own noise in the form of motor noise, etc. (and they almost all do to some extent), the result is not only the original noise. That's why people keep trying to tell you about resonance. Let's say your motor introduces a low level 60Hz hum - one that you may not even be able to hear. That in turn affects the way your stylus (remember - moving microscopic distances very quickly) reproduces mainly multiples of 60Hz, but also many other frequencies, augmenting some and cancelling others. That can clearly change the sound coming out of your speakers. Now apply this to not only motor noise, but any and all noises and resonances transferring through your table, all at the same time, and hopefully you'll see why it matters.
...