By ringing, I mean it vibrates like a bell does when it is struck by a hammer.
The tonearm on a TT needs to resist any type of vibration. This is because the pick up (stylus, cartridge) needs to only 'hear' the vibes made by the record groove. Technics did a great job with the Sl's base, made from a huge chunk of rubber, this damps vibes coming up through the feet quite well.
Unfortunately, they didn't do such a great job with the tonearm, which will pick up too much external information, vibration, and feed it to the pick up and detract from the sound coming from the record surface.
A direct drive TT is more prone to noise coming up from the motor and the ground because there is a direct route from these to the stylus. Belt driven decks try and isolate this by suspending the motor and base (plinth) so as to remove the pick up from the sources of vibration.
This is also why a proper wall mounted record shelf is preferable because it means that vibes from the floor can't easily reach the deck. This is especially a problem if your floors are made of wood or your deck is on a flimsy stand.
These vibrations, which are coming mainly from the music itself but also from footsteps in the room etc, act as feedback. This is because the pick up plays the vibe to the amp, which sends it to the speakers a microsecond later. They play the vibe and then the vibe travels back to the pick up through the air or through the plinth. A pick up is basically a microphone so as soon as the pick up hears this vibe it plays it back - again - a microsecond or more later. You CAN hear this, it will loosen the bass and treble so the sound isn't as tight as it could be.
Some real enthusiasts actually site the record deck in a separate room from the speakers so as to avoid this interference.
As I said before, the better your amp and speakers, the more you need to attend to these details as you'll soon start hearing them.
It's a tough call for the manufacturers. They need the tone arm to do all this damping and yet still be light enough not to chisel its way through the record. Hence the increased use of light but strong 'space age' materials like titanium, carbon fibre etc. And of course they need to do it down to a price, especially on a mass market deck like the Sl1200.
Anyone wanting to see some really nice retro TTs should visit :
[the vintage knob](
http://www.thevintageknob.org)
You can check my own deck here:
[sony ps-x65](
http://www.thevintageknob.org/SONY/sony ... PSX65.html)