joessportster Posted May 30, 2019 Share Posted May 30, 2019 So in my Novice understanding I was just thinking that the speed fluctuations on some TT's is due to the various amount of AC at different Outlets. In my Home these can vary by as much as 10 volts Depending how far down the line an outlet may be. So I'm thinking why not get a VARIAC set it at a constant 110, 115 or ? Why wouldn't that do about as good as the 1000.00 + various speed controllers sold by the likes of VPI, Walker, etc..... Now I understand there controllers are constantly variable and always adjusting depending on the speed fluctuations, or amount of voltage coming in . But if I have the power at a constant via a transformer / Variac wouldn't I generally get a constant dependable speed. Thoughts ? I bring this up because someone expressed interest in my 1400.00 VPI SDS, I personally c an not hear minor differences in speed from 1 day to the next. I was shocked to find the SDS last sold for 1400 and I am now curious why a better steady voltage would not do basically the same thing as my SDS Quote Link to comment Share on other sites More sharing options...
Wirrunna Posted May 31, 2019 Share Posted May 31, 2019 Disclaimer - I haven't bothered with TT technology for 30 years. The TT motors back in the day were mainly synchronous and relied on a constant mains frequency rather than voltage for their speed. The platter also used to be heavy to provide a fly wheel effect, especially when driven by an elastic belt. Technics used to build a turntable with a quartz crystal controlled ac power supply with extremely accurate frequency for their synchronous motor. So, in my opinion, a variac will not help TT speed fluctuations. 1 Quote Link to comment Share on other sites More sharing options...
Marvel Posted May 31, 2019 Share Posted May 31, 2019 4 hours ago, Wirrunna said: Technics used to build a turntable with a quartz crystal controlled ac power supply with extremely accurate frequency for their synchronous motor. Still do ... Quote Link to comment Share on other sites More sharing options...
WMcD Posted May 31, 2019 Share Posted May 31, 2019 You can read: https://en.wikipedia.org/wiki/Synchronization_(alternating_current) I've read someplace (long ago) that the entire US electrical grid is because of the above synchronized from coast to coast. I don't know if the article said where the frequency is set but it is very accurate and therefore so too is the 60 Hz signal. The ordinary wall clock, like a turntable, has a synchronous motor and thus is extremely accurate. Or at least as accurate as the nationwide grid. I think portions of the grid will be shed if it can't maintain frequency. Further, this is somewhat relate to the selection of 78, 45, and 33 1/3 rpm for turntable speeds. Back in the day, the cutting turntable and probably some playback turntables where gear driven (not belt driven) from the synchronous motor. The turntable speeds were based on gear ratios which must be integer fractions based on number or teeth. WMcD 1 Quote Link to comment Share on other sites More sharing options...
Schu Posted May 31, 2019 Share Posted May 31, 2019 I'm shocked that an sds sold for 1400 to. I got considerably less for mine... probably about $300. Quote Link to comment Share on other sites More sharing options...
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