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Turntables thump when turning off?

Why?  I have used 4 different tables and three phono stages in 2 different systems and all of them produce a pretty loud thump when turning off especially, sometimes when turning on.  I have been muting the system each time I turn off as it seems a little much to be letting such a thump reach the speakers.  Is there a cure?  lift grounds?  arrange cables? I was getting a pretty decent hum at times and I've noticed careful routing of the cable to the phono preamp makes a huge difference in this.  

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ebm
9,311 posts
 

Ground the motor.

fiesta75
1,378 posts
 

Try the above suggestions, you can do it.

apogeum
34 posts
 

Hard to imagine that a snubber cap across the power switch would be missing or broken. But I would definitely check.

More distance between turntable power switch and phono pre might already be the solution. Is the power cable to the turntable very close/parallel to the interconnects from the cartridge to the phone-pre? After all the snubber only minimizes the problem and doesn't neutralize it totally.

If nothing works and you are really “desperate” you can build in an extra switch that only turns off the low voltage connection to the motor. You would lose the warranty but the problem would be fixed. But I would first try disconnecting the motor manually (unplug the cable if possible) instead of using the switch and see if the problem is gone.

zavato's avatar
zavato
1,403 posts
 

Well known issue with VPI and Rega tables. A cap across the power switch of the right value is the answer. I had that issue years ago when I owned a Rega. 

lewm
13,110 posts
 

.01uF HV ceramic cap across the switch.

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