jon tiltman wrote:I had a birch ply built for my 401. It was really heavy and the deck bolted hard into it but it caused rumble and I couldn't bear to use the deck. I've still got the 401 though, it's been expertly overhauled and has a new idler and I'm going to try two part skeletal slate with roller blocks between the layers to see if that does it.
If that's no good I'll stick with the SP10mkII.
It shouldnt rumble
.When I was rebuilding my Commonwealth I would run it just propped up and listened to its chassis with a stethescope. A few things on my turntable were causing rumble, one the idler tyre, two the idler bearing and the main bearing. Fortunatly the main bearing was not worn it was just a pitted ball bearing causing its noise and the wrong lube. I experimented with different lubes and eventually got it silent. The idler bearing was very noisy, it is a brass sleeve bearing. Even after replacement it took a while of running to bed in with me flushing it with oil from time to time. I left it running for hours just propped up while I did this. The idler tyre gave me the most trouble though, I tried adding an O ring tyre to the tyre this although very quiet ran slow. The fix was eventually two things one the idler was not running square to the platter so it was scrubbing, and two the rubber was a bit hard so I took it to a friends and I used his laith to take a few mm of rubber off to get to the softer stuff underneath while also making the idler perfectly round.
When I finally got to mount it in the new plinth it was totally without rumble with any cart even at very high volumes.
If your turntable rumbles I doubt it is an issue with the plinth, the plinth can only do so much, there must be a problem somewere even if it has been overhauled. My Commonwealth runs virtually silent listening with a stethescope without its plinth. Spin the idler with the platter off while listening to check the idler bearing, this is often missed when lubing also. Make sure there is the correct oil in the main bearing, if it is still noisy flush it and relube. Dont forget to check the motor mounts and make sure the motor bearings are properly lubed too as this was also a source of noise with my turntable. If it is your idler wheel I would be contacting the person who overhauled it.
Here is my Commonwealth totally siezed when I got it.viewtopic.php?t=34547