isolated armboard

Having finished making my first TT about a year ago, work on the Mk-II is just about due.
I've been really happy with the results of my first attempt, basically it's made using the motor, subplatter and bearing from a rega p2-24 along with the rb300 arm. I has an acylic platter made. The motor is housed seperatley in a solid wooden box, the rest of the table is made from 2 sheets of granite sandwiching a sheet of cork to dampen the ringing from the granite.

For the Mk-II I plan to use something other than granite... just because granit is so difficult to work with, but experiment more with different materials to sandwich. Can anyone recommend any combinations...?

I am also considering having a sprung or isolated armboard. I have been looking at sandbox insolation platforms and have been thinking on how to build one into a turntable to place the armboard on, isolating it from the rest of the TT.... Before i start trying to figure out how to cope with the rega mounting system running through the sand, are there any other problems I haven't thought of?
has anyone done this before?
is it a good idea?

but how about sprung arm boards, like the LP12?
I see your point, backed up by rega putting those metal braces on their better TT's to increase regidity between arm and platter bearing... so have I missed something or are there 2 very different schools of thought here?
what are the pros and cons of both methods?


2007-01-12 6:01 pm
In the case of the LP12, and similar designs, the armboard and the platter are attached to a single, rigid, chassis (the sub-chassis); this assembly of chassis, armboard, platter and arm is then decoupled via springs from the plinth (to which the motor is attached via the top-plate). The arm is not decoupled from the platter (well, not in the way you suggest at any rate).

(this much is TT design 101 ;))
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2007-01-12 6:01 pm
There is no harm in trying it - in fact, I would encourage you to experiment.

But what I am describing is not what you are describing (at least, not if I am interpreting your posts correctly).

In the case of the Linn (and all similar decks), the springs are not under the armboard on its own, they are under a secondary structure to which is attached both the platter and the armboard.
oh really, i have to admit never seeing one in real life. I always thought the armboard was free to wobble inependantly of the rest of the turntable.

I'm seeing your point... out of interest I will experiment, but I suspect there are numerous problems with this idea... we'll see.
I've experimented a little with the bike tube, but it's a little cruder than I want... I would like to be able to use about a 5 inch section of the innertube, sealed at bothends with the valve in the middle... so I could pump up individual balls to adjust the height with the valves protruding through the bottom of my shelf. But I can't find a way to seal the cut ends of the tube.

Filling the tube with sand is an idea... I'm not sure yet if it's a good one or bad one. To make better use of the sands properties, maybe a tube of thinner rubber might be better.... all I can think of is sand filled condoms. :)