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Old 14th August 2001, 12:18 AM   #1
arnach is offline arnach  United States
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Hello,

I have an Oracle Delphi turntable and am interested in building a DIY turntable stand. I am experienced with a table saw and etc. and have a CNC mill so construction is not a problem.

The Oracle is my only source, it feeds a phono preamp in another location feeding a power amp, all spaced out minimize cable length as I installed a passive attenuator in the phono preamp (heavenly sound.)

I was thinking of a MDF box, on spikes into the carpet, filled with sand with an MDF platform riding on top of the sand, then a 80-100lb slab of granite spiked on top of it, then the turntable on top of this slab?

The granite would be enough to kill all vibrations due to its weight and the sand would absorb vibrations from the table, in theory, thus attacking vibration at both sources? Or does this not work?

Comments?

Thanks,

Aaron Finley
arnach5@hotmail.com

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Old 14th August 2001, 12:30 AM   #2
Super is offline Super  United States
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With that much weight and damping material, there shouldn't be a problem. However, in some DIY system, rubber bushings or "blue tack" is used, to offer further damping/isolation. If your turntable isnt spiked, you may want to put these or something similar between it and the granite slab. This method of practice is also common when placing un-spiked speakers on their stands.
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Old 14th August 2001, 04:16 AM   #3
arnach is offline arnach  United States
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Default hm

How would my idea compare to such commercial offerings as the Symposium or the passive Vibraplane? Should I consider using an air tube instead of sand, or adding an air tube above the sand?

Thanks, --arnach
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Old 14th August 2001, 04:26 AM   #4
Super is offline Super  United States
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Although not familiar with analog/turntables, I too have been looking into making a high quality audio rack for my cd player in particular. Although I'm not familiar with Symposium, here's what one man had to say about the Vibraplane and his DIY alternative: http://www.audioreview.com/reviews/R...uct_6199.shtml
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Old 15th August 2001, 01:36 AM   #5
Super is offline Super  United States
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After doing a search on component stands through Google, I came across this link: http://www.ecoustics.com/Home/Access..._Rack_Reviews/

Its a page of links to reviews on many stands and isolation devices, and most of the links are active. Most of the reviews offer details about the sonic qualities and give pricing, but I found it more useful to look at the designs of some of the more effective units. I saw one that was similar to your design, but the platform that you were going to make out of MDF had an air gasket surrounding it, primarily for balancing purposes.

I dont really see how the gasket was useful, since it semi-coupled the floating platform to the cabinet, which in theory would cause greater energy transfer TO the platform. Your free floating design seems more feasible. An easy way to level it would be to purchase a small, dome shaped bubble level to seat on it while positioning it. You could then rock it or tap on it to easily level it.
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Old 15th August 2001, 02:31 AM   #6
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Aaron,
First, define what frequencies you're trying to isolate. Footfalls or music?
What's your floor made of? Concrete or wood?
Note that the Delphi, being an open chassis design, will still accept air-borne vibrations, no matter what you do underneath.

Grey
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Old 16th August 2001, 01:19 PM   #7
arnach is offline arnach  United States
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Default Ok


I am trying to provide as a good an isolation platform for the turntable as I can without having to buy a commercial model. I suppose that would include both footfalls and music.

I have wood floors, they are solid oak, and the house was built somewhere in the early 1900s, and the walls are about 1-2 ft. thick. Therefore there are none of the usual problems with wood floors as I can stomp around with the turntable not on any platform and it won't cause any problems.

What do you suggest?

Thanks,

Aaron Finley
arnach5@hotmail.com
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Old 17th August 2001, 01:25 AM   #8
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Aaron,
Think of a turntable suspension as a lowpass filter circuit. The lower your F3, the more isolation you're going to get from vibration. Footfalls, being way down in the single-digit Hz range, are a blue-blooded bitch to get rid of. Fortunately, it doesn't sound as though that's a problem.
Springs work well, but are difficult to damp without "short-circuiting the filter." Felt threaded through the coils is the usual answer (and was used on the Delphi, as I recall), but is far from a perfect solution.
Sand is as dead as one could ask for, but it depends on resistive losses and isn't really a good 'capacitor' or 'inductor' like you need for a filter. Add to that the fact that it tends to pack after a while, and it pretty much becomes useless for this application. (It's great for mass-loading speaker cabinets and such, but that's a whole 'nother ball of wax.)
Large pieces of foam might be a good thing to try if you could get the right density.
Sorbothane would be nice if you have access to large slabs of it, as it's inherently self-damped.
Smallish inner tubes work well. There are several commercial products selling for obscene amounts of money that are nothing more than a shallow box with an inner tube inside that supports a flat table top on which to place your turntable. Wood is fine. Stone is fine. Another good bet is Corian, the faux marble stuff.
A variation on this idea that I'm going to try as soon as I get time is to use these cute little air-pillows that you see as packing material sometimes. I've been collecting the pillows for several months now and I think I've finally got a good assortment of sizes to play with. A few quick passes with my table saw should give me a nice rectangle of plywood for a top, and I'll just lay out the pillows underneath. If that doesn't work, I'll probably just go buy an inner tube.
Keep in mind that, like all filter circuits, you can run these things in series: i.e. tube/plywood/tube/plywood, etc. to get further isolation. If you're using scrap plywood or MDF and free air-pillows, you don't have to worry about dropping several hundred dollars for every isolation platform. Stack 'em all the way up from the floor to waist height, if you want.
Be sure to test the thing for resonance; you may need to fiddle with it if it gets too wobbly. If you're using an inner tube, try different inflations. If you're using air-pillows, try taking some out or putting more in (I think...bear in mind that I haven't tried this one yet. I'll report here if/when I get this done--life's been a little hectic here.)
With the Delphi, you might consider removing the dust cover and making a hood that will close over the entire turntable, sealing the whole caboodle against vibration (and dust, for that matter). Yes, yes, yes...I know--the whole Oracle sales spiel was that the thing was open on purpose. I was never convinced by their logic on that point--just something to think about.

Grey
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Old 4th February 2011, 08:12 PM   #9
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First post. New reader. Might be the completely wrong location.
I have a technics turntable brand new in a box from about 1990. Works great except no needle iirc.

Now, it occurred to me that this technics has a strobe and uses it to control the RPM's precisely.

So I'd like to consider using the turntable as a base for 3d scanning - where it seems to me that accuracy in being able to rotate the model in precise increments would be very useful.

So - has anyone tried something like this? Is it a good idea?

Ideally, I'd like some kind of vernier or button to move the turntable a precise amount.

I'll happily respond with model numbers if people think its a good idea. Secondly I'm a completely moron with a soldiering iron - so it has to be a project a moron could handle.

TIA!
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Old 4th February 2011, 08:25 PM   #10
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Quote:
Originally Posted by chrispedersen View Post
Might be the completely wrong location.
Abslolutely. You should rather start a new thread as your query has nothing to do with turntable stands.

I know nothing about 3d scanning but dare think a stepper mottor is probably much preferable if you want precise increments.
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