Granite block and inner tube...

To isolate a turntable from an equipment rack: I'ts cheap and cheerful,but does it work? Seems to make perfect sense,but does anyone here use this method?

 

Indeed....Don't want to open a can of worms as to what is the optimum level of inflation for sonic perfection though

 

I did,yes: then googled it,and it seems to be commonly employed,but was hoping from input from a "user" here!

 

I can't imagine an inner tube creating stability of any kind.

 

I've used mass loaded, partially deflated inner tubes -- small ones from like hand truck wheels and I've used three for stability and only slightly inflated them, which I think is the key to isolation down to very low frequencies -- and yes it does seem to work. I guess the key is how much mass in term of the shelf (granite or whatever) and the table is loading the inner tubes, and you do need to re-level the tubes every now and then (like annually).....but it works much like other more properly engineered and easier to use but much more expensive pneumatic isolating techniques.

 

Some people poo poo granite and say it rings too much. Personally, I like the idea of something very massive and mass-y below something that isn't, and it's worked well for me. However, instead of using an inner tube, I use racquetballs cut in half, then stuck into these square things you stick under, say, the leg of a couch. (see link below) They just sort of pop into these square things and stay there, and provide kind of what the inner tube provides. Unlike the inner tube, it's easy to level, because you're on 3 points. Apart from hanging the turntable from the ceiling, I've found this to work best.

Now, leveling is a whole different story. I don't know what other people do, but I use a bullseye level on the platter itself. I level the turntable so that the platter is level in all points in the swing of the arc that the stylus would make from outer to inner edge. That's often different from level for, say, the plinth. My theory is that it should be level where it matters most...where diamond meets vinyl.

http://www.amazon.com/MINTCRAFT-FE-...25305682&sr=1-3&keywords=mintcraft+caster+cup

 

More than one big bucks isolation platform employees an air bladder

A nicely finished box with a top plate and sides so you don't see it

In short, yes, air bladders (inner tubes) are very effective at isolating front end pieces from vibration and shock

The only issue you may encounter is getting the piece of equipment or turntable to sit level

Works better (easier to level) if you put the air bladder in some sort of box or frame

You can build a nice one with inexpensive wood, pieces of stock cuts like 2"x2" (whatever you need to fit the tube you want to use) Paint or stain to suite your tastes

Another approach is to build yourself a shallow box, pour some sand in it and "float" your granite piece on top of that, just make the inner edges of the box slightly larger than the stone slab so they don't touch

You can go as far as you'd like with a simple but effective approach like this:
http://www.tnt-audio.com/clinica/sandblaster_e.html

 

Been there done that! I like the granite in a sandbox, but use Herbie's feet under the box. Inner tubes always loose air and they are very hard to level. I have Herbie's pucks under the towers of my TT, even on an Adona Stand the difference was audible.

sean

 

While it may "work", it looks like hell IMO

 

Pneumatic isolation via air under pressure is commonly used for things like sensitive lab equipment -- microscopes and such -- in devices like this: http://www.newport.com/BenchTop-Compact-Vibration-Isolation-Platform/139761/1033/info.aspx which is kind of that the mass loaded partially inflated inner tube home set up is intended to be a sort of jury rigged DIY version of. The principle is the same.

 

"While it may "work", it looks like hell IMO"
True,but I want to listen to it,not look at it

 

My main equipment support is an Oak/air suspended system originally called 'Voodoo' but I believe out of manufacture for at least 10 years. Each shelf has 2 or 3 small valves which are inflated by a small bicycle type pump and rise about 10-12mm, about 1/2 inch when full. The air bladders are not visible as the shelves consist of an inner and outer box frame so as the inner part rises (which the equipment sits on), everything stays neat within the outer frame. I also made a further 4 shelves myself using the same principle and 3 small 'childrens bicycle' inner tubes inside each

Although I have owned this for about 15 years, it still works perfectly with no signs of failure or perishing and only requires 'topping up' about once a year - my own versions need this more frequently. The top (turntable) shelf is not air suspended mainly for the reasons others have mentioned - it would most likely require regular adjustment so I site the TT on an 18mm acrylic base, sitting on 6 'half' squash balls which sit directly onto the wood

I originally used metal/glass support racks, then stone/slate shelves in place of glass and this included sand filling the hollow legs but I felt that music had a slightly hard, bright edge. The combination of Oak/air suspension gives a nicer and, to my ears, more natural 'organic' sound to the music (the floor and walls are all solid so there are few resonance issues either)

 

Many thanks for all the help to date,I figure it would cost next to nothing to experiment,and if the general theory proved to be worthwhile,it would give credence to looking towards something purpose built along the same lines.

 

Before I wall-shelved, I found that some squash balls (complete, NOT halved) and a decent chopping board on top did the trick and didn't look quite so Heath-Robinson.

Drill some decent sized holes (8-12mm or so?) in the board in a triangular arrangement so the top of the squash balls can be located in the holes for stability. A squash ball is 40mm diameter so won't fall through an 8-12mm hole, but it also won't roll off.

 

Sounds a lot better than an inner tube....and the indentations for stability makes good sense....thanks!

 

I enjoy both aspects.

 

I tried it once...all I can say is, just don't.

 

Works for me isolating from footfalls and I don't have a problem leveling. I've done it for a while so I don't know if it makes any sonic difference. All I know is I can walk around freely without hearing anything or skipping

 

I use sorbothane. I just use their calculator to work out the size of each piece I should be using for the given weight, and job done. Much less mucking around than bicycle tubes etc.

 

I've had one of the air bladder isolation platforms, never again. They expand and contract with slight changes in temperature, resulting level problems. It was nothing but a hassle.
Friends who had VPI TNT's when they used air bladders had the same issued. Constant maintenance!

 

Two key points about the bicycle inner tube concept.

Firstly you should only inflate the tube just enough to support the gear. More and the effect is weakened.

Secondly, you should place a drinking straw underneath the tube, so it looks like a 'Q'. The reason is to make sure the air held between the tube and the bottom and top shelves can expand and contract.

More info here:

http://www.barrydiamentaudio.com/vibration.htm

 

Just set this up last night, but I have a lot more tweaking to do. I like the look of it fine, and it is level when the lid is closed, but when I open it to put a record on it leans back. I may just keep the cover off, or buy a big aftermarket cover to sit over the whole thing.

Before this, I just had a set of vibrapods and almost any footfall would cause a skip. Now it takes a deliberate footfall or stomp to cause a skip. Not perfect, but definitely better!

 

Put it on a wall-mounted shelf and dance your @rse off !!