Sonic Barrier damping sheets vs cork

Another choice is the lead weights sold at hobby shops and fish & tackle shops. Lead is an excellent damper, and possesses very high mass for it's volume. Pretty cheap, too.

No other comments, specifically about the merits of cork as a damping  material? 

I like cork quite a bit particularly around circuit boards and transformers. Lead not so much.

I have a friend (Pete Curry, bassist/recording engineer in Los Straitjackets) who put down a cork floor (over concrete) in his studio. Sounds pretty good---cuts down on reflections, but is not too dead. So Geoff, how come no likey lead as mass damper? I'm about to put some little stick-on lead weights (like for wheel balancing) on the counterweight of my pickup arm to increase it's mass (so's it can be closer to the arm's pivot, thereby lowering it's effective mass). No?

In most applications I’ve tried lead it hurts the sound especially in the bass, makes it sound weird. And lead seems like SUCH an ideal material. Not too soft, not too hard.  Lol  Maybe you will have better luck than I.

Cork would not be helpful.

Why not good ol' Sorbothane?

Why not Sorbothane?  Mainly because Sorbothane is one of the worst materials ever foistede upon unsuspecting and gullible audiophiles. And it seems like the perfect material, right? Not too hard, not too soft. The only worse materials, if that's even possible, are lead and SONEX.

I used VMAX Damping Pads on my Jolida phono stage. The material is self adhesive and pretty easy to install. I also took the time to apply RF Shielding to the MC sections. I don’t have a clue regarding Cork and it’s acoustic values. Good Luck!

Unlike Geoffkaits experience with sorbothane - I have used it with great effect to completely deaden all vibrations on my rack and shelving.

HOWEVER - YOU DO have to know what density of sorbothane to use - a rating of 40 or 50 should suffice for most audio uses and softer is not better. See link to fact sheet below

EXPERIMENT with sheet thickness. I use 1/10" thick only - I have also tried 1/8", which was also effective, but offered no benefit over 1/10"
- sheets thicker than 1/8" should be avoided for audio use

I did try a double layer of 1/10 " on my TT feet once but it degraded the sound - made it muddy

FOR SURE - stay away from purpose built  Sobothane feet that look like half of a ball - they are useless for most all audio applications and can degrade performance severely

ALSO - sorbothane from different sources (i.e. some eBay vendors) are not made to the same standards - the first sheets I purchased were great - never left any residue or damaged the surface they were placed on
- but the second sheets seemed to leave a mark/residue on wood based products. Just buy from the US sites, they seem to be the original product

My main uses:
- I place it between the metal rails of my rack and the shelf that rests on them 
- I also use it for the DIY ball-bearing feet that support all of my components - see "My System" for details

NOTE: you do not need to cover the entire surface with it, just a small piece (or several smaller pieces) will be more effective and their position can also make a difference

I also have a small piece on the chassis my Moon Audio phono stage.

It's not perfect, but for some uses it is very good.

Here's all you need to know about Sorbothane
http://www.sorbothane.com/Data/Sites/31/pdfs/product-guides/Sorbothane-SPG.pdf

It's not a panacea - but for "some applications" it is very effective

Regards...