How important is an audio rack?

It matters a GREAT deal for ss as well as tubes. I can clearly hear my ss amps change character depending on what they rest upon. Believe it or not (and I had a hard time with this one) my MFA Reference TVC Preamp is incredibly sensitive to what it sits atop. For instance, my AMR dac loves my Silencer in active mode, my MFA likes the Silencer in non-active mode but not active isolation mode. The MFA is a completely passive device using only transformers for it's duties so I thought it would be least affected; turns out it is highly susceptible to vibrational issues. I know of no device including my Mac Mini music server which is immune to the platform underneath... to state otherwise as some have done in this thread.., well lets just say that would not be my experience. I would suggest you experiment for yourself.

Again, I am still amazed at the changes which can be wrought regardless of the device in question simply due to what a device rests upon or what rests upon a device.

Audiofun, I would agree that to the degree a rack improves isolation of components they are essential. The real question is do any racks do enough? I grant that WAF is important and some racks do have such appeal, but I have never heard a rack that does all there is to be done. Basically anytime you have current moving in a wire, you have a magnetic field that will induce current flow in other wiring. If you further have motion of the magnetic field from vibrations, it will induce other information into your audio. The best circuit would be in a straight line and totally free of any motion. Tubes can be very microphonic but then again so can capacitors.

Vibration is the bete noire of audio.

It's very important to dealers due to relatively high markup/profit margin compared to actual electronic gear I'd bet.

A solid foundation to support gear is important to keep it stable, especially components with physical moving parts that directly impact sound like a turntable. A solid foundation never hurts. It's an insurance policy at a minimum. Search audiogon threads for lots of good info on the topic.

Tbg: I agree with everything you have stated. I would also add that I do not pretend to understand everything I hear when I change footers..etc. For instance, a device like the MFA TVC or dacs for that matter (I am aware that although the TVC is passive it is an electro-mechanical device (transformers and all)) defies logic in how sensitive it is to the body it rests upon.

I think your' explanation of placing existing magnetic fields in motion compounding things has great merit.

The Silencer is an amazing device in that you see no motion with the naked eye and yet the effect it bestows upon the sound is undeniable.

Racks matter:) And yes they can be expensive LOL... I have a Bassocontinuo Reference but for my second system I am thinking of trying Steve Blinns new Ref Rack which I just saw on this site about 20 min ago.

Just put isoblocks under everything.