How important is an audio rack?

It is much easier to set down the names of those who do know something; saves a lot of paper or electricity also. Whatever you place your gear on has an effect on sound quality; as do various suspension devices. I demonstrated this to a couple of skeptical friends recently. A simple method is to separate the responses of those who have actually tried something from the ones who "KNOW" in advance what would happen. Many companies do their best to isolate their products from mechanical vibration; my Naim Superline's circuitry rests on springs for isolation; some of Conrad Johnson's preamps do something similar; external crossovers are generally conceded to give the best sound. All good racks and isolation devices do is to apply damping externally rather than internally. Unlike some audio accessories it is quite easy to make measurements of vibration; that such vibrations have no affect on sound quality is simply as assumption that is contradicted by the experience of many of us.

I in fact use, and was a dealer for, the Star Sound rack that Studiosoundman refers to. I don't feel that this biases me terribly as 1. I have never sold any and 2. they are not currently being produced. They are quite effective but there are many others which use various methods of construction which work as well. My Linn LP12 sits on an old Russ Andrews Torlite stand which proved better FOR IT than the TT shelf of my rack [just as Linn predicted it would]. Either high mass or low mass stands can work if they are properly designed and built. I was using slate platforms under my TTs in the early 80s so I was an early adapter of vibration control. If you are into DIY there are many effective possibilities out there.

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.