How to isolate turntable from footstep shake or vibration

Mounting a turntable on the most solid rack or wall shelf might cure a footfall problem but it will not isolate a turntable. Only the mechanical filtering of a proper suspension will do that along with a proper dust cover or keeping the turntable in another room from the speakers. 

@williewonka , Those feet do not offer isolation. Those center posts used to stabilize the magnets ruin any isolation the feet provide except in the perfectly vertical axis. 

user510, I have intimate experience with both the AR XA and I have owned 2 LP 12s. They are both potentially unstable and do not handle footfalls well just as ghdprentice indicates. A Sota you can rap on the surface and dance the jig on springy floor and it will not care. It is all about the self centering stability of the suspension that count.

@williewonka , Sitting a turntable on opposing magnets is similar to sitting a turntable on springs and would be very unstable without some kind of lateral support. Hanging a turntable from attracting magnets would be an interesting project. My instinct says it would not perform any better than hanging a turntable from springs but would be a lot more expensive.

user510, there are well designed turntables suspensions and not so well designed suspensions. Suspended turntables that have their sub chassis sitting on springs like the AR XA, LP 12 and Thorens turntables are inherently unstable and they tend to oscillate laterally when aggravated. They will skip with footfalls sometimes even more readily than unsuspended turntables. Suspended turntables that have their sub chassis hanging from the springs are inherently stable and want to maintain their resting positions. This category includes SME, some Basis and Sota turntables. They will not skip with footfalls. You can put them on a collapsible card table and they will operate fine without any audible consequence.  

@atmasphere, it sounds more like damping rather than isolation although it probably isolates at certain frequencies. If you want to have some fun put the stylus down on a stationary record and hook your phono stage to an oscilloscope. Then play a sine wave sweep loudly and see what gets through. I plan on doing this with the Sota when I finally get it. 

@atmasphere, isomerically isolated? Does that mean rubber feet? A suspension requires a resonance frequency in and around 3 Hz. Dohmann I think uses 1 Hz vertically and 1.5 Hz laterally.
Put your stylus down on a stationary record, close the dust cover and turn up the volume. Then go look at your woofers. Keep an eye on the woofers as you walk around and even tap on things. With my old Sota I could hit the plinth vertically with a hammer and the woofer would not even twitch. Most woofers will be fluttering from the environmental rumble which is due to anything from the washing machine in the other room to the truck running down the street. Mass might change the amplitude a little but it will not stop it like a suspension will. How much does it really matter? Most people would never know it was there. None of us could hear it directly over the music. However if you have subwoofers and room correction with a lot of power it can cause the drivers to bottom out and can increase distortion. For me it is important because I run my subwoofers up to 120 Hz where the distortion would be obvious. I doubt any of us could hear it under 40 Hz. Of course there is the psychological benefit of knowing nothing can get to your turntable.

Mass does not solve everything. There is loads of environmental rumble that will transmit through anything. When it gets bad enough buildings fall over. Church bells weight tons and they ring like crazy. The only way to isolate a turntable is to suspend it. 

Darn millercarbon, I am stuck agreeing. In medical school we learn to do things perfectly according to the state of the art at the time by learning from people who already do it perfectly. But, looking back at history it took a lot of baby steps to get there. Perfect is only a perspective in time. As time changes so does perfection. I am sure if da Vinci were alive today he would show you are all the places he made mistakes on the Mona Lisa. 
Being a perfectionist does not mean you are paralyzed. It certainly means you are never happy with what you do, or what anybody does for that matter. It is not a very happy place to be.

Ah, another happy Sota user. Hope that sash doesn't break! Very creative though.

@atmasphere, My Sota has always been on a sturdy cabinet. The new one will be on a granite countertop sitting on a cabinet made of 1.5" walnut plywood loaded with over 1000 records on top of a concrete slab. 

Seeing that distortion on the oscilloscope certainly indicates a problem with that Sota or the way it was set up. Could be an interaction with the Sota's suspension tuning and the mass of the tonearm/cartridge with the cartridge compliance. It would not be airborne as that would not quiet down when the Sota was placed on a better rack. 

I have an oscilloscope program so when I get the table I'll have a look and see if there is any unusual distortion at various frequencies. 

@wolf_garcia , I though guitar amps were chosen based on the distortion they produced. How can you tell if a tube is microphonic or not if the amp is distorting it's backside off? Tube guitar amps are desirable because of the distortion they produce! (at least that is how I understand it) Interesting point though. Same for automobile systems although tubes are long gone in those.

@lewm, My understanding is that Upscale Audio and RAM labs do grade their tubes on microphonics and two other parameters. And, what do those tube rubber band damper rings that ARC supplies do? They obviously dampen the glass. Does that decrease microphonics? Are they the reason I can tap on the tubes and not hear it through the system?
I was tapping on the tubes because one of them went bad and I was trying to figure out which one it was. Tapping did not help.

@atmasphere , I have been using a Sota since 1981 and have had it on everything you can think of playing through ESLs. I have not found anything to be as important as using a dust cover during play attenuating airborne vibration by as much as 20 dB (not sure how accurate the meter was). Like protective earmuffs for your cartridge. And, everyone thinks this is poison (except Mark Dohmann). I guess like guitar amps everyone likes listening to distortion? With subtle differences I guess people prefer sticking with mythology than really listening? Boggles the mind. 

@lewm , I am very simple minded Lou.Insted of buying very elaborate isolation plateforms I would prefer buying equipment that is not affected by the minimal amount of vibration present in a sturdy cabinet. I find it interesting that I see systems with elaborate platforms for the electronics and a turntable that sits on simple feet. I get a Sota mostly because it has a dynamite suspension and is impervious to anything happening around it. The same can be said of several other turntables but not the majority and it is very hard trying to get the message through that heavy plinths do not qualify as a suspension. Turntables are different because it is their job to "measure" vibration. No other component does this and is near as sensitive in this regard. Maybe some tube equipment is susceptible. You and Ralph would be far more knowledgeable on that subject than I am. I only have one tubed unit. But, I have a hard time believing and piece of electronic equipment would be as sensitive as a turntable.  

@atmasphere,  I don't believe in miracles. ARC put tube "prophylactics" (damping rings?) on the tubes. I have no idea if this cuts "microphonics" 
@lewm , I'm not talking about hitting the tubes with a baseball bat, just light tapping. Yes the PH3-SE is a hybrid design. I think it uses a FET front end.  At some point you have to rely on experience. (and people you trust)

The next question is if tubes are microphonic how much energy or input does it take to make them sing and how does this affect sound quality. Will putting a tube phono stage on an isolation base change the degree or level of microphonics and can this be quantified. What about solid state. My preamp is digital. When I get home I'll put a wooden block on it and bang the block with a hammer to see what happens. That is way more energy transferred to the chassis than anything being transmitted by air or through it's feet. Once turntable is set up I'll do the same to the phono stage, the Oppo and the Apple mini to see what kind of noise I can generate. Next, I'll put my cell phone's volume up all the way and put it on speaker phone. Then I'll put the phone directly on each piece of equipment and I'll run a slow frequency sweep through the phone (what ever frequencies the phone will transmit). With the phone in direct contact with each unit that should transfer more energy to the unit than any system can. The the volume on my system turned all the way up we will see if we can hear anything!

@atmasphere and @lewm , I can tap on the 6922's in an ARC PH3SE and hear absolutely nothing with the volume turned up. I'm sure if I tap hard enough I could get an audible result. But tapping on the tube would have a lot more energy then you would get with air bourn vibration. I use super quiet tubes. My instinct is if a unit is sensitive to tube microphonics perhaps you might consider another unit. My only current experience in regards to tubes is my phono stage. So it is limited. But, having to spend money on effective vibration elimination would bother me. I would prefer spending the money on a better phono stage that was not so effected. 
The cabinet my system is in is also extremely rigid, more so than anything you can purchase. My system is immensely powerful using a total of 4000 watts, two 8 foot ESLs and four 12" subwoofers (soon to be 8) and the only device I feel the need to isolate is the turntable which comes so equipped. As I previously mentioned I can put the phono stage and turntable right on top of a subwoofer with no ill effect I can hear. You never want to trust what anybody "hears" and I certainly can not say this applies to every phono stage or preamp as I have only tested one. 
However, If lewm and atmasphere insist there are electronics so effected I am sure this is true. But, If the military can make electronics that are immune to vibration so can the high end audio industry. As far as I can tell none of the electronics I have excepting the turntable are sensitive to air bourn vibration. In the cabinet they are in structural vibration is not an issue. Maybe people should spend the money on a solid cabinet instead of isolation devices. 
@melm , I never have to change my balls. Perhaps you need a turntable that has no balls, something like one of those Audio Technica direct drive tables:-)

@lewm , as far as F22 avionics are concerned I doubt the government would publish such information. For certain as you suggest the "brain" is oriented to gravity and it knows it's altitude and ground speed. It also knows how to fly the plane. There is no way you can protect the brain from the wild forces applied to it during aggressive maneuvering. The plane is capable of pulling at least 6 G's in any direction, more than any human could stand without a flight suit that supplies counter pressure. That would pull the wings off a 737. This is a lot more force than any coincidental vibration and there is no way to protect the electronics from this. They are just built to take it. I seriously doubt there is any "micro instability" Would you strap yourself into a Mach 2 fighter plane that relied on micro unstable electronics? I wonder what "micro instability" of 20,000 pound thrust vectoring would do?

@lewm, the Russians used tubes in their military avionics until the mid 70s I think. You would think just looking at a tube with it's delicate appearing insides that it would be sensitive to vibration. Is this reality or lay instinct? I use a tube phono stage which uses 6922's. It is not the tiniest bit sensitive to vibration, at least as far as I can hear and I have done some pretty crazy things. I have 25 foot long RCA interconnects from my Krell amplifier days so we put my turntable and phono stage on top of a subwoofer just for fun and to prove that the Sota was impervious to vibration. I had no intension of testing the phono stage. But, tonearm interconnects are only so long so the phono stage went with the turntable. I'll bet you can guess the results. I think the high end was slightly rolled off but my brain would think that anyway because it knows to much about the effect of length on single ended interconnects. Otherwise, everything sounded exactly the same as before I moved the turntable set up. But again this was subjective and only an indicator.  I have never seen any proof that tube electronics are sensitive to vibration. If you have seen some I would love to see it. As far as what people hear?  Subjective evidence is an indicator. It does not rise to the level of proof. Lay instinct is a horrendous trap I think most of us have fallen for at one time or another. I certainly have which is probable the reason I treat these issues more cautiously. I am not about to go out and spend money on an anti vibration platform for my phono stage. I have no reason to.

mglik, the advantages of isolating a turntable are rather obvious but a preamp? If electronics were sensitive to vibration F22's would be crashing all over the place. For those of you who do not know what an F22 is it is a fighter jet that can not fly without computer control. The pilot tells the computer what he wants to do and the computer does it for him. The control inputs are to complicated for a human. There is no manual option.

Esputnix, that is wonderful. I could not believe Oracle would make such a design error. It is nice not to have to tip toe around;-)

@cleeds, certainly an old Sota is not going to be the quietest turntable around but a record is at least one order of magnitude noisier than that old Sota. My new one, which will hopefully show up next month is as quiet as it gets. 
I use a calibrated mic to "listen" to my system all the time. It's program has an oscilloscope function and I can plot a frequency response curve which for this purpose needs to be near field. Rumble is a constant. Record noise is not. It is also much louder than rumble. But, you do not even have to measure it. You can see it in the subwoofers excursions. 
To be short, there is plenty of noise between 3 and 12 Hz. With a flat record it is true that between 0 and 12 Hz is relatively quiet. Relatively. 
It is also true that a sub sonic filter will be useful particularly for the idler wheel drive people. For people like me who use subwoofers boosted to realistic levels subsonic filters are essential for vinyl users unless you never listen over 75 dB.  Also if you do not want to rocket your subwoofer drivers into the next county a mute switch is a nice addition. 

@cleeds, not a tone arm resonance problem at all. It is set perfectly at 8 Hz (horizontal. vertical is a little higher 9-10 Hz.) The cartridge is reading irregularities in the records surface. No record is absolutely flat. Unfiltered the subwoofers will gladly try to reproduce this. They are not projecting any "sound" into the room. They are no where near large enough to produce those frequencies but, if there is an electrical signal at 8 Hz they will gladly flap around at 8 Hz adding distortion to the sound you want to hear. In my case each subwoofer has 1800 Class AB watts behind it that will amplify right down to DC. Filtering all this garbage below 18 Hz cleans up the signal very audibly. You would have absolutely no problem hearing it. 

@cleeds , that is right, flat to 20 hz at 1 meter. There is no full range loudspeaker I know of capable of reproducing the bottom two octaves in your average room at realistic levels. You have to be able to have separate control of that part of the spectrum. Your average room requires at least two 15" or four 12" subwoofer drivers to do the job. Room control and a lot of power help. To get the sensations of a live performance you have to be able to boost the low end 5 to 10 dB  sloping up from 100 Hz  to 18 Hz. Smaller drivers have to take overly long excursions to do this and distortion levels are much higher. 
At any rate, adding a bad subwoofer system is worse than no subwoofer at all so I can understand why many people do not.

@cleeds , you obviously have no experience with powerful subwoofers and turntables.

Sub sonic filters are not Band-Aids. A sub sonic filter is essential if you are using a turntable with powerful subwoofers. I can play records without the filter all the way up to 85 to 90 dB before there is a noticeable degradation in sound quality. This is with the old Sota Sapphire and Syrinx PU 3 tonearm. It is not feedback, it is distortion. If I turn the filter on the distortion disappears. This is with a digital filter not an analog one. The problem is not the turntable. It could not be happier. The problem is the subwoofers trying to reproduce every little irregularity on the record causing the woofers to make long excursions. If I turn the volume up loud enough I can get the voice coils to hit their stops making a very painful sound.  
Since the signal has already been digitized creating a subsonic filter takes just a little programming. It does not add any distortion or phase shift unlike an analog filter. 

At any rate Lewm is correct. Putting a suspended turntable on springs will probably have an adverse affect. The problem here is the Oracle's springs are not isolating the sub chassis from footfall. Either because they are tuned to the wrong frequency or they are poorly dampened and unstable. The only solution other than changing turntables would be a wall shelf if the wall does not shake. 

That is disappointing. It means that vibration is getting to the sub chassis in spite of the suspension either through a poorly designed suspension or directly vibrating the sub chassis. You can try damping the suspension by stuffing some foam in the springs. Later versions of the Oracle add adjustable damping. Subwoofers are a huge problem for turntables especially if you have them set where they should be. The low frequencies will fibrate the tonearm directly through the air. It is very important to use a subsonic filter and digital filtering is the only way you can do this effectively without injuring the bass. I roll off at 18 Hz 80 dB/oct. I use a Sota and a large subwoofer array and have absolutely no issues. The turntable is however on a very heavy cabinet on a concrete sub floor. I have used the Sota on several wood floors over the years without any difficulty and have seen SME's and Basis tables do the same.  Adding mass under the table usually does not help. The floor just bounces at a different frequency. There is a chance that the problem is not vertical vibration but lateral vibration in which case using a sturdier rack and damping the springs will help. You still should look into a subsonic filter.