What isolation feet under your amp with great result?

For fun, I just ordered some springs yesterday.  I tried to go with something shallow enough so my amps wouldn't look weird and something wide enough for stability.  Regarding the spring constant, I ordered springs where the total weight per spring would be just a touch over one-half the spring's maximum capacity. 

@rixthetrick 
Since you use springs extensively, would you provide a recommendation for sizing the capacity of the springs compared to the weight they will each support?  I have some springs arriving today to try under my 70-pound amplifiers.  The maximum capacity of the springs I ordered is slightly less than one-half of the weight they will each support.  Are there pros and cons related to sizing them, i.e., stiffer or softer?

@rixthetrick 
What is on top of the amps now are two (on each amp) of these heavy little brass suckers that Dan finished in black with Isodamp elastomer material on the bottom:
https://edensoundaudio.com/shop/fatboy-disc/

I like the Isoacoustics carpet disc suggestion.  The smaller ones for the Gaia III are 1-11/16 inches in diameter so would fit a medium sized spring but they are 1.75 inches tall, which may be too tall for my situation.  I am thinking about how I could leave the Sound Anchor stands spiked to the floor and then put the springs beneath the speakers but that would negate the benefit of the additional 65-pound weight provided by the SA stands.  More consideration is needed.  First I will do some listening and decide whether I like springs under my amps before I modify my speaker set up.

I just completed a partial virtual system page update including a shot of one of the SMc amplifiers that is supported on springs (you can't see them) over the SRA platform, which is sitting on a low-profile Sound Anchor stand.

The vulcanized rubber hockey pucks are way harder than typical rubber footers.  Anyone else have a clue as to their damping abilities vs. other typical options discussed here? 
I would be interested in trying them under my 70-pound amplifiers, which sit on SRA platforms.  The SRA guys said it doesn't matter which footers I use when using their platforms while the amp designer strongly suggested Stillpoints so the amps are currently on Stillpoint footers over SRA platforms.  I have no sonic issues but it seems I could use the Stillpoints under some of my more sensitive front-end gear if their use under the amplifiers is redundent.
The Machina Dynamica springs mentioned above are also interesting to me and while elegant from an engineering perspective, not so much visually.  I believe these are valve springs for small engines.  The trick is finding the right spring for the weight being supported.

Hockey pucks consist of vulcanized rubber.  In the audiophile world, rubber is not generally known for being a desirable footer material.  The vulcanizing process results in a rubber material with increased rigidity and durability, as well as other changes in the mechanical and electrical properties.  Many here report using hockey puck footers under their gear and speakers. Therefore, does the vulcanizing process result in a rubber material that has damping and support properties which are better than those of unvulcanized rubber footers?   

Silent Running Audio (SRA) platforms work great under my amps.  You need to have the platforms made (or refurbished) for your specific amplifier(s), i.e., weight, size, and footer location.  With their platforms, you can use your amp's existing footers.  Their platforms are expensive though.  One of their taglines - 

Informed by its work in the aerospace, military, electronics and medical industries, the company is renowned for the effectiveness of its mission-critical solutions—whether applied to advanced fighter jets, nuclear submarines, electron microscopes or high-end audio systems.

@mahlman 

Right now both of my legs are the same length.

As a suspected "naysayer" I am compelled to challenge your assertion and ask whether you have measurements to substantiate your claim?  Have you opened this belief up to study and confirmation by independent observers?  Did you pay a significant upcharge for a pair of perfectly matched legs and would it really affect performance if one leg was say, 1/8th inch shorter or longer?  I owe it to this forum to protect unsuspecting readers from being deceived by those making unsubstantiated claims of perfectly matched legs.

@rixthetrick - I received my springs yesterday and replaced the Stillpoints under my amps.  The springs I purchased look identical to the Machina Dynamica springs and cost me about $35 for 12 of them.

The amps now sit on 5 springs each, over purpose-designed SRA Ohio-Class XL+² platforms, which each sit on low profile, heavy Sound Anchor stands that are spiked through low-profile carpet into the concrete slab-on-grade floor.

I am glad I ordered extra springs since I realized the front ends of the amps are much heavier than the rear, due to the very large toroidal transformer in each.  Since I had extra, I was able to place a fifth spring directly under the holding bolt for the transformers and that was sufficient to level out the front and rear of the amplifier nicely.  The springs are not quite half-way to their fully compressed state resulting in plenty of play remaining up and down.

The compressed height of the springs is almost identical to the height of the Stillpoints so visually it looks great - I cannot even see the springs.  I need to post some upgraded system pictures since I realize I do not even have the new SMc Audio amps posted yet and they look pretty cool on the SRA stands.

Too soon to determine the sonic impact yet, but t if these sound good then I have 8 Stillpoint minis to use under other gear, or to sell.

I would like to try springs under my speakers which are on Sound Anchor Signature Stands and are currently spiked to the concrete.  I have a couple of challenges being that they are purposely tilted with the front being a little bit higher, plus the issue of the weight distribution being not exactly even.  The weight is about 170 pounds for each speaker/stand combination.  If I go with springs, I would want them to be very low profile.  I will give it some thought.  My other option for decoupling would be to try Herbie's Audio Lab Giant Threaded Stud Gliders at about $300 for 8 of them.  They would handle the tilt and provide a secure connection to the bottom of the Sound Anchor speaker stands.   Some here have reported good luck with those but I am a little concerned about either the Gliders or the springs sitting directly on carpet.  Maybe I should try hockey pucks first just to see what I think about the sound decoupled.

Any of you try these?https://www.amazon.com/Nobsound-Aluminum-Speakers-Isolation-Amplifiers/dp/B07K9ZYP84/ref=cm_cr_arp_d_product_top?ie=UTF8

Been poking around a bit and these look even better visually since the springs are enclosed in black or silver CNC’d aluminum footers.  It seems the top stud could be rethreaded as needed so they could be connected/threaded directly to the speaker base or, in my case, to my Sound Anchor stands.  A little tall for my situation but inexpensive and might be worth a try.
https://www.aliexpress.com/item/4000590928789.html?gps-id=pcDetailBottomMoreOtherSeller&scm=1007.14976.157518.0&scm_id=1007.14976.157518.0&scm-url=1007.14976.157518.0&pvid=11102f24-cd15-4a4e-ac19-de9b31b2c1e6&_t=gps-id:pcDetailBottomMoreOtherSeller,scm-url:1007.14976.157518.0,pvid:11102f24-cd15-4a4e-ac19-de9b31b2c1e6,tpp_buckets:668%230%23131923%230_668%23808%233772%23984_668%23888%233325%234_4976%230%23157518%230_4976%232711%237538%23214_4976%233104%239653%2310_4976%233141%239887%235_668%232846%238109%23246_668%232717%237565%23783_668%231000022185%231000066056%230_668%233422%2315392%2369

I like the springs (just like those by M-D) that I put under my amps so far, but I wanted to maintain a lower profile under my speakers so just ordered Herbie’s Giant Fat Gliders to try in the place of the Sound Anchor spikes.

@sjeesjie 

Noob question perhaps, but how can isolated feet contribute to better sound quality?

Search couple vs decouple here and over on audioasylum and you will find as much information as you will care to read.  IMO, the answer is - it depends....on so many things that there is no one size fits all answer.  In the end, the result is subjective.
In  my system, the amps are decoupled by sitting on springs over Silent Running Audio platforms, but the platforms are coupled to heavy Sound Anchor stands that are spiked (i.e., coupled) to the concrete floor.  My speakers are bolted to heavy (I.e., 70 pound) Sound Anchor stands that are spiked to the floor.  Next week, I am going to try decoupling them using Herbie’s products. I will find out then which sounds better to me.

@lowrider57, glad to hear the EVPs are working.  I certainly considered them and have not ruled them out for support under my speakers but the cost would be about $800.

In my searching around, I came across Owens Corning 703 and 705, which are rigid fiberglass boards that are commonly used for acoustical damping purposes.  The data sheets for the 703/705 materials (particularly compressive strength and associated deformation) seem quite similar to the technical information reported for the EVP material and the photos of the material look similar, except the EVPs have been painted black.  I am thinking about a DIY project using 705 pads under my speakers and including the metal plates and rubber, similar to those used for the EVPs.  I have not heard of anybody else trying this as a DIY project.  It will probably be a bit of work, but fun.  If successful, I could do my two subs too and I suspect the DIY cost would be quite a bit less than the $1,600 it would cost me to do my main speakers and two subs. 

My recent decoupling experience has improved the sound of my system.  Although there were no glaring issues with the sound before, after decoupling my amps, speakers, and subs, I would describe the subtle, positive changes as enhanced clarity and coherence, particularly throughout the midrange, and perhaps less edginess that is most noticeable on poorly recorded material.   I have not noticed a loss of bass but if I do with further listening, I can adjust for that with my dual subs.

The options for decoupling are many and except for EVPs, really not that expensive.

• Springs - Basically what Geoff at Machina Dynamica has been recommending for years.  There are several good sources and the trick is getting the right size and stiffness for your application.  Even stiff springs for higher loads should be less than about $10 each.  I have posted some pictures on my system page showing the use of cups on the top, bottom, or both when using springs.
• Herbie's - Their dBNeutralizer based products seem to be working well under my subs and main speakers.
• EVPs - Equipment Vibration Protectors by A/V RoomService - many have reported excellent results.
• DIY EVPs - May be possible to make from Owens Corning 703 or 705 material, although I have not yet tried it.  If I were to make these, I would sandwich a 4x4 inch square of one-inch thick 705 between thin square steel or aluminum sheet, paint that black, and then use very thin (70 Duro) 4x4 inch Sorbothane sheets on the outsides over the sheet steel or aluminum.  After considering, I have concluded the DIY version may save some money if you need many of them but for a few, it may be better to purchase these directly from A/V RoomService. 
• Sorbothane - Many write this material off as unsuitable for audio purposes but, after looking into it, I wonder if they were using incorrect sizes or Durometer values.  The material seems to have a good reputation as a vibration isolator outside of the high-end audiophile community.  Below is a link that provides some guidance on selecting the appropriate size and durometer values for different applications.  A set of eight for my two main speakers would only be $100.
• https://www.sorbothane.com/Data/Sites/31/pdfs/product-guides/Sorbothane-SPG.pdf
  
• Air Bladders - Many believe these to be very effective and you can read posts about folks DIY'ing them in the late 90's and 2000's.  I used them under electronics for years.
• Hockey Pucks - These are hard vulcanized rubber and I cannot comment on how they sound but more than a few use them for decoupling speakers.

@tweak1 , Geoff has been saying "mass on springs" for years, and after the past two months of trial and error I have ended up with springs under my heavy speakers and amps.  The spring stiffness (i.e., spring rate), load capacity, diameter, and height are all important considerations.  I have used heat shrink to damp the single springs and even that was a learning experience wrt the size and thickness of the heat shrink used and how those factors affect the performance of the spring, as well as the need to put a hole in the heat shrink to prevent an air lock.  The heat shrink also improves the look (pics on my system page) and prevents scratching on the bottom of your components or the tops of your rack shelves.  I also have a bunch of Herbie's products here (Giant Fat Dots and Gliders) and based on my experience so far I would have a hard time deciding whether springs or Herbie's footers sound better. 

The EVPs by A/V RoomService Ltd. seem to have a strong following by those seeking a decoupling alternative.  The primary isolation appears to come from an "air spring" resulting from Owens Corning 703 or 705 one-inch thick rigid fiberglass board, which is then faced with #4 brushed Stainless Steel sheet and either felt or rubber.   I have considered making these and believe you could probably get most of the way there by simply installing the board.  I would also be curious to try using the board to make equipment platforms but since I already have platforms and am using springs under my speakers I have not yet been motivated enough to spend the time to make the stuff.