Amazing anti-vibration feet

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maty

Re: Amazing anti-vibration feet
« Reply #20 on: 20 May 2016, 11:43 am »
The good thing about my second hand AV that allows me to experiment.

My very cheap DIY improvements relating to vibration damping have been effective but I must admit that other improvements that I have made have noticed much more in the sound.

How much bigger are capacitors and their number, as well as transformers be more noticed improvement (especially if you have "tons" of DC -and RFI/EMI too- in mains like me).

Martyn

Re: Amazing anti-vibration feet
« Reply #21 on: 20 May 2016, 04:24 pm »
Silicone (not silicon, which is a completely different material) has been around for a long time. I have had some silicone instrument feet in my parts bin since the beginning of the 1980s. Silicone is all the rage at the moment, because high temperature silicone has appeared in kitchen products, which has raised its profile and made it a household word. One of silicone's useful properties is its tackiness, which makes it non-slip and also pick up dirt (which rinses off easily).

Silicone, urethane, vinyl, latex, natural rubber - most elastomers, in fact - will provide anti-vibration properties if used appropriately. The choice of material and subsequent design will depend on the specific application. Sorbothane, which is a proprietary name for a form of urethane, is particularly well-regarded for audio applications.

Contact area is certainly important. If the contact area is small, the material may squash too much and become essentially solid and therefore useless for our purposes; if the contact area is large, it might not squash at all (in which case it is already essentially solid). So experiment with different elastomers, different contact areas, and different numbers of pads until you find a combination that deflects under the weight of your equipment by no more than, say, one third of the unloaded height. Put them under "hard points" like the corners of speaker cabinets; don't put them in the middle of panels where the vibration is likely to be greatest.

In the industrial world, the design and choice of AV mount is extremely complex. Some of the considerations are: the mass to be supported, the exciting frequency and its amplitude, the resonant frequency of the final assembly, and a multitude of environmental considerations (this is far from an exhaustive list). The most effective mount works best under one specific set of conditions; beyond that, it's always a compromise. If you're trying to isolate your loudspeaker from the floor, you're probably trying to do so across a range of frequencies and for a few resonant frequencies in particular. Any AV mount is going to be a compromise. If you want to get close to perfection, try suspending your speaker from the ceiling in a cradle of high test fishing line! Make sure you find a ceiling joist of roof truss first.

Before you try this, here's something else to think about. Our main problem is isolating the cabinet vibration - caused by speakers themselves - from the rest of the world. What if your speaker cabinets are perfectly dead, i.e. they don't produce any vibration? If this were the case, you wouldn't need any vibration isolation! While few (if any) speaker cabinets are perfectly dead, many of the better designed ones should be getting quite close. So at the risk of starting a wave of outrageous comment, I'm going to suggest that the poorer your speakers, the more you need resilient mounts. Putting it another way, if you hear a big difference when you put your speakers on anti-vibration feet, you might consider buying (or building) better speakers. If you don't hear a difference, congratulations!

Nothing wrong with being a cheap sceptic!

Armaegis

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Re: Amazing anti-vibration feet
« Reply #22 on: 20 May 2016, 04:56 pm »
Along the lines of this thread, yes as a structural engineer with some vibration (seismic) background

Same here as a mech eng with light background in vibration control. At the end of the day, all you want is your desired object to be as still as possible, and this requires minimizing it's self-generated vibes, as well as minimizing external vibes from getting in. I have rather extensive experience working on electron microscopes where I'm not even allowed to talk in the lab because I have a deep voice which literally ruins the results of the scan.

Here are some of the basics of vibration control:
1) mass loading: simple enough, the heavier something is the less it moves/vibrates from motor forces; you see people sometimes stack weights on their gear

2) damping: any type of material (typically softer) which absorbs physical vibration energy and converts into something else (usually heat)
2b) external wiggly damping thing: not applicable to audio gear, but sometimes you can actually attach wobbly arm/spring-like devices

3a) coupling: mechanical connection to another object, usually to make it stiffer or effectively heavier; like spiking your components to the shelf or ground
3b) de-coupling: whoops maybe the floor or shelf is actually transmitting vibrations from elsewhere, so now you want to isolate your gear from the offending vibrations

So rather than audio gear I'm just going to use an example from my labs with the big honkin' electron microscopes. First of all the the vacuum specimen chamber sits on a small block of concrete which is suspended on a hydraulic cushion. The vacuum pump itself sits in a separate box on the floor. The hose passes through the main body of the SEM gear first, to limit any more vibration from the pump transferring through the hose. The entire body of the SEM machine (which itself is heavy) sits on a massive concrete block. This entire thing is suspended from the floor (in the basement) on a large steel frame that touches the ground via springs.

We are in the basement so to isolate from any vibrations in the building. But decoupled from the ground because of traffic. The giant concrete slab is basically a mass buffer for anything that does make it through, and to minimize vibrations from the SEM machinery itself. The vacuum chamber further floats, so isolate from the slab and machinery. And still I'm not allowed to talk, because then my voice even at low volume excites the air which touches the vacuum chamber and that's enough to ruin a scan.

If we're talking speakers, make 'em heavy either by loading the speaker itself or connecting to a slab/ground or both. Unless the ground is shaky, in which case decoupling may be better. Or do both by coupling to a heavy slab and then float the slab.

With tube gear, I guess you want to stop the tubes from moving. External vibrations are probably the biggest culprit here, unless you've got some ugly transformer shenanigans going on.

Yadda yadda.

Mike B.

Re: Amazing anti-vibration feet
« Reply #23 on: 20 May 2016, 04:57 pm »
The only thing I would recommend is that the threaded stud be made from brass. The idea of dissimilar metal couplers has been around for a long time. It was either Mike VansEvers or Michael Green who made it part of the AV scene a couple decades back. Many of us use brass screws on our steel cases and to mount speakers to enclosures. 

Armaegis

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Re: Amazing anti-vibration feet
« Reply #24 on: 20 May 2016, 04:59 pm »
The only thing I would recommend is that the threaded stud be made from brass. The idea of dissimilar metal couplers has been around for a long time. It was either Mike VansEvers or Michael Green who made it part of the AV scene a couple decades back. Many of us use brass screws on our steel cases and to mount speakers to enclosures. 
What is the benefit of dissimilar metal for screws? Simply make them softer to absorb vibration?

mresseguie

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Re: Amazing anti-vibration feet
« Reply #25 on: 20 May 2016, 05:21 pm »
Same here as a mech eng with light background in vibration control. At the end of the day, all you want is your desired object to be as still as possible, and this requires minimizing it's self-generated vibes, as well as minimizing external vibes from getting in. I have rather extensive experience working on electron microscopes where I'm not even allowed to talk in the lab because I have a deep voice which literally ruins the results of the scan.

Here are some of the basics of vibration control:
1) mass loading: simple enough, the heavier something is the less it moves/vibrates from motor forces; you see people sometimes stack weights on their gear

2) damping: any type of material (typically softer) which absorbs physical vibration energy and converts into something else (usually heat)
2b) external wiggly damping thing: not applicable to audio gear, but sometimes you can actually attach wobbly arm/spring-like devices

3a) coupling: mechanical connection to another object, usually to make it stiffer or effectively heavier; like spiking your components to the shelf or ground
3b) de-coupling: whoops maybe the floor or shelf is actually transmitting vibrations from elsewhere, so now you want to isolate your gear from the offending vibrations

So rather than audio gear I'm just going to use an example from my labs with the big honkin' electron microscopes. First of all the the vacuum specimen chamber sits on a small block of concrete which is suspended on a hydraulic cushion. The vacuum pump itself sits in a separate box on the floor. The hose passes through the main body of the SEM gear first, to limit any more vibration from the pump transferring through the hose. The entire body of the SEM machine (which itself is heavy) sits on a massive concrete block. This entire thing is suspended from the floor (in the basement) on a large steel frame that touches the ground via springs.

We are in the basement so to isolate from any vibrations in the building. But decoupled from the ground because of traffic. The giant concrete slab is basically a mass buffer for anything that does make it through, and to minimize vibrations from the SEM machinery itself. The vacuum chamber further floats, so isolate from the slab and machinery. And still I'm not allowed to talk, because then my voice even at low volume excites the air which touches the vacuum chamber and that's enough to ruin a scan.

If we're talking speakers, make 'em heavy either by loading the speaker itself or connecting to a slab/ground or both. Unless the ground is shaky, in which case decoupling may be better. Or do both by coupling to a heavy slab and then float the slab.

With tube gear, I guess you want to stop the tubes from moving. External vibrations are probably the biggest culprit here, unless you've got some ugly transformer shenanigans going on.

Yadda yadda.

Now that was interesting. It's a peek into a world I know little or nothing about.  :thumb:

In your avatar picture - is your dance partner decoupled from the floor, but coupled to you?  :wink:

DaveC113

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Re: Amazing anti-vibration feet
« Reply #26 on: 20 May 2016, 05:39 pm »
Some good comments, but in the end you can achieve a wide range of results which are largely subjective in nature. It is possible for damping to sound as if "it sucks the life out of the music", especially when using soft viscoelastic material. Subjectively, many/most seem to prefer damping methods that use harder material, probably due to less energy storage. An example is Furutech's stainless steel/carbon fiber parts, they are exactly the same as some of the lower end parts apart from the SS/carbon bodies. Yet the subjective sound is VERY different and many people find the fairly large increase in price worthwhile, and this is ONLY because of damping properties. Then there is the fact that many people might prefer different kinds of damping depending on what the component being damped is.

For speakers I've experimented a lot and think isolation is the only good solution, every speaker cabinet vibrates and if allowed to drive the floor always results in bad results vs a good isolation scheme. I think speaker designers rarely take this into account, if ever, but it can make a huge difference. I've found IsoAcoustics stands to be very effective and reasonably priced.


DaveC113

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Re: Amazing anti-vibration feet
« Reply #27 on: 20 May 2016, 05:41 pm »
The only thing I would recommend is that the threaded stud be made from brass. The idea of dissimilar metal couplers has been around for a long time. It was either Mike VansEvers or Michael Green who made it part of the AV scene a couple decades back. Many of us use brass screws on our steel cases and to mount speakers to enclosures.

Brass screws for speaker drivers do sound different, and better imo, vs steel... This was posted years ago in the Omega forum and many people tried it, the owner ended up switching to brass after trying it himself.

Armaegis

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Re: Amazing anti-vibration feet
« Reply #28 on: 20 May 2016, 05:59 pm »
Now that was interesting. It's a peek into a world I know little or nothing about.  :thumb:

In your avatar picture - is your dance partner decoupled from the floor, but coupled to you?  :wink:

Technically yes, but in that instance I am perhaps better described as the damping system  :lol:
Initial impulse was the jump, and I provide the critical damping (actually it leans more in the direction of overdamping from a harmonics viewpoint) so that there is no oscillation before landing.

Martyn

Re: Amazing anti-vibration feet
« Reply #29 on: 20 May 2016, 09:18 pm »
Good write-up, Armaegis...very interesting! It's been a very long time since I've had to do any serious vibration control and I've forgotten more than I know. More recently, I worked at an astrophysics research lab, but not in any engineering capacity (which is just as well). You can probably imagine the level of precision and stability that's required for imaging an extremely small area of space that's an extremely long distance away...and this has to be achieved with an instrument that's moving and has varying gravitational vectors and wind loads.

You summed it all up very nicely early on when you said: "At the end of the day, all you want is your desired object to be as still as possible...". Your subsequent description should be particularly useful for anyone trying to deal with external excitation, such as with turntables where external vibration is likely to be picked up by the stylus, tracking weight may vary, and in extreme cases the stylus may jump. I expect this might apply to vacuum tubes as well, although I'm not qualified to say to what extent.

Moving along, I don't know how it's possible for damping to suck the life out of the music, other than by over-damping the interior of a speaker cabinet, but that's not what we're discussing here. I suspect that the manufacturers of some low-end speakers deliberately allow their enclosures to resonate - and might rely on a degree of coupling with the floor as well - in order to add some boom to what would otherwise be a rather thin sound (nothing you do will make these sound good). It should be fairly obvious that if you can keep your desired object still, then damping becomes unnecessary and over-damping is impossible.

As for brass screws sounding better than steel, I think that would be better as the subject for another thread. I can't imagine the scientific basis for such a claim, but I am always open to new knowledge and would very interested to read any objective studies that support this and were performed under controlled conditions. In my opinion, the most likely outcome of using dissimilar metals would be galvanic corrosion.

DaveC113

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Re: Amazing anti-vibration feet
« Reply #30 on: 20 May 2016, 10:27 pm »
Good write-up, Armaegis...very interesting! It's been a very long time since I've had to do any serious vibration control and I've forgotten more than I know. More recently, I worked at an astrophysics research lab, but not in any engineering capacity (which is just as well). You can probably imagine the level of precision and stability that's required for imaging an extremely small area of space that's an extremely long distance away...and this has to be achieved with an instrument that's moving and has varying gravitational vectors and wind loads.

You summed it all up very nicely early on when you said: "At the end of the day, all you want is your desired object to be as still as possible...". Your subsequent description should be particularly useful for anyone trying to deal with external excitation, such as with turntables where external vibration is likely to be picked up by the stylus, tracking weight may vary, and in extreme cases the stylus may jump. I expect this might apply to vacuum tubes as well, although I'm not qualified to say to what extent.

Moving along, I don't know how it's possible for damping to suck the life out of the music, other than by over-damping the interior of a speaker cabinet, but that's not what we're discussing here. I suspect that the manufacturers of some low-end speakers deliberately allow their enclosures to resonate - and might rely on a degree of coupling with the floor as well - in order to add some boom to what would otherwise be a rather thin sound (nothing you do will make these sound good). It should be fairly obvious that if you can keep your desired object still, then damping becomes unnecessary and over-damping is impossible.

As for brass screws sounding better than steel, I think that would be better as the subject for another thread. I can't imagine the scientific basis for such a claim, but I am always open to new knowledge and would very interested to read any objective studies that support this and were performed under controlled conditions. In my opinion, the most likely outcome of using dissimilar metals would be galvanic corrosion.

I can't say either, but if you try putting very soft viscoelastic material under your components this is what happens. The only thing I can think of is along the lines of energy storage and the fact that subjectively, harder materials usually sounds much better. This is for components and not speakers, the IsoAcoustics stands I mentioned would be very soft, almost allowing the speaker to "float" in the horizontal plane.

On brass screws there is certainly a large difference in material properties vs steel, and that's the fastener that is clamping the driver frame to the baffle so it's certainly possible the material the screw is made out of would have an effect on the way the driver is coupled to the baffle.

Armaegis

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Re: Amazing anti-vibration feet
« Reply #31 on: 20 May 2016, 10:39 pm »
Moving along, I don't know how it's possible for damping to suck the life out of the music, other than by over-damping the interior of a speaker cabinet, but that's not what we're discussing here.

I always feel car analogies are cliche, but I'll use one here to illustrate. The comparison here is to the shocks of your car, and how it behaves when you hit a speed bump. If the shocks are very soft, you car may bounce for quite a while after the initial shock. If the shocks are too hard, the initial bump is going to hit hard because nothing was absorbed.

If we think of it as an impulse response on a chart, with low damping your line is going to wobble back and forth across the centre line for a long time. The thing is, the very first return to zero is quite fast. With too much damping, it never oscillates but also takes a long time to return to zero. So when we choose a damping scheme (in this specific scenario), we want the initial return to zero to be as fast as possible, with as little oscillation as possible.

Now in terms of speakers and acoustic pressure and ports and box configs and transmission lines blah blah blah, it is more complicated than that, the term damping there is... kinda slightly a misnomer.

JLM

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Re: Amazing anti-vibration feet
« Reply #32 on: 21 May 2016, 12:30 am »
In theory, lots of considerations:

- Is the vibration from self (motors, humming transformers, drivers); air borne; other sources; or from the support (shelf, rack, floor)
- As mentioned the resonant frequency(ies) and mass of the piece and support (shelf, rack, floor)
- Structural stiffness of all the parts of the piece, especially the panel where supports are point located
- Set supports isolate, hard supports couple
- As mass increases resonant frequency goes down and the energy required to resonate goes up

Generally I recommend soft supports for soft (wooden) floors (isolate everything) and hard supports for hard (concrete) floors (couple everything).  For instance spiked speakers on a wooden floor (over a crawl space which can act like a huge resonator) could be a huge problem, especially if your turntable is supported over the same crawl space.  OTOH spiking gear to a concrete slab can greatly increase mass and reduce resonances.

So there is no single or simply answer.  I've yet to see a vendor offer a variety of solutions or recommendations for their use.  So I remain a skeptic.

Martyn

Re: Amazing anti-vibration feet
« Reply #33 on: 21 May 2016, 12:40 am »
I can't say either, but if you try putting very soft viscoelastic material under your components this is what happens. The only thing I can think of is along the lines of energy storage and the fact that subjectively, harder materials usually sounds much better. This is for components and not speakers...

On brass screws there is certainly a large difference in material properties vs steel, and that's the fastener that is clamping the driver frame to the baffle so it's certainly possible the material the screw is made out of would have an effect on the way the driver is coupled to the baffle.


Well, you're going to have a hard time convincing me that solid state electronics with no moving parts can produce any  audible vibration, with the possible exception of buzzing transformers. Buzzing transformers need to be replaced or individually isolated in order to avoid excitation of the chassis. For solid state equipment like optical disc players, again it's the drive system that needs to be replaced or isolated. Even so, it would have to be a poorly made or badly worn drive system if it were to produce noise that's above the background noise level in the room. I soft-mounted the toroids in my home-built kit amp just for good measure and I replaced the cooling fan on my sub-woofer amp with one that has a noise level around 25dB (if I remember correctly). I don't believe that the musical sound produced by solid state electronics is affected by vibration from external sources - especially digital electronics - but again I'm willing to stand corrected if anyone can show me the objective studies.

Conventional wisdom with respect to speaker baffles is to take the route that Armaegis alluded to: clamp a stiff, relatively light basket to a massive baffle such that they effectively become one. This is down to the tension that you can generate in the basket mounting fasteners, which is why I use machine screws into threaded inserts rather than wood screws into the baffle itself. Of course, you can generate more tension in a steel fastener than in a brass one of the same type, so I'd favour steel over brass for this application, although I doubt whether it makes any meaningful difference unless the size of the fastener is marginal. Here's the key concept: if the tension in the screws exceed the force trying to separate the basket from the baffle, the basket isn't going to move.

An alternative approach might be to soft-mount the drive to the baffle in order to minimise the direct transmission of vibration into the baffle and the rest of the cabinet. I haven't tried this, although I'd quite like to. However, there's a trade-off if the basket is allowed to move relative to the baffle (which soft-mounting would do). I think you'd aim to have the basket critically damped, but I don't know how you'd achieve that with the appropriate instrumentation. I suppose you could "shoot" the driver to measure the time delay with speaker measuring software and keep tweaking the mounting screws. Either way, the tension in the screws will probably be less than when solid mounted (depending on the type of mount used). The big problem is how do you seal the driver in the baffle? Inevitably you would end up using a thick elastomeric gasket partially compressed in an attempt to both seal and soft-mount.

This is an interesting discussion, but it should probably be in The Lab now.

Martyn

Re: Amazing anti-vibration feet
« Reply #34 on: 21 May 2016, 12:42 am »
In theory, lots of considerations:

- Is the vibration from self (motors, humming transformers, drivers); air borne; other sources; or from the support (shelf, rack, floor)
- As mentioned the resonant frequency(ies) and mass of the piece and support (shelf, rack, floor)
- Structural stiffness of all the parts of the piece, especially the panel where supports are point located
- Set supports isolate, hard supports couple
- As mass increases resonant frequency goes down and the energy required to resonate goes up

Generally I recommend soft supports for soft (wooden) floors (isolate everything) and hard supports for hard (concrete) floors (couple everything).  For instance spiked speakers on a wooden floor (over a crawl space which can act like a huge resonator) could be a huge problem, especially if your turntable is supported over the same crawl space.  OTOH spiking gear to a concrete slab can greatly increase mass and reduce resonances.

So there is no single or simply answer.  I've yet to see a vendor offer a variety of solutions or recommendations for their use.  So I remain a skeptic.


Nice summary.

DaveC113

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Re: Amazing anti-vibration feet
« Reply #35 on: 21 May 2016, 12:48 am »

Well, you're going to have a hard time convincing me that solid state electronics with no moving parts can produce any  audible vibration, with the possible exception of buzzing transformers. Buzzing transformers need to be replaced or individually isolated in order to avoid excitation of the chassis. For solid state equipment like optical disc players, again it's the drive system that needs to be replaced or isolated. Even so, it would have to be a poorly made or badly worn drive system if it were to produce noise that's above the background noise level in the room. I soft-mounted the toroids in my home-built kit amp just for good measure and I replaced the cooling fan on my sub-woofer amp with one that has a noise level around 25dB (if I remember correctly). I don't believe that the musical sound produced by solid state electronics is affected by vibration from external sources - especially digital electronics - but again I'm willing to stand corrected if anyone can show me the objective studies.

Conventional wisdom with respect to speaker baffles is to take the route that Armaegis alluded to: clamp a stiff, relatively light basket to a massive baffle such that they effectively become one. This is down to the tension that you can generate in the basket mounting fasteners, which is why I use machine screws into threaded inserts rather than wood screws into the baffle itself. Of course, you can generate more tension in a steel fastener than in a brass one of the same type, so I'd favour steel over brass for this application, although I doubt whether it makes any meaningful difference unless the size of the fastener is marginal. Here's the key concept: if the tension in the screws exceed the force trying to separate the basket from the baffle, the basket isn't going to move.

An alternative approach might be to soft-mount the drive to the baffle in order to minimise the direct transmission of vibration into the baffle and the rest of the cabinet. I haven't tried this, although I'd quite like to. However, there's a trade-off if the basket is allowed to move relative to the baffle (which soft-mounting would do). I think you'd aim to have the basket critically damped, but I don't know how you'd achieve that with the appropriate instrumentation. I suppose you could "shoot" the driver to measure the time delay with speaker measuring software and keep tweaking the mounting screws. Either way, the tension in the screws will probably be less than when solid mounted (depending on the type of mount used). The big problem is how do you seal the driver in the baffle? Inevitably you would end up using a thick elastomeric gasket partially compressed in an attempt to both seal and soft-mount.

This is an interesting discussion, but it should probably be in The Lab now.

Since it's OT all I'll say is these things, if examined closely, are often more complicated than we might think. For fasteners, young's modulus, the internal damping/resonant properties of the materials might also be factors along with tension... so often experimentation and empirical analysis are the most effective tools. If you try using brass driver fasteners I'd bet you'll hear a difference.


DaveC113

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Re: Amazing anti-vibration feet
« Reply #36 on: 21 May 2016, 12:49 am »

Generally I recommend soft supports for soft (wooden) floors (isolate everything) and hard supports for hard (concrete) floors (couple everything).

In practice, coupling speakers is never a good idea.

Martyn

Re: Amazing anti-vibration feet
« Reply #37 on: 21 May 2016, 12:54 am »
Since it's OT all I'll say is these things, if examined closely, are often more complicated than we might think. For fasteners, young's modulus, the internal damping/resonant properties of the materials might also be factors along with tension... so often experimentation and empirical analysis are the most effective tools. If you try using brass driver fasteners I'd bet you'll hear a difference.

Young's Modulus doesn't really matter as long as the tension in the screws exceeds...etc.etc. The rest is insignificant when compared to the vibration that's going on in the basket!


rustydoglim

Re: Amazing anti-vibration feet
« Reply #38 on: 22 May 2016, 07:54 pm »
I am glad to have started the discussion. We know amps very well, to the point we can shape any sound out of class-D and hybrid designs that could not be done several years ago. But vibration effect on electronics is something we don't know how to correlate. As I have said, we dare not sell something we don't know very well. It is a very nice feet anyway.

Doublej

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Re: Amazing anti-vibration feet
« Reply #39 on: 22 May 2016, 10:50 pm »
I am glad to have started the discussion. We know amps very well, to the point we can shape any sound out of class-D and hybrid designs that could not be done several years ago. But vibration effect on electronics is something we don't know how to correlate. As I have said, we dare not sell something we don't know very well. It is a very nice feet anyway.

Can you shape an amp to sound like a Carver?  :icon_lol: