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Vibration Isolation

djkool

djkool

Guest
Nov 13, 2013
95
3
Grand Rapids, Michigan
#1
I'm curious if anyone does anything in particular to isolate the tubes in their amp heads from the vibration of the speaker cab..or if no one worries about this at all Does everyone stack their amp on their cab? Anyone use any cushioning, etc.? I've had several tube amps that developed distortion from speaker vibration at higher volumes and I expect that tube vibration shortens theirlife and may lead to making them go microphonic.

Anyone else concerned about this or have a particular solution?
 
#5
I made four, high density foam amp-feet isolators... ;) out of old X-box packing foam... Used self adhesive felt to make them look pretty and they sit under the feet of whatever amp I use, on the top cab... Seems to have reduced the vibration to the amp quite a lot :)

I too am a little worried about all that transferred vibration and surface mount components, tubes and SMPS/digital amps. Funny thing is I never thought twice about it in 20 years of SS amps like my GK400 RB, but I'm less confident with the class D's... Hope I'm just being paranoid.
 
#8
djkool said:
I'm curious if anyone does anything in particular to isolate the tubes in their amp heads from the vibration of the speaker cab..or if no one worries about this at all Does everyone stack their amp on their cab? Anyone use any cushioning, etc.? I've had several tube amps that developed distortion from speaker vibration at higher volumes and I expect that tube vibration shortens theirlife and may lead to making them go microphonic.

Anyone else concerned about this or have a particular solution?
Click to expand...

I commonly use an Auralex GRAMMA Pad for this exact purpose. They are well made, and really not very expensive ($40).

IMG_8822.jpg
 
#9
beans-on-toast said:
Interlocking floor mats cut to size. Inexpensive and does the job.

http://www.walmart.com/ip/Norsk-Sto...-Square-Feet-Multi-Color-4-Piece-Set/13253265
Click to expand...

This... the sorbothane and equivalent materials linked above are the pro-grade engineering solution but the cheap floor pads are a material good enough for a problem of this scope and easy to get.

If you want to get fancy check the deflection - goal should be about 10% reduction in thickness of the pad when loaded with the full weight of your rack + accessories [if anything goes on top of the rack] - cut and/or stack smaller pieces to achieve.
 
#11
Foz said:
This... the sorbothane and equivalent materials linked above are the pro-grade engineering solution but the cheap floor pads are a material good enough for a problem of this scope and easy to get.
Click to expand...

Sorbothane feet have been in use in lots of home stereo systems for a long time, quite effectively, too, and they are not very expensive (of course foam padding from Wal-Mart or Jo-Ann Fabric is much cheaper but I am willing to spend a few more $$, perhaps, for my rig (they cost around the same as a good set of bass strings and last far longer - decades).
 
#13
Sorbothane feet have been in use in lots of home stereo systems for a long time...
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Sorbothane will do more than that - it is used in vibration damping / isolation applications for building foundations, ship frames, urban railroad lines and the like :hyper: so I agree it would certainly last forever in an audiophile/MI application where a floor mat might need to be replaced every 5-10 years more or less.

The real trick though is getting the loading correct. If you get that wrong it doesn't matter how long it lasts - it just wrong for a long long time.
 
#16
I've been concerned about the relationship between my vibrations/mojo going through the cab and the many delicate tubes in my head. My favorite live rig for modern progressive metal is a Mesa PH 410 driven hard... that thing produces some heavy vibrations. I just use a folded up towel and place my amp on it. I keep it in the back of my rack case when I'm transporting which also protects my power tubes from my cables possibly bouncing around in there.
 
#18
djkool said:
Some great ideas! Thanks for responding. I guess I have quite a few options to explore.

I'm curious if the person who suggested a target of 10% deflection/compression is baseing this on any testing or development of a damage boundary using instrumentation.
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Neither/both/sorta... its a rule-of-thumb short-cut based on what properly designed systems look like under the static load.

If you are doing this sort of thing in a serious application you would never look at the problem this way. In that case you would need to get it all right the first time because changing dampening material after construction would be so difficult/expensive = have the spring parameters spec'd by an engineer and then run the design past the part manufacturer if possible [the Sorbothane guys will do this].

At any time during the design process, Sorbothane engineers are available to assist you in any way.
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[Invalid or Expired Link Removed]

But if you just knocking around with found parts on a small scale project - for a quick and dirty run at the problem - just get deflection to 10% with a reasonably soft spring and you know you have loaded the spring but are still at the soft end of an effective system and thus it'll do you some good over a broad frequency range of excitations. Once you have eyeballed it to 10% deflection its "suck it and see" - unless you want to measure - in which case glue a piezo to the load and measure away.

From the pdf design guide:
The most effective static deflection for Sorbothane with a shape factor between 0.3 and 1.0 is in the range of 10-20%.
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#19
You can get samples of rubber gym flooring tiles. They are approximately 2'x2'. They are usually fairly dense, soft rubber foam, and once you get over the old tire smell of them, they work well. Since you are getting samples only, the price is right.
 
#20
djkool said:
I'm curious if anyone does anything in particular to isolate the tubes in their amp heads from the vibration of the speaker cab..or if no one worries about this at all Does everyone stack their amp on their cab? Anyone use any cushioning, etc.? I've had several tube amps that developed distortion from speaker vibration at higher volumes and I expect that tube vibration shortens their life and may lead to making them go microphonic.

Anyone else concerned about this or have a particular solution?
Click to expand...

Invalid Link Removed have quite a few solutions. ;)
 

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