Isolation tweaks

[Doc B]

Hey, it's a DHT preamp. We knew that microphony was a potential issue when we came up with the design. So I am starting a thread in which we will offer some ideas for isolation and damping.

After a little experimentation this week I have an initial tweak - 1-1/4" 30D Sorbothane hemispheres under each of the four corners of the chassis. I got some off ebay for $17 for the set. Tried smaller and higher durometer ones. They were not as effective, this one seems the sweet spot for the weight of the preamp (~12.4 lbs) and the dimension of the wood base panels. They should help to keep the floor/rack/shelf borne vibration out of the preamp chassis and they look pretty good.

A second and really cheapass approach that is very effective is to put each corner of the wood base on a folded piece of the larger bubble size bubble wrap. We folded four 6" squares over twice to make four roughly 2x2, four layer pads. This looks very lotech/dumpster diver/trailer park if that is the look you are going for.

Based upon a little experimentation yesterday I am also looking into an interesting tube damper concept, that I will share more about once I have given it a try.

 

[Doc B]

My tube damper test subject showed up today. Seems to help.

 

[Doc B]

And here is a close up of the amount of compression of one of the 30D 1-1/4" Sorbothane hemispheres on the base. These really do work well to cut down vibration from the shelf.

 

[Grainger49]

Dan, your tube damper looks like the ring off of a giant condom.  What is it?

 

[dbishopbliss]

Dan, your tube damper looks like the ring off of a giant condom.  What is it?

That condom looks sort of small to me. 

 

[Doc B]

I need to do a little more research before I share the details.

 

[Grainger49]

David,

I guess it depends on which tube it is on.  On my 76 drivers it is small, on the 300B a good bit larger.  But I've never seen the roll/ring that thick.

 

[saildoctor]

I use round welded stainless and bronze rings all the time at work.  Maybe plasti-dipped they could work as dampers?  Or maybe as is?  Hmm.. i should try this out.

 

[ssssly]

I thought it looked like one of those rings you see at the carnival. Where you have to toss it over a bottle neck to win a stuffed animal.

Could start a new fad Doc. The bottlehead ring toss.

 

[Doc B]

I thought it looked like one of those rings you see at the carnival. Where you have to toss it over a bottle neck to win a stuffed animal.

Could start a new fad Doc. The bottlehead ring toss.

Ah shoot, I've been figured out! The other part of the package is an equipment rack made of giant stuffed animals.

 

[4krow]

Those kind of Sorbothane work good for me too, but a word of caution, they tend to be sticky, and most surfaces will show marks where they have sat. If sitting on top of a painted surface, it can really be bad, to the point that paint will have permanent marks. Sometimes, I use Scotch tape on the feet to provide a barrier. In spite of this problem, I still use Sorbothane feet for a lot of my components.

 

[Doc B]

Very good point. They are really sticky, to the point where some smaller ones would stay stuck to the shelf when I pulled the preamp up! Tape is a good idea. I was thinking maybe talcum powder or pledge furniture polish, but those probably wouldn't last very long.

 

[ssssly]

My trick for those sticky Sorbothane balls is a cutting board.

Whatever those super thin, white cutting boards are made out of is actually a pretty decent dampening material (at least the ones they sell at the Japanese dollar store). And if you have a hole saw around the size of the Sorbothane ball you can make a nice little coaster out of it to protect your stuff.

 

[RPMac]

What about the felt furniture pads on the bottom of the sorbothane pads?

 

[4krow]

Ya know, I actually did try that. Funny thing was, they wouldn't stay on. For some reason, the chemistry just wasn't there.

 

[saildoctor]

Has anyone tried washing their sorbothane feet first before using?  Is it possible the marks are being made by the mold release left after manufacturing?

 

[johnsonad]

My trick for those sticky Sorbothane balls is a cutting board.

Whatever those super thin, white cutting boards are made out of is actually a pretty decent dampening material (at least the ones they sell at the Japanese dollar store). And if you have a hole saw around the size of the Sorbothane ball you can make a nice little coaster out of it to protect your stuff.

Funny, I was about to throw one of those away!  Nothing like the 100 Yen store for all your daily needs.  I miss that store!  My wife hates the cheapy cutting board and now it will have a new use

 

[Grainger49]

Kerry,

After you wash sorbothane it becomes tacky after you dry it.  I have some HUGE AudioQuest sorbothane pucks that have been on squares of polypropylene plastic since a week after I bought them.  I also still have some shiny rings they left on my oak equipment cabinet from 15 years ago.

 

[4krow]

Yah, I had some of those big Audioquest feet too. I wonder what ever happened to them? Now they would cost a lot!

 

[ssssly]

My trick for those sticky Sorbothane balls is a cutting board.

Whatever those super thin, white cutting boards are made out of is actually a pretty decent dampening material (at least the ones they sell at the Japanese dollar store). And if you have a hole saw around the size of the Sorbothane ball you can make a nice little coaster out of it to protect your stuff.

Funny, I was about to throw one of those away!  Nothing like the 100 Yen store for all your daily needs.  I miss that store!  My wife hates the cheapy cutting board and now it will have a new use

Where in Japan are you located?

Has anyone tried washing their sorbothane feet first before using?  Is it possible the marks are being made by the mold release left after manufacturing?

I'm pretty sure sorbothane actually bonds to petrochemicals. Will literally strip paint, finishes, and permanently bond to plastic.