dampening tube sockets with silicone gasket.

[SoulFetish]

I had been putting off replacing the tube sockets in my amp, because the sockets I'm retrofitting my amp with use a smaller diameter mounting hole and would have looked like garbage leaving the hole the way it is. There is no good way to try and shrink existing holes already drilled in a chassis and make it look great. covering them over always looks lazy to me. Anyway, I decided to use the opportunity to experiment with an Idea I had to try and dampen chassis and tube microphonics. Ultimately, the quickest way for me to move forward with the idea involved drilling out flat washers to the hole diameter I needed for my belton 9-pins. The thought (and actual work) of drilling out flat washers accurately, and drilling into my amplifier with everything still mounted blows so bad that I put it off for over two months. I'm not going go into how i set up drilling the flat washers and masking out my entire amp, unless someone wants to know, because it's a thankless d*ck punch of a job to do right and make it look good. But, I did want to share how I created dampening rings to take advantage of isolating the tube sockets from the chassis. At first I was trying to come up with some way to use RTV, but it would have been extremely difficult to control trying to free-hand something right from the tube. So, then I began thinking about possibly creating some sort of mold, but It would have been time consuming, and robably costly. Then it hit me... I can use a silicone baking sheet as a base material. It met all the criteria I needed for this experiment. This is how I'm going about it:




Thant's the progress as of tonight, and I'll use an xacto to trim the silicone flush with each ring and remove the rest.

[tedmich]

nice project, I seem to remember a tube amp design book with lots of vibration isolation of the tube boards using neat flying trapeze mounts and o-rings, perhaps Morgan Jones?

The Nylon lock nuts aren't a bad idea but they don't function unless the threads engage the nylon insert up top in the final assembly. Nuts with captive star washers at the base often work better, with a lower profile, and also handle heat better IME.

[SoulFetish]

nice project, I seem to remember a tube amp design book with lots of vibration isolation of the tube boards using neat flying trapeze mounts and o-rings, perhaps Morgan Jones?

The Nylon lock nuts aren't a bad idea but they don't function unless the threads engage the nylon insert up top in the final assembly. Nuts with captive star washers at the base often work better, with a lower profile, and also handle heat better IME.

Yeah, those M3 screws are too short. They were speced for the older setup, I’m just using them for mock-ups. The Morgan Jones book on actual tube amp construction is hands down, the best one on the subject IMO. His chapter on “metal work for Poets” (I think it’s called) is fantastic. He provides great examples of hand tools which I’ve found to be invaluable. One of the best tools I ever bought was a countersink/deburring hand tool set. But, I suppose I feel that way about every good tool I buy

[bob p]

My hat is off to you for trying to tackle two problems at once -- resizing over-sized holes and coming up with a suspension damping solution for the microphonics problem. With the way that tubes are being made today fabricators should be paying more attention to damping solutions. I for one, would like to see those detailed pics you were reluctant to post.

I have had a similar project in mind, but like you I kept putting it off. One of the things that gave me reservations about using foam rubber pads ( in a Fender type amp where the tubes are hanging from the chassis) is fire resistance. With the inverted tube designs the sockets and chassis can get pretty hot. Putting your damping material right up against the heat source always gave me pause. I was more inclined to think about cutting out a large rectangular hole to accommodate an array of tubes with hard mounts on a separate sub-chassis, and subjecting that sub-chassis to shock mounting, rather than shock mounting every individual tube. Doing it that way I could effectively isolate the heat source from the potentially flammable materials. I never got past the ideation stage. I don't think it'd be a big deal with tubes that were mounted upright like a Marshall design. I'm sure there are some high temp tolerant solutions out there. Would you happen to know the fire resistance rating on the silicone you're using?

I don't mean to offend, but since we had that recent threat that fussed about "comprised and comprises" with square waves and sine waves, I'll throw this out for consideration: dampening means to wet with water. Damping is the term that we're looking for here. The words are very commonly interchanged, like affect and effect.

BTW, nice bevels on those large holes. I like that kind of attention to detail in a fabrication project. Did you cut those larger holes in the chassis yourself?

[olddawg]

Why not simply just use small silicon O-rings on the screws and suspend the sockets like a Reverb tank? You could also use 2 small rectangles of metal stock drilled with 2 holes and use the original mounting holes. If mounted from the bottom it would look clean and seems much easier.

[SoulFetish]

My hat is off to you for trying to tackle two problems at once -- resizing over-sized holes and coming up with a suspension damping solution for the microphonics problem. With the way that tubes are being made today fabricators should be paying more attention to damping solutions. I for one, would like to see those detailed pics you were reluctant to post.

I have had a similar project in mind, but like you I kept putting it off. One of the things that gave me reservations about using foam rubber pads ( in a Fender type amp where the tubes are hanging from the chassis) is fire resistance. With the inverted tube designs the sockets and chassis can get pretty hot. Putting your damping material right up against the heat source always gave me pause. I was more inclined to think about cutting out a large rectangular hole to accommodate an array of tubes with hard mounts on a separate sub-chassis, and subjecting that sub-chassis to shock mounting, rather than shock mounting every individual tube. Doing it that way I could effectively isolate the heat source from the potentially flammable materials. I never got past the ideation stage. I don't think it'd be a big deal with tubes that were mounted upright like a Marshall design. I'm sure there are some high temp tolerant solutions out there. Would you happen to know the fire resistance rating on the silicone you're using?

I don't mean to offend, but since we had that recent threat that fussed about "comprised and comprises" with square waves and sine waves, I'll throw this out for consideration: dampening means to wet with water. Damping is the term that we're looking for here. The words are very commonly interchanged, like affect and effect.

BTW, nice bevels on those large holes. I like that kind of attention to detail in a fabrication project. Did you cut those larger holes in the chassis yourself?

Ha! You’re right. I did mean damping. Thanks for catching that. (It was late).

By the way, I don’t get offended when people catch a mistake and point out the error to me. What would offend me is someone not having enough respect for me to think I’d rather be stupid than embarrassed.
I’ll see what I can find out about the materials fire specs.

[trobbins]

Nice use of a common silicone mat product for a left-field application. It is difficult to make it all look neat and tidy. I'd suggest inserting a small diameter rubber o-ring under the nyloc (it won't be seen), and possibly sizing out the bolt hole and beveling the hole for the o-ring a titch - that should help isolate the bolt from the chassis. I've also found that silicone insulated wire (especially the small diameter gauge stuff) makes for equally compliant wiring - I've just done that for a vintage amp with 2x 6J7.

The final compliance and acceleration frequency attenuation provided by the weight of the tube/socket and the silicone sheet would be interesting to determine.

Ciao, Tim

https://www.dalmura.com.au/static/Mi...n%20valves.pdf

[bob p]

I'm thinking somebody has to make silicone shoulder washers. Those would be just the ticket for centering a screw in a hole while isolating it. I wonder if McMaster might carry something like that in Viton or silicone.

[trobbins]

Baking tray and two sizes of hole punch

[g1]

By the way, I don’t get offended when people catch a mistake and point out the error to me. What would offend me is someone not having enough respect for me to think I’d rather be stupid than embarrassed.

Then I'm duty bound to point out your error of calling ignorance stupidity.

[Enzo]

Illliterite Dummass!!!

I'm thinking somebody has to make silicone shoulder washers

Grommets. If for some reason you just had to not have the ring on both sides, carefully shave off half the grommet with a fresh Xacto blade.

[nsubulysses]

https://www.mcmaster.com/#push-in-grommets/=1a0xzhn

[nosaj]

I'm thinking somebody has to make silicone shoulder washers. Those would be just the ticket for centering a screw in a hole while isolating it. I wonder if McMaster might carry something like that in Viton or silicone.

Rhodes piano screws have a rubber grommet like your suggesting.

nosaj

[bob p]

Rhodes piano screws

There we go -- Fender shows us that they're all a bunch of Illiterate Dumbasses again. lol.

I'm happy to say that I haven't been near a Rhodes with it's cover off since the 1970s. I love the way they sound, there is nothing like them, but I remember fussy keyboard guys complaining about them not tolerating transport all that well. They were always tinkering with their actions after moving them.

Back to the isolation topic -- Of course there's more than one way to skin a cat. There's the right way and there's the kludge way. The proper device for the suggested task is a shoulder washer. It's what they're designed for. Grommets could be used but they're designed for a different purpose. Of course they could be made to work and I wouldn't doubt that a lot of people would misuse them to get the job done. But that's what separates designers and fabricators from fixers. Engineer types choose the best part for the task and later on technicians laugh at them and substitute something handy that will do the job.

[nosaj]

There we go -- Fender shows us that they're all a bunch of Illiterate Dumbasses again. lol.

I'm happy to say that I haven't been near a Rhodes with it's cover off since the 1970s. I love the way they sound, there is nothing like them, but I remember fussy keyboard guys complaining about them not tolerating transport all that well. They were always tinkering with their actions after moving them.

Back to the isolation topic -- Of course there's more than one way to skin a cat. There's the right way and there's the kludge way. The proper device for the suggested task is a shoulder washer. It's what they're designed for. Grommets could be used but they're designed for a different purpose. Of course they could be made to work and I wouldn't doubt that a lot of people would misuse them to get the job done. But that's what separates designers and fabricators from fixers. Engineer types choose the best part for the task and later on technicians laugh at them and substitute something handy that will do the job.

Guess I missed the joke.

nosaj