Bottlehead Forum
Bottlehead Kits => BeePre => Topic started by: Doc B. on February 14, 2013, 12:29:31 PM
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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.
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My tube damper test subject showed up today. Seems to help.
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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.
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Dan, your tube damper looks like the ring off of a giant condom. What is it?
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Dan, your tube damper looks like the ring off of a giant condom. What is it?
That condom looks sort of small to me. :-)
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I need to do a little more research before I share the details.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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What about the felt furniture pads on the bottom of the sorbothane pads?
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Ya know, I actually did try that. Funny thing was, they wouldn't stay on. For some reason, the chemistry just wasn't there.
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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?
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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 :)
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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.
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Yah, I had some of those big Audioquest feet too. I wonder what ever happened to them? Now they would cost a lot!
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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.
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I was in Yokosuka up until mid December of last year. I've since moved to San Diego.
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I'm pretty sure sorbothane actually bonds to petrochemicals. Will literally strip paint, finishes, and permanently bond to plastic.
..how about Sorbothane HEMISPHERE with Urethane Coating? part#0510124-30-10, 1.25"/30A rated load 2-4lbs.
(i'm thinking the 1.5"/30A @ rated load of 4-7lbs could be better in the long run # 0510134-30-10)
I haven't looked into pricing and min quantities, if high, we could do a group buy?
http://www.sorbothane.com/faq.php
http://www.sorbothane.com/blog/wp-content/uploads/2012/12/11-26-12-Sorbothane_SPG_11.2012_v4.pdf
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Note that the PDF says "underloading will result in poor isolation". The preamp weighs about 12.4 lbs (now 13.4 with my new tube dampers), well within the spec for four 1-1/4" hemispheres, but too light for the 1-1/2" ones.
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Whoever mentioned the washing before use may be onto something for the sticking/marking problem - from the sorbothane site on "adhesive recommendations":
"Sorbothane, Inc. uses silicone-based mold release agents for most components. The surface silicone must be removed prior to attempting a bond. Parts can be washed with mild detergents, rinsed with clean water and air-dried. Alternately, rubbing the surface lightly with alcohol or Methyl Ethyl Ketone (MEK) will clean off the silicone and "activate" the Sorbothane skin. Do not soak parts in water, alcohol, or MEK prior to assembly."
Note that this doesn't necessarily mean the cleaned surface wouldn't be sticky. It sounds like it might actually have some tack to it. However, it might also be easier to bond some kind of non-marring layer to it after cleaning.
It sounds like adding a non-stick layer might reduce damping a bit. If the 'furniture-side' surface were allowed to slide, say, wouldn't the dampers just slide, and not have any displacement relative to the supported piece of equipment (say, a BeePre), and thus not get into the damping act? So I'm thinking maybe a non-marring, flexible layer that still has 'traction' on the 'furniture-side' would be better.
Or maybe it's just the coffee talking...
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Depends on how much of the vibration dampening is from mechanical isolation and how much is from dissipation of the vibration as heat.
The loading recommendations are an attempt to find some equilibrium between the two that is more effective than either alone for the product.
Surface decoupling could be bad or good depending on the mass of the object and the level of the decoupling. In this case it shouldn't matter too much. Under the suggested load, regardless of how clean you get it, you shouldn't be changing the coupling of Sorbothane by any appreciable amount.
Now, placing another surface in between (such as the cutting board I suggested) could. Would be interesting to try out different combinations to see if they made a noticeable difference.
My guess, would be that to make a large enough difference, the second surface would have to drastically decouple. Such as placing the Sorbothane on a small glass disk and then placing the glass disc on another smooth surface.
Anyone conduct any similar experiments?
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I like these ideas. It is true that about anything that you do can have an(unwanted) effect. I have toyed with the idea that the cutting board could be used, allowing the Sorbothane to stick to it. Then, place the cutting board into a box(no edges touching) mostly filled with sand. I know that this may seem extreme for an amp, but there would be little doubt that mechanical transfer would be reduced. Put Sorbothane on the bottom of the box, and here we go again...
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I didn't have much luck trying to locate a wholesale price for the damper rings, so I am going to share the retail source and folks can buy them for themselves. Just remember that when someone tells you about "the ultimate 300B tube damper" everyone is using, that good old Doc is the one who dug it up:
http://www.belart.com/shop/183070005-vikemreg-vinyl-coated-lead-ring-p-183070005.html (http://www.belart.com/shop/183070005-vikemreg-vinyl-coated-lead-ring-p-183070005.html)
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Re: vinyl coated lead ring, "cushioned surface is chemically resistant", no specs on temp range. 300B's get hot, will 4 - 8 hour listening sessions/prolonged use cause them stick to the tube and or with vinyl pulling off of the ring being permanently bonded to the vacuum tube?
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I might not be the brightest bulb on the Xmas tree, but yeah, even I thought to check if they would melt before I recommended them. The rings don't even get that hot, easily cool enough to lift off the hot tube tube to demonstrate the effect on microphony. And I often run our system 10-12 hours at a time.
Am I vindicated? ;)
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- just to be clear, your link is to the 1/2lb ring, is that the recommended
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If you look at the published dimensions the 1/2 lb. ring is the one that will fit over the top of the EH 300B we supply with the kits. If you use other brands of shouldered tubes or a globe shaped tube - which I do not necessarily recommend because they can be more microphonic than the shouldered tubes - or you wish to try this on something other than a 300B you may wish to evaluate the published dimensions of the other ring sizes. I suspect the 1/2 lb ring would fit most shouldered and globe style 300Bs but I have not measured any but the EHs and TJ globes.
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Whenever I go to the hardware store, the clerks know just to let me be. What I am looking for they have never heard of, and what I am using it for they have never thought of. Such is the case here. But I still wonder if there might be a way to make your own. If it's anything like coffee, I am better to just pay the $3 and let someone else do it. This does seem to be a really good idea. Maybe I can use truck bedliner spray on tubes Heh heh
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Dan,
You are going to make me post a picture of my Lava Lamp. That was my Birthday present to me last year. The Eros was the year before. Quite a difference!
Does the same ring go around a 2A3?
Thanks,
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Here they are on Ken Rad 2A3s in the Stereomour built to demo our awesome new Bottlehead/Orca system. I have not listened to this setup. And I will say that I don't really notice a microphony issue with either 300Bs or 2A3s in amplifiers, with the occasional exception of globe style tubes. I also don't know if the increased dissipation of a 300B in an amp would create a potential heat issue for the vinyl or not. Remember that we are running the 300B very gently in the BeePre, only about 10W of plate dissipation.
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Does the same ring go around a 2A3?
I measured a few ST shape tubes. 1/2Lb i.d. ring fits my RCA and Sylvania 2A3's. Shug 2A3-Z could fit either the 1/2Lb or 1LB. JJ 2A3-40 would require the 1Lb i.d.
Only 300B's on hand which i plan to use are Sophia Princess, they can fit either 1/2Lb or 1Lb ring with possibly only one smaller contact point using the heavier 1Lb 2" i.d. vs two points of contact with the 1/2LB 1.7" i.d.
I don't know how or if the ring weight (2X) or surface area contact would affect the intended purpose? Compelled to ask, given i was wrong about upping the sorbothane hemisphere's size:\
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Didn't the Coneheads use rings too?
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I can't answer to what the effect will be if you change the weight of the ring, other than to say you may need to re-evaluate what sorbothane hemispheres you use since the overall weight of the preamp will change. Sometimes the data comes out in a more timely and useful fashion if more than one person does the experiment.
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Note that the PDF says "underloading will result in poor isolation". The preamp weighs about 12.4 lbs (now 13.4 with my new tube dampers), well within the spec for four 1-1/4" hemispheres, but too light for the 1-1/2" ones.
Rated load is 2-4Lbs (1.25"), and 4-7Lbs (1.5"), so 1.25" hemispheres should be good with either size ring.
Unless i read otherwise, i'll get the 1.25" hemi's and hold off on ordering rings 'till i hear the BP without them.
I'm thinking if the .5Lb ring is working for you then why possibly stress the tube with more weight? Conversely, the larger 1Lb ring/one contact point when fitted on the Sophia tube may trap less heat allowing the tube to maintain a more constant temp?? IDK???
Again this is all just thinking out loud, 300B's are expensive tubes for me to be tweaking with.
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Dan,
What differences do you hear between the EH and TJ tubes in the BeePre?
Jim
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Dan,
Nice find! When you do get to hear the stereomour with these rings, if there is any noticeable difference with the rings, could you let us know?
-- Jim
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@jdm - TJs sound a little better to me, however that one in the photo is old and worn out so it actually sounds worse. And I found them to be fairly microphonic in the preamp application.
@Jim R. - I hope that we will have the Orca setup going next week, but it might not be all together until we get back from Axpona. I will report if I hear a difference with the dampers on the Stereomour tubes.
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I ordered a pair of these a couple of weeks ago and only today received the shipping notice. It seems we depleted their stock :)
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I've had good results with Herbie's Audio Lab isolation and damping products, including Tenderfeet (the Tendersoft variety) under the Stereomour. Very affordable, and with a 90 day guaranty.
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FWIW looking at the specs the Tenderfeet seem pretty much like the Sorbothane hemispheres.
The tube dampers look to be considerably less massive than the lead rings, so it would be difficult to guess how they compare.
If Herbie wants to loan us some samples for comparison I would be happy to post my observations.
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The lead rings work great! They are inexpensive and I highly recommend them for the BreePre
Deb
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I'm laughing because just yesterday I made the observation "everything works better with lead in it". :)
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Ok, that does it, it just so happens that I bought a bunch of lead sheets. They are thin and small, just the thing to wrap around a tube. Here goes nothin'
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Lead is not a very good damping material for vacuum tubes. Lead has a definite and annoying characteristic twang in the upper mids and the more massive the lead is, the more it will impose its sonic character into the music, and lacks the contra-vibrational energies to combat a lot of the very high-frequency, acute vibration that causes a lot of glare in the music.
Vinyl coating the lead will undoubtedly diminish the lead's detrimental character, but vinyl itself is not a great damping material either. With a vinyl-coated lead ring, you'll have basically a mass-loading weight, which does not provide a whole solution to micro-vibration damping and microphonics. 300B tubes usually don't get particularly hot, and vinyl might hold up for the short term, but surely will not hold up to hotter-running bottle-shaped tubes and other hot-running power or rectifier tubes.
Herbie's Audio Lab's vacuum tube dampers do not rely on mass. With their vibration-absorbing and dissipating C-rings, less mass is most beneficial for rapid vibratational energy dissipation and sonic neutrality. Mildly tempered titanium is ideal for this.
In regard to a previous post, Tenderfoot isolation feet are not similar to Sorbothane, nitrile rubbers, Isopods, etc. These materials, especially Sorbothane, provide a sonic trade-off--you get some vibration absorption but at the same time some loss of linearity due to resonance and reverberation being introduced into the vibrational environment. These materials provide a mid-fi tweak at best, a system contaminant at worst.
Tenderfoot isolation feet are a silicone-based, proprietary material formulated specifically to deal with the vibrational environment affecting home audio, not just a general-purpose manufacturing supply material like Sorbothane.
To bring out more of the best inherent potential of your gear, including Bottlehead products, you want to employ accessories and tweaks that provide sonic improvements only, not trade-offs.
DocB: If you would like to audition any of Herbie's Audio Lab isolation products, I'll be happy to comply. Just shoot me an e-mail or message with your request.
Steve Herbelin
Herbie's Audio Lab
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Steve,
Many thanks for the info. There is a sea of tweeks and ideas out there, but no promises. I wasn't aware of the shortcomings of Sorbothane. Too bad, it's readily available and easy to use. As far as damping sheets do have some advice? I'm all ears.
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I just ordered a set of the tenderfeet and will let everyone know my impression when I gt them
Deb
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4krow: Herbie's Audio Lab has a variety of damping sheets that are effective as a decoupling/isolation interface for many audio applications. More info here: http://herbiesaudiolab.net/gb.htm#gasket (http://herbiesaudiolab.net/gb.htm#gasket)
To clarify an earlier post a bit, Sorbothane tends to cause a loss of linearity in the audible sonic music reproduction. Sometimes bloops and/or valleys in the bass, emphasis or attenuation in some of the higher frequencies. A "linear" sound reproduction would be faithful to the source material.
Steve
Herbie's Audio Lab
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Steve,
I have looked at your site, and I have also heard from many people about your tube dampeners. Given that the 3S4 tube is very microphonic, I opted to purchase the tube dampeners that you offer. If there is a tell tale tube out there, it must be the 3S4. This will be greatly appreciated if it works like it should. More to coma about that. In the meantime, I will remove the Sorbothane rig that is on each tube.
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I use Herbie's Ultrasonic SS Tube dampers for my Ultimate Quickie and think they do help with microphonics. One discrepancy though was that the rings were slightly too big and I had to bend them a bit to get them snug. It wasn't as easy as it sounds.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi576.photobucket.com%2Falbums%2Fss207%2Fcorndog642%2FBottlehead%2520Quickie%2FIMG_6781_zpsea11e3b9.jpg&hash=ee9559a73dae99b92fc83ee60c0b9eb8030be700)
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Hi, Rob. As indicated on our website, 7-pin miniature tubes like 3S4 use a size "7" damping instrument. In the pic, it looks like you've got a slightly larger UltraSonic SS-9 (appropriate for 9-pin miniature tubes) re-sized to fit the small 3S4 tube. I think maybe we sent you the wrong size. Looks like you've got a good fit though, and everything should work very well.
BTW, It's a lot easier to bend the titanium C-ring to a larger diameter than it is to bend it smaller.
Steve
Herbie's Audio Lab
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Re the sticky isolaters, try some of those coasters that you usually find in bars under them, that should take care of the marks on the furniture. Also how about sitting the whole unit on top of a small inner tube. If that works, a plinth could be made to surround the tube.
Bernie.
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Some personal observations on isolation with my BeePre. It has the 1.25" sorbathane half's under the base to start with and the small rings under the 300B's. Today I received the Bel Art lead weights that Dan recommended. Previously I had been using some of Herbies rings on the 300B's. With the BeeQuiet, I hear ringing through the speakers with each volume change. I used this as the mechanically induced microphany I was trying to control. This was by ear with my 100 dB sensitive speakers in a quiet room with no source playing.
First without anything on the tubes I get a moderate sustained ring through the speakers with each change on the volume. Next with the Herbies the ring and decay was reduced from having nothing at all. Next was with the lead weights and this significantly reduced the ring and decay, much more so than with the rings alone and to a very low level. Lastly I tried with both weight and ring and I heard no difference from with the weights alone.
I'll listen to some familiar recordings today and post if I hear any difference with play and if I can find the time, I'll measure the ring on my scope to give some hard numbers to what I'm hearing :)
Great find Dan and thank you for posting about them!
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- Re: sticky isolators. I've been testing the Urethane Coated Hemispheres fora little over a month now under my tube amp^, (using higher 1.25"/50A instead of 1.24"/30A, the amp weights more then a Bee).
So far the urthane coated hemi's have been great as far as not leaving sticky residue etc on surfaces. Can't comment on what they're supposed to do as my amp wasn't having any trouble prior, used it to emulate the heat aspect of the Bee as i've yet to build mine^.
I had difficulty finding a supplier for the Urethane Coated Hemi's. Let me know if anyone is interested in doing a group buy from Sorbothane Inc.?
Sorbothane HEMISPHERE with Urethane Coating part#0510124-30-10, 1.25"/30A rated load 2-4lbs.
http://www.sorbothane.com/blog/wp-content/uploads/2012/12/11-26-12-Sorbothane_SPG_11.2012_v4.pdf
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- johnsonad, thanks for posting your tube damper findings.
^my Bee build is on hold for chrome plating, i'm told spring is their busiest time of year.
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Hwy, thanks for the Sorbothane info. There are a lot of uses for this product(I walk on one everyday). One of these days, I will get the sorbo mallet. Also, did you notice that some of the hemispheres have felt on the bottom? hmmmm
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Thanks Aaron. I guess sometimes that physics degree I got a zillion years ago pays off. Maybe part of what is happening is the added mass of the lead ring helps the tube base make better contact with the silicone ring under it. So you have not only the new constrained layer damping effect of the lead and vinyl on top, but also the one created by the silicone ring sandwiched between the tube base and socket is made more effective. Neither material is super squishy, but they do have some damping effect.
There was a day when I could have written a multi-page solution of the sprung masses, with error analysis. But that was a loooong time ago. And now days I have PJ and PB to be my brain.
I do share Steve's concern that the vinyl on the ring might not hold up to a 300B running full zoot in an amp. I've had them on the much cooler running BeePre 300Bs now for several weeks, running about 8 or 9 hours a day with no ill effects. The rings don't get very hot, they lift right off the tube and the vinyl shows no deformation. But that's at 10W dissipation, whereas the Paramount 300Bs run at about 24W. And for that matter I don't see any real need to do this as I have not heard any microphony from Paramount 300Bs. So consider this a strong recommendation not to try the rings on Paramounts.
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I have no problems wit the rings and heat. I think the rings are a simple elegant isolation tweak that works incredibly well.
Even with my dogs running around in front of my system there is no issues with microphonics!
Deb
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The rings will straight melt to the tubes on the paramount. At least they did on mine.
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I'm sorry that you had to take one for the team but thank you for posting your experience .
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They didn't burst into flames or anything, but the covering definitely melted. Didn't permanently stick to the tube either, but again it did melt. I found a seller on amazon who had them for like $5 a piece. So not a huge monetary investment ruined either.
Probably just strip the cover off powder coat them, and wrap them in teflon.
They didn't make a huge difference anyway. I just think they look cool.
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A couple rolls of Teflon plumbers tape, might be enough to keep them from melting...John
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I realize that this doesn't exactly go in this thread, since I am talking about my Quickie, but I have tried the Herbies tube dampers. Since they wer mentioned previously in this thread, it seemed ok. Having said that, I have a short term impression about the results. With the 3S4 tubes, damping of any sort is beneficial as compared to nothing. As much as I enjoy these tubes, micro-phonics are in full swing and can even lead to a harshness of the treble, as well as a muddiness in the bass. Suffice it to say that tube dampers did as much as anything else I've tried, with an improvement in the treble harshness. I can now turn the little Q up higher w/o fear of ear pain/wincing. You know, waiting for that part in the song that is as edgey as a rusty razor. Less offensive, but quite welcome is the increased bass definition that I heard. Back to notes not thuds(not quite that dramatic but you get the point). So, at such a low price, these dampers are one of my no-brainers, or ,or, you can continue you Frankenstien experiments ERIC,,,,I won't judge.
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A couple rolls of Teflon plumbers tape, might be enough to keep them from melting...John
or you could apply a bead of http://www.americansealantsinc.com/asi-502-industrial-silicone-sealant-adhesive/ ? "withstands constant operating temperatures from -70 to +400 degrees F."
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I tried the Herbies Tender Feet. To me I notice no difference between them and the sorbathane feet. At least the Tender Feet will not destroy the finish on my furniture.
Debra
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Deb,
I'll second that! The Sorbothane has to be watched for it's wicked traits. I've ruined a couple of paint in the learning curve. I might try the Tenderfeet....we'll see.
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I've been tweaking all day. Had to re-tube the Transporter. The Beepre is so transparent I was hearing 1's and 0's.
The old preamps didn't resolve as much detail so I tubed the Transporter to give me more detail. I had to dial it back for the Beepre.
Just put 3 Mapleshade Isoblocks under the Beepre. $24 for 4. No marks on the shelf from Isoblocks.
That brought everything together! Beautiful, musical mid-range, great bass and flawless highs.
Now how long can I keep my hands off? I might need the Vikem rings....
Kevin
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Yeah, the damper rings may not be ideal on the Paramount.
I just happened to read this thread after returning from being away for the weekend. I read where sssly's damper rings melted onto his tubes.
I turned to look at my Paramounts, onto which I'd placed some of those same rings. Turns out I'd left them on all weekend long while I was gone.
Fortunately, it made it easy to lift the rings off (with some cloth insulation - they were warm!).
Turns out, they kind of melt and scorch or burn....otoh, they're easy to lift off when hot.
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Vibrapods with cork circles underneath to protect the shelves. Don't notice really much difference vs the stock feet. But can't hurt particularly since the BeePre shares the shelf sith the rumbly idler wheel tt.
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What size and hardness of sorbathane for use on the Paramounts?
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Sorbothane has different densities, as you already know. At the Sorbothane website there information regarding which density will accomidate the given weight.
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A quick update, I'm happy with the Tender Feet purchase. The other halves that Dan had recommended worked well but are less than 50% of their original height and mark up anything they are placed on as others have observed. The Tender Feet make as much of a difference and hold their shape without marking what they are placed on.
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EDIT ** - Asked and answered. I'm a dope. it is 2am, so I don't feel too badly. the other sizes were different weights. Here is the new link:
https://www.belart.com/bel-art-f18307-0005-round-0-5lb-lead-ring-flask-weight-with-vikem-vinyl-coating-for-125-500ml-flasks.html
So apparently since Doc released his secret regarding the .5lb tube damping rings, Bellart has widened their offerings to include different width flask sizes. Not being up on my standard lab grade equipment measurements, anyone have some guidance here? The link provided :
http://www.belart.com/shop/183070005-vikemreg-vinyl-coated-lead-ring-p-183070005.html
Is also no longer valid, but after 3+ years, not a surprise.
Thanks in advance!
Ewing