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In Reply to: RE: RC Filter Progress To Date posted by Maxamillion on May 08, 2010 at 09:19:11
I ran across something called GelWax (made by Yaley) today in a crafts store, and it might just be perfect for potting the RC filters. It is actually mineral oil which is gelled with the addition of a polymer - the grade I bought has the consistency and resilience of firm gelatin ( but is stronger), yet it melts easily on a stovetop and can be poured into a mold. I can press my finger about 1" deep into it without it breaking apart, and when I release the pressure it springs back to its original form; it is also non-conductive and clear. Apparently it is used to make candles containing inclusions like glitter, etc. I'm thinking it might be perfect for this application as it will absorb vibrations, is non-conductive and can be removed for later tweaking (as opposed to epoxy!).Once I give it a try I'll share the results.
Edits: 05/08/10 05/08/10 05/08/10 05/09/10Follow Ups:
you try getting it in 1/2" pvc without burning yourself :) Seems like it would be easy but I never pulled it off.
Anyhow, that produced some great cables and now it makes more sense as to why.
THough long term the gelwax always seemed to change colors or absorb them or leach them from other things. So I would be worried about the longterm effects on the materials it is around.
FWIW, I havent used it in say 6 years.
Thanks for the info. I gave up on the GelWax idea for various reasons, probably the biggest was that the melting point of the GelWax is higher than the melting point of the ABS containers I was going to pour it into! It is also a bit too springy to absorb vibrations optimally - I went with Mortite pressed onto the caps and resistor instead.
First, try it without a vibe damping compound. I suggest this for a reason!
Mineral oil has its uses, but while it is non-conductive, it does convert electrical energy to heat energy. This is not the application I'd use it with at all, though who knows what might work....
What you should try, if you can still find it, is Microsorb. If you can't get that anymore, then try blu-tak or cotton balls. The latter are very good to use between between the components and the TI and also between the TI and box if you need it.
You will want to connect the TI into a roll. Ask Al how you should do this. Make sure that you fit the TI so that it doesn't short out your components (Rs and Cs).
A la CDC, I tried different grounding schemes, as I told you before. None, grounded to outlet by separate wire, and various AWGs of wire. As CDC said, the 12 or 14 AWG grounding to the outlet by separate wire DOES work best in my system too.
As per Al, silver mica caps do work best in my system for speaker cable filters. I also use a 3 or 4 R-C array here.
Thanks for the tips. Mineral/paraffin oil and waxes are used in capacitors all the time, where they can encounter much more electrical energy than the GelWax will here, so I'm not too worried about that, in fact I have PIO caps in my tube preamp getting way more voltage. Waxes are used all the time for electronics potting - the guitar guys like a 80/20 mix of paraffin and beeswax for potting pickups, and I was actually looking for paraffin wax when I stumbled upon the GelWax, which has a higher melting and ignition point than paraffin. As for converting that energy to heat - great! That's exactly what I want the resistor to do with the RF energy, so the more the better. The advantage I see with GelWax over paraffin/beeswax is its rubber-like consistency; it's very resilient and should make an excellent damping compound - next time you're in a crafts store check it out, it's pretty cool stuff.All that said, I wouldn't use it in an AC line filter - too much energy there.
Edits: 05/08/10 05/08/10 05/08/10
Maxamillion, bartc, Al a couple of us have sucessfully used linseed oil, but you need to wrap caps in silk or cotton and load it with oil, which eventually has a lovely gel like feel. I scalped all the caps in my cdp and pre prior to linseed oil damping, but never again prob, as its too time intensive - works nicely on opamps etc. Think I'll look into blu-tak or mortite and equivalents. Thanks for the posts.
You realize that it does eventually solidify sort of, not just gel. Linseed oil has been used for centuries in oil painting as a medium. That means that it does eventually dessicate or El Greco's work would be running off the canvas! Al has cautioned in the past about using organic materials that harden like that.Meantime, mineral oil is good for turning vibes into heat (or so I read and have found in using it) and does not dessicate quickly at all.
Frankly, I like Max's solution of mortite and then potting. Makes most sense to me.
I'm using either Microsorb or Al's cotton batting solutions for the damping and both work fine.
Edits: 05/19/10
Hope you see this bartc.
Didn't have (easy) access to Microsorb (I don't live in the US) so moved on and tried Blu-tak, Power Tack actually, but I suspect there's not a large difference - it met what I figured was required.
I used it to damp the backs of my speakers Beryllium drivers, the woofers aluminium spiders/frames, the crossover. You need to know that I used boat loads of the stuff - you also need to know that its been terrifically successfull.
I suspect it'll be like Mortite and will harden somewhat over time - I'll check in 5yrs!
Last was the crossover - late last night I compared a finished speaker ie all drivers HEAVILY damped, crossover HEAVILY damped, with the speaker that had the drivers damped only. The undamped crossover is the only difference.
Well I'm stunned at the difference I can hear - it ain't subtle. Worst case scenario I guess - crossover directly behind the woofer.
Yes points well made - but according to my test pot, it'll be a long time before its a problem - my cdp and pre will have departed! I rather like the prospect I read via DIY I think > oil based modelling clay. One poster used it in speakers in the 70s and it is still fine - seemingly it never hardens. Well suited to the backs of drivers apparently.
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