Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Quickie => Topic started by: aragorn723 on August 23, 2014, 03:41:54 PM
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Tonight I was at home depot and got an idea for reducing microphonics on the quickie:
http://www.homedepot.com/p/SharkBite-3-4-in-Disconnect-Clip-U712A/100638161?keyword=sharkbite+3%2F4+disconnect+clip
It's for disconnecting sharkbite connections (quick-disconnects for copper pipe) and made of plastic. Think it might work? It looks like the commercial tube dampers (except for the bright orange, which could be fixed with a little paint!) and maybe with a rubber band around the inside it will fit snugly on the 3s4 tubes. Thanks,
Dave
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My experience has been that a lot of mass does a better job of keeping out microphony than soft dampers. That said, the quickie tubes don't get very warm at all, so I don't see any reason not to try them.
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what's the easiest way to add mass to the tubes?
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A lot can be done by coupling the chassis to something massive, like a big piece of stone.
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Can anyone share some pics of this ? I tried some rubber bands around the tubes (which doesn't look very nice but reduced some of the microphonics!) but there is still ringing if I tap on the tubes. Thanks,
Dave
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Why are you tapping on the tubes?
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I've had a problem with micro phonics with all the tubes I've tried. The original GE, NOS Mullards, French RT and a couple of $1 ones. I've used tubes for 25+ years (primarily 6DJ8 and 12AX7) and have never had this problem even when tapping on the tube. With my Q, if I turn the volume up all the way, they ring (without any music playing), even through my 85 db speakers. Of course, it I tap the tube, they ring loudly.
Is this a common problem with the 3s4 tube?
Lary
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Some microphonics in directly heated tunes isn't uncommon, and turning everything up all the way you to excite it is generally well beyond what listening conditions would present.
The same mechanism can come into play with a turntable that is too well coupled to the low frequency energy from speakers.
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All battery tubes have very fine filament wire, since it has to get hot enough to emit electrons but gets very little power - 3S4 gets about 2.4% of what a 2A3 gets, or 5.3% of what a 6DJ8 takes. And the filament is the active terminal - in the indirectly heated tubes there is a cathode surrounding the heater element, which is in the form of a tube and much much stiffer than a piece of fine wire.
On the plus side, the low power consumption makes battery operation possible.
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Why are you tapping on the tubes?
The idea was to confirm how effective the rubber bands are. They don't prevent ringing when tapping on the tubes or chassis, but prevents ringing when playing music, which is the idea of the quickie 8) Is there any reason to do anything more to prevent ringing ? For now this is a good temporary solution, just not very aesthetically pleasing.
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Thanks for the info PB and PJ.
Lary
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I got very lucky. I ordered some nos 3s4 tubes, make unspecified by the seller. They sent me some labeled: Canadian Westinghouse JAN CK 3S4. My guess is they are from 1962. They are much much less microphonic than the ones I had (they still are to some degree, but you have to be trying to get them to ring). So tubes are going to vary also. My guess is that the military spec manufacture is the cause in this case, but they were still under $5 apiece. I put some O-rings from the surplus store on them, but I think I leave them on because it kinda looks cool.
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I did this to mine:
http://bottlehead.com/smf/index.php?topic=3817.0 (http://bottlehead.com/smf/index.php?topic=3817.0)
Also found that the longer I leave it on the better it gets even without damping.
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I did something similar to my tubes originally, but used velcro inside copper couplings instead, and got loud popping noises. Why does aluminum tape work better?
Dave
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That is odd. I have a couple of Brent Jesse's "Copper Stoppers" which are nothing more than a heavy copper tube with Velcro in them. I use them on my 12A type tubes. Never had an issue with them.
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The only thing i can guess is maybe the copper shorted to the base of one of the tube sockets?