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I finished my Quickie today after receiving it Friday night. It was a very straightforward and enjoyable build, and the instructions were very clear. Thanks to Doc and the crew for another great kit. (I built and modified an original Foreplay many years ago, which has just started to give me problems.)
After confirming all the voltage measurements, I plugged it into my system to try it out. I like the way it sounds so far, but I am getting definite microphonics in both channels, one more than the other. If I tap the chassis plate, there is a clear ring coming from the speakers. I am inexperienced with this issue. Is this a product of the specific tubes, the type of tube, or something I could have done better during the build? What is the best procedure for diagnosing the cause and eliminating the problem? I would appreciate any input.
Peter Wendell
Follow Ups:
Google Herbie's Audio Lab, and check out some of his products. ie. Tube dampers, audio feet, and a wealth of other information regarding the stuff he recomends for your problem. They can really work.
Bernie.
With the prototype in the lab, I found setting it on a cloth deadened out any speaker inspired microphonics.
Thanks for the feedback. I haven't yet noticed any adverse effects on the music, which is really all that matters. I'm just glad to know it isn't something going on with my build.
My amp/speaker combo isn't that sensitive. I've got an old pair of Maggie Tympani IVs that I've gotten pretty attached to. Since they really need lots of power to shine, and I'm not rich, I can't really afford to use tube power amps so I'm using a Bryston power amp. I really liked the sound of my Foreplay in this system, and since it is currently Tango Uniform, I'm going to enjoy the Quickie for a while. I have a B&K transistor pre-amp as well, but it just doesn't do it for me any more.
Once I get a good feel for the how the Quickie is performing, I'll look into some mods. I'm looking forward to hearing about how other peoples' builds are turning out.
Peter Wendell
Yes, it's the tubes. The plastic chassis helps a bit. Using a less sensitive amp/speaker combo will help (see the white paper on the Bottlehead Community page, near the top).
On the prototype we tried copper tape around the tube, with a pigtail to ground even. Didn't help much. I suspect that suspending the tube socket so vibrations don't reach the tube will be more useful than damping the tube envelope - but I figure, this is a really creative and experimental community, the really good ideas will come out on the forum over the next year or two.
Meanwhile, don't tap the chassis plate! :^)
I may be wrong, but I think I heard that 3S4's have that reputation. If so, I'll follow the discussions about taming microphonics with interest.
I have microphonic tubes myself, such as 26's and the 45's that are in my main amp, and it doesn't bother me at all. But I have found that it does bother others.
Sorry, I know this post didn't help at all.
Triamp... Take a load off!
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