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In Reply to: Sorry, no bangs on reversing 'lytic cap to DC. (long) posted by cheap-Jack on February 26, 2007 at 12:44:05:
This post left me scrathing my head.
I've used tantalum caps for years as bypasses for rails and coupling caps for RF amps.If there is one thing I've learned by nasty experience it is that tantalums have ZERO tolerance of reverse biasing and ZERO tolerance of overvoltage.
I can only assume that source impedance of the battery was high enough to prevent a destructive amount of current to flow. Reverse biased tantalums or parallel reverse connected tantalums have absolutely no place in any audio gear you want to last more than 1/2 a second.
Don't do it !!!
Cheers,
Ian
Follow Ups:
Hi.The test I carried out last about 5 minutes before I restored back to its correct polarity to the battery supply. The rest was history.
Why don't you ask John Curl the condiition of his low frequency harmonic distortion measurement on ying-yang paralleling two tantalum caps in his paper: "Omitted factors in audio circuit design", presented to the Audio Engineering Society decades back. John kindly faxed me a full copy only recently on my request.
It is his paper gave me the idea of experimenting such reversed
polarity parallelling tantalum caps for coupling in voltage gain stages. I am as skeptical like you guys. But I don't hearsay by the textbooks. I want to see how to make use of such distortion cancellation feature without bang-bang.Let me reiterate again the statemnet he made in his paper since you missed my posts last month on this same topic.
"One consequence of the subsonic information is the distortion caused by electrolytic caps when coupling between stages with zero DC potential across the terminals. Back-to-back coupling or nonpolar
tantalums will reduce this distortion.One EFFECTIVE compromise is to place two tantalum caps side-by-side in REVERSED phase. This doubles the capacitances while effecting a first order cancellation of the distortion in the caps."
What "absolutely no place in any audio gears"? If I were a "whoose", many here were hearsay ostriches digging their heads in the sand.
c-J
This is very different than what you are doing.Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hi.That's why I am yet to find out from John Curl how exactly he arranged his measurement decades back.
Of course, it will be different from what I am experimenting. So what would you suggest me to do?
Don't tell me to replace the original 'ltytic caps with a buiky film caps again as no more space is avaiable on the PCB for any buiky stuffs.
c-J
Could you direct me to John Curl's paper?Even though I have not read his paper I'm sure he did not intend to have people hook up caps with the voltage backwards.
Thanks, Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hi.Read up my post above to you. Also email me yr fax no so I can fax over his paper.
Thanks but I don't have a fax. Can you scan it and email it?Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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