[Boatanchors] Fw: Re: Disc caps vs paper caps

[J. Forster]

IMO, Teflon caps, except in a few very specialized instrumentation
applications, are a total waste of money.

YMMV,

-John

==============


> Yes, ceramic capacitors are "microphonic" to differing degrees, but you
> can use them for RF or Audio bypass to ground with no ill effect. The best
> ones for Audio coupling between stages and output (in my opinion) are
> Teflon, if you can afford them, followed by Poly caps. There are probably
> others.
>
> 73 Kees K5BCQ
>
> ---------- Original Message ----------
> From: "J. Forster" <jfor at quikus.com>
> To: "Glen Zook" <gzook at yahoo.com>
> Cc: "Boatanchors at mailman.qth.net" <boatanchors at mailman.qth.net>, Mark
> Foltarz <foltarz at rocketmail.com>
> Subject: Re: [Boatanchors] Disc caps vs paper caps
> Date: Thu, 27 Sep 2012 07:58:42 -0700 (PDT)
>
>> There have been cases where using disc ceramic capacitors as the
>> coupling
>> capacitors in audio circuits has resulted in problems. &#65533;This is
>> usually
>> due to the fact that, under certain circumstances and with certain
>> capacitors, the capacitors can act as a transducer and the audio can
>> actually be heard from the capacitor!
>
> True. This is the piezoelectric effect I mentioned a couple oif days ago.
> Because they are reversible electro-mechanical transducers, they equally
> can avt as crude microphones, vicking up vibration auch as hum.
>
>> Many people can tell a slight difference between the use of disc ceramic
>> capacitors and the new "poly" types of capacitors when used as coupling
>> capacitors in audio stages. &#65533;
>
> Somehow, this is very suspect to me. Hum level, perhaps.
>
>> However, for practical communications use,
>> that difference is so slight as not to make any real difference in how
>> the signal "sounds". &#65533;For high fidelity audio applications, that
>> difference may, or may not, be noticed.
>
> IMO, only noticable with the "golden ear" crowd.
>
>> For bypass use, at both r.f. and audio frequencies, use of a disc
>> ceramic
>> capacitor works fine with the advantage of the disc ceramic capacitors
>> being that they are usually much less expensive than the other types of
>> capacitors.
>> &#65533;
>> Glen, K9STH
>
> As to use as vibrator snubbing capacitors, they are PROBABLY OK. I am not
> 100% certain. Some years ago, I set out to formally analyze a vibrator
> circuit. It is by no means anywhere near as simple as it looks. I suspect
> most of the design and application information has been gained by "cut and
> try".
>
> Generally, you want the capacitor to be big enough such that the capacitor
> will store an equal amount of energy as the inductor without overvoltaging
> the contacts.
>
> Best,
>
> -John
>
> =================
>
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