Re: Capacitor Question

From	jimp@specsol.spam.sux.com
Newsgroups	sci.physics
Subject	Re: Capacitor Question
Date	2015-11-04 22:20 +0000
Organization	A noiseless patient Spider
Message-ID	<gtcqgc-mok.ln1@mail.specsol.com> (permalink)
References	(6 earlier) <pan.2015.11.04.07.08.15@localhost.localdomain> <oe6qgc-b2k.ln1@mail.specsol.com> <pan.2015.11.04.20.51.23@localhost.localdomain> <5o8qgc-29k.ln1@mail.specsol.com> <pan.2015.11.04.21.53.14@localhost.localdomain>

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Fabian Russell <root@localhost.localdomain> wrote:
> On Wed, 04 Nov 2015 21:08:53 +0000, jimp wrote:
> 
>> 
>> Right, which is why you spend close to $100 for one capacitor.
>>
> 
> That's not me.  That's benj the thrifty shopper.  He couldn't rival
> the average housewife in terms of financial prudence.
> 
> But maybe you help with this one.
> 
> I have an audio power amplifier built with discrete PNP (or is it NPN?)
> transistors. (Yes, they still make them in droves.)
> 
> The design uses two transistors in a "mirror image" configuration with
> one to handle the positive swings and the other to handle the negative
> swings (there is a name for this config but I can't recall what it is).
> There are some extra parts to cancel the bias currents and other things
> but the design is nothing more than that.
> 
> It performs very well with no distortion whatsoever.
> 
> Now I use this amp to power my headphones, although it can kick out
> a lot more power if needed.
>  
> I need music to help me with my workouts on my exercise machines,
> thus I have the amp right next to my machine in the basement.
> The headphones are attached to the amp with about 10 feet of
> audio cable.
> 
> I have another exercise machine on the first floor.  Rather than
> carry the amp up from basement to first floor and back again, I
> decided to run about 50 feet of audio cable from the basement amp
> to the headphones on the first floor (the distance is not quite 50 feet
> but it always better to have a little more than less).
> 
> So everything is the same, except for an extra 40 feet of audio
> cable between amp and headphones (1K ohm input impedance).
> 
> However, when I switched on the power and output, a fuse on one
> rail of the power supply blew out after a few seconds -- and these
> are 2 amp fuses!
> 
> What is happening?
> 
> I could put an oscilloscope on the output and observe what happens
> but I don't want to blow another fuse -- and possibly mess up my
> circuit.
> 
> I strongly suspect that the extra cable length is somehow inducing
> oscillations at some supra-audio frequency and these oscillations
> are drawing a lot of current from the supply.
> 
> So how can I fix it?
> 
> How about a nice choke (inductor) on the output?
 
If it is oscillating it is likely that your amplifier does not like
inductive loads, i.e. all that cable, so adding an inductor will probably
just make it worse.

If it were me, I would shit can all that wire and buy a set of wireless
stereo headphones, which can be had for well under $50 these days.


-- 
Jim Pennino

Thread

Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-03 22:14 +0000
  Re: Capacitor Question gilber34 <fafa@invalid.com> - 2015-11-03 16:35 -0600
    Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-03 22:59 +0000
      Re: Capacitor Question gilber34 <fafa@invalid.com> - 2015-11-03 18:10 -0600
  Re: Capacitor Question jimp@specsol.spam.sux.com - 2015-11-03 22:47 +0000
    Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-03 23:07 +0000
      Re: Capacitor Question jimp@specsol.spam.sux.com - 2015-11-03 23:20 +0000
        Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-03 23:42 +0000
        Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-04 02:49 +0000
          Re: Capacitor Question gilber34 <fafa@invalid.com> - 2015-11-03 21:40 -0600
            Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-04 04:01 +0000
              Re: Capacitor Question jimp@specsol.spam.sux.com - 2015-11-04 06:03 +0000
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-04 07:07 +0000
                Re: Capacitor Question jimp@specsol.spam.sux.com - 2015-11-04 20:29 +0000
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-04 20:51 +0000
                Re: Capacitor Question jimp@specsol.spam.sux.com - 2015-11-04 21:08 +0000
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-04 21:53 +0000
                Re: Capacitor Question jimp@specsol.spam.sux.com - 2015-11-04 22:20 +0000
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-04 22:42 +0000
                Re: Capacitor Question jimp@specsol.spam.sux.com - 2015-11-04 23:07 +0000
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-05 00:28 +0000
                Re: Capacitor Question jimp@specsol.spam.sux.com - 2015-11-05 00:46 +0000
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-05 00:39 +0000
                Re: Capacitor Question jimp@specsol.spam.sux.com - 2015-11-05 00:58 +0000
                Re: Capacitor Question benj <none@gmail.com> - 2015-11-04 18:25 -0500
                Re: Capacitor Question benj <none@gmail.com> - 2015-11-04 18:37 -0500
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-05 00:09 +0000
                Re: Capacitor Question benj <nobody@gmail.com> - 2015-11-04 21:35 -0500
                Re: Capacitor Question gilber34 <fafa@invalid.com> - 2015-11-04 21:51 -0600
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-05 04:19 +0000
                Re: Capacitor Question gilber34 <fafa@invalid.com> - 2015-11-05 11:10 -0600
                Re: Capacitor Question "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-11-05 09:15 -0800
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-05 18:08 +0000
                Re: Capacitor Question jimp@specsol.spam.sux.com - 2015-11-05 19:26 +0000
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-05 19:44 +0000
                Re: Capacitor Question jimp@specsol.spam.sux.com - 2015-11-05 19:56 +0000
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-05 20:53 +0000
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-05 21:52 +0000
                Re: Capacitor Question benj <none@gmail.com> - 2015-11-04 18:41 -0500
                Re: Capacitor Question gilber34 <fafa@invalid.com> - 2015-11-04 21:54 -0600
          Re: Capacitor Question benj <nobody@gmail.com> - 2015-11-04 02:17 -0500
            Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-04 07:30 +0000
              Re: Capacitor Question gilber34 <fafa@invalid.com> - 2015-11-04 07:48 -0600
              Re: Capacitor Question benj <nobody@gmail.com> - 2015-11-04 14:04 -0500
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-04 19:28 +0000
                Re: Capacitor Question benj <none@gmail.com> - 2015-11-04 18:49 -0500
                Re: Capacitor Question gilber34 <fafa@invalid.com> - 2015-11-04 20:41 -0600
                Re: Capacitor Question Fabian Russell <root@localhost.localdomain> - 2015-11-05 03:16 +0000
                Re: Capacitor Question gilber34 <fafa@invalid.com> - 2015-11-04 21:58 -0600
          Re: Capacitor Question "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-11-04 12:14 -0800
            Re: Capacitor Question benj <none@gmail.com> - 2015-11-04 18:44 -0500
              Re: Capacitor Question gilber34 <fafa@invalid.com> - 2015-11-04 20:41 -0600
  Re: Capacitor Question gyansorova@gmail.com - 2015-11-05 16:34 -0800

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