Re: Capacitor Question

From	Fabian Russell <root@localhost.localdomain>
Newsgroups	sci.physics
Subject	Re: Capacitor Question
Date	2015-11-04 21:53 +0000
Organization	NewsGuy - Unlimited Usenet $23.95
Message-ID	<pan.2015.11.04.21.53.14@localhost.localdomain> (permalink)
References	(7 earlier) <smjogc-c7e.ln1@mail.specsol.com> <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>

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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?

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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