Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!ucsd!pacbell.com!pacbell!osc!jgk
From: jgk@osc.COM (Joe Keane)
Newsgroups: sci.electronics
Subject: Re: Sony, are you listening?
Summary: Use an op-amp.
Message-ID: <3726@osc.COM>
Date: 29 Aug 90 22:03:43 GMT
References: <59154@bbn.BBN.COM> <1990Aug28.014604.10361@acheron.uucp>
Reply-To: jgk@osc.COM (Joe Keane)
Organization: Object Sciences Corp., Menlo Park, CA
Lines: 10

A line-level output is high impedance, and just isn't designed to put out lots
of power.  You shouldn't be drawing more than a milliwatt.  That's not to say
you can't, but if you push it you'll get some distortion.  A transformer may
shift the impedance, but it won't change the power situation.

What to do?  Many op-amps drive headphones just fine.  Not just any random
one, you want `high output' so check the specs for output power.  You probably
want some voltage scaling, so you need two resistors too.  If you want to get
fancy, one can be a pot, and you get a volume control.  Total parts cost could
be under a buck, assuming you hook into the TV's power supply.