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Path: utzoo!watmath!wateng!aopal
From: aopal@wateng.UUCP (Ajoy Opal)
Newsgroups: net.audio
Subject: Re: question
Message-ID: <2247@wateng.UUCP>
Date: Fri, 5-Apr-85 10:19:46 EST
Article-I.D.: wateng.2247
Posted: Fri Apr  5 10:19:46 1985
Date-Received: Sat, 6-Apr-85 01:57:38 EST
References: <458@bonnie.UUCP>
Organization: U of Waterloo, Ontario
Lines: 42

> *** REPLACE THIS LINE WITH YOUR MESSAGE ***
> Here's the situation:
> I have two headphone signals (walkman + stereo keyboard) that I
> want to mix together to hear on one headphone.
> Can you 'Y' this stuff togther directly or do you need a mixer.
> I tried mixing both left channels and both right channels but
> the mixer attenuated the signals a lot.
> Is is possible to mix speaker level signals?
> Thanks
> John


Yes , it is possible, but if you attempt to mix signals at the output
directly one amplifier will basically be attempting to drive the output
of one amplifier against another...ie they would blow up, if it were'nt
for the short circuit protection provided by the makers of both
the stereo keyboard and walkman.

A crude way of mixing would be to use three resistors in a "Y" 
configuration, but this will result in some (maybe a lot ) attenuation
in the signal.


	   walman out  ---/\/\/\/\----|
			  20 ohms     |
				      |
				      ----   mixed output
				      |
				      |
				      |
	keyboard       ----/\/\/\/-----
      output	          20 ohms

the values are not exact. Larger values will attenuate the signal
but will provide better mixing. Larger relative vaules of the walkman
resistance shall decrease the amount of signal from the walkman, and
similarly for the keyboard output.

The best place to do the mixing is at some stage prior the output
section...and then feed the whole signal to a an output stage.

ray