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From: sjc@angband.UUCP (Steve Correll)
Newsgroups: net.audio
Subject: Re: question
Message-ID: <51@angband.UUCP>
Date: Tue, 2-Apr-85 14:24:31 EST
Article-I.D.: angband.51
Posted: Tue Apr  2 14:24:31 1985
Date-Received: Thu, 4-Apr-85 06:51:32 EST
References: <458@bonnie.UUCP>
Organization: S-1 Project, LLNL
Lines: 26

> 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?

Generally, no. A good audio amplifier strives to present an output (or
"source") impedance much lower than that of the speaker, so when you
connect two amplifier outputs together, each amp looks almost like a
short-circuit to the other.

Because high-powered hi-fi amps put out much higher voltage than
headphones require, many amps have a fairly large resistor between the
last amplifier stage and the headphone output. In such cases, you can
mix signals by connecting the headphone outputs together.  I suspect
that the Walkman lacks such a resistor, however, since its amplifier is
low-powered enough to begin with that it matches the characteristics of
headphones directly.

I don't understand why your mixer attenuates the signals too much. Does
the mixer have an output intended for headphones? A mixer output meant to
drive an amplifier probably won't produce enough power to drive headphones.
-- 
                                                           --Steve Correll
sjc@s1-b.ARPA, ...!decvax!decwrl!mordor!sjc, or ...!ucbvax!dual!mordor!sjc