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From: wanttaja@ssc-vax.UUCP (Ronald J Wanttaja)
Newsgroups: net.micro.cbm
Subject: Re: sound for monitor (direct speaker hookup)
Message-ID: <713@ssc-vax.UUCP>
Date: Tue, 7-May-85 13:32:44 EDT
Article-I.D.: ssc-vax.713
Posted: Tue May  7 13:32:44 1985
Date-Received: Wed, 8-May-85 05:42:38 EDT
References: <1134@sjuvax.UUCP>
Distribution: net
Organization: Boeing Aerospace Co., Seattle, WA
Lines: 25

> On the cheaper sided (for those who want sound but not excellent quality
>  I suggest just hooking the output to a regular 8 ohm speaker. If you
> don't have the appropriate plugs, Radio Shack sells these very cheap.
> like I said the sound quality is about as good as a TV speaker but the
> only difference is that you cannot adjust the volume. Those who are
> experienced at fiddling with electronics could probably fix this.
> 

Hmmmph.  I used to do that with 555 timer ics.  Worked fine for about 30
sec, then BLOOOOIE.  It may work on the '64, but I would want to put a
little isolation in to protect the computer, as I suspect the output
impedance of the computer audio is higher than eight ohms.  Either:
1.  Use a 1000 ohm/8 ohm audio output transformer (available from Rat Shack
for about $1.50).  1000 ohm side to audio output and ground, 8 ohm side to
the speaker leads.  You could even wire a 10K pot into the audio side for a
volume control.
2.  Put a 100 microfarad capacitor in series with the speaker, to stop the
DC and let the audio signal through.  This is how I got my 555s to last
longer :-).

The whole thing also depends on whether the '64 has enough audio output to
drive a speaker without amplification.  Try an earphone :-).

				    Ron Wanttaja
				    (ssc-vax!wanttaja)