Play external speakrs/turn off bult-in?

On a beige G3 with OS 9.1 - Running sound to my home stereo with the RCA cables from the RCA output jacks on my machine, but the built-in speaker plays also! (unlike plugging into the headphone jack, which turns it off)
In my Sound control panel, I ONLY see "built-in" as an input option, no "external", so "built in" stays selected as a default, (which I assume is why it still plays).
How come there is no external choice? Do I need to re-install the control panel or some other thing to add this choice? Or is it something the system senses somehow? any help appreciated!
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Take a 1/8" stereo patch cable and run it to the stereo out jack on the back of the machine. Thatll mute the internal speaker.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Apple OS

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.