Re: [Phys-l] amplifier

["Carolan, Barry" <Barry.Carolan@dpcdsb.org>]

I'd keep an eye out at yard/garage sales in springtime.  It's amazing how many people will sell decent amplifiers (10 or 15 years old but still working great) for $1- $5, especially when so many people want to replace their old amps with "surround sound" amps. You will need to buy a mini-plug to RCA cable at radioshack or a dollar store to connect your ipod.  The back of a decent amp will have plugs that you can quickly switch the speakers out of phase with each other.  

________________________________

From: phys-l-bounces@carnot.physics.buffalo.edu on behalf of Arlyn DeBruyckere
Sent: Wed 4/2/2008 8:33 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] amplifier



Amplified speakers for computers are rather inexpensive (I got some for
about $20). Cut the cord on the "last speaker" (the one without the
controls etc) and reconnect the wires backward. If you still want to
normally use these speakers I suppose you could put on some RCA male and
female connectors or other similar connectors and switch them as
required. Otherwise just keep the modified set for your experiments.

Anthony Lapinski wrote:
> I'm teaching about sound and want to reverse speaker wires (red/black) to
> show constructive/destructive interference of sound waves (music) with two
> speakers/microphones and an oscilloscope. In the past I used cassette
> tapes, an old boom box (volume turned up), and old speakers. I would
> reverse the (red/black) wire connection (via alligator clips) for one
> speaker while the music played. A bit cumbersome, but it worked.
>
> I now have some songs on the computer (iTunes) and wish to repeat the
> demo. However, the old stereo speakers (connected via the earphone jack on
> the computer) are not loud enough. The new computer speakers are very
> loud, because of the amplifier built in, but I don't want to strip the
> wires on them.
>
> So I need an "inexpensive" amplifier to boost the loudness from the
> computer (1/8 "earphone jack) to my old speakers. Does anyone know where I
> could purchase such an item? I assume Radio Shack might have some stuff.
>
> Any better ways to do this demo?
>
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