Mono Amp for strange purpose needed

[electro noob]

So I am in need of a cheap, mono amp and quality isn't really important other than it shouldn't be a distorted, garbled mess. I have a speaker that was blown in a self powered, studio monitor. I replaced it and now have this speaker sitting here and actually have a use for it. I have repaired the speaker well enough to be used again for my purposes and wanted to make a cymascope of sorts. The problem is that the amp that I had for the speaker is still sitting in the studio monitor where it's supposed to be (and will be staying). So I need a way to power this 8" woofer (it's from a Mackie HR824 and I don't know if it's a 4ohm or 8 ohm speaker).

I plan on plugging it into my computer and running a wave oscillator program to send sine, triangle, and square waves through the speaker, so that is why quality isn't all that important. It would be nice if the sine wave actually sounded more or less like a sine wave, but that it is the most beautiful, pure sound wave ever heard doesn't matter one bit.

So, cheap, radio shack based parts... got any links for an amp schematic that will do the job?

Thanks!

[sregor]

Many choices. Don't know what your radio shack has, but most can be found online. Most expensive part is usually the power supply, unless you have something lined up. Chip amps I would consider would be tda2003 or tda7240. The data sheets have schematics. Google should turn up more schematics. I would probably go to a few Goodwill or Salvation Army stores and by a cheap amp or receiver for a few bucks. YMMV. Happy Hunting.

[BinaryMike]

The LM1875 is cheap, available, and easy to work with. Its datasheet has everything you need to be successful.

[uzernaam]

Cymascope? WOW

I have listened to a talk radio program on Laura Lee radio where they talked about cymascopes and the Egyptian tombs.

Also read about them, and how it is probable that aliens construct their UFOs using these techniques in Zero-G

David Icke has a lot to say about vibration and structure...

All in all, a fascinating avenue of study. Best of luck to you!

[AndrewT]

Originally Posted by electro noob

. So I need a way to power this 8" woofer (it's from a Mackie HR824 and I don't know if it's a 4ohm or 8 ohm speaker)

measure the Voice Coil resistance.
If it's around 3r0 (3ohms) then it's a 4ohm speaker.
If it's around 6r0 then it's an 8ohm speaker.

Check your DMM on resistance measurement with the two probes shorted to each other.
DMM rarely read 0r0. Often they indicate 0r1 to 0r5 with the probes shorted. Subtract the "shorted resistance" from any low resistance measurements you take.

[mikje]

MCM electronics has a few simple ones. You'd need a power supply.
Kemo Electronic Products at MCM Electronics
Mike

[electro noob]

There are some doable kits there, though I think I jumped the gun a bit. For now I'm going to make the actual scope using a known good amplifier, then once I know everything works I'll break into one of these and complete the rig. Thanks for the info all!