Test amp that can not be short circuited.

[CyrusZ]

Hey everyone,

 

I am working on building a little battery powered amp that I can use for testing juke box installation's. We primarily do stage work but we have been getting more and more installs at bars (low budget). What keeps happening is we walk in to some dive bar that has been wired wrong 10 times over, and we get asked to rezone speakers, or we are installing speakers where old ones may have been, lots of troubleshooting. I do not want to run fresh line, I know that is the right way to do it but try explaining a invoice to a bartender for something they say worked great yesterday and the more I look at any wiring at these bars the more I hate setting foot in these fire traps, I do have the owner sign a liability agreement first.

 

If I had a small 20w amp with multimeter test leads I could run around and probe and see where sound comes out or if any sound even comes out, but what happens when you connect to a crossed line... I got to thinking and want to make sure this makes sense to other people not just me.

 

If I make a little amp with a tone test generator and internally put a 4ohm resistor in series with one of the speaker leads then if you were to short the 2 lines the amp would still get a 4ohm load to push in to, if connected to a low ohm situation such as 6x 8ohm loads the amp would still see 5.33ohms. Does that sound correct?

 

Ideally the little amp would also have a mic and speaker with some other modes such as talk though, or listen (to test an amp) and a multimeter display to show ohm load of the connected speakers and some form of isolation incase someone connects to a 120v or to an amp while sending test tone. I have seen some line testers like this for XLR but nothing for speaker loads so if you know of one I would love to hear about it.

[Jivemaster]

If your test amp is 4 ohm safe then your idea of a 4 ohm limit resistor is fine for dead circuit testing.

 

Put the price up so that cheap jobs don't even bother you! Proper price proper jobs are ones that you can do well and profitably and safely.