Troubleshooting help!

[KyleHarty 10+ year member]

This has me kinda baffled, I'm wondering what anyone's thoughts are.

I'm putting in a 2 channel Class AB (old US Amps) to run my sub, which is 1 dual 2 ohm. I just got the amp and got everything together to put it in, the sub is wired in series to a 4 ohm load and the amp's bridged.

The amp was turning on but no sound so I switched interconnects with one of the other amps and that didn't work (other amp played while the sub amp still didn't). I checked the impedence across the speaker terminals of the amp and it read 0.2 so I went to pull the sub out and check for a loose connection but when I disconnected the wires from the amp they read 3.3 ohms. Hooked it back up, back to 0.2. I hooked it up to each channel individually and it read 3.3 and played on both channels seperately but when I bridged it again it did the same thing, no sound and the multimeter read 0.2.

I'd rather not but I have to think something's wrong with the amp but is there any other reason it'd be doing this, and why would both channels work but it won't work bridged? I don't know much about the electrical inside the amp but it seems strange to me that it's not showing any load when bridged when there's one present. Is there a different circuitry inside the amp for bridging that could be shorted out or something?

If anyone has any thoughts or suggestions I'd appreciate it. I was thinking of wiring each coil directly to the amp and seeing if it'll run 2 ohm stereo if I can't get figure out what else is going on.

Thanks!

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[Imshirazy 10+ year member]

What's the specific amp

 

[KyleHarty 10+ year member]

'99 US Amps Xterminator 400X.

 

[KyleHarty 10+ year member]

I just pulled the sub out and hooked it up free-air with one voice coil wired to each channel (amp running 2 ohm stereo) and it seems to be working, at least it's playing. I guess I could just run it that way, means I'm gonna have run new wires through my box but it should work just as well assuming the amp doesn't act up in this configuration. I'll try it and hope it works although any insight into this would be great.