Stereo head unit and multi-meter question?
06-15-2004, 11:08 PM
#1
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Stereo head unit and multi-meter question?
If I attatch a DMM to the sub-out RCA plugs, and my receiver has 4 volt pre and sub outs, I should get a 4 volt reading with the engine and radio on, right?? I got ZERO, which is why (I assume) my sub isn't putting out any sound.
Head unit shot? Or is it a fuse inside the unit that controls the pre outs?? It's an Alpine 7894, BTW.
Thanks.
Head unit shot? Or is it a fuse inside the unit that controls the pre outs?? It's an Alpine 7894, BTW.
Thanks.
06-16-2004, 12:37 AM
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With pink noise or a test tone below the internal sub crossover frequency, at max volume, you should get a detectable voltage - make sure you're checking in AC as well as DC, audio signal doesn't "look" like DC. Easiest way would be to plug the HU into a home audio amp/recievers and try powering some speakers as a test.
Sam
Sam
06-16-2004, 06:31 AM
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You have to turn the sub on, then usually theres a sub volume, my 9815 you push the rotary volume and it gives you sub control.
And it will only put out 4 volts at max volume. Thats one of the little things about some Alpine decks that some of the "OMG MUST HAVE 4 15 INCH SUBS WITH 20KWATTS OF AMPS" morons **** and moan about.
And it will only put out 4 volts at max volume. Thats one of the little things about some Alpine decks that some of the "OMG MUST HAVE 4 15 INCH SUBS WITH 20KWATTS OF AMPS" morons **** and moan about.
06-16-2004, 07:30 AM
#5
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The sub is on...says it right on the display. But I'm getting no sound out of it. I even changed the RCA cables, thinking there was a problem with them. Nope. Still no sound. It worked fine with the Blau, going off the front speaker wires for signal.
Has to be the radio, right? I have the sub volume all the way up, half way up, still no sound...
Has to be the radio, right? I have the sub volume all the way up, half way up, still no sound...
06-16-2004, 11:56 PM
#6
Audio signal is A/C, not a DC signal.
To test audio voltage, set volt/ohm meter to Volts A/C. The red lead of the meter needs to make contact to the inner center electrode of the rca, the black lead needs to touch the outer shield of the RCA, however touching it to the chassis of the radio should work just fine(the outer shielding of the RCA on most aftermarket decks rests at chassis ground).
The 4 volt rms rating is tested using test tones, usually 1khz, and an osciloscope to detect clipping. Using that same test tone with the sub x-over frequency turned off, you should be able to read a voltage of close to 6volts or so at full volume. If you try reading the voltage playing music, depending on your meter you may not get a reading, as the voltage will fluctuate quickly with the beat of the music. If you have a nice enough meter, you may get readings upwards to 3volts.
To test audio voltage, set volt/ohm meter to Volts A/C. The red lead of the meter needs to make contact to the inner center electrode of the rca, the black lead needs to touch the outer shield of the RCA, however touching it to the chassis of the radio should work just fine(the outer shielding of the RCA on most aftermarket decks rests at chassis ground).
The 4 volt rms rating is tested using test tones, usually 1khz, and an osciloscope to detect clipping. Using that same test tone with the sub x-over frequency turned off, you should be able to read a voltage of close to 6volts or so at full volume. If you try reading the voltage playing music, depending on your meter you may not get a reading, as the voltage will fluctuate quickly with the beat of the music. If you have a nice enough meter, you may get readings upwards to 3volts.
