# how do I test rca output?



## heyhi (Apr 29, 2014)

I wanna check if my headunit is really putting out 5v. The reason is I had a 2 v output headunit before and I set my gains with a dmm and when I put this 5 v headunit I actually had to turn my gains up instead of down to get the ac voltage I needed wich was 15.
I used the same test tone and same dmm


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## vulgamore89 (Oct 27, 2013)

Use a dmm and put the leads on RCA jacks. 

As far as turning the gains down, that's what should have happened. Most amp gain knobs are backwards if you think about it. If your input voltage from rcas is higher the amp gain will be lower and vice versa


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## Victor_inox (Apr 27, 2012)

vulgamore89 said:


> Use a dmm and put the leads on RCA jacks.
> 
> As far as turning the gains down, that's what should have happened. Most amp gain knobs are backwards if you think about it. If your input voltage from rcas is higher the amp gain will be lower and vice versa


You answer confusing. I'll try.
It depends on manufacturer. Lets say your amp gains marked 0.1 to 10 V
far counter clockwise would be 0.1V- max gain. Say it would be 7 o'clock position If 2V would be somewhere around 12 o'clock that 5V would be around 3-4 o'clock. Is that makes sense? Vulgar correct, gains works backwards. From the top of my head Eclipse works that way. 
on some amps gains marked level and works backwards. clockwise increase sensitivity. set your gains with dmm and forget about it.


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## vulgamore89 (Oct 27, 2013)

Yeah could've been more clear I guess. 

Back to testing RCA voltage. I can't remember if you need to use a test tone or not. But unplug your rcas from the amp and turn your headunit volume all the way up. Then use your dmm and put the leads on the RCA jacks, not the shields. Also remember that your EQ, loudness, and other settings can change the output voltage of your headunit


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## minbari (Mar 3, 2011)

heyhi said:


> I wanna check if my headunit is really putting out 5v. The reason is I had a 2 v output headunit before and I set my gains with a dmm and when I put this 5 v headunit I actually had to turn my gains up instead of down to get the ac voltage I needed wich was 15.
> I used the same test tone and same dmm


does it sound bad? unless you have a performance issue I wouldnt worry about it. 2vac is plenty signal to get good and loud and still have good SQ. higher voltage outputs will allow you to turn your gains down, but unless you are having a noise floor issues, kinda pointless.


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## SPLEclipse (Aug 17, 2012)

You need to use a test tone. Use 60hz for the reason I explained in one of your other threads. Make sure your internal headunit filters (crossover, eq) are all off or set to flat to get full signal at the frequency you're testing. If you use music you'll be all over the place. The positive probe goes on the center pin, negative probe goes on the shield. Take care not to let the probes short either against each other or to anything other than what they are supposed to be in contact with or you will damage your headunit. Do not plug/unplug the RCAs with the system playing. Do not let the RCAs touch any part of the car if you have the system on.

Even though the headunit says "5v" or "2v" or whatever, it's pretty meaningless without defining where and how they are measuring the waveform. A 5v peak-to-peak measurement will have almost the same amplitude as a 2v peak (either positive or negative) measurement, or an even lower voltage rated at RMS.


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