# multimeter to test RCAs?



## masnow (Jul 7, 2017)

Trying to spare ya'll a long undiagnosed problem if I can. How can I most simply test my RCAs for proper function and/or my preouts from the HU?


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## seafish (Aug 1, 2012)

Probably easiest just to swap the rca(s) cables that you want to check with a known good pair.

If the problem disappears with the new cable, then the cable was the issue...if the problem persists with the new cable, then the problem is elsewhere.


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## SkizeR (Apr 19, 2011)

set multimeter to AC voltage. Play test tone on repeat. turn volume up. positive lead to center pin, negative lead to outer shield. dont short them.


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## mumbles (Jul 26, 2010)

With a multimeter;
Test connectivity between center pin to center pin on each end of cable. Should be zero ohms

Repeat for ground shield to ground shield, again zero ohms

Finally, test between center pin and ground shield at one end of the cable and the meter *should not budge at all!* If it give you a quick reading but goes to zero, there is a short between the center lead and the ground shield

It could be just one tiny signal conductor strand touching the ground, but it will cause you nothing but headaches!


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## bbfoto (Aug 28, 2005)

EDITED a bit for clarity because I'm OCD!  ...



SkizeR said:


> (*To Test your Head Unit's Preamp Outputs*) set multimeter to AC voltage. Play a test tone (1kHz Sine Wave) on repeat. turn volume up. positive lead to center pin, negative lead to outer shield. dont short them!


...If your head unit has "4 Volt Preouts", as you turn the volume up from 0 to Max, the DMM should read anywhere from 0.0-0.1 Volts to ~4.0 Volts. It may or may not reach the full 4.0 volt output, but should come close, say 3.7 Volts.

To confirm that it is outputting a "clean" musical signal, you can also use a simple L/R Male RCA to 1/8" Female Stereo Miniplug adapter so that you can plug in a pair of cheap 3.5mm miniplug (non-Lightning connector) iPhone or other earbud type headphones directly to your head unit's RCA preouts.

Start with the HU volume at Zero, play a music CD or sine wave test tone, and slowly turn the volume up while listening. You should hear a clean, undistorted signal. The headphones themselves will distort if they are overdriven by the HU output, but this should be at a level that's too loud to listen to anyway.

*Hosa YMR-197 3.5 mm TRSF to Dual RCA Stereo Breakout Cable*










*+*










You can also *Test your RCA Cables* by placing them BETWEEN your HU and this adapter+headphone setup.  Results should be the same.


EDITED for clarity...



mumbles said:


> *(To Test your RCA Interconnect Cables with a DMM*, first, completely disconnect your RCA cables at both ends)...Now, with a multimeter (set to read Resistance in OHMS);
> 
> Test connectivity (or "Continuity") between center pin to center pin on each end of the cable. The DMM should read Zero (0.00) Ohms. This should show the same reading as when you touch the positive & negative probe tips of the DMM together directly.
> 
> ...


Amazon's "TACKLife" house brand and series of DMM's are great for the money and great to have on hand for all types of testing...

*Amazon TackLife Digital Multi-Meter*


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## masnow (Jul 7, 2017)

Well, what I did on my lunch break is hooked my ipod directly to the amplifier. I receeived crystal clear audio output. So excited, I checked all of the channels (much of which I'm not currently using) and they all sound great of my headphone to rca split cable. Going to replace the three cables with a 12ft set (the ones I have are 15's and they are longer than necissary. going to try that ysplit to headphones to test headunit output. Reasonable?


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## bbfoto (Aug 28, 2005)

masnow said:


> Well, what I did on my lunch break is hooked my ipod directly to the amplifier. I receeived crystal clear audio output. So excited, I checked all of the channels (much of which I'm not currently using) and they all sound great of my headphone to rca split cable. Going to replace the three cables with a 12ft set (the ones I have are 15's and they are longer than necissary. going to try that ysplit to headphones to test headunit output. Reasonable?


Congrats.

Yeah, sounds good. It's always best to keep the RCA cables as short as possible. You'll have less signal loss and less chance of picking up induced noise through the cables. The only instance where I would use longer RCA cables, is when you need to route around a "noisy device" in the vehicle, such as a computer module, relay, or electric fuel pump, etc.

If you can afford new RCA cables, you can afford the DMM that I linked to above...it's just $13 shipped (if you have Amazon Prime). There are many other DMM's in this TackLife lineup that are great as well (both less expensive & more expensive). Just add some alligator clips and/or "Plunger Mini-hook" leads and you are set for life.


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