alpine 9856

[Ali1]

Alpine 9856- How do I know if my HU is going bad? Is there such thing like "the HU is not giving enough of a good signal to the amp"? The loudness/vibration is not the same nomore and i can notice it easily. At volume 26, i knew exactly how it felt inside the car, and it's just not the same anymore. I checked for any loose connections, everything seems fine. Checked my settings just incase anyone touched it, but the settings are also fine. Same with the HU, everything is the same. So maybe my HU is taking a S**t on me? How can i tell if my HU is going bad?

[nick]

mabe your gettin used to it

[ROE]

it's common for people to "get used" to their system. however, if you want to verify your pre-out voltage. meause the ac voltage with a dmm. if you have you sub level set to 15 and volume set to around 3/4 of the max, it should produce ~4V reading.

[Ali1]

that model is 2v though.......

[Ali1]

where should I place my dmm leads at?

[quakerroatmeal]

Not to mean to hijack but I'm also curious how you'd test your preamp voltage.

[ROE]

Originally Posted by Ali1

that model is 2v though.......

thanks for the correction.

Originally Posted by Ali1

where should I place my dmm leads at?

find an old or spare rca cable. cut it in half so you can strip the internal wires. depending on the rca, the ground Wire will be exposed once you cut the wire. it should surround the positive insulated wire that should be located in the center. once you locate the postive wire, strip enough of the surround so you can attached a probe. do the same with the ground wire. be sure to isolate both so they won't cause a short.

here's a pic of what i made:

the clear wire is the positive contact. the black wire is heat shrink which protects the negative contact. it originally surrounds the clear postive wire when first cut. i then soldered the ends so the wires won't fray.

anyhow, once connected, set you dmm to measure ac voltage. if you dmm is not automatic, be sure to select an appropiate range. set you sub level to max, 15, and your master hu volume to 3/4 of max. at this setting, you pre-out voltage should be around 2V.

Originally Posted by quakerroatmeal

Not to mean to hijack but I'm also curious how you'd test your preamp voltage.

if this questions is referred to me, i did the same method i posted above but with an o-scope instead of a dmm.

[Ali1]

I'm sorta confused, Can i just use the current RCAs i have now? If the RCAs are already labeled black and red for me(newer ones), can't i just hook the DMM to the back of the HU and let them touch the RCAs?

[ROE]

yes, you can. however, you won't get an as good connection. this is becuase you have to insert the positive probe into the female rca and try to clamp the negative probe to the ring of the rca. the simple rca mod i posted helps to resolve this problem as you simply clamp both probes to the exposed wires.

[Ali1]

you got a video laying around that shows how to do it like the video that shows how to tell clipping from your O-scope?

[Ali1]

sorry for the bothering, but let me get this straight. So i can do this :

Grab my DMM and place it on my RCAS on the back of my HU. Switch the setting to AC voltage. Turn the volume to 3/4, will i get any results this way?

It's just that I don't feel the same vibrations anymore. I monitor my subs everyday when i leave somewhere and park, i always look at my subs/voltage. So i know what I'm feeling and i definately don't get the same feeling even with volume at 30-35. I try to perceive it as "I am used to it", but it's definately not the same....

[ROE]

as, i mentioned, you do not need to make the rca mod that i posted. however after doing it many times, i find it to be very helpful.

being that the rear rca outputs of the hu are female, you have to insert the positive probe (without the alligator clip) into the rca. then, with the alligator clip attached, clamp the negative probe to the ring of the rca. it will be tricky as the amount of space provided is very tight, but it can be done. once connected, set your dmm to measure ac voltage.

the other method is to measure the voltage at the amp side. however, this will take into account the resistance of the rca wire, thus alter your voltage reading slighty. however, it will be easier to connect your probes as it will be a male rca connection. with this method, you need both probes to have the alligator clipse attached. clamp the postive probe to the center pin and the negative probe to the ring. once connected, set your dmm to measure ac voltage.

[Ali1]

aligator clip?

[ROE]

pictures are worth a thousand words

here's a pic of the my little mod with the probes attached the exposed wires with alligator clips


here's the device connected to the rca pre-out (a female rca). as an example, i'm using a barrell connector.


if you decide not to use the device, you need clamp the negative probe to the ring and insert the postive probe into the female rca. you'll have to jiggle the positive probe until you get a secure connection and hold it in place.


if you decided to measure the voltage at the amp side (male rca), you need to use both alligator clips. clamp the positive to the tip and the negative to the ring. make sure the clips do not touch or you'll create a short.

[Ali1]

so how do i connect my DMM to the alligator clips? Are these located at ace hardware/menards? So all i need is one rca wire, what about the other?

[SoundDesignMaster]

Im guessing that your DMM has to have them or you can just hold the probes in place.

[ROE]

it depends if they came with your dmm. if not, you can get them from an eletronics store. as for the rca's, you measure one side at a time.

btw, if you don't have alligator clips, just probe the pre-outs with your probes. you will still be able to measure a voltage. i'm just used to doing it this way since i've done it many times.

[Ali1]

so I'm supposed to have one side of the RCA inside the HU, while the other I am testing with my DMM. And while I'm doing all this, i should be playing my HU at 3/4 or right before distortion?

[Ali1]

Originally Posted by Ali1

so I'm supposed to have one side of the RCA inside the HU, while the other I am testing with my DMM. And while I'm doing all this, i should be playing my HU at 3/4 or right before distortion?

Maybe my RCAs went bad? I really dunno, it's used to be loud at bass -7, but now it's different. In order for me to get it that loud again, i have to turn up the bass on the HU to 0. Doesn't this sound like a HU problem?

[ROE]

it depends on where you measure the voltage. if you measure from the hu, you measure directly of the female rca. if you measure at the amp end, you measure of the male rca.

yes, set your hu to around 3/4 of max volume and play a 50hz tone since you are testing the pre-out of your sub.

[Ali1]

And one of the RCAs are going to be inside the HU, while the other I am testing with the DMM? does it matter which one i shuld test? So each of those has a + and a -?

[ROE]

i don't uderstand what you are saying. from the pics i posted, which method are you trying to use.

yes, each rca channel as a + and -.

[Ali1]

I am talking about measuring voltage at the HU. if i am measuring at the HU, i put one side of the RCA inside the HU, while the other i test it with my DMM? One of them are suppose to touch the ring, and the other is supposed to touch the inside? If my DMM leads touch together, that creates a short?Will that cause any damage to the HU or just the DMM?


I am referring to the third pic you posted. So while i do what you did in the 3rd pic, the other RCA is inside the HU correct?

[ROE]

since you are referring to third pic, you do not connect a rca to your sub pre-out on the hu. as pictured in the pic, you connect your dmm directly to the pre-out rca. the negative probe is clamped to the ring and the positive probe is inserted into the rca.

as for the other rca, you can leave it connected.

[Fallen]

Thats a really good explanation. If you don't understand maybe you should take it to an installer, since it doesnt get any easier than this. Good luck with your head unit. one thing i want to mention, do you have any CDs from when you first got it? I thought mine was getting quieter, but it turns out I had "volume leveling" turned on when I burnt my new CDs.