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Must Read If You Are Running Oem Hu + Loc + Aftermarket Amp

jrmeade77

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jrmeade77 Enthusiast

jrmeade77

Posted
Posted

I've been trying to figure out the audible "hiss" that is coming from my speakers with JL Audio amp + PAC AUDIO LOC + OEM head unit (2011 Sierra non-bose). I considered trying one of ArcAudio's processors to "clean up" the sound. After email with tech support I found out that they have had issues with GM head units having a high noise floor and poor sound quality with aftermarket amps and LOCs.

 

Here is the email correspondence:

 

Me: I recently installed a 4 channel amp and 4 new door speakers for a 2011 Sierra Crew Cab (non-bose).

I kept the factory head unit and currently am using a PAC-AUDIO LOC. I am having some issues

with "amp hiss", which I'm told is normal. The hiss can be heard at low volumes and does not get

louder as the volume is turned up. It is also driving me crazy as I don't always listen to my music

turned all the way up. My local shop told me I could mostly eliminate this noise with a aftermarket

head unit with a 4-5 volt preamp output. Of course with install and add-ons for the steering wheel

controls etc, it would cost around $800. My question is, does the SRI Signal summing module eliminate this noise?

 

ArcAudio: The SRI can only reproduce what it receives and if the head unit has hiss then that's what it will reproduce. I have a question. If you pull the RCAs off the amp do you still get a hiss? If this is the case then it's the amp you are hearing not the headunit.

 

Me: If I pull the RCAs I get no hiss.

 

ArcAudio: When you added the LOC and the amp you "unloaded" the stock head unit. We have seen this cause problems on the GM head units. Add some resistance across the stock speaker wires. Connect them across the + and - speaker wires before the LOC. This "dummy" load solves a lot of problems with the GM head units. I would try that first. If you switch to the SRI you will almost certainly have to do this as its inputs have no load across them. I've attached a drawing that shows how and where to add these resistors. This may not solve the problem but we have seen positive results from this.

 

GM_load_SIM.pdf

 

I hope might help someone out.

GM_load_SIM.pdf

GM_load_SIM.pdf

GM_load_SIM.pdf

jrmeade77 Enthusiast

jrmeade77

Posted
  • Author
Posted

Yes. The above is something that I probably won't do, but thought it might help someone out. I have high level inputs on the amp and am going to remove the LOC all together and see if that works.

aesalazar Enthusiast

aesalazar

Posted
Posted

Let us know how it works out. I have a new JL amp coming which also has the ability to accept speaker level inputs by slicing the RCA. Curious to how it sounds.

 

Ernie

  • 3 weeks later...
arctictwist Enthusiast

arctictwist

Posted
Posted
Let us know how it works out. I have a new JL amp coming which also has the ability to accept speaker level inputs by slicing the RCA. Curious to how it sounds.

 

Ernie

 

how did this work out for you? i was thinking of replacing all with components as my stock driver side front speakers are SHOT.

aesalazar Enthusiast

aesalazar

Posted
Posted

The doors came out fairly well. Still working on getting the bad head unit swap :lol: .

 

Anyway, for the doors I attached some pics. I got the Scosche bracket adapters for the woofers in the doors:

 

http://www.amazon.com/gp/product/B0015A8Q7S

 

Worked well. I ended up using screws long enough to hold the speakers on but also reach the steal of the door so it was a solid mount (that took some precision when it came to lining things up).

 

The tweeters were a decent amount of work. Not hard, just time consuming. Had to carve out the stock covers and epoxied the mounts for the new tweets to the pillar. Then put a piece of dynamat behind it to double as sound deadening and double stick tap. That thing aint going anywhere. These are the top of the line JL Audio 6.5's, ZR-650 CSI's which may not be in everyone's budget. But with any line the principal would be about the same.

 

Back to the original topic, the Advent OGM1 hu I ended up with actually has RCA outs so the issue of loading the non-used channel never came up.

 

Ernie

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Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

I am using stock head unit, with two amps, sub, and changed out all 4 factory with Polk Audio stuff, amps are polk audio as well. They used some line out adaptors, sorry do not know what product they used for the line out adaptors.

 

I have been using the same audio guy for 20 years, on all my cars/trucks. I used to get involved in all the audio changes I wanted to make, would research it all, test drive everything, then he would do the install. Now, I tell him what I want to end up with, and let him do all the research and planning. He comes back with a price, and then he basically tells me he is doing for that money. He knows I am very fussy, and that I have no problem letting him know I don't like it.

 

This is a long way to say, I don't have any hiss, and I have asked him if he had to do anything to correct a hissing from the amp. He says the line out convertors he used are the best ones there are, and with them there is no hiss. The only thing I do not like is the volume of the chimes is too loud. I will get the name from him when the truck goes in to get the heated seats wiring run to the dash. Did I mention I am getting a two tone custom leather interior with heated seats done as I type this? I can't wait to get the truck back.

arctictwist Enthusiast

arctictwist

Posted
Posted

Ernie you ended up with a factor unit that had pre amp outputs? How can i find out, if possible without ripping open my dash, if mine has them?

aesalazar Enthusiast

aesalazar

Posted
Posted
Ernie you ended up with a factor unit that had pre amp outputs? How can i find out, if possible without ripping open my dash, if mine has them?

 

 

No, I got an Advent OGM1 which is being talked about in the other post. That has RCA outs. But it not working anymore and am still trying to get the seller to send me a new one. Bit of a PITA.

 

Ernie

arctictwist Enthusiast

arctictwist

Posted
Posted
Ernie you ended up with a factor unit that had pre amp outputs? How can i find out, if possible without ripping open my dash, if mine has them?

 

 

No, I got an Advent OGM1 which is being talked about in the other post. That has RCA outs. But it not working anymore and am still trying to get the seller to send me a new one. Bit of a PITA.

 

Ernie

 

 

 

oh ok. misread that. thats what i get for scanning.

  • 2 weeks later...
Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

I finally found out what they put in my truck for the line out adapters.. Cache CLOC+D. I have no issues at all with noise.

  • 6 months later...
birdman7389 Enthusiast

birdman7389

Posted
Posted

Wow. This is great info, thanks for posting.

 

I'm having the same issues, time for a radio shack run.....

  • 2 years later...
qwank Senior Enthusiast

qwank

Posted
Posted

Bumping an old thread, but I tried adding the 4 resistors in the speaker circuits per the wiring diagram posted above and the hiss noise didn't change at all.

 

Has anyone figured out a fix for the hissing noise when using LOCs?

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