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How to Wire Aftermarket Radio to Factory Amp

261K views 240 replies 64 participants last post by  Ragnarok-504 
#1 · (Edited)
This diagram is ONLY for the SC, EX, and EX-P with the factory double-DIN radio, amplifier, and subwoofer. This is NOT for the DX or LX.

The first picture shows how the radio is basically wired from Honda. The radio puts out a line-level(low-level) signal to the amplifier thru the big black harness. It puts out a mono signal for the subwoofer via the small black harness with white guts. The amplifier then sends the amplified signal out to the speakers and subwoofer. Note the sub is dual voice coil but uses a mono signal.
 

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#51 ·
I know on my D3 I pretty much had to have to sub out on 4 out of 6 to be close to the factory radio's output on the sub channel. So like BigAl said, check the x-over and the level.
 
#52 ·
thought id ask the question here instead of pming bigal

since i JUST got my head unit in today and since i wont have any install time till sat around 4 i wanted to poll this audiance and ask the following

i jsut recived the pioneer f90bt

shall i bypass the stock amp and power the front four speakers from the reciver its self or should i use the 3 aux outs and wire into the stock amp with a wireing harness

then amp and speaker upgrades wont be shipped for a few weeks and id love to have the nav now and customize my avic before the rest of the goodies come in

ive looked over the wireing diagrams, none of the cabling is "frightening" its all cables to me but for sound quality and the such i was currious what other E users have done when using an aftermarket HU with the rest factory

and YES i have read that other guys (the harley tech) problems he had with this setup and im aware of the phasing issues jsut wanted insight how you all would do it

so

HU with indash amp ---> speakers
run an aux out to the factory amp ---> sub

or

HU 3 aux outs ---> all the appropriate inputs on the factory amp


remember its gunna be taken apart in a month for the rest of the install
thanks guys, cant wait for your recomendations
 
#53 ·
In my opinion, if your gonna be adding external amps for all speakers later, it's easier to just run line level out for F,R & S right now. You can basically do the entire install in the dash cavity and in a very short time. It's easy and cheap.
 
#55 ·
NOPE. Grab a metra 70-1725 for super easy rca plug in for the front and rear,then add your own RCA end for the sub. 8)
 
#58 ·
Yea, I forget that part cause mine didn't need it :-|
 
#60 ·
Metra 1721 vs 1725 harness adapter

I have a 2004 EX with factory AMP and sub.
I'm installing a pioneer DEHP510UB for use with factory speakers for now.
The stereo shop sold me the metra 1721 harness instead of 1725.

They say they think the factory amp is ok to accept the speaker wire input as opposed to the 1725's line level RCA plugs.
"That's the way we've always done it"
Are they correct?

I've already got this 1721 all soldered up and ready to plug in.
I've made the RCA cable deal to power the amp.

Should I buy the AMP bypass harness and use the Pioneers internal amp?
Or go trade this 1721 for the 1725?

Am i gonna burn up the factory amp?
Thanks. Ben
 
#62 ·
If your going to maintain the use of the factory amp, I would suggest feeding it a line level signal, not the powered output of the headunits internal amplifier. I will say this now though, because I know somebody is going to come and argue that I am wrong...it can and will work using the headunit's output to feed the factory amp, but I personally don't believe it to be the best way. Also, no power needed for the antenna on your 04.
 
#63 ·
thanks a ton for the quick response.
I'm a novice at car audio, but pretty good with electronics.
i'm not getting much help from the shop where i bought.
they are a little irritated i think that i didn't hire them to do it.

i cannot get this thing to work, but i'm learning a TON.

i've been messing with it all evening. (3 nights now)
i went ahead and plugged it all in tonight using the 1721 adapter.
i made an RCA plug to power the amp.
Still no sound.
then i made another plug to power the amp using the blue/white wire from the HU that's intended for powering external devices.
then i grounded the other wire.

i still cannot get any sound.

I think there is a setting in the HU to turn off the internal Amp.
will that change the standard speaker wires to line level?

Is there a chance the factory amp is not working since i'm trying to feed it the powered output?
 
#64 ·
Bypass Factory AMP?

If you were me......

would you just bypass the factory AMP?
i like good quality sound, but i'm not the type that has modified the sound systems in all my cars with huge woofers and amps.

i dont listed to loud thumpin' stuff, just country, rock, and lots of talk radio and audio books.

Ben.
 
#65 ·
What head unit are you installing?

What do you mean you made an RCA plug to power the amp?

You grounded what other wire?

I just used the factory amp, it made for a very easy installation. I plan on installing a 4 channel amp under the passenger seat eventually though.

Is there any way you can provide a picture of how you have the radio's harness wired into the 70-1721?
 
#66 ·
#67 ·
I see that your uploading a pic, i will wait to see it. Do you have any instant messenger programs?
 
#70 ·
the pics i posted don't have the rca to power adapter i made.
i couldn't get the system to work with that setup.

so then i wired it up as shown in the pics.
the read lead comes from the blue/white wire from the aftermarket HU.
Blck wire ground.

those two should power the amp
 
#78 ·
NO no no, the blue/white wire from the headunit should mate with a wire that would be on the part of the harness that plugs into the 1721, not the sub portion....feeding power into that sub connector like your doing is wrong and could damage the factory amp.
 
#72 ·
What wire on the 1721 do you have the blue/white wire from the headunit hooked to? It should be hooked to the blue wire. Does the headunit even turn on?
 
#74 ·
Herein Lies the problem.
the 1721 has no Blue wire.

so the head units blue/white is connected to my hillbilly homemade red wire to plug into the amps factory little black plug.

yes the HU turns on.

just no sound.
 
#75 ·
Ok...you should be pretty much color for color from the pioneer to the 1721


pioneer 1721
red red
yellow yellow
black black
blue/white blue
white white
white/blk white/bll
etc.....

The rca 'trick' has NOTHING to do with power, it just provides signal from the head unit to the sub portion of the factory amp. If you don't have the blue/white hooked to blue, the factory amp will not turn on.
 
#76 ·
what i haven't done is to open the passenger side kick panel to check with a V.O.Meter if power is getting down there.

i checked it at the back side of the little black plug and it gets 12v when HU is on and nothing when the HU is off. just like it's supposed to.

So, i think i'm powering the amp just fine.
just no sound.

and i'm gonna run out of beer if i mess with this too many more evenings.
 
#79 ·
You got a jenky azz harness....there's your problem.
 
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