OEM amp bypass without an electrical lightshow..... (1 Viewer)

[GaFJC]

I have a '00 100 series and replaced the OEM head unit (Matsushita #86120-0C040 [Toyota model # A56811 6 disc)] roughly two years ago with a JVC KW-AV71BT (support.jvc.com/consumer/product.jsp?modelId=MODL029189) and retained the factory amp (Matsushita #86280-60210).

I am now hearing the dreaded whine from the amp that occurs before it fails. The whine is sporadic but occurring more and more frequently.

I ordered the Metra 70-8116 Factory Amplifier Bypass Harness that comes with 70-8113 (Amazon.com: Metra 70-8116 Factory Amplifier Bypass Harness for Select 2000-2004 Toyota Vehicles with Amplified JBL System: Car Electronics). I thought I would simply bypass the OEM amp and let the JVC head unit power the OEM speakers.

I now have a few challenges.

The Metra harness apparently fits the JBL system so the 70-8116 works but the 70-8113 does not. Additionally, even if I don't use the 8113 and instead solder or crimp connections I've come to the conclusion that I do not know what wires to connect.

I am very handy with most things mechanical but wiring is new to me!

Any help would be most appreciated.

 

[brooa]

if it was me, i would just run all new speaker cable from the headunit to the speakers. that way you are not relying on crappy stock wiring and just get rid of the amp all together.

 

[silverbullitt]

The whine you hear is from a bad ground. Try regrounding the ground wire to another spot on the truck

 

[GaFJC]

The whine you hear is from a bad ground. Try regrounding the ground wire to another spot on the truck

Thanks, Silverbullitt. I've read that as well, but thought that would result in a constant whine and not one that was random regardless of road condition?

 

[LBridges]

A bad ground induced whine (ground loop) produces a whine that is proportional to the engine speed (actually really to the RPMs of the alternator).

I suggest you run speaker wire from the headunit back to the amp space under the PS seat, and splice into the wires from the amp output to the door speakers. Does your LC use a OEM subwoofer? I doubt the replaceme3nt headunit has speaker level subwoofer out - maybe you already have that covered, just thinkin' and wonderin' here.

 

[Wilsil]

I have bypassed the amp for the speakers.

 

[GaFJC]

A bad ground induced whine (ground loop) produces a whine that is proportional to the engine speed (actually really to the RPMs of the alternator).

I suggest you run speaker wire from the headunit back to the amp space under the PS seat, and splice into the wires from the amp output to the door speakers. Does your LC use a OEM subwoofer? I doubt the replaceme3nt headunit has speaker level subwoofer out - maybe you already have that covered, just thinkin' and wonderin' here.

Should I run new ground wires for the chassis ground and the amplifier shield ground?

 

[LBridges]

Should I run new ground wires for the chassis ground and the amplifier shield ground?

You quoted me so I will attempt an answer. But keep in mind I have an LX with the Nakamichi system so my answer may not be accurate for your case.

For the Nak, the headunit and the amp share a common chassis ground - it's a brown wire attached to the floor via bolt just in front of the amp. If your amp has a similar ground then no need to add ground wire. Just run speaker wires back to the amp, then depending on future plans pull (or cut) the amp output to the speaker wires. Then join those to the speaker wire coming from the aftermarket headunit. That way you avoid the headaches of trying to get wiring into the doors. Should not that running the speaker wire all the way from the headunit to the speakers in the door would be the preferred method - but I'm lazy, hence the first path I suggested.

 

[GaFJC]

You quoted me so I will attempt an answer. But keep in mind I have an LX with the Nakamichi system so my answer may not be accurate for your case.

For the Nak, the headunit and the amp share a common chassis ground - it's a brown wire attached to the floor via bolt just in front of the amp. If your amp has a similar ground then no need to add ground wire. Just run speaker wires back to the amp, then depending on future plans pull (or cut) the amp output to the speaker wires. Then join those to the speaker wire coming from the aftermarket headunit. That way you avoid the headaches of trying to get wiring into the doors. Should not that running the speaker wire all the way from the headunit to the speakers in the door would be the preferred method - but I'm lazy, hence the first path I suggested.

Great and thanks. If I am understanding this I run new speaker wires from the head unit to the appropriate speaker wires post amp on the 16 wire plug. My ground is exactly the same as yours.

 

[LBridges]

If I am understanding this I run new speaker wires from the head unit to the appropriate speaker wires post amp on the 16 wire plug.

Exactly. Myself being lazy, it saves me trying to push wire into the doors and back to the subwoofer area.

 

[GaFJC]

This may be a stupid question: after running the eight new speak wires (4 positive and 4 negative) I can leave the amp plugged in to power the subwoofer, correct?

I have ordered supplies and will be tackling this tomorrow night....

 

[Emcd]

yes, that's exactly what I did. you need to plug it in to get power sent to the HU anyway. it won't work unless it's plugged in at the amp. it sounds 1M times better.

 

[GaFJC]

Knocked it out last night and this morning. All seems to be working well. Many thanks to everyone, including RobRed and tlcfaq.com, who provided help.

 

[Mike6158]

What did you do with your old (factory) amp?

Most electronics that are around 15 years old will start to have electrolytic capacitor failure. They start "looking like a resistor" instead of blocking DC like they are supposed to.

They aren't made to last forever. Surface mount electrolytic caps have a life rating of 1,000 (42 days continuous) - 10,000 hours (a little over a year continuous). Radial, leaded, general purpose electrolytics have about the same life but can go as high as 20,000 hours (2 years and change continuous)

Here's the elephant in the room They don't put 10,000 - 20,000 hour caps in most consumer good because they cost too much. Now you know why sh*t doesn't last anymore.