Mach 460 No audio Bad front amp?

[Sn8kebitten]

Hello all. I have a 1996 Cobra convertible that I recently bought back. I’m trying to fix the issues it’s gained since I sold it in 2015. One of the not so serious but more annoying problems is no music lol. The head unit powers on fine, but no sound comes out.

The previous owner told me one day he was driving, heard a pop from the speakers, then no more audio. He never bothered looking into it. The car still has the original Mach 460 setup, but with the Pioneer head unit that I installed way back in 2010. Prior to that, it already had a Kenwood unit from 2003 that worked fine, I just wanted to upgrade for an aux input to connect my phone. From what I vaguely remember, there was no bass coming from any speaker and I was clueless how to fix that, so I ended up just adding an amp and two 12s in the trunk lol which are long gone now.

Now I can hear a soft “thump” from the speakers when I turn the key off, but that’s all I can get out of it. From what I’ve been reading, I feel like it’s the front amp beneath the stereo that’s bad. There are a few on eBay, but I’d hate to buy one and it not fix my problem. I’ve already checked the audio amp fuse under the hood and radio fuse under the steering wheel, and I pulled the kick panel out to make sure that connector people mention is still securely in place.

I attached a few pics of the mess of wiring if that helps anything. If you guys have any other recommendations, I would really appreciate them. Thank you

 

[ttocs]

the amps have long been known to be a source of battery drains and the speakers have dry rotted and worn out long ago. The easiest way to fix this problem is to replace the speakers and you can easily bypass the amps.

 

[Sn8kebitten]

the amps have long been known to be a source of battery drains and the speakers have dry rotted and worn out long ago. The easiest way to fix this problem is to replace the speakers and you can easily bypass the amps.

I’ll be honest with you, I’m one of those “clueless about anything electrical” people lol is there a write up on replacing the speakers and running new wiring throughout the car with a new amp? I’ve never really done anything like that before but I’d like to learn

 

[ttocs]

That is just it ya don't even need to run new wires. There is a harness in the dash that goes from there directly to the tweeters so if you use that harness for the speaker output on the deck, then when you replace the speakers you just use the tweeters wiring for your new speakers and your done. Since you already added a sub it will probably sound better.

To start you need a 70-1777 harness from metra as it will have the speaker harness. It has the same power harness that you already have but you can't buy it alone. After that you need to pick out some speakers.

 

[Mustang5L5]

The front amp does feed the two rear amps. Essentially the line-out signal goes from the head unit to the front amp, which powers the 4 smaller speakers in the front and rear.

Then, two cables come out to feed the rear two amps. One amp does the front two door speakers and the other amp does the rear main speakers.

Typically there's a slight delay of about 1 second with the Mach 460 system for the rear amps to power on. When you turn the music on, you immediately hear the 4 small tweeters off the front amp, and then a second or so later you'll hear a faint pop and should hear the 4 main speakers.

The fact that you hear the pop suggests the rear amps are coming on, but there's no signal. could be a bad front amp, or could even be a bad head unit as these head units have constant issues as they age.

EDIT: however it looks like you have an aftermarket head unit. Unfortunately I don't have any way to test to see if the issue is the amp short of swapping a different one in.

 

[Sn8kebitten]

That is just it ya don't even need to run new wires. There is a harness in the dash that goes from there directly to the tweeters so if you use that harness for the speaker output on the deck, then when you replace the speakers you just use the tweeters wiring for your new speakers and your done. Since you already added a sub it will probably sound better.

To start you need a 70-1777 harness from metra as it will have the speaker harness. It has the same power harness that you already have but you can't buy it alone. After that you need to pick out some speakers.

Crutchfield is listing a 70-1770 as the harness for mine. Is that what I need? And so what you’re saying is if I remove the plug that connects the tweeters to the front amp, then plug it into the deck using the 70-1770, it will also power the door speakers and rear speakers, bypassing the front amp completely?

 

[ttocs]

1770 was it, it has been 20 years since I was using those numbers. if you pull the deck out and look on the inside of the hole on the passenger side you will see a black 8 pin harness clipped to the side(assuming it has not been moved). You will disconnect it and then wire your decks speaker output to that new harness. Now when you replace the speakers there are 2 sets of wires, one for the tweeter and one for the woofer. Ignore the woofers wires and use the tweeters wires and you will have a full range signal for your speakers.

 

[Sn8kebitten]

Okay I have the harness ordered. I haven’t decided on speakers yet, but why are the oem door speakers incompatible with the amp bypass setup?

1770 was it, it has been 20 years since I was using those numbers. if you pull the deck out and look on the inside of the hole on the passenger side you will see a black 8 pin harness clipped to the side(assuming it has not been moved). You will disconnect it and then wire your decks speaker output to that new harness. Now when you replace the speakers there are 2 sets of wires, one for the tweeter and one for the woofer. Ignore the woofers wires and use the tweeters wires and you will have a full range signal for your speakers.

 

[Mustang5L5]

Okay I have the harness ordered. I haven’t decided on speakers yet, but why are the oem door speakers incompatible with the amp bypass setup?

The mach 460 system is sort of an "all-or-nothing" setup when it comes to amps and speakers. The mains (not the tweeters) are 6 ohm speakers.

So if you pop in 4 ohm speakers, it's a significant increase in power required by the amp/head unit.

 

[Sn8kebitten]

So once I bypass the amp, the aftermarket head unit will power 4 ohm aftermarket speakers better than it could the 6 ohm OEM speakers?

 

[ttocs]

remember that the stock speakers are 20 years old and more than likely when you take them out you will see the surrounds are dry rotted. You are replace a 6 ohm low range woofer with a 4 ohm full range driver. Honestly the mach system was good for its time but that time has passed and full range drivers, or components and a sub will sound better off the deck than the mach system did with the amps.

 

[Sn8kebitten]

The connector made it today. So all I need to do is undo the spliced 8 wires on the left hand side of the black connector that plugs into the back of the head unit, then connect them to the matching colored wires of this new connector, then plug that into that black 8 pin that’s pinned to the far right and I’m good to go once I replace the door speakers?

 

[ttocs]

as long as you use the tweeters signal wire to drive the speaker, yes you have just bypassed the amps. When you do this do yourself the favor of at least disconnecting the power harness going to the amp, or pulling it out completely. Even with no signal they can drain the battery if the power is connected.

 

[Sn8kebitten]

as long as you use the tweeters signal wire to drive the speaker, yes you have just bypassed the amps. When you do this do yourself the favor of at least disconnecting the power harness going to the amp, or pulling it out completely. Even with no signal they can drain the battery if the power is connected.

Gotcha so just disconnect the signal wire from the tweeters, connect them to the new door speakers and I’m good. I’ll pick out some speakers here shortly. So what would I need to do in the future if I wanted the rear speakers to work too? Sorry for all the questions, just trying to learn as I go. I really appreciate all the advice

 

[ttocs]

the exact same thing, you can use the same speakers, and same speaker wires off of the tweeters in the back.

 

[Sn8kebitten]

the exact same thing, you can use the same speakers, and same speaker wires off of the tweeters in the back.

I honestly didn’t know there were tweeters in the rear lol so when you say I need to use the tweeter signal wires to power the new door speakers, do you mean I need to depin both wires from the tweeter pigtails, then cut them and crimp a butt connector to each wire to connect both wires to each door speaker?

 

[ttocs]

they are right next to the woofer. you will disconnect them with a harness and you can either get a harness to clip onto it or cut it off

 

[Sn8kebitten]

they are right next to the woofer. you will disconnect them with a harness and you can either get a harness to clip onto it or cut it off

Alright I’ve got it taken apart now. Which wires here do I need to use?
Edit:so I actually ordered a speaker adaptor harness kit 72-5512 that plugs into the woofer pigtail and then into the new speakers so I wouldn’t have to cut the wires. I wasn’t even thinking about how I’m not using those woofer wires, so at first I was bummed, but now I see the tweeter pigtail is the exact same type of pigtail so I assume I’ll be good to use that one there. Going to work on this today and see how it goes. Thanks for all the help

 

[Sn8kebitten]

It works! I’m ecstatic lol I bought this Cobra back April of last year and this was just one of the many issues I’ve been needing to tackle. It was my first car that I bought from my uncle back in 2009, and regrettably sold in 2015 when I discovered the terrible world of car loans. I really appreciate the help in getting the audio back up and going. I don’t live in town like I did back then so 22 mile trips on the highway every day aren’t as fun with 4.10s and no music. Thanks a lot

 

[Call me Chief]

So, mine too. Just got a '96 SVT convertible and no music Head unit powers up and tunes to local station but no sound. Checked the fuses under the hood and inside car and they are OK. Was going to eventually replace the radio unit with something that I can play my phone through, but I guess eventually means next week now.