bypassing the JBL Amplifier

[warwgn]

My JBL Amp has kicked the bucket, so I have had no radio for a while now. I've been getting by with the FM transmitter on my Cell phone, but I need some tunes.

The head unit, and speakers are all fine. is there a way that I can bypass the amp? Can I do it in the trunk, or do I have to rip my dash apart?

another option is: does anyone have a spare JBL Amp that they'd be willing to give up?

[White Lincoln]

Hmmmm..... looking at oldschools garage recently seems he may have one... (Mark VII grave yard).

[CDW6212R]

Were there just two amplifiers in the Mark VII's? My first one had the big amp, and this one has the smaller amp. They can't be swapped can they?

[gadget73]

You cannot bypass the amp. The head unit doesn't have enough power to drive the speakers. The only answer is to replace it, or replace the stock stereo with something that can drive the speakers, and use the bypass harness.

Yes there are two different amps. The big black JBL amp and the smaller silver Premium amp. They can be swapped for one another. There is another one for earlier models, the football amp, which is generally incompatible with anything other than a trash can.

[warwgn]

Thain,

I don't have the stock stereo. I have an aftermarket Clarion AM/FM/CD player that was installed by a previous owner.

[artbaileyjr]

Were there just two amplifiers in the Mark VII's? My first one had the big amp, and this one has the smaller amp. They can't be swapped can they?

They CAN be swapped. Just unplug the premium and plug in the JBL. The difference is immediately realized; even with the premium (2 way) speakers vs. JBL (3 way).

The screw holes are already in place under the package tray so mounting is almost already done for you. It's very easy.

There were thee amps during the model run. The fist was used from 1984-1988 and was unique to itself.

[CDW6212R]

Very cool, thanks. I've also been without a radio for a long time, and I don't know if it's the amp or the radio. I've got Kenwood speakers in it from my first car.

[artbaileyjr]

Very cool, thanks. I've also been without a radio for a long time, and I don't know if it's the amp or the radio. I've got Kenwood speakers in it from my first car.

My pleasure. I did provide some misinformation, though. The first generation amp ran from 1984-1987, not 1988.

Art

[gadget73]

Thain,

I don't have the stock stereo. I have an aftermarket Clarion AM/FM/CD player that was installed by a previous owner.

ok, well in that case the answer is maybe. You'll need to know if they used the speaker-level outputs on the stereo, or the RCA jacks. if its the speaker level outputs (the wires, not the RCA plugs) then all you need is the amplifier bypass harness. Unplug the amp, plug in the bypass harness, and away you go. If its using the RCA jacks, you'll need to change the install kit that the radio is using to the type that uses the speaker wires, and then add the bypass harness.

[phoenix]

What I've discovered is that even with the smaller amp, swapping to 3-ways makes a WORLD of a difference. I could not believe the difference. The only "foreign" component in my system is the pre-amp in the aftermarket head unit (which is why I haven't yet installed the JBL amp, it blows the fuse right away), so I'm guessing it enhances the 3-ways beyond how a stock head unit might have fared. But man, what a difference just those two rear speakers by themselves had made!

Primarily the bass. 2-ways sounded like a Walkman in a tin can by comparison.

[warwgn]

Thain,

I don't have the stock stereo. I have an aftermarket Clarion AM/FM/CD player that was installed by a previous owner.

ok, well in that case the answer is maybe. You'll need to know if they used the speaker-level outputs on the stereo, or the RCA jacks. if its the speaker level outputs (the wires, not the RCA plugs) then all you need is the amplifier bypass harness. Unplug the amp, plug in the bypass harness, and away you go. If its using the RCA jacks, you'll need to change the install kit that the radio is using to the type that uses the speaker wires, and then add the bypass harness.

Ok, so you're saying that I DO have to rip my dash apart to check and change the harness? I was hoping to avoid that, but if there is no way around it, then them's the breaks.

[gadget73]

Well, either way you need the bypass harness in the trunk. Get that and install it. If you have sound, then all is well. If you don't have sound, you'll have to look into it further. I'm going to go out on a limb and say that most stereo install kits are using the speaker level outputs, so most likely its fine. Coincidentally, thats also why the JBL amps blow up when used with an aftermarket stereo. They are expecting a line-level signal that won't even drive a speaker, not 30 watts of power.

[warwgn]

As I said before, the entire Stereo system is factory stock original... except for the aftermarket head unit. Everything still works fine, but because the amplifier is crapped out, I have no sound.

[gadget73]

If you did'nt already have a separate aftermarket amplifier installed then your stereo isn't wired with the rca jacks, and you don't have to do anything in the dash.

There are instal harnesses available that connect the RCA jacks on an aftermarket head unit to the JBL or Premium amp. Not many people sell them or know they exist, but they do. This is really the only proper way to do a JBL amp with an aftermarket head unit since use of that part will keep the amp from being overdriven and burned up. Chances are that he doesn't have one though.

[mikeceli]

The JBL amp in my 88 failed and blew it's fuse. My radio repair guy fixed the amp, for approx. $150.

[Mondragon]

hey guys if you have a junk yard by you look in the lincoln continintal. they have a small amp in them, it will have the small plug on one side the large one on the other. . they will eather be black or silver they will work. also can be found in mecr. cougers and tunderberds. I bought 1 just the other day so i would have tunes again till work picked up and i could get a jbl back, the small one worked great. it came out of a continital. there are all ready mounting spots in our marks to mount them. I have an atremarket radio to with wireing harnesses to conect to stock radio harness. Like i said the small amp works just fine. any junk yard should have any of these cars and the amp is super cheap. hope this helps

[gadget73]

The silver one is the premium sound amp. Some of the Continentals have the JBL amp too, as do 80s Towncars. 80s townies with a JBL are fairly uncommon though. The 90s Towncar JBL amp has subwoofer outputs. Not entirely sure if you can just drop one of those in place of a Mark VII JBL amp but one of these days I want to try it. I'd like to add a small sub to my car, and if I can do it using all factory equipment it would be pretty cool.

[artbaileyjr]

The silver one is the premium sound amp. Some of the Continentals have the JBL amp too, as do 80s Towncars. 80s townies with a JBL are fairly uncommon though. The 90s Towncar JBL amp has subwoofer outputs. Not entirely sure if you can just drop one of those in place of a Mark VII JBL amp but one of these days I want to try it. I'd like to add a small sub to my car, and if I can do it using all factory equipment it would be pretty cool.

I gave that a try. It has a satellite amp that piggybacks to the main amp and drives the sub. Everything connected. (Plugs on the main amp were the same) I came up with absolutely no sound. To be fair; I put all of 5 minutes time into it, then put it on the shelf for another day. It is probably something simple; I just didn't have the time to work it through that day, and it's been on the shelf ever since.

Onto the other subject. You CAN drive the JBL with the outputs of an aftermarket head unit. The rears have a floating ground and will get pi$$ed if you try to connect the negatives (spk out -) on everything I've tried except for "Sony" brand. Any other brands (and I've installed a few) will give you trouble if you try to connect them line for line. If you blow the JBL, it's because you were trying to drive it WAY beyond it's limits or you just did something stupid like connect the outputs of an arc welder to the inputs. Whenever you connect the speaker outputs of an aftermarket head unit to the inputs of a factory amp, THERE IS A SERIOUS IMPEDANCE ISSUE, but it will make sound. The "Premium Sound" (small amp) also works the same with the same impedance issues. The pre 1988 amp offers it's own challenge but again will work with enough patience. Simply throw the instructions and provided recommended connection schematic relative to the rear speakers away. (all amps) They are useless (for the better part).

Crutchfield still can provide an amp bypass harness and/or an impedance matching device, but I have removed them on several cars I purchased and drove the JBL directly with the aftermarket head unit(s) until a suitable OEM or modified OEM head unit could be installed.

If it's add on goodies you are looking for, simply send your head unit to Paul Protos and tell him what you want.

If you want to try to drive the JBL with your speaker outputs, try one of these. I don't like 'um and pull them out, but I have my own way of making things work.



Good luck.

("Been there, done that!") Art

[Mondragon]

The silver one is the premium sound amp. Some of the Continentals have the JBL amp too, as do 80s Towncars. 80s townies with a JBL are fairly uncommon though. The 90s Towncar JBL amp has subwoofer outputs. Not entirely sure if you can just drop one of those in place of a Mark VII JBL amp but one of these days I want to try it. I'd like to add a small sub to my car, and if I can do it using all factory equipment it would be pretty cool.

I seen one like that that had a extra jack line but was not sure if it would work. hmm also seen a small silver one that had fins all the way across the top. ment to pick that one up to. it was the same size as the other black or silver amps but was finned like the jbl unlike the black one I got that was just finned on the sides. But as far as the JBL's so far I have not found one at any yard yet.
Great topic Im sure this will be helpfull to all, now Ill be sure to check the towncars to. know we just need picks of all the amps that will work with our marks.

[artbaileyjr]

These are the two amps that were typical to the Mark VII even though the "Premium Sound" amp in the image was harvested from a '92 Conti. It's the same for all intents and purposes. The small finned aluminum colored amp is also a plug and play replacement (sorry, no image) as is the one that is black and marked "JBL".

Just for reference sake, the pre '88 amp is pictured below and is not compatible with ANY of the above amps. It is a totally different animal.



Art

[ZeroSymbolic7188]

I just want to make sure that I understand the info in this thread properly because I have blown my JBL amplifier.

I have an after market Pioneer SuperTunerIIId Head Unit. Alpine 6.5's in the front and Kenwood 6X9's in the back.

The guys at the Audio shop gave me a bypass harness and everything works, but I have lost a LOT of volume and Low End.

I want to achieve the sound that I had when the amplifier was working.

Here are my questions:

1. Can I simply just turn up the volume and bass with the bypass harness or will I blow something? This seams like the easiest fix.
2. If option one is a no go, is the premium silver as good as the JBL?
3. If it isn't can I get some kind of after market amp to make this all work out?
4. If I wanted to repair the JBL what kind of shop would I call to see about that?

[CDW6212R]

A separate amp will almost always be louder and cleaner sounding than a head unit that has a tiny internal amp. If the harness is the correct one, turn up the volume until you detect the distortion. That's your limit.

Send the JBL to Paul Protos for rebuilding, like the other dash components. He's the best for that.

The clearest sound should come from a HU with RCA cables, leading to high end amp(s), and then to speakers. Most HU's have around 1% distortion, a good amp should be better than 0.1%, and great would be like the old Nakamichi PA amps, at .003% distortion.

[WHITEOXLSC]

I just want to make sure that I understand the info in this thread properly because I have blown my JBL amplifier.

2. If option one is a no go, is the premium silver as good as the JBL?

No they are not, but they will interchange with one in other. The silver (sometimes black) are about 80 watts (20 X 4) whereas the big JBL is 140 watt (35 X 4) with lower distortion. You have two choices, either get your 20 plus year old JBL amp professionally rebuilt by Paul Protos and risk blowing it again or get something more compatible to your head unit. The original Ford/JBL system is an awesome system when it is functioning as designed. The components were all designed to work together as a system and they did so very well. BUT one thing to keep in mind is that these are now 20 plus something years old and will need service at times, especially if pushed to it's limits. The only thing you had left in yours is the JBL amp, which is really not compatible with much of anything other than the Ford/JBL head units it was designed to work with. People have used different components mixed with the JBL system with varying rates of success. My suggestion is since you pretty much removed most of the JBL system, go out and buy an amp compatible to your head unit, instead of doing the guessing game. Don't toss the JBL amp, as it has some value even in it's non-working state. It can be rebuilt....

PS it doesn't hurt to Email Paul and ask if the head unit you are using with the amp is causing it to go poof, or is it old age
This is my original that blew it's fuse one day. Going to send it back to Paul for a complete rebuild in the near future. I am using one that I picked up from the Pick n Pull, but since it is the same age I am sure it will go someday........

[mikeceli]

When my JBL amp failed, I took it to a Radio Repair Man, who fixed it up just fine! Maybe $150? I forget.