Factory fader removed, causes cutouts with the aftermarket headunit

[dictoresno]

Just installed a Blaupunkt Beverly Hills after my father's 20+ year old Blaupunkt Nevada was DOA in his 86 Carerra he gave me. Followed the same colored wiring for the new unit, it works just fine except for the fade and balance.

the factory fader was removed years ago, and the Blaupunkt was installed along with a Sony CD changer in the glove box. CD changer was removed years ago after a factory harness rewire but the regular Blaupunkt head unit and a circa 1987 ADS Power Plate 100 amp remained mounted under the passenger seat.

I recently took possession of the car and replaced the Blaupunkt unit with a new Beverly Hills model, kept the ADS Power Plate amp and replaced the speakers with new Infinity models. for the most part, everything works great and sounds perfect.

but I noticed if I play with the fade or balance, the car favors the rear speakers and can entirely cut out the front ones when it shouldn't. I have a feeling the removal of the factory fader is causing this. I read a few threads discussing a 6 pin connector that's under the center console that is where the 4 speakers grounds and power wires meet and could be causing the issue.

anyone else have the issue where the sound system sounds fine, but adjusting the fade or balance really messes with the sound after removing the factory fader?

the amp is connected to the head unit via brand new RCA cables. for the most part, the front/rear fade sounds good (sound favors the rear a little) and the front speakers are definitely working and hitting. but like I said, if I play with the fade or left/right balance, it tried to cut out the front speakers. here us a pic of my Power Plate, but im sure the factory fader having been removed is an issue.

[blucille]

A couple of things.

I would start by disconnecting one speaker/amp output at a time and see when the problem goes away. It sounds like one output might be shorted. It doesn’t take much for a strand or 2 of speaker wire to touch the other output terminal.

It’s also possible one speaker somewhere is out of phase, this will sounds like a significant reduction in low frequencies as you adjust the balance or fader back towards the center from mostly left or right or front or back.

Since the 6 pin connector is driving 4 speakers, you are sharing some grounds on that connector, most likely between the front pair and the rear pair, just be sure all 4 speakers and seeing minimal resistance on the ground speaker terminal at the amp.

[darrin]

dictorsno -- the amp pictured above is a 2 channel amp, it's fed by a stereo rca signal from the radio and feeds a stereo pair of speaker outputs. I'd first check to confirm that all 4 speakers are indeed powered by this 2 channel amp, as you appear to indicate above. You could do this by simply disconnecting the RCA cable feeding the amp and confirming sound no longer comes from any of the 4 speakers. Report back once you've observed the effect of disconnecting the rca cable from the amp.

If this test confirms that both the front and rear left speakers are powered by the amp, then all 4 speakers are being powered by either the radio's front or rear speaker outputs and the radio's fader would affect sound output only when it's significantly limiting the signal going to its outputs feeding the amp.

The balance issue's a bit more perplexing (especially if all 4 speakers are powered by the 2 channel amp) -- I'd follow the process bluecille outlined above to see if you can identify a shorted output.

It's less than ideal to power all 4 speakers from a single amp designed to power 1 speaker per channel. I'd recommend remedying this by a) rewiring the speakers so that only the front/door speakers are powered by the ads amp (I use the same amp in my targa to power my door speakers and it sounds really nice), and then either b) feeding the rear speakers with the amp built into your radio, or c) leaving the rear speakers off altogether (I find that I have better sound in my targa w/o the rear speakers on).

[dictoresno]

Originally Posted by darrin

dictorsno -- the amp pictured above is a 2 channel amp, it's fed by a stereo rca signal from the radio and feeds a stereo pair of speaker outputs. I'd first check to confirm that all 4 speakers are indeed powered by this 2 channel amp, as you appear to indicate above. You could do this by simply disconnecting the RCA cable feeding the amp and confirming sound no longer comes from any of the 4 speakers. Report back once you've observed the effect of disconnecting the rca cable from the amp.

If this test confirms that both the front and rear left speakers are powered by the amp, then all 4 speakers are being powered by either the radio's front or rear speaker outputs and the radio's fader would affect sound output only when it's significantly limiting the signal going to its outputs feeding the amp.

The balance issue's a bit more perplexing (especially if all 4 speakers are powered by the 2 channel amp) -- I'd follow the process bluecille outlined above to see if you can identify a shorted output.

It's less than ideal to power all 4 speakers from a single amp designed to power 1 speaker per channel. I'd recommend remedying this by a) rewiring the speakers so that only the front/door speakers are powered by the ads amp (I use the same amp in my targa to power my door speakers and it sounds really nice), and then either b) feeding the rear speakers with the amp built into your radio, or c) leaving the rear speakers off altogether (I find that I have better sound in my targa w/o the rear speakers on).

thanks for your insight. when I installed the new radio, I did see there were RCA plugs under the dash that feed the amp. I was not really under the passenger seat to review the amps wiring, but im going to need to go back under there to test which speakers are powered by what. I totally didn't realize it was a 2 channel amp. even with the fade and balance set to 0 all four speakers work as they should, the rear deck speakers seem to overpower the fronts. not sure if that's due to the acoustics of the car or if they are the ones powered by the amp.

ill have to dive back in and check to see what's going on with the wiring when I go to replace the glovebox insert. that way ill have full access to the wiring behind the dash. I did recall there are some old RCA plugs that I believe someone may have spliced onto the ends of the speaker wires. I don't know, the system was installed back in 1988. ill need to test it all out and possibly just remove the Power Plate and opt for a normal 4 channel Alpine as a new replacement for it.

[blucille]

I know you're not that far from me, I'd be happy to help.

[dictoresno]

So it looks like I made a mistake, this is a Power Plate 120, not a 100. This model is has a "2 Speaker/4 Speaker" button and it was in 4 Speaker mode. I assume this means the channels are bridged? sorry for the blurry pics. the RCA inputs run from the back of the headunit to the inputs on the amp. but it looks like the RCA wires are yellow sheathed under the dash but black on the amp.




worth noting, the white RCA wire on the amp wasn't fully seated and the collar wasn't screwed in (2nd pic of the amp). I tightened it up and will re-test the sound later.

as for the speaker wires, there's only two pair going into the amp (green/green yellow and gray/gray yellow. I don't see those on the factory wiring diagram.



after screwing in the RCA terminal, it appears the front and rear speakers both hit equally and sound great. adjusting the F/R fade and then L/R balance is still funky. but now that the audio sounds better after screwing in that cable, there is no need to mess with it.

one thing I can't stand however is the radio will lose its bluetooth connection after parking for awhile and I will need to re-pair it. wonder if its not getting a constant 12v.

[dictoresno]

I decided to remove the old original RCA plugs, and assuming they run from the amp to the kick panel where they need another set to get to the radio as pictured. I decided to just buy a 15 foot male to male RCA plugged input wire. That way, I can make one complete run to the amp from the radio for inputs instead of needing two sets of RCA wires.

as for the speakers, I assume the two pairs of L and R speaker outputs feed both front and rears, as pictured in the wiring diagram from the original factory manual for the P120. two of the 4 speakers must feed off of the other two. I guess this could explain why the fade and balance don't work properly if they are wired in this format.

[blucille]

I believe the dash mounted fader takes speaker-level input and sends it out. In other words it could be wired one of two ways.

Speaker level output from the head unit starts as left-right only and feeds 4 speakers. Or. After the amp. 2 of the outputs feed the fader and gets fed to 4 speakers from there.

[dictoresno]

I don't even see the factory fader on the wiring diagrams, with or without the audio pack.

[fallingat120mph]

After trying to make the original wiring (with fader also, 86 coupe) I gave up and undated everything.

I remember the fader wiring and fader itself from the factory was a rats nest of sorts. Removing all the wiring in regards to the stereo system was eye opening.

New power, speaker and amp wiring are all direct to and fro from the head unit...speakers all wired from new amp, of course...

Probably not what you want to hear necessarily, but after going through a little of what you are going through, updating some things, mostly the factory wiring (removal) really made things very clear about the old system and just how dated it was.

Old wiring, no relays, questionable grounding...food for thought.


Erik

[dictoresno]

I guess the reality is I don’t need the fader and I’m not looking to explore its functionality. In its current wiring, the system has worked fine for the past 30+ years. I just noticed that when I mess with the balance and fade, it doesn’t do what I figured it would. But now that I see the way the amp is wired and how it’s running four channels off of a two channel amp, there’s obviously much deeper wiring going on that the original installer did that I really don’t wanna mess with. I think my original curiosity as to why the system did not sound as even as it should be was because the RCA plug was not secure on the amp. Now that it is, the system sounds much better, balanced front and rear.

The only thing like I said that I think I will do is just replace the RCA plugs that come out of the amp that go under the passenger side kick panel and then get sent through a second set of RCA plugs to the radio and just replaced them with one long strand of unbroken cables to minimize the chances of sound loss.


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[dictoresno]

so I abandoned the original RCA plugs and ran a net set to the amp. while the stereo was on, I was able to tell that by pulling the Left RCA jack, it cut out the rear speakers and by pulling the Right one, it cut out the fronts. so they are wired that way instead of true left and right.