This past weekend I had the console/radio out to add an after market amp to the stock system. I used the two line level outs and the common to connect to a piece of RCA cable (Per Southbound’s awesome instructions!) then a splitter to send that signal to the front and rear amp inputs (no fader control). I tied the EQ out pairs together, but left the HU inputs open as I was not going to use the HU’s amp, but I HAVE SLIGHT INTERFERENCE/Noise.

I’m wondering now if I should have also connected the HU outputs (that I attached to my home made RCA cable end) to the HU inputs as well, maybe that would take care of the interference noise, but don’t know if this would take some signal from the output to the amp and/or cause even more noise for the amp to pick up.

At first I was planning to send the line level output to a Pioneer 6500 EQ then out to the amp, so I would still have fader control but I just could not get it to work through the EQ, so I had to route it directly to the amp and thus loose fader control.

The noise is not very loud and is only noticeable either with very low volume or during the quiet time in between tracks.

Iggy, Southbound, Bozzchem, anyone!, do you have any suggestions?

 

is this an aftermarket amp??? where did u run ur constant 12v and also ur rca??? cause that can cause a leak also...

 

Ran the 12v from the batt through a very small grommet just above the accelerator peddal, and then ran the RCAs under the right hand plastic air duct and around the parimiter of the passenger foot well to an aftermarket MTX thunder 4200x amp.

I'm sure the RCA's are close to power cables as it leaves the HU though, don't see a way around that??

 

Sorry guy, I can't help you here. This is exactly why I just ditched the whole Blose thing and went aftermarket.

I don't mind getting my hands dirty but this was more than I wanted to deal with.

Iggy and Southbound are the best ones to help you.

I have read about Iggy or someone else having a noise probllem that they later discovered the cause of.

I'd try doing a search using Iggy and see if it comes up for you.

Good luck and let us know how you fix it.

BTW, can you describe the type of noise you're getting? Does it change with the rpm of the engine or is it just a constant noise that never increases in volume?

It looks like you made your own RCAs...are you sure you've shielded them properly?

 

The sound is like a whirring/whining noise, and yes it does go up and down in pitch with engine RPM.

The RCA's I made were from an old set that I just cut about 10 inches of the end of and attached the bare wire ends to the HU out's and common. I could re-do that with one that I know is sheelded, not sure if this one is.

I'm thinking if I cannot get it to stop whining, then I'll try the full HU bypass and then us the HU speaker out's with LOC's and see how that goes.

When I have more cash flow i'd love to replace the whole thing too. I just hope that streeteffectz comes down on his $100 price tag for the dash kit, then maybe i'll consider it in the near future.

Till then, I'll have to make do with what i've got.

 

Leijie,
You are no doubt becoming aware of how sensitive the Bose HU-EQ combo is regarding noise. I ran into the same problem you have.

My recommendation would be to reconnect the HU ins and outs as they were and simply splice into the line outs. The problem with the way you have it now is that the HU wants some kind of feedback, weather it is from the EQ or even the HU itself. With the HU inputs open like you have there is some kind of ground loop created.

You don’t seem too concerned with fader control so the simple splice into the line outs effectively gives you a clean signal BEFORE the nasty EQ does its nasty little deed. In my case I wanted full fade and balance control so I had to use the speaker outs with a couple of LOCS to convert the signal. Of course, in doing so, I had to do the full bypass of the EQ which Southbound & I finally got figured out. Judging from your post I would hazard to guess you have done your homework on the issue.

I hope I didn’t confuse you; Southbound is a literary genius when it comes to getting the point across clearly.

You may have seen these but here is some good reading:

link1
link2
link3
link4

Good luck and let us know how it works out.

Iggy

 

Thanks Iggy! I had not thought of that one, (leaving the wiring stock and tapping the outs only). I’ll try that first.

And yes I have spent many an hour on this site reading through Southbound and your posts on this subject, and boy do I appreciate all the time and effort you guys have put in to it. Before I began this project I copied and pasted tons of information, photos, diagrams etc from you both to enable me to do this and made up my own set of documented instructions. Also the photos from www.carstereohelp.com on how to disassemble the console were totally invaluable.

I’m interested though, is the trade off (cleaner signal) of using the speaker outs through LOC’s worth it to retain balance control? How is the sound? I would think it may have more bass/treble being that it has already been amplified once?

The reason I ask is that even with the Polk’s in all doors (got one set from Bozzchem) there is still not enough treble for me, sounds muffled and low soundstage. Maybe I need to try the LOC’s with the EQ still hooked up! Or maybe I can just add a set of tweeters to the A post gusset, piggybacked off the Polk’s through a crossover. But seeing as i'm strapped for cash right now that idea will have to wait a while.

If you found that the bypass (in’s to out’s, L,R & common) using speaker outs with LOC’s worked for you and you don’t get any noise, and of course you get to keep fader control, would you recommend this configuration? Or if I can get rid of the noise by your other suggestion and don’t mind not having fader control, is the preferred way still to use the pre-amped L & R output as Southy wrote about?

I think I’ll try it set up like all of the above and see what happens.

Love this forum by the way! So glad I stumbled across it.

 

leijie,
Any luck?

Iggy

 

Hi Iggy.

I have not had time to take it all apart again this weekend. I hope to have time this comming weekend.

I'll let you know how it turns out. I plan on trying with the LOC's also so I can listen to the sound difference.

I'll post here when it's done.

THanks again!

 

leijie,

You have come to the right place. You can thank Iggy for coming to your rescue. He has dealt with the HU/EQ routine more than I have, and he has documented the correct bypass method in great detail.

I have been out of touch with the board for awhile as I am completely swamped at my real job.

If you don't have any luck soon, I'll try to clear some cobwebs from my head and see if I can give any other suggestions.

The only thing that comes to mind to me is in the way that you made up your RCAs as well as what Iggy has told you about the need for the HU/EQ input and outputs to all be terminated in some manner. THEY DO NOT LIKE TO REMAIN OPEN. The HU line inputs and line outputs are UNBALANCED... meaning that they have THREE wires involved. A PLUS, A MINUS, and A COMMON. An RCA plug is made to have ONLY TWO connections. So how did you connect the three wires to a two wire RCA connector? Get a good quality shielded cable for use in this application, and then explain EXACTLY how you connected which wire (using the description and color) from the HU to the RCA connector. You most likely have unbalanced a balanced line level signal which would be very suseptable to picking up eingine and electrical noise.

There should be very little noticeable sound quality difference whether you use the speaker outs or the line outs. As long as you DON'T go through the EQ, the bass and treble should be FLAT throughout the rest of the amplification stages. In theory the line outs should be slightly cleaner... but they are more difficult to deal with because of the whole balanced/unbalanced issue. Plus you lose the fader option, etc. The speaker outs are TWO WIRE UNBALANCED BUT FLOATING outputs. DO NOT TOUCH EITHER OF THE SPEAKER OUTPUT WIRES TO CHASSIS GROUND. BUT, Once you have performed the simple and CORRECT method of bypassing the EQ... The two wire speaker outs can be connected directly to a two wire RCA connector and should feed a floating LOC just fine without causing the noise issue. In fact, if you use the speaker outs to a LOC... you are BETTER off to use a TWISTED PAIR of wires instead of the shielded cable to connect to an RCA. Speaker outputs typically do NOT like to see the extra capacitance of shielded cable (they become unstable) So if the amp is all the way back in the trunk, then be sure to use twisted pair wiring IF you are taking the feed from the HU SPEAKER ouputs. If you are using LINE LEVEL signals then USE SHIELDED CABLE. If the AMP is up under the dash somehow... then you could probably get away with a short run of shielded cable in either configuration. The BEST WIRE to use if you are using the HU speaker outputs to feed a LOC would be to use a SHIELDED TWISTED PAIR of wires. This would be a cable with two twisted wires inside of a foil/shielded jacket all covered by an insulating outer sleeve. (Belden 8451 is an example) Connect one of the twisted pair wires (typically red) between the Positive Amp connection and the center pin of the RCA. Connect the other twisted pair wire (typically black) between the Negative Amp connection and the body of the RCA. Connect the SHIELD of the cable to the COMMON wire of the LINE LEVEL HU SIGNAL you are feeding from. LEAVE IT UNCONNECTED AT THE RCA END. This type of configuration will maintain the BALANCED signal while providing a STATIC shield. IF you tie the shield along with the negative wire to the body of the RCA you will UNBALANCE the signal. If you are using the SPEAKER outs of the HU... Connect the RCA per the same instructions just given EXCEPT connect the SHIELD of the cable to CHASSIS GROUND AT ONE END ONLY! Again DO NOT CONNECT THE SHIELD TO THE RCA ITSELF. Leave it open at the RCA end. You will short out the HU SPEAKER output stage if you do. The GOOD thing is that the HU is very forgiving and can survive a shorted output. It goes into a self protect foldback mode until the short is removed. SO don't be timid about trying different wiring configurations, until you come up with the one that works best for you... BUT try NOT to test that protection circuitry anymore than you have to. If you have shorted ONE speaker output.... ALL speakers will shut down.

ANY ADDITIONAL AMP MOD will add such better SQ to your system, that I wouldn't worry about which HU output you use from that standpoint. I would use the output which is the easiest to tame in terms of noise and buzz and whine etc.

I'm kind of surprised that the Polks are not bright enough for you. They are definitely too bright with the EQ still in circuit. I didn't really listen to them too long when I had my system in the EQ bypassed mode, because of the loss of overall gain. In your case you have the extra amp to makeup the gain just like Iggy's system... So you should sound fine. Once you have gone to the work of adding the amp... there are other speakers that you could choose from WITHOUT having to do any rolloff mod, etc.

Damn... there I just went again into a rambling session. arrrggghhhh

Good luck! Good to hear from you Iggy!
Southy