Alternator whine and other noise problems.

I am at my wits end trying to solve system noise issues. I am dealing with 3 separate problems that all cropped up at the same time. I have a new alternator whine, a low rumbling static like sound, and system hiss that all cropped up when I installed a DSP into my system.

Background:

I received a Dayton DSP-408 for my birthday last week. Got it installed 5 days ago and have been chasing noise ever since.

my old setup that was noise free was a older pioneer hu into a PG tantrum 600.4 with two channels feeding front passives and two channels bridged to my sub. Being a single amp system I had the power and ground wires direct to the amp, no distribution blocks needed.

My new setup is Hu to DSP-408 using the same 2 pairs of rca cables that i already had in place. from the dsp I have 2 new short rcas to the old PG amp. added a third set to a MTX thunder ta202 to power my tweeters. I re used the same power and ground cables by running them into distribution blocks and than ran new power and ground wires from there to both amps plus the dsp.

after installing I keyed on the system and I immediately noticed a system hiss and a low rumble sound coming from my door woofers and my sub. after lowering the main volume on the dsp I got the hiss to a manageable level and after some experimenting I found that the rumble only occurs when I have my HU set to disc. it does not make the noise when using the tuner or aux input. I initially thought it was no big deal because I use my aux in 90% of the time.

After finishing a basic set up of the DSP i finally started the engine and than I was greeted by a very loud whining noise. as a temporary band-aid I was able to lower the main volume on the dsp another 20 points to get it to the point of minor annoyance as opposed to piercingly shrill.

Things that I have tried to isolate or eliminate the noise:

I replaced the factory ground cable from the battery to the chassis with a much larger wire. no change.

Ran a new dedicated ground from the battery to the HU. Made the noise worse.

ran a temporary connection from the oem radio ground wire the the HU chassis. The noise got slightly better.

Removed the oem ground and the direct to battery ground and installed a ground wire from the HU to my distribution block so everything in the system has a common ground. noise is the same as it was running the oem radio ground but better than it was running a ground wire direct to the battery.

tried testing the system with the HU out of the dash and resting on my knee. no change.

I tried disconnecting the rcas from the back of the HU to see if I was picking up noise in the cables. with the system powered up and the rcas connected to the dsp but not the HU my alternator whine is gone but my noise floor hiss is still present.

Tried swapping to an old Kenwood HU that I had sitting around. Noise is unchanged.

I double checked and freshly sanded my ground point in the trunk to see if that would help. No change to the noise.

The last thing I can think of to try is looking for a different part of the chassis to ground my distribution block which I am going to attempt later today.

If that fails than the only other things I can think of would be to add some dedicated ground cables for the alternator housing and the engine block to see if somehow i have a week factory ground causing an issue underhood, pulling a A/C ripple wave form on the charging system under load, or ordering a set of ground loop isolators like these https://www.crutchfield.com/p_127SNI1/PAC-SNI-1.html

now that I have a taste of what a fully active system can do I do not want to go back to passives again but these noise problems are killing me.

Any tips or suggestions would be very appreciated.

The only additional troubleshooting ideas I can come up with is to run a temporary ground wire from the HU back to where the amps and DSP is grounded. You may also try running RCA's across the top of the carpet directly from the HU to the DSP to see if it's maybe picking up something along the way. Last idea is to wrap a wire around the RCA shield at the HU and grounding it. I was thinking it could be a pico fuse inside the Pioneer, but you said you tried a Kenwood, so that eliminates it as a suspect...unless you have multiple issues.

What kind of rca's are you running? I prefer shielded cables in a standard unbalanced setup.

Currently I have the head unit grounded to the same point as the amps and dsp. no joy from that change.

i am running a mixed pair of rcas. one is a twisted pair the other is a coaxial type. beyond that i dont know much about rca cables but i can google it and see if i can provide more details if needed.

I will go digging to see if i can scrounge up a long enough rca to try a test run across the cabin.

one thing that has crossed my mind more than once is could i have a faulty dsp? I know the dayton units are not as nice as say a helix or what not and i have read that some people have noise problems with them. I just don't like to jump right to condemning a brand new part unless I can prove it is bad.

thanks for the replies gentleman. I will try some more things asap and get back with the results.

Just finished another round of testing. Tried grounding the outer rca ring to the HU. No change.

Ran another rca from the HU to the dsp across the seats. No change.

Unplugged the antenna lead. No change.

checked the alternator ouput. Found i am holding 14.1 volts at the battery under standard load (high beams, A/C on etc...) with 27mV ac ripple through the diode tree.

Are you using the Dayton master volume controller? Heard they can be noisy.


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No on the wired remote controller and yes on the bluetooth adapter. and just in case it matters the noise is the same with and without the BT dongle installed.

As another test I ran an extension cord out to the car and powered the DSP off of the supplied 110v adapter with the 12v in fuse removed. No change in the noise.

The only thing I have found that seems to eliminate the noise is to unplug the rcas from either the HU output or the dsp input.

As far as I can tell the noise is not present when the rcas are disconnected and I am streaming BT audio direct to the dsp.

Would it be possible that I have had a problem all along but it was masked by the passive crossovers? that is one way I could explain why I have noise issues on a previously noise free system but I have no clue if that is even possible.

Could be - are you able to change the RCA’s from the headunit to the DSP to confirm?


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I have tried a spare set of rca cables. noise unchanged. at this point i am seriously considering ordering a set of ground loop isolators. after reviewing the different kinds of rca cables available I will try and check all of my gear to see if they are single ended or differential inputs and maybe will try ordering some new rcas of the correct type as needed.

from what I gathered looking at the owners manual last night it seems implied that my PG amp uses differential inputs. I am going to guess that my mtx amp and my dsp us single ended inputs. if I can prove that to be the case than maybe swapping from twisted pair style to a set of shielded coaxial rcas may be of use for some of my gear.

Disconnect the input on the DSP and see if the problem continues. If so, disconnect the DSP output. If the problem goes away, it's definitely the DSP. If not, keep going down the chain until it goes away.

...process of elimination....

The noise floor with the engine off I believe is native to the dsp. I can get the master volume up to about 60/66 before i hear any noise with the engine off. With the engine running the alternator whine becomes audible about 38/66 on the master volume.

If I open the circuit between the HU and the dsp the alternator whine goes away but the base system noise remains. the system hiss near max volume is something I can live with as I can get my spl up to where I want it around 52-55/66.

I am starting to think I may have 2 bad HU's because I can disconnect the rcas from the HU and leave them connected to the dsp and the whine stops.

I am using twisted pair type rcas which after doing some google fu last night may be the wrong type for my needs. I need to confirm what type of input the dayton dsp 408 uses. I suspect it is single ended and not differential.

I am going to go digging through my boxes of odds and ends to see if I can dig up some shielded rcas to try as the ones I tested with yesterday were also a twisted pair design.

I am also going to bug my brother to see if I can borrow his HU for a test. His is only a few months old and I know it does not have any noise issues in his car.

Best case at this point is looking like a couple pairs of new rcas of a shielded type might solve the issue and worst case is I may need a new HU.

I will report back as things develop as well as checking periodically to respond to other peoples posts.

thank you all for the help and support. having other minds to bounce ideas off of is helping me keep my sanity as I work through this issue.

Quote:

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Originally Posted by Fernpatch

The noise floor with the engine off I believe is native to the dsp. I can get the master volume up to about 60/66 before i hear any noise with the engine off. With the engine running the alternator whine becomes audible about 38/66 on the master volume.

If I open the circuit between the HU and the dsp the alternator whine goes away but the base system noise remains. the system hiss near max volume is something I can live with as I can get my spl up to where I want it around 52-55/66.

I am starting to think I may have 2 bad HU's because I can disconnect the rcas from the HU and leave them connected to the dsp and the whine stops.

I am using twisted pair type rcas which after doing some google fu last night may be the wrong type for my needs. I need to confirm what type of input the dayton dsp 408 uses. I suspect it is single ended and not differential.

I am going to go digging through my boxes of odds and ends to see if I can dig up some shielded rcas to try as the ones I tested with yesterday were also a twisted pair design.

I am also going to bug my brother to see if I can borrow his HU for a test. His is only a few months old and I know it does not have any noise issues in his car.

Best case at this point is looking like a couple pairs of new rcas of a shielded type might solve the issue and worst case is I may need a new HU.

I will report back as things develop as well as checking periodically to respond to other peoples posts.

thank you all for the help and support. having other minds to bounce ideas off of is helping me keep my sanity as I work through this issue.

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YOU ARE NOT CRAZY, your HU's are NOT BAD, your RCA's aren't bad, your grounding isn't bad. Simplest way to verify if it's the DSP is run RCA from HU to amp. NO noise?(99.9999% you will say NOPE)

So that leaves the DSP as the culprit. I am of the similar history with OLD equipment but ZERO NOISE.......swap in this DSP and UGGGH! I thought I had a bad unit, ordered another.......back ordered....waited a month.......NEW UNIT........SAME NOISE RESULTS. UGGG.

Talking with Parts Direct where I bought it and their customer service team for months now. They said there is a prototype unit getting sent to them but who knows how long it will take to get to them for testing. So it's OBVIOUSLY a hardware or manufacturing issue.

My only hope is that if I put the bluetooth USB in that I can feed the DSP music directly but unsure how I would control volume as it would likely not be from the radio. Might be able to get me by till the MFG gets their you know what together and fixes the issue.

I agree that ACTIVE is WORLDS ahead of my old Clarion crossover that had NO NOISE for the past 21 years of use!(not kidding 21+ years actually) Using the same HU, same amps too!

Stop killing yourself trying different HU's, ground points etc. The only fix MAYBE could be ground isolation of the RCA's but even then still might not be it. It's DEFINITELY NOT your wiring or shielded/unshielded RCA's.

I signed onto this site just to post this so I may never get back here for anything other than to monitor this thread. If I find out anything new I will surely try and circle back around here to post it.

Background on me. Started back in 1994 working at a stereo shop and have been a stereo fanatic ever since but I KNOW how to install things correctly! I am no engineer but the installation and diagnostics I got! Did basically the same..........AM I GOING CRAZY routine you did.

Good luck!

it's nice to know I am not the only one to go nuts over a noise issue like this. at this point i have a mostly functional work around in place by reworking my gain structure. the noise is still there but it is low enough in intensity that i can only hear it on quite passages.

at this point I am waiting on doing anything until next month. if all goes well I will be ordering a measurement mic, some ground loop isolators, and some caps for tweeter protection duty after my next pay check. If i can't kill the whine with the addition of the isolators than I think my next step will be to contact tech support at Parts express and see if they have any other ideas.

at this point the only thing I know for sure is that eventually this mis adventure will be behind me and that it will be worth it in the end. 20 years of playing with car audio and even in a minimally tuned state this is one of the best sounding systems I have ever built. I have no doubt that once i get it sorted and fine tuned it will be the best I have ever done.

hopefully in about 2 weeks I will have all my needed tools to get this resolved and fully tuned.

I agree with Pinky. If you had no noise without the dsp then noise with it it's the dsp. It's the only thing that has changed. I've been through this myself and had to quiet things down with gain structure trickery to mask it. If it weren't for the ground lift switch on my Helix I'd have ground noise right now.

I am not familiar with the Helix but I assume that "lifting the ground" with a switch performs a similar function as a ground lop isolator inline with the rcas would do? if so than hopefully the isolators I ordered last night are going to be my ticket to moving past this headache and getting on with fine tuning and loving my newly improved system.

according to my tracking number my order from PE should be waiting for me when I get home from work today. Should have updates and hopefully a solution this weekend. next up is learn how to use REW and start taking base line measurements so I can dial in a tune with hard data instead of by ear. I am looking forward to learning some new skills soon.

Wired in some protection caps for the tweeters and installed a set of ground loop isolators. my noise and my bass both vanished. Removed the isolator from my sub out and got my bass back. after a few test drives I have noticed on one brief instance where my whine started to come back briefly and than went away again. Long term I think I may need to look into a higher quality isolator device as the cheapies I bought have a few quirks.

Overall I am happy that i no longer have a constant whine in the background any more. I am now changing my attention to getting set up for measurements. Hopefully I will be able to start a new tuning thread soon.