[Nura]

Hi! I have run into a noise issue with my new install & any help will be sincerely appreciated.

Car : 2017 Maruti Suzuki Alto 800 (a very small Indian hatchback)
HU : Alpine CDA 9887 (been using it for 14 years without any problems) connected to DSP with a pair of RCAs
DSP : Audison Bit One (using a DSP for the first time)
Amp : Audison AV 5.1k HD
Front : Hertz Mille Legend 2 way (passive, plan to go active after a few months)
Sub : Audison Voce AV 12 in sealed enclosure
DSP and Amp installed on wooden board fixed to back of rear seat
RCAs and power cables run on opposite sides of car

Problem
Clicking noise while playing a CD at very low volume
Alternator hum when stepping on gas
Noise gets obscured by the music at increased volumes but the music sounds terrible

Aux instead of Master
If I switch off the Alpine HU and attach iPad or iPhone to DSP via aux cable and switch DRC from Master to Aux 1 there is no noise whatsoever and the music plays beautifully
Aux cable is running on same side of car as RCAs

Efforts made and results

Switched on Alpine HU
Selected FM radio
Noise - Same

Selected CD with no disc in drive
Noise - Disappeared

Removed HU's ground wire which was going into the harness & grounded it to the chassis
Noise - Same

Unplugged radio antenna from HU and removed from vehicle
Noise - Same

Removed HU from dash without disconnecting and moved it around
Noise - Same

Disconnected RCAs from DSP
Noise - Disappeared

Reconnected RCAs to DSP and disconnected them from HU
Noise - Disappeared

Replaced battery negative to chassis cable with a thicker one
Noise : Same

Plans
Replace engine ground cable with thicker
Replace alternator ground cable with thicker
Test with another HU if I can procure one

My gut feeling is that the Alpine HU has gone bad. But shouldn't one expect a defective HU to emit noise also in no disc mode?
My sincerest thanks in advance for your replies and apologies for the long post.

 

[Lonestardiver]

By selecting CD you are working through a different electrical/electronic/circuit path. So the issue is likely in that area if I read your posting correctly. If the noise is related to just that input circuit then that area is likely where the problem lies.

Regardless, the alternator hum could be due to rectifires going out in the alternator or poor filtering in the alternator. A choke on the power line (positive) usually blocks the AC hum you speak of.

How old is your HU? Do you have one you can quickly swap out to see if the problem persists? That would be a quick validation that at least some of your issues are HU related.

 

[Nura]

Thank you for replying, Lonestardiver.
The noise is present in radio as well as CD mode. However there is no noise when I use Apple Music on an iPhone or iPad connected to the DSP via aux cable. Hopefully Apple Lossless will be here soon and I may not feel the need to use the HU at all.
The HU is quite old. I bought it about 14 years ago and used it in another car for about 10 years. When I sold that car I transferred it to this vehicle.
Thanks for the suggestion of the choke on the power line.

 

[miniSQ]

DSP : Audison Bit One (using a DSP for the first time)

Can you bypass the Bit One? they can be noisy.
DSP : Audison Bit One (using a DSP for the first time)

 

[Nura]

Thanks for your suggestion miniSQ.
Is this how I do it?
Disconnect the AD link cable from the amp
Disconnect the RCAs from the Bit One and connect to the amp
Do I leave the AC link cable connected or do I need to disconnect that too?

 

[cman]

Well it sounds like it is your headunit if the noise is only there when your headunit RCA's are hooked up...

If you are wanting to keep the headunit the only thing you could try since you have already tried moving around the ground wires on the HU would be to get an RCA ground loop isolator that connects in line on your RCA's

 

[cman]

I should also add, if your DSP is in line down signal from your HU on your RCA's then it could also very well be it. You need to remove variables from your RCA signal path to determine what it is. You have already determined it is something in the RCA signal path by removing the RCAs the noise stopped... so its either your headunit or your DSP if it is also hooked up in line on your RCA signal path... which I would guess it is..although you said you were using passive crossovers up front?

 

[Nura]

I should also add, if your DSP is in line down signal from your HU on your RCA's then it could also very well be it. You need to remove variables from your RCA signal path to determine what it is. You have already determined it is something in the RCA signal path by removing the RCAs the noise stopped... so its either your headunit or your DSP if it is also hooked up in line on your RCA signal path... which I would guess it is..although you said you were using passive crossovers up front?

Thanks for your replies, cman.
This is how the gear is linked HU, RCAs, DSP, AD link and AC link cables, amp, speaker wires, crossovers, front speakers. Same amp is also connected to the sub. There are no RCAs between the DSP and amp. If I disconnect the DSP ends of the RCAs, keeping the other ends connected to the HU, there's no noise. There's also no noise if I reconnect the RCAs to the DSP and disconnect the other ends from the HU.
Because of the noise issue, I have mostly been listening to music from my iPad or iPhone connected to the DSP via an aux cable. There is no noise in this circuit.
I also feel that when I am playing a CD the speakers on the right side sound a wee bit louder than those on the left. I checked the balance controls on both the HU as well as the DRC. They are in the centre.
However, the music seems perfectly balanced right and left when the iPad and iPhone are being used.

 

[cman]

Thanks for your replies, cman.
This is how the gear is linked HU, RCAs, DSP, AD link and AC link cables, amp, speaker wires, crossovers, front speakers. Same amp is also connected to the sub. There are no RCAs between the DSP and amp. If I disconnect the DSP ends of the RCAs, keeping the other ends connected to the HU, there's no noise. There's also no noise if I reconnect the RCAs to the DSP and disconnect the other ends from the HU.
Because of the noise issue, I have mostly been listening to music from my iPad or iPhone connected to the DSP via an aux cable. There is no noise in this circuit.
I also feel that when I am playing a CD the speakers on the right side sound a wee bit louder than those on the left. I checked the balance controls on both the HU as well as the DRC. They are in the centre.
However, the music seems perfectly balanced right and left when the iPad and iPhone are being used.

OK Great, I just realized you said the noise disappears when you disconnect the RCA's from your headunit. That pretty much solves the mystery. It is definitely your headunit. The headunit is not nessicarily bad per say, sometimes it is just how certain devices function when connected together. Some play well adn some create different ground potentials and pick up noise...

I would get a ground loop isolator. They are pretty generic so any decent quality one should do just fine. You can find them on ebay, Amazon, they connect in line on your RCA's and you should be able to get rid of the alternator whine... If that does not work, I would try hooking something else up to the RCA's... Like maybe a DVD player and see if it also creates the noise like your headunit does when connected

 

[Nura]

OK Great, I just realized you said the noise disappears when you disconnect the RCA's from your headunit. That pretty much solves the mystery. It is definitely your headunit. The headunit is not nessicarily bad per say, sometimes it is just how certain devices function when connected together. Some play well adn some create different ground potentials and pick up noise...

I would get a ground loop isolator. They are pretty generic so any decent quality one should do just fine. You can find them on ebay, Amazon, they connect in line on your RCA's and you should be able to get rid of the alternator whine... If that does not work, I would try hooking something else up to the RCA's... Like maybe a DVD player and see if it also creates the noise like your headunit does when connected

Thanks again, cman. Yes, finding a ground loop isolator shouldn't be too difficult.
Can we safely rule out noise from "dirty power" to the HU? Because this I think needs an in-line power noise filter, which doesn't seem to be available here on Amazon.

 

[dumdum]

I’d put money on the bit one…

 

[dumdum]

OK Great, I just realized you said the noise disappears when you disconnect the RCA's from your headunit. That pretty much solves the mystery. It is definitely your headunit. The headunit is not nessicarily bad per say, sometimes it is just how certain devices function when connected together. Some play well adn some create different ground potentials and pick up noise...

I would get a ground loop isolator. They are pretty generic so any decent quality one should do just fine. You can find them on ebay, Amazon, they connect in line on your RCA's and you should be able to get rid of the alternator whine... If that does not work, I would try hooking something else up to the RCA's... Like maybe a DVD player and see if it also creates the noise like your headunit does when connected

You remove a ground loop, where the ground loop is from isn’t nesc the headunit… it could be rcas, hu, processor… it doesn’t mean it’s any one item, and definitely not 100% the hu…

a ground loop isolator may band aid it… but if the processor is new I would suggest nipping to the shop (or if it’s from eBay return it) and asking them if they have a different brand of dsp to try, from experience I won’t fit or tune bit ones, too many… guess what I’m gonna say… noise issues sadly

I hate to sound like a broken record, but helix are pretty damn awesome although I’m not sure of cost vs a bit one

 

[cman]

You remove a ground loop, where the ground loop is from isn’t nesc the headunit… it could be rcas, hu, processor… it doesn’t mean it’s any one item, and definitely not 100% the hu…

a ground loop isolator may band aid it… but if the processor is new I would suggest nipping to the shop (or if it’s from eBay return it) and asking them if they have a different brand of dsp to try, from experience I won’t fit or tune bit ones, too many… guess what I’m gonna say… noise issues sadly

I hate to sound like a broken record, but helix are pretty damn awesome although I’m not sure of cost vs a bit one

Dumdum is right, the Ground loop isolator is kind of a band aid.. but they generally work pretty well. Thats why i mentioned trying hooking up a DVD player to the RCAs his headunit was hooked up to... to eliminate the variables

I do not think it is the DSP because he said once he disconnects the RCA's from the back of his headunit while the DSP is still on, the noise disappears.. correct?

 

[cman]

Also, the power filter could or could not work on the power for the headunit... its basically isolating it similar to what a ground loop isolator is doing on the RCA's...

It's a process of elimination

 

[Driftdad541]

The Audison bit one is known to be noisy as has been said by MiniSQ...but as a general rule of thumb its never a bad idea to run your ground from the head unit to the rear of your vehicle and connect with the rest of your gear. I use a ground distribution block for all my grounds in the system and have had success in doing so. Some people will run a ground wire from the battery to the rear but I've just grounded to the subframe/chassis rail and kept everything in the rear compartment on one ground separately from the battery and it's been a non issue. Peter from PSSOUND also runs his grounds the same way so I figure it's definitely legit. He also had issues with noise from the Bit one in a customer's car if I'm not mistaken.

 

[Bass Face]

Good sir, I think the main issue is the fact that all this great gear is in a Maruti.....

 

[dumdum]

Dumdum is right, the Ground loop isolator is kind of a band aid.. but they generally work pretty well. Thats why i mentioned trying hooking up a DVD player to the RCAs his headunit was hooked up to... to eliminate the variables

I do not think it is the DSP because he said once he disconnects the RCA's from the back of his headunit while the DSP is still on, the noise disappears.. correct?

How is a ground loop formed? It’s a small amount of current/voltage differential between grounded components (important) which induces a small potential to cause a small current to flow between devices

If you have a helix and have adep turned on you get a ground loop, disconnect the rcas and you lose the noise… it’s 100% the adep being enabled that causes the noise, but by your theory it must be the hu… that’s an example of how a dsp can create noise…

it just means some link in a chain has been undone, you can unplug rcas and break the chain, it doesn’t mean it’s one component or the other, break the chain at any point and it will silence you could unground the hu while it’s chassis is touching the amplifier and it should remedy the issue also unless it’s a grounding issue in the dsp which I have encountered a few times…

using a none grounded component like a DVD player or phone will remove the ground loop no matter where it’s created as the ground to the source needs to be present to cause the loop, it’s all one big chain, he has done this already with an auxiliary in, it certainly doesn’t mean it’s the hu, I don’t think I have ever had a ground loop caused by an alpine hu, Rcas and bit ones, a fair few times (I have also had it with pioneer with the pico fuse being blown, but that is down to user error)

 

[Nura]

You remove a ground loop, where the ground loop is from isn’t nesc the headunit… it could be rcas, hu, processor… it doesn’t mean it’s any one item, and definitely not 100% the hu…

a ground loop isolator may band aid it… but if the processor is new I would suggest nipping to the shop (or if it’s from eBay return it) and asking them if they have a different brand of dsp to try, from experience I won’t fit or tune bit ones, too many… guess what I’m gonna say… noise issues sadly

I hate to sound like a broken record, but helix are pretty damn awesome although I’m not sure of cost vs a bit one

Thanks for this suggestion, dumdum. I probably won't be able to return the Bit One. I bought it new but more than 1.5 years ago. Because of the prevailing conditions, this install took way too long. Wish I had come to DIYMA earlier. I would almost certainly have bought a Helix DSP.

 

[Nura]

Dumdum is right, the Ground loop isolator is kind of a band aid.. but they generally work pretty well. Thats why i mentioned trying hooking up a DVD player to the RCAs his headunit was hooked up to... to eliminate the variables

I do not think it is the DSP because he said once he disconnects the RCA's from the back of his headunit while the DSP is still on, the noise disappears.. correct?

Thanks for your reply, cman. Yes, this is what's been happening.

 

[Nura]

The Audison bit one is known to be noisy as has been said by MiniSQ...but as a general rule of thumb its never a bad idea to run your ground from the head unit to the rear of your vehicle and connect with the rest of your gear. I use a ground distribution block for all my grounds in the system and have had success in doing so. Some people will run a ground wire from the battery to the rear but I've just grounded to the subframe/chassis rail and kept everything in the rear compartment on one ground separately from the battery and it's been a non issue. Peter from PSSOUND also runs his grounds the same way so I figure it's definitely legit. He also had issues with noise from the Bit one in a customer's car if I'm not mistaken.

Thanks for your suggestion, Driftdad541. I will certainly try it out & report.