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TOPIC: Noise in system with engine on

Noise in system with engine on 3 weeks 4 days ago #44136

  • AfghanVet
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New install - the previous DSP showed this same issue - CDSP 8x12 DL is quite with engine off - with engine on there is a high pitched whine coming from the speakers - it doesn't increase with throttle - it is not affected by volume knob of car or wireless remote.

My installer has moved the grounding point of the DSP once already, and the noise was lessened, but not eliminated. I'm wondering if anyone has had experience with adding a device that would isolate better or have a 'filtering' affect?
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Noise in system with engine on 3 weeks 2 days ago #44236

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@AfghanVet

Mmh, this is weird.. this would be the first 8x12DL with any noise issues.. knowing we have 130dB DACs, I doubt it's the case of the unit here. Something else is going with your install or amps downstreams especially if the issue happens with another DSP. It "may" looks like the DSP is the culprit but that doesn't mean it's generating the noise... It could very well be because it's just closing the audio chain.

If the noise doesn't change with frequency, it's not engine whine.. it's digital noise that's most likely generated in your chain.
Standard troubleshooting applies.
a) Check your wiring and replace/swap wiring
b) Make sure your Head unit doesn't have any "unconnected wire connected to the unit (can induce noise to the active one.
c) Check your amps that they aren't the culprit. i.e. when audio connected, maybe they get noise.
d) Check your gain structure. i.e. lower your amp levels, increase the 8x12 levels.
e) What is your source here? line level or high level from a HU?

I don't think that 8x12DL is the issue here but more figuring out the above typical system audio tuning.. Just a thought.

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Noise in system with engine on 3 weeks 2 days ago #44246

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I witnessed the noise in AfghanVet's car this past weekend. It wasn't loud but loud enough to be annoying after you notice it and also a possible point killer in competition.

As this noise was already present with previous equipment - I would agree this is not an issue with the CDSP but the vehicle/install. The car is a late Model Audi S4 which has quite a bit of electronic gadgetry in it. I believe he is using analog & digital inputs on the CDSP.

Here is what I would do:

1) Grounding: Has the resistance between the DSP ground point and battery negative post been measured? Also, Is the ground to the DSP at a separate point than the amp? - If so has the resistance between those two points been measured?

2) Remove RCA connection on the Analog input to the DSP - Is the noise still present? If not, then it's emanating from the analog source or the interconnect cables between the source and DSP.

3) Remove connection from digital input to determine if it's emanating from that source.

4) If neither source is found to be the culprit then:
- Is the noise present in all speakers? - Mute speaker sets in the plugin to determine.
- If it's found to only be heard in a single speaker set (tweeters for example) then unplug the RCA connection to that amp to see if the noise goes away. If it does then it may be entering through the RCA cable between the DSP and amp. If not, then the noise is emanating from that amp.
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Noise in system with engine on 3 weeks 2 days ago #44250

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Thank you to the support team and to Ryan for providing feedback and a listing of helpful things to try.

I was in a bit of a rush when I made the first post. This wasn't aimed at 'this DSP is noisy!' or anything like that. It was mostly that the DSP (whichever DSP is in there) is related to my noise issue, and is there a product that MiniDSP produces that might combat it?

As Ryan stated - late model Audi S4 with pro install (nothing wonky / jenky with install). With the previous DSP in, we removed the RCAs from the DSP (to the amps) and had silence. That at least was encouraging to me that it wasn't background hiss from my amps.

Stock HU to MoBridge DA3 - toslink out to MiniDSP.
A&K SR15 DAP - shielded RCA to MiniDSP

I conferred with my installer today (he will have the car again soon), and he reminded me that he had let me know this is heterodyne noise (Radio Frequency Induced) that is being introduced into the system when some system is initiated when the car is started. So I/We will go through the various steps to see if we can determine where it is coming in.

With this seemingly being RFI noise - would the miniDC Isolator be something that could be thrown at the problem?

Or something like this: www.mouser.com/ProductDetail/MEAN-WELL/S...RsebRuw8c%2FehvS4%3D

I understand that if the problem isn't the DSP, then there isn't any cause for your support team to respond, but I'm hoping someone has encountered this before (what I'm really hoping is that a simple isolator / filter thing will 'fix' it).
Last Edit: 3 weeks 1 day ago by AfghanVet.
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Noise in system with engine on 3 weeks 1 day ago #44251

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Jason, have steps 2 & 3 been performed to rule out noise entering through the inputs?
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Noise in system with engine on 3 weeks 1 day ago #44255

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I arrived back from a trip and was able to quickly check numbers 2 & 3 above.

With the vehicle off, I unplugged the Toslink coming from the MoBridge, and still had the noise when I started the car.

With the vehicle off, I unplugged the analog cable, and still had the noise when I started the car.

The noise is present even when all of the outputs in the plug in are muted - so I couldn't determine if the noise was only coming from one set of speakers (door open to get close to mid range, mid bass - chiming of the warning, etc. makes it impossible to determine if this small amount of noise is coming from the mid range drivers up on the dash.

Tomorrow I'll disconnect the RCAs going to the amps again to determine if any noise is present when the amps are disconnected from the DSP.
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Noise in system with engine on 3 weeks 1 day ago #44263

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Where is the DSP located? Is it mounted in close proximity to any factory wiring or other electrical devices, motors or pumps?

Another thing to try is to power the DSP with an external source (battery) separate from the vehicles power to see if the noise is coming in through the power/ground.
Last Edit: 3 weeks 1 day ago by rccotroneo.
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Noise in system with engine on 4 days 3 hours ago #44469

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rccotroneo wrote:
Where is the DSP located? Is it mounted in close proximity to any factory wiring or other electrical devices, motors or pumps?

Another thing to try is to power the DSP with an external source (battery) separate from the vehicles power to see if the noise is coming in through the power/ground.

Thank You Ryan!

Yes - the DSP is mounted in a 'cubby' in the side of the trunk, and there are many wires back there - none of which appear to affect the system 'in a sense'.

Mark powered the MoBridge and DSP from an external source, and there was little change to the noise. But....he changed the grounding point of both components to the negative ground lug that the battery (mounted in the trunk) uses for its ground. The noise was cut in half! There were a few people that I pointed this out to at Finals that thought I was crazy that I could hear anything, so that is a positive result.

So silent with the engine off, and a faint hum with the engine on, and increased volume of hum when the headlights first come on....diminishing to stable when the HID ballasts are warm. I still have DSP noise floor when the wired remote is turned all the way up (0db) and no music is playing - I have to take it to about -11.5db until the system is silent again. It would be great if it was silent all the way up, then I could just use the source volume to get everything out of the system. At present, I am reducing the wired remote volume to where I can't hear the noise floor and using the source volume - not giving up an extreme amount of volume to the system.
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