# Xtrons HU audio noise?



## ADB (May 7, 2002)

I have always had a feint 'electrical' noise with the Xtrons HU. If you put the keys in the ignition and once the HU has booted up there is an intermittent feint hiss and pop that can be heard. If you play some audio through it (radio, MP3 etc) then it drowns it out, however its always there. If you put the lights on (which causes the backlight on the HU to come on) it is more profound and constant, but still feint. My car has BOSE. There is no such noise with the RNS-E installed.
When I was using VCDS yesterday I noticed that it was worse when VCDS was reading anything - like an old modem sound, but very feint.
I previously tried grounding the chassis of the HU independently, however it made no difference. I have read online various people complaining about the same noise issues and not all Audi owners.

Since there seems to be quite a few Xtrons (and other Android HU) owners on here, do other people get this? Does it just affect Bose? Have you managed to cure or reduce the noise? I am tempted to try another Android HU, however if its just going to be the same behaviour I'll be wasting my money.

Andy


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## TTsdsgomg (Mar 19, 2013)

ADB said:


> I have always had a feint 'electrical' noise with the Xtrons HU. If you put the keys in the ignition and once the HU has booted up there is an intermittent feint hiss and pop that can be heard. If you play some audio through it (radio, MP3 etc) then it drowns it out, however its always there. If you put the lights on (which causes the backlight on the HU to come on) it is more profound and constant, but still feint. My car has BOSE. There is no such noise with the RNS-E installed.
> When I was using VCDS yesterday I noticed that it was worse when VCDS was reading anything - like an old modem sound, but very feint.
> I previously tried grounding the chassis of the HU independently, however it made no difference. I have read online various people complaining about the same noise issues and not all Audi owners.
> 
> ...


I suspect this is due to poor screening within the android units, there must loads of rf waves in a car and the wiring acts like an aerial picks the rf signals up and amplifies them. So my guess most of these cheap units are mass produced and not of the highest quality, you could get lucky with a particular model though.
Back in the day you used to get spark plug crackles as you revved, cant remember what people added I think it was a resistor of some sort :?


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## TTsdsgomg (Mar 19, 2013)

Andy, I'm thinking of one of these units as bit bored with the rns-e, how did you get on with wiring into the BOSE amp 
1/ what wires did you connect
2/ does it switch on correctly
3/ whats your sound quality like
4/ are all the speakers working correctly including sub.


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## ADB (May 7, 2002)

TTsdsgomg said:


> Andy, I'm thinking of one of these units as bit bored with the rns-e, how did you get on with wiring into the BOSE amp
> 1/ what wires did you connect
> 2/ does it switch on correctly
> 3/ whats your sound quality like
> 4/ are all the speakers working correctly including sub.


I just connected it up as per the instructions. Could have done it without the instructions to be honest. Mine is an older PF75ATTAR unit that I replaced the PX3 SoM for a PX5 SoM and have since upgraded to Android 9.0.

The sockets on the HU you can't get wrong as they are all keyed, GPS & WiFi share the same type of SMA screw connector, however they are labelled (newer units have Fakra's), 4 M-to-F phono's labelled FL, FR, RL & RR to connect together, Fakra antenna adapter with power that needs the 'Ant' cable connecting to it (to power up the antenna amplifier) and the 'Amp' power cables that needed joining to power up the Bose amp. There were a few cables I didn't use that are still in the box (video in & out I think?).
I didn't have to make any changes to the quadlock or anything else. It just worked. I did later on cut the reverse wire as I don't have a reversing camera and this was a bit annoying with it switching to a blank screen and turning the audio off. It looks like with later MCU firmware the reverse switching can be disabled in software though.
It powers up with the ignition and takes about 30-seconds to fully boot up from cold. There are settings for the length of time it goes into 'sleep' so a warm start (i.e. within the sleep timer) it comes on immediately. Its like an Android phone or tablet.
All the speakers worked (until my Bose amp got water damaged but that's a different story). I don't believe there is a separate input to the Bose amp for the sub so I am assuming its working. If you muck about with the equaliser the bass is definitely there.
Sound quality is OK apart from the electrical noise. I have updated the MCU with a supposed sound quality improved modified version, however I honestly can't tell the difference..

Cheers
Andy


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## Steve in Ireland (Oct 13, 2017)

People mentioned this "faint noise" but I never heard it from mine.

Then I made up a wifi repeater because the car is parked too far from the house to get any signal. Now, when I start the car and drive off, I hear "the noise" until I'm far enough from home for the wifi connection to drop. Then it goes silent. I'm 100% certain that the Xtrons' audio circuits are picking up interference from the wifi.


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## ADB (May 7, 2002)

Steve in Ireland said:


> People mentioned this "faint noise" but I never heard it from mine.
> 
> Then I made up a wifi repeater because the car is parked too far from the house to get any signal. Now, when I start the car and drive off, I hear "the noise" until I'm far enough from home for the wifi connection to drop. Then it goes silent. I'm 100% certain that the Xtrons' audio circuits are picking up interference from the wifi.


Do you have Bose?
WiFi was one of the suggestions I read previously and I have tried disabling it but it made no difference. I tried a couple of different WiFi antennas as well and these also made no difference. Bluetooth was also mentioned, however there is no way to disable the Bluetooth as its part of the MCU hardware and not native to the Android SoM.

I seem to recall the motherboard had two WiFi solder connections but only one was used and the coaxial cable that was soldered to this that went to the rear SMA connector didn't look the best quality?


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## boffin10 (Jun 12, 2016)

I also have the older PF75ATTAR HU & have spurious noise which increases when the lights are switched on with no audio source playing. I too believe it is an internal EMC issue but it does not bother me as it cannot be heard or may not be there once audio is playing. It's not often I drive without something playing &, as it's a roadster, the usual soft top wind & outside world noise drowns it out anyway.

BTW Andy, I'm about to do the PX3 to PX5 mod., any tips or pitfalls to avoid? At the moment I have Google Play Services inhibited to speed up the HU, but is it noticeably faster with the PX5?


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## John949 (Apr 12, 2017)

I know just enough electonics to know I'm out of my depth when it comes to curing RF pickup, but I do know that to minimise it the output form the head unit and the input to the amplifier must be 'matched' in terms of impedance and voltage levels . (matched here doesn't mean 'the same', it means they must be what the designers intended to minimise pickup). In theory the Bose uses 'standard' line in signals and the Xtrons provides a 'standard' line out, but my experience is that the don't match well. Volume levels are low and you do get pick up.

A car is an electrically noisey environment with ignition pulses, data-buses, and diagnostic signals on the lighting circuit, so it's not surprising that you do get some noise. The amp is also a long way from the head unit, which doesn't help. On one of my cars the biggest culprit is the USB cigar lighter adapter. This is so bad that I can hear radio stations on the aux input!

If it bothers you then you are going to have to experiment. Just moving the wires around can help. Not used them mysef but I've heard good things about ferrites. (These are what the lump on the end of your laptop power lead / USB cable is).

https://www.amazon.co.uk/FERRITE-FILTER ... /B00LA78AM


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## pedracca (Dec 8, 2016)

I had exactly the same as the op with a PF75ATTAR. With the stock non-bose amp it didn't bother me much as once I was rolling it couldn't be barely noticed. But after changing to the SPC-400TT (Audi kit made by Alpine that includes 3way front and an amp) the buzz was crazy.

I first installed one of those EMI filters (this one to be precise) and it helped a bit, but it was still far from being bearable.

Next I did was grounding the negative from the HU to the body and this helped quite a lot. It's still noticeable and still bugs me but at least it doesn't drive you crazy.

A guy from XDA forums said he got rid of the noise after grounding the HU to the body *and* feeding the HU directly from the battery. I will try this when I have time as wiring to our batteries is not an easy job.



boffin10 said:


> BTW Andy, I'm about to do the PX3 to PX5 mod., any tips or pitfalls to avoid? At the moment I have Google Play Services inhibited to speed up the HU, but is it noticeably faster with the PX5?


Hope Andy gives his opinion too. In my opinion it is absolutely worth it, px3 with 1gb of ram is a totally underpowered device for what is intended. PX5 with 4gb is a totally different story. I struggled a lot though because my BT/Wifi chip didn't work after upgrading. Someone on XDA forums shed some light and I finally got it working with an external dongle.



ADB said:


> Sound quality is OK apart from the electrical noise. I have updated the MCU with a supposed sound quality improved modified version, however I honestly can't tell the difference..
> 
> Cheers
> Andy


I'm sure I've read you on XDA too  
Give this an opportunity. I am sure you won't regret it.

Regards!

Pedro.


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## ADB (May 7, 2002)

boffin10 said:


> I also have the older PF75ATTAR HU & have spurious noise which increases when the lights are switched on with no audio source playing. I too believe it is an internal EMC issue but it does not bother me as it cannot be heard or may not be there once audio is playing. It's not often I drive without something playing &, as it's a roadster, the usual soft top wind & outside world noise drowns it out anyway.
> 
> BTW Andy, I'm about to do the PX3 to PX5 mod., any tips or pitfalls to avoid? At the moment I have Google Play Services inhibited to speed up the HU, but is it noticeably faster with the PX5?


Its a doddle to change the board over, however I didn't take any photos whilst I was doing it, I am sure you can find some online though. You could also upgrade to a PX6 SoM as these are also compatible.
What I did was take the thing apart - top off, DVD drive out, disconnect the GPS antenna from the rear of the unit as this is directly connected to the SoM. Remove the two screws holding the SoM in and then lift it out - you might need to apply some pressure on either edge to pop the connector off; i.e. use a non-metallic lever either side near the connector to lift the two corners up.
Then just do everything you did to take it out in reverse.

I ordered the PX5 board (2GB RAM & 32GB ROM) from Witson in China (Bob) back in 2017 and it took a couple of weeks to arrive I think.
It came with Android 6.0 installed which I updated to Android 8.0 with Malaysk's ROM on XDA. I have since updated it again to Android 9.0 using Malaysk's PX5 ROM on XDA. I am still using the version 1.1 he posted there and haven't paid him to update it to the latest 1.2.5.
All the info for upgrading the firmware etc is here - MTCD Software Development

From a speed perspective its night and day. The PX3 was awful with the standard software as well as the Malaysk Android 5.1 ROM he did for PX3 boards. I did the same as you and prevented some apps from running to speed it up.
With the PX5 & Android 9.0 I haven't stopped any apps running. I have been flipping between TomTom NDS, Offline Maps & Navigation & Google Maps for navigation as they each have their pros & cons. At the moment I am using TomTom NDS but this takes a bit of time to load TBH, but once its running its fine. I have my Android 8.1 phone BT paired for hands-free calls and I trigger the WiFi Hotspot to come on when the BT is paired so the HU has Internet access via my phone.
I use Google Play Music and the standard Radio App, other than that I have Torque for occasional playing around as I have a BT ELM327 OBDII dongle.

Good luck


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## ADB (May 7, 2002)

pedracca said:


> I'm sure I've read you on XDA too
> Give this an opportunity. I am sure you won't regret it.
> 
> Regards!
> ...


I have the sound-patched MCU firmware installed for my MTCD/E GS unit (Xtrons). I am not on the latest 3.30 version though - whatever was the version prior to that I am on (3.17? maybe?) - I will probably have some time to put the latest version on now that we're all under house arrest.... I haven't installed the modified Amplifier .APK though - does this make a difference as I can't really tell any difference with just the sound-patched MCU firmware?

EDIT: Ah, sorry. I am using the other sound-patched MCU firmware (sp) rather than this 'bd' version. I have just read the 1st post in that thread and its a combination of the MCU firmware and the modified amplifier .apk.
I might give it a try this week whilst I have nothing else to do...

Andy


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## Steve in Ireland (Oct 13, 2017)

ADB said:


> Do you have Bose?


Yes.
The noise in mine also goes away if I disable wifi. The stock Xtrons ROM would always re-enable it on startup, but I'm now using a modded one (HAL9000). I don't use any internet-based features when I'm on the move.


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## ADB (May 7, 2002)

Steve in Ireland said:


> ADB said:
> 
> 
> > Do you have Bose?
> ...


I wish mine did... There is no difference with mine if I disable WiFi :?


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## ADB (May 7, 2002)

ADB said:


> pedracca said:
> 
> 
> > I'm sure I've read you on XDA too
> ...


Really late reply - sorry...

So my Bose amp woes and the knackered mid-range speaker in the door and the associated troubleshooting led me to try this MCU firmware mod. Short answer - don't.
It screwed up my troubleshooting as the modified MCU firmware reduces the volume massively (which I didn't initially realise). This unfortunately led me to think the Bose amp was knackered again, which it wasn't, however the mid-range speaker in the drivers door was. After I discovered the speaker was faulty (0.02ohm resistance) I replaced it with one I got on eBay. I went on a 300 mile round trip on Tuesday and at 90% volume whilst driving at 30mph+ it just wasn't loud enough. With the previous SP patched firmware the volume at 20% was more than loud enough.

I have since flashed the modified 'SP' version of the MCU firmware and I'm now back to where I was. So back to the short answer of installing the 'BD' patched MCU firmware - don't.
Feint audio noise is still there but everything is working properly. I am convinced the noise is just poor electrical shielding. I copied some files to the HU yesterday from a USB stick when troubleshooting (I have routed the USB cables to the glovebox), and I noticed increased noise when the files were being copied. I repeated a few times and it was pretty consistent.
I am tempted to try one of the latest Xtrons units that have the quadlock built into the unit, however I don't really have the cash to throw at it... Plus I suspect all the niggles that irritate me about the current unit will still be there - CANBUS integration issues.

Andy


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## N6SSA (Mar 29, 2009)

Hi
I don't have an Xtrons HU, but it is very similar looking (unnamed chinese make) Android 9 unit and the issue I have seems the same as other users here, so hoping someone can shed some light on how I may be able to fix this issue with terrible background noise. 
Had this HU just over a year. Car was not on the road to begin with, while we sold the old car, did all sorts of servicing, body repairs and adding bits including this HU. So the fact I had some noise while the car was in the garage was not worrying early on. But now car is out and the noise is horrible. Via the HU I added DAB (not successful yet), TPMS (sort of successful), rear camera (now successful by uisng wires rather than wireless) but for this demonstration all are disconnected. The accessories plug and all usb cables are all disconnected.
First up in the standard Symphony which I put back in temporarily, with the quadlock and aerial connected.






Then we have the new HU, again with just the quadlock and aerial connected, and also an extra earthing cable already connected from HU body to the chassis frame inside the car, as shown in the photo below.









I think the noise is obvious. Same conditions, same phone, same engine noise for comparison, only about 10 minutes later. Wifi does not turn on automatically.






Any suggestions greatfully received.


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## ADB (May 7, 2002)

N6SSA said:


> Hi
> I don't have an Xtrons HU, but it is very similar looking (unnamed chinese make) Android 9 unit and the issue I have seems the same as other users here, so hoping someone can shed some light on how I may be able to fix this issue with terrible background noise.
> Had this HU just over a year. Car was not on the road to begin with, while we sold the old car, did all sorts of servicing, body repairs and adding bits including this HU. So the fact I had some noise while the car was in the garage was not worrying early on. But now car is out and the noise is horrible. Via the HU I added DAB (not successful yet), TPMS (sort of successful), rear camera (now successful by uisng wires rather than wireless) but for this demonstration all are disconnected. The accessories plug and all usb cables are all disconnected.
> First up in the standard Symphony which I put back in temporarily, with the quadlock and aerial connected.
> ...


That noise is way worse than mine. I'd say the HU is faulty.


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## NotTayyeb (Dec 14, 2019)

Agreed that it may just be your HU thats faulty.... My Xtrons does make a bit of noise, but its subtle.... I would be surprised if i could record the sound clearly, its that subtle.


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## N6SSA (Mar 29, 2009)

SInce the HU is now over a year old, I think it's a £200 paperweight. Any ideas on what else I might be able to do within reason to fix the noise?


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## Nicholas2020 (Nov 19, 2020)

I am afraid the audio noise is a general problem of all the aftermarket car stereos today. And not only Audi, but also BMW and other car models of aftermarket car stereos have the audio noise issue.

But please just take it easy. After serching online, I found there is a quick fix for it. All you need is an adapter cable to help you remove all the noise.

Take a look at AK/INIB/NRCBL or AK/INIB/NRCBLBMW cable to help you fix it easily. Cheers.


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## pedracca (Dec 8, 2016)

Nicholas2020 said:


> I am afraid the audio noise is a general problem of all the aftermarket car stereos today. And not only Audi, but also BMW and other car models of aftermarket car stereos have the audio noise issue.
> 
> But please just take it easy. After serching online, I found there is a quick fix for it. All you need is an adapter cable to help you remove all the noise.
> 
> Take a look at AK/INIB/NRCBL or AK/INIB/NRCBLBMW cable to help you fix it easily. Cheers.


Hi, thanks, I think I'm going to try it, I have a hiss in my Xtrons unit that is driving me crazy. But do you know if this harness will decrease audio quality (like RCA EMI filters would do) ?


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