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  • Noise from my audio only when engine is ON

    I know it has been discussed many times and I read a lot of threads but still cannot get rid of this noise. Here is my setup:
    An external sound card output is connected to PAC Turbo1. I need this amplifier because the volume is too low without it. From Turbo1 the output goes to my factory Bose system. When the engine is OFF everything is just fine, but when it is ON I can hear a noise in my speakers which changes as engine rev is goes high. When I disconnect the input from the Turbo1, so it is only connected to my factory stereo I can still hear the noise. In my opionion it means that the sound card and carPC have nothing to do with this noise. I power the Turbo1 from my car lighter socket. I also tried a ground loop isolator but it doesn't help at all. Any ideas ?

  • #2
    It's alternator whine.

    You still have a ground loop you must find.

    Where are you drawing power from for the PAC?

    Were/what is the ground for the PAC?

    You have to ensure a good solid ground for the PAC, draw power form a clean source (ie: not on a power line that also runs an electric motor) and install it away from fans, motors, electric pumps, etc. Otherwise, it will pick up interference.

    That's not the greatest line driver either.

    What did you pay for it? (guessing around 30 bucks) Remember the old saying:

    You get what you pay for..............
    For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.
    Leonardo Da Vinci

    Comment


    • #3
      No worries.

      Forget cig lighter power.
      Place the turbo thing (does it come with speed-stripes) right next the the bose amp! Place the soundcard there too.
      As short cables as possible, exept for the USB cable to the PC.

      You might have a ground loop via PC but it does not matter as long as ground cable between amp and turbo is really short.

      With your setup you've got every chans of getting rid of whining because of the simple fact that you do not have to wire analogue audio back and forth in the car.
      My car installation mp3car thread "showing off project"

      Comment


      • #4
        Thanks guys. I change the power source for PAC Turbo1 from a ligther socket to 12V from my carPC and now even without a ground loop isolator everything is good. There is another problem, when I listen to a mp3 the sound quality is much worse than if I play a CD recorded with this mp3. I play this CD directly from the Bose system and the CarPC is connected to a DVD input of Bose. I use Creative X-MOD USB sound card. Do you have any ideas why the overall quality is so much different ?

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        • #5
          Turbo? Try bypasing it just to see if quality improves.

          Edit:
          I just checked out your soundcard. http://se.europe.creative.com/produc...&product=15913

          Extreme hifi????!!! Veeery suspicious....
          My car installation mp3car thread "showing off project"

          Comment


          • #6
            Hmm I'm not sure if I am able to check it without Turbo1 since the volume is very low and I can hardly hear something. Even with Turbo1 the volume is a little lower than the CD volume.
            Do you think that wires used in the installation can cause the quality issue ?
            I'm also wondering if you can recommend an amplifier which will give me good sound quality for a reasonable price ?

            Comment


            • #7
              Hi FX35 -
              I have a '96 300zx that has a 'Premium' Bose system. I do not know if Bose changed the way they implement Car Audio, but the system I have is Balanced audio (+,-,ground) from the CD changer to the head and amplified speakers. The benefit of balanced audio is high noise rejection.
              Most Automotive audio systems and consumer electronics are unbalanced (+. ground). When connecting unbalanced and balanced components together balancing transformers are needed to make the system work correctly. The common symptom being loss of gain.

              Because of these issues and also Bose's history of using poor/cheap components, most Z owners replace the Bose system as quickly as possible. I'm sure this is much harder (if at all possible) on the new systems like yours with highly integrated systems and features. In your case you will likely need a balancing transformer. See if you can find the pin out for your Bose connector. On mine it listed the signals like this:
              Left front +
              Left front -
              Right front +
              Right front -
              ground
              etc.


              On some equipment you can strap the ground and the - together at the input and get some of your gain back, I would check with the equipment manufacturer if you can, but a transformer is always the better way.

              BTW - I am having the same issue. I am solving it through different means. My "EQ" is a pro audio DSP and is balanced, so it interfaces well with the Bose speakers. I have solved most of my ground issues, but still have a very faint alternator noise I am chasing down.

              You can read more about my system here:
              http://www.mp3car.com/vbulletin/work...m-upgrade.html

              Comment


              • #8
                Originally posted by z_lust View Post
                Hi FX35 -
                I have a '96 300zx that has a 'Premium' Bose system. I do not know if Bose changed the way they implement Car Audio, but the system I have is Balanced audio (+,-,ground) from the CD changer to the head and amplified speakers. The benefit of balanced audio is high noise rejection.
                Most Automotive audio systems and consumer electronics are unbalanced (+. ground). When connecting unbalanced and balanced components together balancing transformers are needed to make the system work correctly. The common symptom being loss of gain.

                Because of these issues and also Bose's history of using poor/cheap components, most Z owners replace the Bose system as quickly as possible. I'm sure this is much harder (if at all possible) on the new systems like yours with highly integrated systems and features. In your case you will likely need a balancing transformer. See if you can find the pin out for your Bose connector. On mine it listed the signals like this:
                Left front +
                Left front -
                Right front +
                Right front -
                ground
                etc.


                On some equipment you can strap the ground and the - together at the input and get some of your gain back, I would check with the equipment manufacturer if you can, but a transformer is always the better way.

                BTW - I am having the same issue. I am solving it through different means. My "EQ" is a pro audio DSP and is balanced, so it interfaces well with the Bose speakers. I have solved most of my ground issues, but still have a very faint alternator noise I am chasing down.

                You can read more about my system here:
                http://www.mp3car.com/vbulletin/work...m-upgrade.html

                The DVD connector on the back of my head unit has the pinout you mentioned above.
                COuld you please have a look at this post where is a user guide I followed to connect my PC to my head unit: http://www.infinitifx.org/phpBB2/viewtopic.php?t=1457
                Do you have any suggestions ?

                I have no idea what this balancing transformer is. Could you please give me an advise ?

                Comment


                • #9
                  Lot of solutions out there. I was looking for an automotive solution I ran across, but now I can not find.

                  You can look for Line Balancing transformers (Jensen is very good) or unbalanced to balanced line drivers. It is like the Turbo1 you have but with the addition of balanced outputs.

                  Some Balancing transformers are passive and do not add gain and do not need power.
                  You could use two of these:
                  http://www.rdlnet.com/product.php?page=164

                  I'll post here if I run across the automotive solution I was talking about. Look at all the usual car audio suppliers like Crutchfield etc.

                  Comment


                  • #10
                    Sorry, been away fro a while.

                    Looked at your handy-man link and z_lust is absolutely correct. Your car has balanced audio. Theoretically you can connect - (or +) to ground and have a standard system (the other way cannot be done) but its possible that Bose has poor design and that this is not possible.

                    I have a cheaper solution and that is to decouple the audio with capacitors. You might need a trafo later to get the quality you need, but it is a simple test to find out if this is the root of your gain problem. Just put a capacitor inbetween the (-) input and ground (common) output from your sound card. 10uF el.lyt. Oh, you need two caps. Do not connect the two (-) together.

                    One more thing, you _can_ get amplification in passive trafos...
                    My car installation mp3car thread "showing off project"

                    Comment


                    • #11
                      Thanks guys for your help.
                      I took out Turbo1 and the sound quality is much better now. Of ocurse the volume is lower but I think I just need a better quality unbalanced-balanced transformer to have it working the right way. As you can see in the guide I sent the left- and right- are connected together. Is there anything wrong with it ?

                      Comment


                      • #12
                        Originally posted by z_lust View Post
                        Lot of solutions out there. I was looking for an automotive solution I ran across, but now I can not find.

                        You can look for Line Balancing transformers (Jensen is very good) or unbalanced to balanced line drivers. It is like the Turbo1 you have but with the addition of balanced outputs.

                        Some Balancing transformers are passive and do not add gain and do not need power.
                        You could use two of these:
                        http://www.rdlnet.com/product.php?page=164

                        I'll post here if I run across the automotive solution I was talking about. Look at all the usual car audio suppliers like Crutchfield etc.
                        sorry but new to this and sorry to hijack , you show a transformer there that converts unbalanced to balanced , but my saab 95 is the same balanced amp , ie left - left + , now do i need one transformer for each speaker ? , so i would have a left and right rcs lead from pc sound card or a usb dac ?

                        Comment


                        • #13
                          So you are on the right track! good news!

                          Balanced means differential input/output.
                          Unbalanced means that the (-) signal lead is ground/shield.

                          Balanced is better in a car. You cannot get ground loops. (unless you connect shield in both ends... Big no-no. You have to have cables with two signal leads per channel and one shield connected in one end only). Also any voltage introduced in chassis (generators etc.) does not affect the signal as it affects both + and - to the same amount. Its called common mode rejection. You can still get noise if you use poor cables. So its better with better cables.

                          Problem is when you mix balanced and unbalanced.

                          If you have balanced input/output theory means no reference to ground and its like the birds on the 16kV high voltage train line. You can connect -right and -left and ground and in effect get an unbalanced input _or_ output. No current. Bird does not burn. And this is what your link suggests that you do, 35!

                          In real life its very often a limitations to this.

                          If your problem 35, was that Bose does not handle a grounded (-)input very well I suggested a way round it (or rather to find out if that is the problem). To decouple the DC with a cap on the (-) lead. Last note was just an attempt to be clear that this ought to be done separately on each channel.

                          Now, since the turbo seemed to be the problem I do not think the problem was ever a balance/unbalance issue. Since you did not get noise but poor quality I should say that your turbo is not up to your standard. Get a better preamp.

                          Did this make it clearer or not? :-)
                          My car installation mp3car thread "showing off project"

                          Comment


                          • #14
                            Originally posted by mrcgibb View Post
                            sorry but new to this and sorry to hijack , you show a transformer there that converts unbalanced to balanced , but my saab 95 is the same balanced amp , ie left - left + , now do i need one transformer for each speaker ? , so i would have a left and right rcs lead from pc sound card or a usb dac ?
                            Are you talking about speaker output? They are normally + and - as bridge coupled power amps are common in car due to low supply voltage (12V rather than 30V). Or maybe your problem is sorted now?

                            (saab 95 btw... I did not know they had a stereo at all...)

                            My car installation mp3car thread "showing off project"

                            Comment


                            • #15
                              bes51659 thanks again. It seems clear right now. The problem is I do not know much about preamplifiers and all this stuff so I'd be glad if someone could recommend which preamp I should consider. I do not want spend much money since I'm getting a new car soon. Another question is can I get really good sound from a PC ? At the moment I have Creative X-MOD USB as a sound card, but I don't think it is the best choice. Maybe I should think of changing it to some high-end USB device.

                              Comment

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