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  • FB to control audio switching?

    I need to leave my headunit in my car so whenever my PC is not in, I'll still have radio. Now I need to figure out someway to switch between the radio and PC when I do have it in the car. I was thinking I could use my version 3 FB to turn off the radio on a button click to use the audio from the PC. Then on another button click turn off the PCI soundcard (possible?) and turn on the radio. That way they'd never overlap sounds.

    1. Does anyone know if this is possible with the FB (I have the FB, but havent even built the PC yet so I havn't had time to play with it)
    2. I know having audio come out of the radio and into the speakers and soundcard at the same time can damage the soundcard, and vice versa if the soundcard is playing music into the radio. Does anyone know if turning the device off like I described above would prevent the signal coming out of one device from damaging the other device.
    3. If it is possible, and there is no risk of damaging the devices in this way, what happens when the FB and computer are out of the car? How could I turn on the radio if there is nothing controlling the realy that FB controlls to turn the radio on and off?

    This is the only way I've come up with switching the audio. It be a lot simplier I think if I could just have both devices outputs plug into a switcher of some sort then have the FB operate the switcher. But I can't find any sort of switcher...only mixers that mix the signals together.

    Thanks

  • #2
    It's a bit pricey, but still an awesome solution, and seems tailor made for what you want to do.

    http://www.rush2112.net/mkportal/mod...8f6207ffa0bb22


    Edit: Don't get me wrong, the FB is awesome and you should find a different use for it... but for audio switching that seems a better solution.
    "stop with the REINSTALLS, what do you think we got some lame-o installer!!!" - mitchjs
    RevFE
    My Shop

    Comment


    • #3
      Well this is a little different. So instead of controlling the power to the radio and soundcard, this device would let me control which audio source is given to the amps. I like the idea...however I see a couple hang ups

      1. I would need one of these devices for each channel. I can't have L/R Tweets, Mids, and Bass being processed by the computer then put into a single input on this box. That defeats all the processing. A box per channel becomes very pricey.
      2. When the computer is out of the car, is this device smart enough to know to use the only input it is getting signal from? I wouldn't have the computer there to switch it over to the radio input otherwise.

      Comment


      • #4
        You need to isolate the 2 inputs - you can't just splice them together & turn one off. You'll eventually damage the output circuit on the PC or Radio (or both). if it's a pioneer h/u, it might not survive initial connection.....

        You haven't given enough information to really give advice - knowing what components you're using would help a lot (sound card, processing, h/u model, speaker setup, etc) It sounds like you want multi-channel from the carPC, but stereo from the radio, not sure how your are planning that to work. You might be able to take the device suggested above & modify it to select channel 1 or channel 2+3+4 if you need 2 + 6 channels. then it depends on how your amps are hooked up (that device wont output 6ch)

        My suggestion would be to use an external processor, then use the FB to switch it's inputs (my RF 360.2 can do that (2ch input, has an external input select + volume), haven't looked at how the signal switches inputs though I'm sure the FB could be adapted to work). You'd run stereo to both inputs, then you can do all your EQ, T/A, x-over in the processor. If you're trying to run 3 way front + sub, that's they only way you'll get sound from your 2ch radio & 6ch computer, if I'm guessing your system correctly. You also tune the 360 via bluetooth, so the CarPC would be useful there

        Comment


        • #5
          Well the reason I can't give too much information is because I'm trying to keep this as universal as possible so I can move it from one car to the next. Each car will be different so its hard to give details about headunits and amps and such.

          Processing must be controlled by the computer (PCI card, external card, doesnt matter in this senario) because I'm not putting seperate processors in each vehicle. This way, when I remove the computer from one vehicle and put it in the next, the processor will come with it and all I have to do is load the saved settings for that particular vehicle.

          In a vehicle without amps: The speakers plug directly into the headunit. What I need, is the speakers to plug into a switch. The headunit would also be plugged into this switch. So when there is no PC, everything works as normal. When you put the PC in the car you plug the audio outputs into this switch. You could then just choose which source you want to use. You would have to have a way to choose without going back and manually pressing the switch in the trunk of the car though.

          In a vehicle with amps: all the same applies except the output of the switch would be to the amps obviously.

          So here is a solution I'm thinking of. At this website How-To: Make a component video switch They show you how to take a KVM and turn it into a switch with RCA plugs instead of VGA and PS2 plugs. They only attach 3 RCAs, but if I modified it for 4 RCAs I think it might work. If the computer is not in, the KVM will switch to its only input automatically. If the computer is in, then you just switch between the radio and computer via a keyboard keypress which you can handle in code.

          this is going a little off topic because the FB is not involved in any of this. But I think it might work as long as that switch does not tamper with the audio signal or degrade it in anyway.

          Comment


          • #6
            You can't drive standard car speakers with your computer audio outputs, they're line level (eg unamplified). You're going to need to run them through the headunit, or through an amplifier.

            For the second situation:
            You can't tie your headunits amplified outputs into the input on an amplifier. You're going to blow out the amplifier. If by chance, the amplifier has high impedance inputs, you could use those... but they usually sound horrible and most amps don't have them.
            "stop with the REINSTALLS, what do you think we got some lame-o installer!!!" - mitchjs
            RevFE
            My Shop

            Comment


            • #7
              Originally posted by malcom2073 View Post
              You can't drive standard car speakers with your computer audio outputs, they're line level (eg unamplified). You're going to need to run them through the headunit, or through an amplifier.
              Hmm...Didn't know that...now I need to find a super small basic amp to use is this situation. Here is where I wouldnt want to upgrade the amps and speakers in the vehicle, just use what is already existing. But if there is no amp in the car, and the speaks are getting their signal from an amplified headunit, I'd need a small amp for the PC to use. Can I rip one from an old headunit or is there anyplace to buy small amps like the ones used in headunits?

              Originally posted by malcom2073 View Post
              For the second situation:
              You can't tie your headunits amplified outputs into the input on an amplifier. You're going to blow out the amplifier. If by chance, the amplifier has high impedance inputs, you could use those... but they usually sound horrible and most amps don't have them.
              My mistake, I didnt clarify on this. When there are amps in the car, I'll be using the RCA outputs of the headunit to go into the switch.

              Comment


              • #8
                I'm not entirely sure about small amplifiers, I've been looking for one myself really. Another issue you might run into, is getting a switch beefy enough to handle how much power you're going to be putting through it.

                The second situation in that case would work, though I'm not sure about the KVM part. I assume you're thinking of using 6 channel out going to a 6 channel amplifier for your 6 speakers? If so, does the headunit output 6 channels over RCA?

                There's gotta be multi-channel audio signal switchers out there.
                "stop with the REINSTALLS, what do you think we got some lame-o installer!!!" - mitchjs
                RevFE
                My Shop

                Comment


                • #9
                  I don't think there is anything on the market, or simple to make that can do what you want to do. You might have more luck trying to get the computer & car(s) to read your mind and just do what you want

                  Almost all makes & models of cars have different audio setups (I work in the manufacturing of 4 different models) so trying to tie 1 solution into multiple setups is a PITA (trust me on this one) then you add in custom setups and you're at another level of hell.

                  You haven't said how far you want to go with processing - is a little eq enough or do you want T/A, x-over etc. if it just eq & stereo - use the Aux input on the car's h/u & run the computer output to that (or a frequency modulator). If you want more (multi-channel, T/A, x-over, etc) you need seperate amps, component & wiring (no stock vehicle).
                  If you want this to work with multiple vehicles, I think that's how you're going to have to go (Aux or a tunable frequency modulator (wired/wireless))

                  There will probably never be a drop-in, 100% solution for a CarPc, let alone a solution that can handle multiple makes, models etc - there's too much variation within the industry for that. Unless we go back to Any-Color-you-want-as-long-as-its-Black type manufacturing (considering the current socialization of the auto makers, we might all be driving VW Beetles soon, so it might be easy to do )

                  Comment


                  • #10
                    Originally posted by Iamthehor View Post
                    You might have more luck trying to get the computer & car(s) to read your mind and just do what you want
                    Yeah, that would be the best..haha.

                    Originally posted by Iamthehor View Post
                    Almost all makes & models of cars have different audio setups (I work in the manufacturing of 4 different models) so trying to tie 1 solution into multiple setups is a PITA (trust me on this one) then you add in custom setups and you're at another level of hell.
                    Looking at any headunit, you either have wires going straight to the speakers, or you have outputs (usually RCA) that goes to an amp or processor or something. Am I wrong by thinking this? Is there something else I could be missing right there at the headunit?

                    I'm just thinking that if I catch the audio at that point, I only have a few different scenarios to think about.
                    1. There is no amp/processing/anything in the car so I need to use the speaker wires on the back of the headunit and an amplified signal from the soundcard on the PC. Put both of them into a switch (if its beefy enough...I can do some testing and determine that) and have the output that I want to go directly to the speakers. It doesnt matter how many channels each device inputs into the switch because at the output of the switch I can combine any channels that need combined and send all the signals where I need them.
                    2. There is an amp or processor or something connected to the stock headunit via RCAs. In this case, I would intersect the RCAs as soon as they left the headunit and run them into the switch. I would then run the rcas out of the PC into the switch. Again, it doesnt matter how many channels were ran into the switch, I would only use what I needed on the output side.
                    3. There is an amp or processor or something connected to the stock headunit via some digital cable....when that day comes...I'll worry about it then. I dont plan on owning a vehicle with that advanced stereo system stock for quite a while..haha.


                    Originally posted by Iamthehor View Post
                    You haven't said how far you want to go with processing - is a little eq enough or do you want T/A, x-over etc. if it just eq & stereo - use the Aux input on the car's h/u & run the computer output to that (or a frequency modulator). If you want more (multi-channel, T/A, x-over, etc) you need seperate amps, component & wiring (no stock vehicle).
                    If you want this to work with multiple vehicles, I think that's how you're going to have to go (Aux or a tunable frequency modulator (wired/wireless))
                    crossovers, eq, times shifts or whatnot will all be handled in software...that should not effect what i'm trying to accomplish. Number of channels will be determined by whats already in the car. If its stock 4 speakers...then the output of my switch I will configure for 4 speakers. If there are 3 amps..then the output of my switch will be configured to send highs, mids, and sub signals to their amps.

                    Comment


                    • #11
                      While in theory you are correct, it's not that simple.

                      I know of no device that can:
                      1 "Intercept" or Split/switch 2 signals with different # of channels (2 & 6) & match output to whatever you are connecting to (this is the really complicated part).
                      2 Handle both low (RCA) and High (amplified) signals separately or simultaneously
                      3 Have correct wiring to hook up to multiple wiring systems.
                      4 Do it without screwing up your sound quality.

                      You could roll your own, but I'm thinking your development cost & time are gonna be outrageous. The only thing i can think of that would work would be a DSP like the RF 360.2 that I have or the discontinued Alpine 701 (can't remember if it has multiple inputs).

                      Audio signals aren't like 12Vdc - you don't just put a switch in the line & expect it to not affect the sound. You're dealing with AC voltage, Impedance & signal degradation on low-level is a major concern (computer line out or RCA for example).

                      A frequency modulator or using the Aux input of the H/U is the most effective, safest & easiest method your going to find. It's 1 audio connection & will not require any electronics knowledge (the freq. modulator will either plug in between the antenna & H/U or transmit on specified freq.) it will also compensate for the different # of channels & still allow processing to be done by the computer (albeit in stereo only). If you were dealing with all the same type of equipment (all H/U driven or all external amp driven), I might make some more complicated suggestions, but there is no good way to deal with both. It would be VERY expensive to build a switch system capable of handling both & that will hold sound quality (impedance matching, etc).

                      Whatever you decide to do DO NOT just tap into the wires behind the radio (either RCA or Speaker) you WILL cause damage to some component - which one depends on a lot of factors. You have to Isolate the 2 inputs (a switch/relay on a speaker-level line will cause problems as well (impedance, resistance, etc)). Just as an example, if you connect the line out of your computer to the speaker wires, you will fry the line out of the sound card - the Voltage of the speaker-level output is ~10X that of the computer output (different components will be different).

                      I won't be staying at a Holiday Inn Express until next week (business trip) but I am an Engineer & work on automotive wiring systems. Not trying to be a dick, but you don't sound like you understand what you are trying to do. Like I said, what you are wanting can be done BUT it's going to be expensive & will need to be custom-tailored to each vehicle you want to install in. WAG, but i bet it would be cheaper to install a CarPC in each vehicle than to design & build your adapter (if done electrically correct, not even thinking audiophile-approved) Something like this will give Hi-Fi audio-snobs hives.

                      Comment


                      • #12
                        I don't think you're being a dick at all. And I really appreciate you taking the time to talk me through this and help me understand it. You're correct when you say I dont know much about what I'm trying to do. I have a computer science degree and the only audio knowledge I have is what i've learned installing the few car systems I've done and working with home audio equipment. My knowledge range on this subject is extremely lacking.

                        Where my little brain is getting hung up is the fact that I feel what I need to accomplish is sooo simple yet I can't figure it out. You're showing me that intercepting the audio will not work easily/cost efficiently. So maybe I need to approach this from a different angle. Maybe I just need to use the forbidden Y splitter backwards, but physically cut the connection to the headunit when I'm using the PC and vice versa when using the headunit. I'm not really sure yet. The last day or so my mind has been on how to split the audio signal. I have to sit down now and try to think of some other method that prevents signal outputting from the headunit and damaging the soundcard. I just can't believe its that difficult.

                        If there was a headunit that would input 4 channels as AUX (dont need left and right I guess, just highs, mids, bass, and sub) and pass them straight through to the amp (whether it be via RCAs to an external amp or through its own built in amp then straight to the speakers) without making adjustments to the processing...that'd be perfect. Or a digital input that would except any number of inputs then pass through without using its own processing. I'm going to go do some reading on headunits and see what i can find.

                        Comment


                        • #13
                          Iamthehor definitely has his shtuff together. Listen to him.

                          Since you have experience with home audio you should think of car audio somewhat the same way. You have speakers connected to the amp with lots of power going to them. All the other components: CD, DVD, cable, sat, VHS, tape, phono... (I'm old) which are line level and the only things ever switched. You can't wire all the inputs together or bypass the amp, or even bypass with just one. There's no 5.1 into a 2.0 amp. The source needs to be in 2.0 mode (just like a 5.1 PC with 2 speakers), and 2.0 into 6.1 just goes to the front 2 speakers and maybe delayed to the back. Every home is different though, and that's your dilemma. There's no one black box solution for every situation. Most cars are like a boombox with 4 speakers/no inputs and you want to run an iPod through it, others have aux, some have line level to amps, ... you get the picture.

                          Comment


                          • #14
                            With a DC signal (digital) or just plain power, your Y-splitter & cut the other input will work. It will do what you expect with an audio signal BUT there is a huge chance of un-intended consequences. There's a HUGE about of "data" in an audio signal - think about it, 20-20k hz worth of freq + volume of each freq. You corrupt even a little & you will hear it. You want as little molestation of the signal as possible (short, straight wires with quality connections).

                            Like i said - the Frequency modulator (preferably wired in-line with the antenna) & using Stereo from the computer is the only way I can think of to keep both H/U & computer & work in any vehicle. If the vehicle has an aux input on the H/U, even easier (you could Y this behind the radio to hide the wires, just DO NOT connect anything else to the Y while the computer is connected). Don't put switches, relays, etc in an audio cable- Period. Giving up either multiple vehicles or multichannel is about the only way you're going to get this to work. Just a thought, but how are you going to control the CarPC anyway? If you're installing a screen in each vehicle, you can do a lot more "custom" jerry-rigging to make this work. I think the 6&2 channel for each vehicle is out, but if you got the cash, this can be done.

                            I may know what I'm doin with this stuff (which is why I'm typing volumes) but I'm a little envious of the CompSci degree - I know enough VB to be dangerous which has left me beating my head against the wall programming for the fusion brain lately. I'm much better at taking stuff apart & making it work better (what I do all day). Car audio is a hobby (but i don't have a carPC, too cheap & I don't want to re-install everything). I do connect my laptop to my 360.2 on long trips - MP3s + GPS & I don't have to worry about it getting stolen - You can't tell i have anything but stock (my sub box is even somewhat camouflaged)

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                            • #15
                              Guys, I am not an electronic person, but I am thinking of something similar with a 4016. The circuit on the right seems very simple and should do the job with 2-3 components. I thnk a suitable NOT gate might be a 4069 or 4049.



                              See : http://www.doctronics.co.uk/4016.htm

                              I am asuming you have an amp in your car.

                              I will be using a different controller to FB but the same concept should work. The link says the circuit is bidirectional so it should also switch two inputs to the one Output. In other words, let A1 and A2 outputs be the left and right channel on the HU and the B1 & B2 outputs be the left and right channels on the Car PC. The A1 & A2 Inputs will go to the L& R inputs on your amp. The earths on the RCA connectors could be wired common. We only care about the signal (centre wire) to switch the audio.

                              So on the FB, we need to use one input and one putput. Let the FB monitor the Amp turn on wire on the HU. When the FB sees a voltage on this wire, it signals the HU is turned on. When this signal is seen, the FB can apply a voltage to the enable wire. Voila! the HU signal goes to the amp and Bob is your uncle, the HU will play to the amp. Turn the HU off and the Car PC will play again.

                              The only issue I can see will be that the line out voltages will be quite different between the PC and the HU so volume will be quite different but you should be able to compensate for this with the HU volume control.
                              RodW
                              2007 Toyota Hilux with a CarPC..

                              Worklog: http://www.mp3car.com/vbulletin/work...ota-hilux.html
                              OziExplorer GPS Embedded in RR: http://www.mp3car.com/vbulletin/sb-s...iexplorer.html

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