Hello all,
I was wondering if the teeming masses could help me with a circuit.
I am trying to make a line mixer with 3 source inputs, one output, and have it powered off 12 v. I am trying to put the 3.5mm stereo outputs from my gps, ipod, and radar detector into the factory aux input for my car radio.
I would like the mp3 to be attenuated once the radar or gps have a message.
My question:
If I use fixed resistance instead on pots, will that accomplish an intentional unbalancing of the 'mix' when the gps/radar has signal?
Do you think that I could get away with a passive mixer for this situation, or would the sound quality just fall off?
Is there a simplier solution to this problem then a mixer?
I have a bunch of plans for mixers but I welcome any input.
Thanks for your time sincerely,
Don Crawford
I was wondering if the teeming masses could help me with a circuit.
I am trying to make a line mixer with 3 source inputs, one output, and have it powered off 12 v. I am trying to put the 3.5mm stereo outputs from my gps, ipod, and radar detector into the factory aux input for my car radio.
I would like the mp3 to be attenuated once the radar or gps have a message.
My question:
If I use fixed resistance instead on pots, will that accomplish an intentional unbalancing of the 'mix' when the gps/radar has signal?
Do you think that I could get away with a passive mixer for this situation, or would the sound quality just fall off?
Is there a simplier solution to this problem then a mixer?
I have a bunch of plans for mixers but I welcome any input.
Thanks for your time sincerely,
Don Crawford
I don't think it has to be that complicated.
It would be easiest if I didn't attenuate the signal and used NO circuits on each input.
But did it make sense what I was trying to describe by using fixed resistance for the inputs instead of potentiometers or variable resistance.
That was went the auxilary signal is sent they always affect the summation the same way every time.
Tell me why I am mistaken with on my use of balance. I am really new to audio but I am not new to signals and electronics. I am talking about the resistance of the circuit for each input will be fixed. The peak current of just the mp3 will generally be less than the mp3 + auxillary inputs peak current. If you have appropriate fixed resistance than the signal for the mp3 should get weaker naturally when the signal of aux is activated?
I don't know if that made any sense.
I guess I am just thinking while I type but I should have some sort of extra resistance on the mp3 line that is added when the aux signal is activated.
Right?
But the above doesn't need anything beyond passive mixing right?
thanks for helping me think this out,
Don
It would be easiest if I didn't attenuate the signal and used NO circuits on each input.
But did it make sense what I was trying to describe by using fixed resistance for the inputs instead of potentiometers or variable resistance.
That was went the auxilary signal is sent they always affect the summation the same way every time.
Tell me why I am mistaken with on my use of balance. I am really new to audio but I am not new to signals and electronics. I am talking about the resistance of the circuit for each input will be fixed. The peak current of just the mp3 will generally be less than the mp3 + auxillary inputs peak current. If you have appropriate fixed resistance than the signal for the mp3 should get weaker naturally when the signal of aux is activated?
I don't know if that made any sense.
I guess I am just thinking while I type but I should have some sort of extra resistance on the mp3 line that is added when the aux signal is activated.
Right?
But the above doesn't need anything beyond passive mixing right?
thanks for helping me think this out,
Don
This IC, as far as I can see, is only a switch. It will not allow the mixing of signals.
Relays would do the same thing but with relays, you could switch all of the connections (including signal grounds) so that there would be no chance of creating ground loops.
Any good quality 4 pole double throw relay would work. You'd need two of them. Use relays that have sockets so that it will be easy to change the relay if it fails.
You'll have to build a trigger circuit that will drive the relays on when the other devices produce audio.
Do you know how much AC voltage the GPS and radar detector produce when they have audio output? Do they both have volume controls for their output signals?
Relays would do the same thing but with relays, you could switch all of the connections (including signal grounds) so that there would be no chance of creating ground loops.
Any good quality 4 pole double throw relay would work. You'd need two of them. Use relays that have sockets so that it will be easy to change the relay if it fails.
You'll have to build a trigger circuit that will drive the relays on when the other devices produce audio.
Do you know how much AC voltage the GPS and radar detector produce when they have audio output? Do they both have volume controls for their output signals?
Man, I was completely looking at that wrong then.
I thought it had a summing circuit. When I read the desciption I felt like it had that capability.
Too bad I bought it already. It will be useful in another project.
If I use relays, I wont necessarily be combining signals. A relay will be a good 'switch' eliminating group loops.
But I guess what you are saying is relays, and some resistance, and bam! Passive mixer?
I get back to you on the GPS and MP3 output when I get back to the house.
I thought it had a summing circuit. When I read the desciption I felt like it had that capability.
Too bad I bought it already. It will be useful in another project.
If I use relays, I wont necessarily be combining signals. A relay will be a good 'switch' eliminating group loops.
But I guess what you are saying is relays, and some resistance, and bam! Passive mixer?
I get back to you on the GPS and MP3 output when I get back to the house.
Radio shack 4pdt with sockets. I've used them in the past and they're pretty reliable. Don't wire all of this up without sockets. If you have a relay fail, it's a real pain to replace it if you solder to the relay.
You should also include 100k ohm drain resistors on all outputs. Many times, you'll get DC leakage through output capacitors (in the devices) and when you switch signals, you will get a pop (without the resistors).
You should also include 100k ohm drain resistors on all outputs. Many times, you'll get DC leakage through output capacitors (in the devices) and when you switch signals, you will get a pop (without the resistors).
Most likely
I have been ignoring this schematic for a while but what do you think of making twin versions of this
http://www.forsselltech.com/downloads/schematics/Summing Buss2.pdf
for solving my problem?
I think I might be able to use that ic as a pretty fancy audio selector if I ever finish my car computer project. But I am convinced now that it isn't going to help much with this.
I have been ignoring this schematic for a while but what do you think of making twin versions of this
http://www.forsselltech.com/downloads/schematics/Summing Buss2.pdf
for solving my problem?
I think I might be able to use that ic as a pretty fancy audio selector if I ever finish my car computer project. But I am convinced now that it isn't going to help much with this.
If you use a mixer and you don't kill the audio from the radar detector and the GPS unit (when they're not producing audio output themselves), you could possibly have noise (hiss) enter the system. The hiss would be audible during quiet passages in the MP3 audio.
To determine if they generate any noise, plug them into the aux input and set the head unit volume as high as you normally have it when listening to MP3s. Do you hear any hiss with either device plugged in? Activate the device so it produces audio and have the volume level on the device set to where you'd use it.
The only thing you gain with a mixer is being able to hear the MP3 player when the GPS or detector are producing output.
To determine if they generate any noise, plug them into the aux input and set the head unit volume as high as you normally have it when listening to MP3s. Do you hear any hiss with either device plugged in? Activate the device so it produces audio and have the volume level on the device set to where you'd use it.
The only thing you gain with a mixer is being able to hear the MP3 player when the GPS or detector are producing output.
Lazy
I took the lazy route. I saw a deal on a rolls mx44 mini mixer. It will be just what I need I think. I am just going to play around with it and throw it behind the dashboard once it is set.
For this hissing issue I thought ahead. The power source for each of these inputs are connected to this thing I found in the bargain bin at O'Reilly's. Its a cigarette adapter splitter that has a remote switch for each of the 3 (or maybe 4) sockets. Its actually sort of fancy. It has clear buttons that light up.
So basically I have gotton lazy.
I might still use up all the parts I bought one something else. No ideas yet.
I took the lazy route. I saw a deal on a rolls mx44 mini mixer. It will be just what I need I think. I am just going to play around with it and throw it behind the dashboard once it is set.
For this hissing issue I thought ahead. The power source for each of these inputs are connected to this thing I found in the bargain bin at O'Reilly's. Its a cigarette adapter splitter that has a remote switch for each of the 3 (or maybe 4) sockets. Its actually sort of fancy. It has clear buttons that light up.
So basically I have gotton lazy.
I might still use up all the parts I bought one something else. No ideas yet.
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