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2 years ago via answers.hackaday.com

I want to automatically switch audio sources in my car using a VOX like feature. I would like to make it a smooth switch (no pops).

I was thinking of using FETs but the Vsg requirement makes it difficult to design. Plus the FET's intrinsic diode means it only blocks in one direction.

Here's the goal: I have an iPod adaptor and a GPS. I listen to the iPod through the car's stereo. I can also listen to the GPS similarly. But switching between the two is a real pain. What I really want is to interrupt the iPod audio with the GPS audio each time the GPS gives out directions. Hence the VOX feature requirement in this audio cut over hack.

-thanks for any help.
Tip for best answer: M$0.65
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opossum | 2 years ago
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A CD4053 can be used to switch line level stereo audio. Use a bipolar (+5/-5 volt) supply to eliminate the need for caps on the inputs and outputs. There won't be any loud pops as long as there isn't a DC offset on the inputs. Use a 10K ohm resistor to ground on the inputs to keep DC offset under control.

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st2000 | 2 years ago Report

- Apologies, it appears the "select best answer time" has timed out. My bad. I gave both you and hairbysubaru (oh, I get it hair-by-subaru) a "consolation" vote.

- Heads up, the next question (part of this project) I want to ask is what makes for a good VOX. I'll go and post that now. Thanks again guys!

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hairbysubaru | 2 years ago
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The LM 13600/LM13700 has always been my goto for this. It may be overkill, but each input can have its own gain-control and an RC network on the Iabc input means that the gain-change can be slow enough to avoid any DC pops. That and the fact that it's an (admittedly enhanced) op-amp means that common-mode means no hum loops.

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M$
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st2000 | 2 years ago Report

not sure how / who get's these follow ups. On the assumption only the immediate last poster (in this case hairbysubaru) I'm going to post it again just so you both (hairbysubaru and opossum) get a copy.

- Apologies, it appears the "select best answer time" has timed out. My bad. I gave both opossum and hairbysubaru (oh, I get it hair-by-subaru) a "consolation" vote.

- Heads up, the next question (part of this project) I want to ask is what makes for a good VOX. I'll go and post that now. Thanks again guys!

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dlciii | 2 years ago
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I know this is the least hack happy answer. I had the same goal as you at one time. But I used a cheap mx44s by rolls. It gives you the ability to make the GPS much louder that the music or the opposite. I actually had 4 inputs. It had voltage regulation on board and could take variable voltage from 9-15 volts DC (great for auto use). I know its sort of lame but for 40 bucks it was cheaper than any home build application I could think up for what I wanted.

You can leave an optional "tip" with Mahalo's virtual currency, Mahalo Dollars. If you are asking a difficult question that might require some research, or if you'd like a wide variety of feedback, a higher tip often leads to more answers to your question.

M$

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