Converting stereo to mono

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prayag2010
 
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Converting stereo to mono

Post by prayag2010 »

Hi,

I recently got into electronics and I am working on a project which includes passing audio to a sub woofer through a Passive RC low pass filter (and an op-amp) . So, I need to mix left & right audio signal before passing it to the Passive RC low pass filter. But by doing so, I would fry my audio source. So, is it safe to insert a 500 ohm (or any other value) resistor on L and R signals before mixing them ? Will it still fry my audio source ?

And can you please suggest a good tutorial (or book) on 555 timers since I am a newbie ?

Thanks for any suggestions or advice !!!

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Franklin97355
 
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Re: Converting stereo to mono

Post by Franklin97355 »


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easternstargeek
 
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Re: Converting stereo to mono

Post by easternstargeek »

I work quite a bit with both professional and consumer audio, but you haven't given us quite enough information to help.

You are, however, exactly right to consider this point- just like you never connect two digital outputs together and run them to a single input, never do the same with audio outputs. You must use some kind of mixer.

I have built passive mixers to combine L&R from an unbalanced stereo line-level source into a single unbalanced line-level input. I use it to connect my iPod to a monaural input channel on my mixing board.

The method is similar to what you have described:
1. Connect all grounds together
2. Wire 1K resistors in series with the source's Left and Right "Hot" leads
3. Tie the other ends of both resistors together, and connect them to the Hot side of the output
4. Wire a 10K resistor between the hot and ground of the output.

The above approach, however, was designed for unbalanced line-level signals. You may get into trouble if you connect the mixer inputs to a power amplifier (or something else). Can you please make a sketch or give a description of what the whole system should look like when you're done?

Be sure to mention:
1. Where are the L&R signals coming from? If not line-level, be very specific.
2. Are the L&R signals going anywhere else besides your passive mixer?
3. If the L&R are coming from a power amplifer, are the outputs ground-referenced or bridged? How much power? What kind of speakers will also be connected?
3. What are the input characteristics of your sub-woofer system?

prayag2010
 
Posts: 22
Joined: Thu Apr 29, 2010 8:44 am

Re: Converting stereo to mono

Post by prayag2010 »

Hi,

Thanks for your reply.

1. The audio is coming from an ipod touch (or any other i-device which has a 30 pin apple connector)
2. Yes, the audio signals are going to two 8-watt speakers, a line-out from my speaker and the sub-woofer and possibly my volume controller circuit that I made (if it works)
I have attached an image with my idea (btw the circles are transistors and the pins are labelled as C, B & E - collector, base and emitter).
I used it because I can't connect it to a potentiometer as I am controlling the volume with a remote using an arduino.
3. No, they are coming from an ipod or iphone.
4. Well, I haven't decided that yet. Can you suggest me some good specs ?

Can you also tell me a way which prevents the audio from coming back to the source. (you must have guessed that I need some protection in my circuit)

Thanks for your help.
Attachments
Volume controller circuit idea0001.jpg
Volume controller circuit idea0001.jpg (648.31 KiB) Viewed 2261 times

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easternstargeek
 
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Re: Converting stereo to mono

Post by easternstargeek »

i'm terribly sorry, but I don't think I can do much with what you have provided so far, but I would like to make a few suggestions since you say that you're new to electronics. Learning how to build things is surprisingly easy. The hard part is figuring out what you need to build. It is even harder to ask others for help- not because we don't want to assist, but because communicating what you want to do when you don't know how to build things can be very challenging. By this post, I am attempting to help you organize your ideas and communicate them to the community so that they are impossible to misunderstand.

1. When anything new is designed, there is the "Concept" and later, the "Implementation" of that concept.

We on this forum know how to implement things, but it's your job to give us enough information to help. This may sound obvious, but I work professionally designing factory automation projects, and believe me- getting the customer to explain what they want us to build can be very difficult, even for other professionals with years of experience in their field.

Right now, you're the expert when it comes to your dream, and we're the experts at figuring out how to get the pieces of that job done. Most folks here also want to give you the support necessary to become an implementation expert too!

2. So far, I see that you have an iPod-like device, two speakers, a sub-woofer and an arduino, and you want to make them all play together somehow. Imagine, for a moment, that you have built your dream system, and that it does everything you want it to do- Please explain to us exactly, "What does it do," "For what purpose," and "how do you operate it." Think about this exercise as if you were writing a marketing brochure or a brief instruction manual.
Also, please tell us which blocks already exist, and which ones still need to be built.

3. Instead of trying to make a schematic diagram, which you don't appear to be ready to do yet- make instead, a "Block" diagram. Separate your system into functions, then describe what each function does. Connect the blocks together with lines AND an arrow that shows which way the signal flows from block to block.

Here is an example of the kind of block diagram I have in mind:
BlockDiagram.jpg
BlockDiagram.jpg (34.21 KiB) Viewed 2251 times
This is the most important part of the design process, so take your time. The great thing about a block diagram is that you can make it as general or as detailed as you want. For example- if you never heard of a "mixer" you wouldn't think to show that block, but if you know that you want the L+R information to go to the subwoofer, then just draw the lines to show it. We'll figure that part out and explain it to you.

Hope you find this helpful. We look forward to your next post!

prayag2010
 
Posts: 22
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Re: Converting stereo to mono

Post by prayag2010 »

Thanks for your reply !!!

I am sorry too for the inconvenience that I caused you but as you suggested, I prepared a block digram and I attached it.

As you mentioned, I have an arduino, 2 speakers and a sub-woofer. I have used the arduino to send commands to the i-device received by the remote for playing, pausing, etc and to control the volume using the circuit that I showed you. But, I am planning to make the sub-woofer external so that I can make the speaker portable. I am also going to output video from the i-pod as it already has video out ( http://pinouts.ru/PortableDevices/ipod_pinout.shtml ) . Moreover I am also going to input & output audio through an external jack (as in mp3 players, etc)


Well, this is my basic plan so far. I hope this works out.......

Once again, thank you for your support so far and I hope you continue to do the same in future !!!!
Attachments
Ipod speaker block digram0001.jpg
Ipod speaker block digram0001.jpg (571.99 KiB) Viewed 2245 times

prayag2010
 
Posts: 22
Joined: Thu Apr 29, 2010 8:44 am

Re: Converting stereo to mono

Post by prayag2010 »

Ummm......

Please skip the mixer block in the digram...... I didn't read the last part of your reply.....
:oops:

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