Several Analog Signals into a Single Signal ?

[WilliamK]

Guys, I'm building a special project, that is a bit secret for now. But I will release more information latter next week, I hope at least. ;-)

My main problem now is how I will address this: I need to be able to put several audio signals into a single signal, without loosing quality, and while still staying ANALOG.

My first idea was to make every signal AM (Amplitude Modulated) working with a very high frequency, around 400Mhz or even more.

Are there Voltage-to-Frequency and Frequency-to-Voltage chips around that would make this very easy to do?

Or should I use another solution?

And thanks for helping me out.

Best Regards, WilliamK

 

[audioguru]

I need to be able to put several audio signals into a single signal, without losing quality, and while still staying ANALOG.

Hi WilliamK,
I guess that you want the audio signals to stay separate so a mixer won't do.
I worked with a large intercom system that multiplexed the audio of 12 conversations or background music selections on a single internal piece of wire. It assigned a "time-slot" to each audio path. The multiplexing occured at a high frequency so that it wasn't audible and the quality was excellent. It worked about the same as an FM stereo or TV stereo decoder, except had more channels.

My first idea was to make every signal AM (Amplitude Modulated) working with a very high frequency, around 400Mhz or even more.

You can use a separate RF carrier for each audio signal and filter and demodulate each one, but it would be complicated.

Are there Voltage-to-Frequency and Frequency-to-Voltage chips around that would make this very easy to do?

V-to-F or F-to-V wouldn't keep the signals separate, unless they have a different audio frequency band.
V-to-F makes FM not AM. :lol:

 

[WilliamK]

Ahhh, multiplexing, a friend told me about that, only now I understand what he means... I would have one master clock and so on...

Strange, I always had in mind that AM was Amplitude Modulated of a Frequency. Hence the v-f thingie... still, maybe I need to learn more. ;-)

Anyway, thanks for the big help. I will try Multiplexing, it sure looks like a good idea.

Wk

 

[WilliamK]

BTW: Off-topic, my wife and I just got back from Canada. Victoria/BC. We would stay for good, but immigration changed a few laws and were nasty to us... maybe we will come back, but only to visit. ;-)

Wk

 

[audioguru]

What was the name of your country when I went to school? :lol:

 

[stevez]

I am not sure how many "several" is but FM stereo is essentially analog and has two channels. You might borrow from this and add more channels.

In a simple sense - take each audio signal and add some constant signal - 20 kHz, 40 kHz, 60 kHz - use it to modulate an FM transmitter - bandwidth is considerable. Subtract teh 20, 40 and 60 at the other end.

 

[stevez]

An afterthought - do a little looking on SCA - a service where they add subcarriers to a regular FM broadcast - much as I described in my first post. I know Ramsey Electronics sells receiver kits with a wide passband and an add-on SCA decoder.

 

[WilliamK]

What was the name of your country when I went to school? :lol:

Hummm, didn't get your joke... :?:

Wk

 

[WilliamK]

About FM: What worries me out is if it won't "degrade" the audio quality. So if I could work on very high freqs, it shouldn't. I know how to make the FM signal at 400Mhz, but I don't know how to "read" it back...

The Multiplexing sounds better, but I still don't know how to make the circuit for it working at a very high frequency.

Wk

 

[Nigel Goodwin]

What was the name of your country when I went to school? :lol:

Hummm, didn't get your joke... :?:

Wk

Probably that he's never heard of your location entry ( as neither have I, nor Google! ).

So please either explain where it might be?, or enter your correct location, it has a bearing on a suprisingly high number of questions!.

 

[WilliamK]

Ahhh, Canada and Brazil. Right now I'm in Brazil.

Wusik is the name of my company, so WUSIKlandia. Get it now? ;-)

Wk

 

[audioguru]

Hi WilliamK,
No wonder I never heard of your country, it was a company!
So many real countries have changed their names since I went to school it is difficult to keep track of them all.
Companies also change their name when they get into trouble. I worked with shoddy Goldstar (Korean) products in 1980. Their name is LG Electronics now.

Keep away from Victoria, BC. It's pretty there but the people have a "stiff upper lip" because most are from the UK and aren't friendly to others.
Cum-on over to the Middle-East of Canada and we'll show you a good time. :lol:

It will take a pile of parts to make an audio multiplexer. Each signal needs to be gated into its time slot by a digital stepper and some analog gates. To decode it you need a sample-and-hold stage and filter for each signal.
Additional complication involves adding "dead-time" between time slots to avoid crosstalk of the audio signals.

An FM demodulator could be a wideband discriminator, pulse counter or phase-locked-loop.

 

[Nigel Goodwin]

Companies also change their name when they get into trouble. I worked with shoddy Goldstar (Korean) products in 1980. Their name is LG Electronics now.

LG stands for "Lucky Goldstar", their name hasn't really 'changed', they just started using it differently.

Companies seem to change their name for no apparent reason?, it really annoys me! - in the UK the "Post Office" changed their name to "Consignia"? - what a totally bizarre thing!. Apparently they paid the guy who thought of the name an absolute fortune, then spent another fortune renaming everything - but the entire country still called it the post office!, and (as far as I'm aware?) they spend a third fortune changing everything back!.

 

[WilliamK]

Guys, thanks for all the help and info so far.

I think I will start my project with something simpler...

I will let all signals to use theyre own wires, as it will be inside one single box, and just use some Matrix-Selector...

Are there special switch or even matrix chips that will carry those analog-sound voltages?

I found some small 8x1 Switches already. But my project will have around 200 wires. :shock:

Wk

 

[Nigel Goodwin]

Guys, thanks for all the help and info so far.

I think I will start my project with something simpler...

I will let all signals to use theyre own wires, as it will be inside one single box, and just use some Matrix-Selector...

I suspect you were being over ambitious?, multiple audio signals down a single wire isn't at all a trivial matter, particularly if you want decent quality and bandwidth!.

 

[WilliamK]

Guys, thanks for all the help and info so far.

I think I will start my project with something simpler...

I will let all signals to use theyre own wires, as it will be inside one single box, and just use some Matrix-Selector...

I suspect you were being over ambitious?, multiple audio signals down a single wire isn't at all a trivial matter, particularly if you want decent quality and bandwidth!.

Indeed, I'm new to this, now I get it.

And yes, quality and bandwidth would be VERY important. So maybe I will do just as I said. A Matrix-Switch. Now I need to find the easiest way. ;-)

Wk

 

[audioguru]

Hi WilliamK,
Go to www.maximic.com and look at their audio-video matrix selector IC's. :lol:

Hi Nigel,
Over here, Northern Electric changed their name to Northern Telecom and paid the guy with that name a fairly big fortune. I had a boss that went to school with that now very rich guy. :lol:

 

[WilliamK]

Hi WilliamK,
Go to www.maximic.com and look at their audio-video matrix selector IC's. :lol:

Sorry to nag, but I can't find it.

Wk

 

[WilliamK]

Guys, thanks for all the help and info so far.

I think I will start my project with something simpler...

I will let all signals to use theyre own wires, as it will be inside one single box, and just use some Matrix-Selector...

I suspect you were being over ambitious?, multiple audio signals down a single wire isn't at all a trivial matter, particularly if you want decent quality and bandwidth!.

Thinking again, I could have 16 signal-paths running 16 signals each. For a total of 256 signals overall. Not bad at all.

I was looking at this:

https://www.electro-tech-online.com/custompdfs/2005/08/DG406-DG407.pdf

But the question is, what would the audio-quality be? Min/Max HZ of the signal and multiplexing? Or this depends on how I drive the clock into it?

Sorry to nag so much, I know I'm a very newbie, but still, any help will be apreciated. ;-)

Wk

 

[WilliamK]

Just found one from Analog-Devices:

https://www.analog.com/UploadedFile...pdf&fterm=Multiplexer&fterm=Multiplexer&la=en

Wk