# Amplifier with multiple inputs?

#### navyguy

Joined Sep 27, 2019
48
Not sure if I’m on the right forum and might be a dumb question but my audio project requires an stereo/amplifier with at least 4 inputs from various sources and all 4 sources need to be heard through the speakers at the same time.
Wondering if that’s a common thing easily available or do I need to add a mixing device or
????

Any help greatly appreciated.
Thanks

#### Bernard

Joined Aug 7, 2008
5,251
Depending on signal levels available, a simple resistive mixer could be used., maybe 4:1 or better an
OP Amp mixer.

#### BobTPH

Joined Jun 5, 2013
2,016
You might find an audio amp with a 4 way mixer built in, but it will likely cost more than just adding a mixer in front of an ordinary amp.

Bob

#### navyguy

Joined Sep 27, 2019
48
Ok thanks. I think I may have already found the answer or at least half of it. A simple inexpensive 4 channel mixer should be fine but also need to not only run the outputs into the stereo amp but also need to run those same outputs into a
sound -to-light control board. IE the 4 sources of audio will also be independently flashing lights on and off according to the sounds the devices are making.

#### djsfantasi

Joined Apr 11, 2010
5,570
Ok thanks. I think I may have already found the answer or at least half of it. A simple inexpensive 4 channel mixer should be fine but also need to not only run the outputs into the stereo amp but also need to run those same outputs into a sound -to-light control board. IE the 4 sources of audio will also be independently flashing lights on and off according to the sounds the devices are making.
I had almost the exact same problem. I bought a $60 professional mixer. My inputs were mono, so I bought mono to stereo patch cables. I used one stereo channel for the sound and the second for the sound-to-light board. Also check the mixer. Some have aux outputs that can be used for the same purpose. I bought the Behringer Xenyx 802. The 502 may work also. Thread Starter #### navyguy Joined Sep 27, 2019 48 I had almost the exact same problem. I bought a$60 professional mixer. My inputs were mono, so I bought mono to stereo patch cables. I used one stereo channel for the sound and the second for the sound-to-light board.
Also check the mixer. Some have aux outputs that can be used for the same purpose.
Lol. I was hoping to get your thoughts on this.
Actually I’m probably confusing others including myself.
Ok. I’ll try this again.
I’ll have 4 separate sources of audio. (Thunder soundtrack, canons firing soundtrack, pirates talking and the sound of hurricane winds) The thunder will trigger the lights to simulate lightning. The canon fire soundtrack will fire off a light bulb inside the canons barrels. (Tracking me so far?)

The thunder and canon soundtracks need to be first amplified in order to trigger the light to sound devices which I’ve already built.
Until the 4 sources of audio are all tied into the amplifier input, they cannot be mixed together.

Thanks

#### djsfantasi

Joined Apr 11, 2010
5,570
Lol. I was hoping to get your thoughts on this.
Actually I’m probably confusing others including myself.
Ok. I’ll try this again.
I’ll have 4 separate sources of audio. (Thunder soundtrack, canons firing soundtrack, pirates talking and the sound of hurricane winds) The thunder will trigger the lights to simulate lightning. The canon fire soundtrack will fire off a light bulb inside the canons barrels. (Tracking me so far?)

The thunder and canon soundtracks need to be first amplified in order to trigger the light to sound devices which I’ve already built.
Until the 4 sources of audio are all tied into the input, they cannot be mixed together.

Thanks
Makes perfect sense. My proposal should address that...

Except...

I don’t get what you mean by or why you felt the need to add
Until the 4 sources of audio are all tied into the input, they cannot be mixed together
You still didn’t answer my question. Are the sources stereo or mono? And if they are stereo, do they have to be?

#### djsfantasi

Joined Apr 11, 2010
5,570
And as a side note, to be realistic, the lights should trigger the thunder. In the world, we see the lightning, there is a pause and then we hear the thunder

#### AnalogKid

Joined Aug 1, 2013
8,099
Like this:

four audio sources, line level or less.
four amplifier/buffer stages. Each stage provides some gain and a low output impedance for driving downstream stuff.
each stage has two connections to its output:
1 resistor going to a summing network at the input to the audio amplifier
1 wire going to a trigger circuit for lights/effects.

First, each gain stage is adjusted so its output is large enough to trigger the effects. Second, the resistors to the summing point are adjusted so each audio source is the correct level relative to the other sources.

or something like that?

ak

#### bertus

Joined Apr 5, 2008
20,040
Hello,

Did you have a look at the mixer part of project 94a I posted?

Bertus

#### djsfantasi

Joined Apr 11, 2010
5,570
Like this:

four audio sources, line level or less.
four amplifier/buffer stages. Each stage provides some gain and a low output impedance for driving downstream stuff.
each stage has two connections to its output:
1 resistor going to a summing network at the input to the audio amplifier
1 wire going to a trigger circuit for lights/effects.

First, each gain stage is adjusted so its output is large enough to trigger the effects. Second, the resistors to the summing point are adjusted so each audio source is the correct level relative to the other sources.

or something like that?

ak
I have no problem with that, given that the sources are MONO. And hence why I keep asking the question.

Otherwise, don’t you end up with two trigger inputs to light/effects? Do you use both? Or which do you use? Or (there are other possibilities, but to mention them would further muddle the problem).

#### djsfantasi

Joined Apr 11, 2010
5,570
Hello,

Did you have a look at the mixer part of project 94a I posted?

View attachment 187583

Bertus
Given that each input is sufficient to drive two nodes with a 50K resistor...

I agree.

#### navyguy

Joined Sep 27, 2019
48
I have no problem with that, given that the sources are MONO. And hence why I keep asking the question.

Otherwise, don’t you end up with two trigger inputs to light/effects? Do you use both? Or which do you use? Or (there are other possibilities, but to mention them would further muddle the problem).

Sorry. Mono will work I believe.

Thanks so much.

#### navyguy

Joined Sep 27, 2019
48
Thanks so much everyone.
I’m still at work do not having much time to look at all the great help.
I’ll be reading up on everything tonight hopefully.

#### navyguy

Joined Sep 27, 2019
48
And as a side note, to be realistic, the lights should trigger the thunder. In the world, we see the lightning, there is a pause and then we hear the thunder
Yes your absolutely right.. here in California so few even know that. I’m from Ohio and it’s absolutely correct. If you have a circuit in mind let me know.

Thanks !!!

#### djsfantasi

Joined Apr 11, 2010
5,570
Yes your absolutely right.. here in California so few even know that. I’m from Ohio and it’s absolutely correct. If you have a circuit in mind let me know.

Thanks !!!
So you say you have four sources
1. Thunder
2. Cannon
3. Wind
4. Pirates
I’m guessing source #4 won’t trigger an effect. Numbers 1 & 2 will and the sounds should occur after the effect - not the other way around. Source #3 may or may not have an effect (are you going to use fans?). If not, it can be treated the same as the pirates talking. If you have fans, I’d treat it like effects 1&2, but with a zero delay.

This design has an effect triggering the sound with a delay (variable, but dependent on the source).

The question is... What is the source of the sound (MP3 player, recordable sound module, ...). And how is that source triggered? And can the trigger be replaced with an intermediate module?

It then simplifies to the following for each channel:
• Effect trigger
• Effect control
• Sound trigger
• Sound source
• Mixer

#### AnalogKid

Joined Aug 1, 2013
8,099
Otherwise, don’t you end up with two trigger inputs to light/effects? Do you use both? Or which do you use? Or (there are other possibilities, but to mention them would further muddle the problem).
In post #7 he identifies four sources, two effects, and describes two of the many possible configurations. The system I described is intended for at most one effect per source.

ak

#### navyguy

Joined Sep 27, 2019
48
Awsum guys. Still need to read each response in more detail later.
Anything out there not too expensive that I can record all 4 sounds on separate tracks then with each track having its own output? Then I can install a splitter for the 2 tracks between the recorded output and a mixer? The splitter will go to the lightning machine and the canons.