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I have a question that is a little bit of "engineering nature". Why can't I plug an audio signal(music from computer) and bass/guitar in the same speaker if I somehow wire outputs together without some device or mixer? I know that these two signals will be added to each other, but will it result in distorted signal or I could hear the difference between music and guitar? And what are 2 input AMPs made of if that is the case?

Matija Stankovic
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    This is a bit woolly at the moment. It's not clear *exactly* what the signal train is that you want to try. Please be clarer, and it'll help you find goodd, helpful answers. – Tim Apr 26 '21 at 15:53
  • Mixer, yes; hokey DIY, no. Please add details of precisely what you're trying to do. – Tetsujin Apr 26 '21 at 16:06
  • Please explain what you want to achieve. As of now it seems to me like an https://xyproblem.info/ – user1079505 Apr 26 '21 at 18:06
  • Ok, I will explain this problem. I want to know, why cant we use DIY hokey. What can Mixer do that DIY hokey cant? What is the difference, I know that mixer is more complex than DIY hokey. – Matija Stankovic Apr 26 '21 at 19:01
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    @tetsujin what's an hokey? Search engines don't help on that one :/... – Tom Apr 26 '21 at 19:08
  • @MatijaStankovic what do _you_ mean by mixer? Mixers typically mix low level signals that are then amplified, not the amplified signals going to speakers. What is a hokey? Please explain what are you trying to do. – user1079505 Apr 26 '21 at 20:28
  • My idea was to connect guitar signal and audio(music from computer) together with the same jack. It would be parallel connection, and my question was. How they will affect each other. – Matija Stankovic Apr 27 '21 at 00:15
  • 1. When you say "guitar signal" do you mean signal from the guitar? From an effect pedal? From preamp? Amp? 2. connect to what? 3. In the question you mention two inputs on the amp. What does the manual say about those? – user1079505 Apr 27 '21 at 06:52
  • Does no-one possess a dictionary? Hokey - contrived, poorly-specified, cheap & likely to fall apart. – Tetsujin Apr 27 '21 at 06:53
  • @tetsujin Oh, thanks! I was looking for something more technical... And no I do not have one: these days I don't see enough people to need such a big book to hammer them with O:) – Tom Apr 27 '21 at 08:00
  • This question seems quite clear to me. "Given two analog audio outputs, why can't I mix them by simply plugging them into a speaker in parallel? What will happen if I do? If you can't mix audio signals that way, then how do amps with multiple inputs do it?" – Tanner Swett Apr 27 '21 at 21:12
  • Analog audio doesn't work in a logical-path way unfortunately. The analog audio will go into the amp but also into the other piece of gear, shoving an input into an output. Depending on circuitry this will sometimes work ok (but not optimal) sometimes distort and sometimes cause damage. Amps with multiple inputs do it in a lot of ways, but a simple example is a buffer, often provided by an op amp. A buffer reads the signal on the input but also blocks that input signal from progressing, while giving a copy of that signal on the output, basically, it gets technical! – OwenM Apr 28 '21 at 22:49

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If you simply want to connect two sources to the same speaker, this is usually a big no-no. The problem is that the two sources will also be connected to each other, and they will try to drive each other, and neither one is meant to be driven by anything, so there is potential equipment damage.

However, if you are only connecting passive guitars or basses, then you should be fine. The pickups do not put out much power and will not be damaged by each other. You can wire two pickups in parallel on a Jazz bass, and there's no reason they must be on the same bass...

I wouldn't attempt doing this with a music source + an instrument.

Edward
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  • Wiring two guitars together is not a great idea either. You indeed won't burn anything, but each guitar volume and tone pots will affect sound of both instruments. If one of the guitars produces larger signal, you won't be able to compensate for it. – user1079505 Apr 26 '21 at 20:25
  • I don't mean to suggest that it's a good idea to wire two guitars together, but I think that wiring two guitars in parallel would not couple the controls like you say. Wiring in series would though. – Edward Apr 26 '21 at 21:26
  • Yes it would. If you short signal to ground, it doesn't matter where the short is. – user1079505 Apr 26 '21 at 22:29
  • Oh, I don't know much about guitar electronics. I'm thinking that you could still have the two pickups in parallel to each other and have separate volume knobs just as a jazz bass has, but I suppose that would require some surgery. – Edward Apr 27 '21 at 00:38
  • @user1079505 This actually depends on the output load, if any, after the volume pots. Basically, it will depends on specific hardware implementation... – Tom Apr 27 '21 at 08:02
  • If you put two guitars into a passive 2into1 box like a simple transformer isolated combiner then the results are variable, but usually turning down guitar A also turns down guitar B (and visa versa), as guitars A's signal short to ground is connected to guitar B, which happily finds ground in the same place. I use this system regularly when teaching for a quick and easy way to connect two instruments, but it's just a hack. To isolate two instruments directly connected requires luck that both have a high output load, or some more elaborate circuitry... – OwenM Apr 28 '21 at 22:44