I am thinking about starting a project where I will need to split an input audio signal (from a guitar) into two matching output signals. To put it simply, I need to "Y" an audio signal. Sounds pretty simple, right? I'm wondering what the best approach is though. First of all, are there any IC's out there that would make this easy? If not, how might I go about doing this without an IC? I was talking to a friend at work and one suggestion was to amplify the input and send it through two audio transformers. Does that sound like an acceptable solution? Any help would be appreciated.
Many guitar amps have dual inputs (1 & 2), so you can run a lead from jack 2 of one amp to jack 1 of the other - the plug into jack 1 of the first amp.
Hi Phil. Thanks for the quick response. Guitar equipment is kind of what this is for but think more along the line of building an effects pedal than running one guitar into two amps. Leaving the application out of this, what I need to do is split one input signal into two "isolated" output signals that will have a 1 dB gain. Using a plain "Y," the gain on each output would be less than 1 dB and would depend on each output's load.
Surely there is an IC that would do something like this.
What you need is a 'circuit' not 'an IC', an IC on its own is not enough. The kind of IC normally used within audio preamp circuits is an op-amp and there are several dozen or so very acceptable types suitable for audio ranging from tens of cents each to tens of dollars for esoteric ones.
I suggest that you buffer the guitar output with an op-amp stage, this will prevent the 2 loads affecting the sound of the guitar. Transformer isoaltion of the 2 outputs may not be necessary depending on what you plan to conenct them too. More info please.
Basically if you don't use some type of buffer then the two devices, unless very high impedence, will interact with each other.
If you don't have any op amps/buffers handy then you could try just making a y cable. If the inputs to the two devices your trying to connect to are high impedence then it will probably work. If not then a buffer should work.
Basically what happens is that one or both of the device load the guitar so that you are not sampling the true signal. Adding buffer's isolates the guitar from the devices. Any op amp should work but there are many specifically for audio that will do a better job(probably any will do if your not trying to make hi fi).
There may or may not be specific IC's that do this but probably quicker just to use some op amps if you got them. The transformers would work but probably not the easiest way unless you happen to have two audio transformers handy. With the op amps you will need a power source and that is probably its biggest drawback.
What kinda devices are you trying to run the guitar signal into? Most should have high impedence inputs in the first place so you probably should need to do this.
You can configure the op amps as buffers or amplifiers as they will accomplish the same goal but the amplifier will obviously amplify the signal(Which you could add a pot to make it variable).
Thanks for the reply Graham. This will be battery powered and what each output will be connected to could vary, which is why it is important that the load of one output not have much effect on the other. Maybe an output will be connected to an amp, maybe another effects pedal, who knows. Standard musical electronics though.
I have a few op-amps laying around actually but I'm still not sure how I would get two output from a conventional 8-pin op-amp. Adding an op- amp would buffer the input and give me a single amplified output but how would I split that output is the question. If I used an instrument as an input to an op-amp and used the output as one of the two outputs I am after, could that output be used as the input to another op-amp without affecting the "quality" of the signal? Essentially, what I am getting at is "chaining" op-amps so each output is being used as the input for another op-amp AND being sent off somewhere for someone's eventual listening pleasure.
There are implications here regarding battery life versus some aspect of performance, notably the ultimate signal to noise ratio but I reckon you'll be OK with TI's TLC27x op-amps (that's a low power type). The current draw of various audio op-amps varies significantly.
Exactly. The guitar on its own likes to see a very high impedance load or the 'tone' will be affected.
Ok. As long as there are no potential 'earth loop' issues, you won't need the outputs to be transformer isolated from each other.
Conceptually, you just need 2 'isolating resistors' driving the 2 output jacks connected to a common output from the buffer stage.
but
With those 2 resistors. That's all you need to avoid any unwanted loading effects on one output influencing the other output. You could of course add more buffers but that'll decrease battery life.
the
Absolutely yes.
The multiple buffering is the kind of thing you'll find in high-end pro kit but is not strictly necessary in your application IMHO.
Thanks again for the reply Graham. That helped a lot and I think I have a good starting point (along with the help of an electrical engineer friend of mine.) Actually, I figure I will be running this off of a power adapter so battery life shouldn't be much of an issue. Using multiple op-amps might be overkill but I might do it just to try to preserve the all-important "tone." Some guitar people are so picky about things that might have the slightest effect on a signal's sound.
Man, so much hostility. :-) I'm a computer programmer and I see a lot of responses like yours where people are trying to weed out who is genuine and who is asking for answers to homework. If it makes you feel any better, I'm asking for myself, even if I'm far from an expert about all this.
Maybe my application doesn't required buffered outputs and unity gain. But here is what I was getting at. I am fairly new at most of this but I'm trying to accomplish something that I think would be fairly straight forward - take an audio signal and get two high quality "copies" with similar gain and where the load on one won't affect the other. What I was asking was how that is generally accomplished.
And actually, now that I think about it, maybe an exact 1dB gain isn't necessary but something pretty close would be. Many guitar effects that might be used in conjunction with what I am working on will depend on the signal's gain. Overdrive/distortion is probably the best example of an effect that depends on gain. An input signal is amplified to the point that it passes a threshold in a component (diode, transistors, vacuum tube) where clipping occurs. If your input has less gain, less clipping will occur, which is why it would be important to keep the outputs' gain close to that of the input.
The little difference in noise isn't going to matter in this app and the 8x series are cheaper.
What a wanker..
You're a waste of Band Space.
Btw, I just added "Wanker" to my spell check, it obviously never heard of it how ever, i've have and seen the ramblings of a wanker!. Just thought you might want to know that little tidbit..
--
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