I want to build a circuit that allows me to remix(?) left and right channels from a normal stereo in a custom fashion. In other words, I would have 4 knobs: one that controls level of left channel to right ear, one that controls level of right channel to right ear, one that controls level of left channel to left ear and one that controls level of right channel to left ear.
Can I do this with a buffer (simple op amp) circuit maybe (4 total op amps) with pots to control gain?
I predict you will be unhappy with the results of repanning existing mixed and panned left and right channels, but I understand you want to build something, evidently. Maybe someone else has some ideas. I feel suffciently chastised for saying anything at all.
More or less. You can probably get away with only 2 op amps, for L and R output summers. Each would sum the outputs of its own pair of L and R input gain pots. If you use simple inverting summers, then of course the outputs will be inverted. If that matters (and it sometimes does) you can follow each summer with another inverting stage.
Best regards,
Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis
I greatly appreciate any leads on raw circuits, kits or full devices
I'm really hoping to have something I can power with a 9V battery and use it with an ipod-like device
I have to apologize for asking really dumb questions, but I'm a real amature at this stuff.
So would I be able to use a circuit like that shown in:
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I would use one of these for each stereo channel - but then how would I mix the signals? I assume I can't just connect the outputs from the two circuits to mix them correct? Since there is feedback on the opamp circuits, wouldn't this mess up the circuits?
I guess that is what confuses me at a very basic level - is isolation. How can signals be mixed (combined) without feeding back to the other signal? I see if you use an opamp then you are really buffering the original signal and recreating it with another power supply. But then if you combine outputs (physically connect them) from the opamp buffers (to mix signals) you would mess up the function of the individual circuits.
Sorry to ramble - I'm not smart enough to see how this works exactly
You already got the correct lead on a full device. A mini-mixer, for less than $50, will do exactly what you need. (An example would be the Behringer UB802.)
If you really want to build it yourself, you should understand that the parts will probably cost you more than that and the quality you'll end up with will be much lower.
Ah, more requirements emerge. Must be powered with single 9V battery. Any other requirements, while we're at it? For instance, does the output need to be able to drive headphones? Need to be small and portable?
A Rolls Pro Mix IV mini mixer will run on two 9V batteries, and it has a headphone output, and it is small. But it costs $150.
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That *idea* would work as part of your circuit. But you'd need to change a few things. For instance, that circuit requires a split power supply, e.g., two batteries rather than one. (The supply circuitry isn't shown at all; the thing that makes it clear is that the non-inverting inputs of the opamps are taken directly to ground, rather than to a bias voltage, and there is no DC blocking capacitor on the input or output.)
So, take a look at "mixer" circuits. The idea is that you'll feed each channel individually into one of your panpot circuits, and then you'll use a mixer circuit to mix the panpot left channels together, and likewise the panpot right channels together. And then, if you need, you'll use yet another stage to power the headphones.
So if I take the output of the circuit in panpot.pdf (one for each stereo channel) and feed it to:
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I should be OK?
Stupid follow-up question:
In the mixer circuit, isolation is performed by just the resistances? This keeps the opamps from being affected by the connection of the channels in the mixer?
I guess I might be confused because the currents are almost zero right?
What you use is a "summing amplifier", where the inputs converge through resistors at the opamp's input.
Here's an example:
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The inputs are perfectly isolated from each other, because the opamp will output whatever voltage it needs to to make the differential voltage from the "-" input to the "+" input equal to zero. The 3.3K is only to equalize the bias currents; it's equal to the parallel combination of the three 10K Rs.
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