I have a Mega2560p project that is driving 2x JQ8400 MP3 modules and a Robertsonics WAV trigger board.
I want to mix the output of these 3x modules into a single stereo PAM8406 amplifier.
Now ideally, I should include a level pot for each module, as I have no doubt the outputs will be at different levels. BUT... I could sort that issue out in the coding by setting correct volume levels instead.
Hoping to keep this basic, as it doesn't need to be fancy. I was hoping to find an I2C 4x channel mixer IC, but had no luck.
Before, I have literally linked all the left channels together through 1k resistors and the same with the right channel. It did work, but seems crude.
I found this circuit (attached). Is something this simple gonna cut the mustard?
It might work...
1M is a bit high.
Usually these 1 bjt amplifiers would have an additional resistor from base to ground and a resistor from emitter to ground.
This will not qualify as hifi...
If you use the input scheme as in your starting post, you need only half....
...not 2.
Be aware that you chose a smd. A beginner would better start with a through hole ic. And maybe an ic socket like this 16 Pins IC voet - 16PSOCKET
Also be aware that you need a symmetrical power supply or a 'virtual' earth halfway plus and minus.
Because most opamp circuits use a symmetrical power supply (with plus, zero and minus). But if you add the capacitor you can use arduino ground for your audio. Then you create a voltage halfway to bias the opamp (simply 2 1k resistors in series from plus to minus and a 10 uF cap would do).
At the end you would need another cap to get rid of the bias. Like in your 1 transistor example.
The opamp would allow a linear amplification with very little extra components. Easy control of desired amplification and some 'buffering'.
You don't need a quad op-amp. You just need to build a summing amplifier. One op-amp for mono or two for stereo. Audio mixers are built-around summing amplifiers.
Thanks all. Googling away looking for a suitable 5v summing circuit. SO MUCH incorrect information out there these days. Circuit diagrams all over the place that are entirely incorrect
I have no idea what the impedance of the sources would be. There are 2x JQ8400 MP3 modules and the Wav trigger module.
Even if I did know the impedance, I don't understand how to work anything out.
I was hoping for a simple, single 5v rail, op-amp circuit/summing circuit that was a better design than simply using resistors bundled together.
But, as usual, I am baffled by stuff I don't understand and it's got all complicated (not being unappreciative of your assistance).
I am sure sometimes this stuff just gets way over complex for the outcome you are trying to achieve
Nope... The Wav trigger board has no real info. I would have to do some digging on that or reverse engineering. The Chinese JQ8400 mp3 modules.... no hope (although they are great modules).
Going with this... Found an old Maplins audio projects book in the loft of the workshop and this is the circuit diagram of their QUADRAMIX module you used to be able to buy.
I also have 12v on the board, so I can use that, although it would probably be fine on the 5v.
