Old School Sound Mixing

I want to mix 10 channels of 8 bit audio (sin table) and play them using an 8 bit DAC. What is the correct way to sum these to avoid maxing out the DAC all the time?

Each channel has an independant volume control ranging from 0 to 255 (0 to 1.0). I can limit the max volume for each channel to 32 which seems to work ok. You can hear each channel and there isn't tool much clipping. Of course, the waves sound noisy.

Is there a better way to sum these voices?

Thanks.

I would recomend clamping the resulting mix, you often see waveforms run along the top or bottom of the graph and clamped peaks don't seem to be that audible unless they start detracting from the overall volume (which I think is the area under the graph).

If you have some way of increasing the amplitude at the dac output you can use a stepdown aproach that starts dividing / shifting its ouput in the knowledge the amp on the other side has been stepped up, haven't hooked up a dac circuit before but they may have a reference voltage you can modify to effectively change the gain on the output.

I'm using a MAC (multiply and accumulate) operation and clamping the results so that don't over/under flow. The clamping is audible when all the voices are playing at full volume.

I was considering automatically scaling the max volume of each channel based on how many channels were playing but not sure how that will sound. Only one way to find out...

Thanks.