Dear iangomes - This is an ambitious project. I am building a similar mixer right now. The 1o73 boards are a very good choice for the channel inputs. I do not actually know that board very well. As for the API option, that's fairly easy. The API 312 is the mic pre. The API 325 is the line amp card. You want the 325 but the two circuits are very similar. Do some searching around and find that schematic. It's all over the place.... Actually..... go to Jeff Steiger's on-line store at www.classicapi.com and go to his Reference Documents page. The 325 schematic and other juicy stuff is right there. Jeff also has summing amp cards which are pretty nice (very nice actually). Here are a couple of things to keep in mind. Faderless is fine. EQ-less is fine. But the other functions you mention..... aux sends, busses, inserts.... each function can sometimes require another amplifier. So the actual number of amplifiers required for your design and can grow quickly. But if you're careful you can keep that number down to a reasonable level. One channel amplifier can drive the stereo buss and one or more aux busses. Again, you need to be aware of your loads. Also, don't cheap out on the power supply. Make sure it is plenty large enough for good headroom. We could go on for hours on this. Some guys may chime in with "Oh no..... not another summing mixer.....". Yes, this road has been travelled many times before. But it is still a meritable choice. Ask questions. The guys here will help. Be prepared to spend money. A 24-channel mixer like this is not cheap. DW.
