Hi all, I've been quiet for a while, so you know I must have been thinking hard about a new project! Or...just really busy with work. While the second might be most true, I have been thinking for quite a while (nearly a year now) about a problem that I have, and I finally feel like I'm starting to make some progress. One of the jobs I do is in live entertainment. When I'm working, I am often on a few different communication systems simultaneously. I'm at the point where I now have more systems than ears, which is making things tricky. Here are the three main ones I'm usually hooked up to in some way: 1. Radio - two way radio (walkie talkie) - half duplex 2. Production Intercom - a partyline style full duplex intercom system 3. In-ear monitors - a wireless stereo feed from the sound system (with some things added that the audience doesn't get to hear) The way I currently deal with this is to wear an in-ear monitor in one ear, my intercom headset over the other ear, and have the radio speaker/mic clipped somewhere nearby in the hopes that it will bleed through enough that I can hear it. For the record, that rarely works. In the past, I've tried a small audio mixer to combine the radio output and the in-ear feed into my ears. This was semi successful. It did work, but impedance and signal levels were completely wrong, which made it very touchy. In addition, I was getting audio from the radio via an earphone output jack that is evidently just for show, as I managed to go through 4 speaker/mics which would only last a week or two before the jack stopped making reliable contact. Not fun. I thought that making a custom mixer was going to be the ultimate solution, but that still left the issue of multiple mics. I've been doing some research towards that end, and what I've stumbled upon in much closer to my ultimate goal. There is a market (mainly law enforcement and military) that often use multiple radios and intercoms, and so there are companies that now make devices to connect these all together. As a matter of fact, Carey, a long time PICList member makes these for base and mobile applications. Sadly I need something a bit more portable. For a great example of what I'm talking about, see the Invisio V60 here: http://invisio.com/products/adv-hearing-protection/invisio-v60.aspx and watch the video demo. It's pretty neat. So now the question is, why not just buy a system like that? Not so fast! First of all, I'd be willing to bet they are way out of my price range. I don't have the backing of a major governmental department, but I have sent them a few inquiries. We'll see if they get back to me. Their system also does a lot more than I really need, including "hear through" (their headsets have tiny microphones that can be enabled to allow peripheral hearing), waterproofing (20 metres!), and other fancy bits. It looks quite slick, but I'm starting with the assumption that I can't get one for myself. As a result, I'm starting to look at trying to build something similar, but not quite as sophisticated. I envision a small box that I can connect a headset (or other separate audio input and output device) to, and be able to control where my voice routes to, and what I'm hearing (ideally both volume and L-R panning). It would connect to my radio, controlling its transmit functionality. It would connect to my intercom, allowing me to talk and hear in full duplex. It would also take my in-ear feed and mix it in with my other audio feeds. In my mind there are two approaches to this, analog and digital. Obviously both methods will require some analog interface circuitry. I am already trying to compile the specifications of each device to be able to determine interface specs. In the full analog solution, the mixing will be done in the analog realm, perhaps with some digital control over it (likely via PIC). The digital approach would digitize the signals, and do all of the processing in a DSP of some sort. In terms of my skill set, both of these are a stretch. I am not that experienced in analog, and I've never touched a DSP before. I really like the idea of using a DSP as it could be reconfigured without a circuit redesign. In theory, if I was able to come up with some way to send it commands (UI or computer front end, who knows), the routing and processing could even be changed on the fly. Don't want the radio in the left ear anymore? No problem, make it come out the right ear! The other nice thing about a DSP is that things like compression and limiting would just be a matter of writing the correct programs. Sadly, that's probably out of my reach if I was to try this solo. So I'm looking for help, on two fronts: 1. Can anyone recommend a good starting point to audio DSP? I'm talking mainly about hardware. I've been doing some web searching, and I've come up with a few that I'm already looking into, but I'm curious what others recommend. Dev kits that aren't $2500 would be appreciated. 2. Is anyone interested in teaming up on this? It would make a dandy university project for a student, or a weekend project for someone with more experience than I. And as I'm just doing this for me, there aren't any ridiculous deadlines. Anyway, please let me know what you think. I have been doing a lot of thinking and research on this, but this post is long enough already! Happy New Year :) Josh --=20 A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .