Not a bad design spec. but you'll never make any kind of a living selling them at that price.
Story of my life! :-) Yeah, I just fancy knocking out a small batch and seeing how they go. My initial figures has box+PCB+bits coming to about £150 each for a batch of 10, and add maybe 3 hours of my time soldering and screwing per board (I'm pretty nippy with a soldering iron). So £250-300 is around break-even point for being worth my time to do it (if I include some payback from the time spent designing it in the first place). I doubt it's ever going to take off in a big way, but if I can get it working and flog a few, I'll be quite happy to see people using kit that I've made. It's a bit more rewarding than just building a one-off for yourself.
For what it'd be used for, the only reason I started building my "first draft" design in the first place was as a front-end to my PC recording gear - I thought I'd rather have a crack at it myself and see how it turned out. So if you guys think that's where it's most likely to see action, I guess I'm not a million miles away.
Thanks for the hint on dynamic mic loading, Anahata. I might put that in or leave it out - obviously things get easier if I leave it out! I don't know a lot of this stuff, so thanks for that pointer for something to read up on.
I think I'll stick with a single set of outputs - saves having a whole extra set of connectors on the back (cost and hassle). I suspect the level warning may be redundant anyway, bcos most people would probably have separate VU meters on whatever this is feeding - don't know whether to keep this or just ditch it altogether. For the input sockets, I guess go with the doubles then if you both agree on that. I wasn't planning on having extra TRS inputs as well, just kind of an idea for improvement - those dual-purpose sockets are a neat way of adding features without changing too much.
For the PCB thing, I've heard that theory, Bernard. But I've also got a friend who worked at Tektronix and was part of the team that revamped their range back in the 70s/80s. His word on it was that as soon as they axed the independent connectors and wired-together modular setup and replaced them with PCBs everywhere, their reliability problems simply vanished overnight. I can see the point about "if it's going to waggle then let it waggle a bit". But there's also the angle of "stop it waggling in the first place". Once the socket in question is soldered to the PCB in four points, has two extra mounting pins, and is screwed to the front panel, it's pretty well held! And of course the other thing from my POV is that soldering and assembly is significantly faster, like maybe 2-3 minutes per connector - multiply by 8 and by number of boxes, and that's significant! I guess I'll see how my first-draft version holds up with my use (I'm a little heavy-handed with my gear ;-) and make up my mind from that.
I thought about an external PSU too, but it doesn't really look practical. Extra cost for an extra box for starters, plus you've got more hassle on protecting the outputs from the PSU and the inputs to your kit. It needs a balanced +/- supply for driving the main stuff and a higher input for the phantom power, so it's not like I could use a standard wall-wart to drive it anyway (or not without step-up converters inside, which are the kiss of death for audio). And toroidal transformers are as near no-noise as makes no difference, so there shouldn't be any noticeable effect from that. Box-wise it'll all go in a 1U rack-mount - I've found a place (Holt Broadcast Supplies) who do some nice sturdy boxes and make small production runs of custom boxes (drill/punch/engrave/silkscreen).
OK, thanks for the feedback there - some very positive ideas on what to be looking at. I wouldn't hold your breath on anything happening soon though! ;-) But if I ever do get this going, I'll sling you both a couple to have a play with...
Graham.
PS. I could do you a picture of my "Mark I", but it wouldn't be at all representative and I'd only get embarrassed at all the things it doesn't do. :-/