rick's got it exactly... I'm like "HEY I can make that too!"
I'll probably build more than a few stupid useless things along the way. Uhm, like this one. :)There are three on the bench right now, my hybrid 4-headwize-projects mic preamp/mixer/limiter/amp, experimenting with getting toggles mounted for digi pots, and because I missed out on all the early days of this stuff I'm doing greg's ifr510 in a bulky "old school" metal project case with big-assed knobs and neon panel light and stuff. Right now it looks like a bench supply. I want to do a discrete opamp stage for gain, but I'm kinda glad I don't have to if I get lost. (as soon as someone specs a component, it's gone)
Chu, I think the led res was 1.2k. I did this last week or so (see it's still got that linear Piher pot?) It's buttoned up but I'll look. the V ref res also affects the led current and I kept tinkering... I wasn't too worried about power, c'mon it's 16 AA batteries. I just did it until I liked the brightness, and it just ended up being 18mA (12mA was a foobar). Also not mentioned was I had to bypass the +12, the bottom 2 leds kept staying lit.. noise. I thought I'd have to couple the input but just bypassing got rid of it (or at least lowered it so the leds stay off with no signal)
Now here's the question: Did I do it correctly? Is this normally how you'd add additional circuits to something? I thought stealing the power from the batteries might have made it sound different, and I also thought that tapping into the signal to get the feed for the VUs would alter the sound. Neither seems to be true... but would you normally build separate stages with regulators? and stealing signal, should I have buffered it with an opamp and stolen it from there? Another opamp before the gain stage to power the meter? I also thought I might fry something by taking power from only the +12 side and ground, cause it's virtual anyways... but hooking it to -12 didn't do anything so it had to go to ground. (My only references were a few web pages and the 3915 datasheet)
I'm lost, but hey its fun.
posted 07-30-2000 01:17 PM CST (US) 
