"Denny Esterline" writes: > > >> I >> would have dearly loved to have all TTL or all CMOS at the time, but I >> would sometimes put a pull-down or pull-up resistor here or there to >> make things work. Don't try this at home, kids. > > >No no no.. DO try this at home kids. It's not like it a safety issue, and >I'm willing to bet you learned a lot from the experience. You don't learn >how things work by following good engineering practices, you learn by doing >something in an obscure way that forces you to deal with the details, then You are right. It's not a safety issue. I was kind of joking about all the cluging I had to do and how it would be hard to duplicate the same circuit quickly. It was a fabulous learning exercise. Last night, I was digging through an old box of open-reel tape, most of it blank, but I found a reel I had recorded that Summer of the audio output of that A/D-D/A demonstrater. I had taken a tape of a good-quality recording of a radio newscast along with a snippet of music and fed it through the device and then recorded it on another tape recorder. So, today, my memory is refreshed as to exactly how it or rather how bad it sounded. I had used a 6 KHZ sampling rate instead of 8 as I previously stated. Mr. Myquist, therefore, would only let 3 KHZ through. The recording is very noisy with audible heterodynes between the FM oscillator and the sampling gate. There is also a strong 60-HZ hum which was probably a ground loop between the tape recorder and the blocking capacitor between that and the modulation input on the MC4024. It kind of reminded me of listening to a very cheesy digital voice recorder with no low-pass filter at all over a badly-tuned television set in which birdies and vertical sync hum are only 10 or 15 DB below the audio. It was _ba-a-a-a-d._ About ten years later, I took the AC and DC circuit design courses that OSU offered while I worked here. All that tinkering I had done over all these years helped tremendously in lab. I was able to usually make our projects work and sometimes even help fellow students get out of jams and I think a lot of that came from the experience of just playing with circuits. I remember talking with my fellow students and noticing how some of them were there because somebody told them they could earn a lot of money. Nothing wrong with that, but life is a lot more fun if you do things you like and maybe you can make some money also. This stuff is way too involved to be in if you don't really enjoy it. That's probably why I am not financially rich today. I have to be able to at least stand what I am doing. So much for philosophy. Martin McCormick WB5AGZ Stillwater, OK OSU Information Technology Department Network Operations Group -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist