schriste@uceng.UC.EDU (Steven V. Christensen) (04/17/91)
On a related (well, sort of) note, regarding Electronic Guitar Tuning, that was precicely what our first Electronic Design project was this quarter. And let me tell you, that it is mucho difficult to quantify a vibrating guitar string without resorting to DSP technology (we were using strict analog). It was basically a mic, and amp, a filter to get rid of hi-freq garbage, and then the most futile attempt at a half-a-dozen methods to get a good signal to send to a freq-voltage converter (to determine if a string is in tune or not). Depending on 1) how the string was plucked, 2) where it was plucked, 3) how hard it was plucked, 4) how in-tune it already was, and 5) the phase of the moon, we got different results. Harmonics were popping in and out of the signal as the string amplitude diminished, and I can under- stand 1), 2) and 3) for this cause. Most surprizing was 4): Apparently there are natural harmonic resonating frequencies of the body of the guitar which heighten or dampen various harmonics. It also changed depending on how I dampened the vibration of the guitar with my body. All in all, a very frustrating project! Now to write up the report and explain why it didn't work 100%.... Steven Christensen Univ. of Cincinnati -- Steven V. Christensen U.C. College of Eng. schriste@uceng.uc.edu For the adventurous: svc@elf0.uucp
asd@cbnewsj.att.com (Adam S. Denton) (04/18/91)
In article <8078@uceng.UC.EDU> schriste@uceng.UC.EDU (Steven V. Christensen) writes: >And let me tell you, that it is mucho difficult to quantify a vibrating >guitar string without resorting to DSP technology (we were using strict >analog). I bet you 100 capacitors of your choice that you didn't try a phase-locked loop, or did not try one correctly. A PLL, properly designed, will do EXACTLY what you want, and do extremely well. You toss the raw harmonic-infested string sound to the input, and out comes a nice, clean fundamental square/triangle/whatever wave to go to your F2V. The PLL can also do F2V but is typically not as accurate as a circuit designed specifically for that purpose. >It was basically a mic, and amp, a filter to get rid of hi-freq garbage, >and then the most futile attempt at a half-a-dozen methods to get a good >signal to send to a freq-voltage converter (to determine if a string is >in tune or not). If you insert a properly-designed PLL in between, you'll succeed. Trust me. Begin with the (LM, uA, NE, ...) 565 data sheet and associated application notes. Signetics has about a zillion (+/- a few) of them on the 565. Adam Denton asd@mtqua.att.com
joeld@hpnmdla.hp.com (Joel Dunsmore) (04/18/91)
In sci.electronics, schriste@uceng.UC.EDU (Steven V. Christensen) writes: >All in all, a very frustrating project! Now to write up the report and explain > why it didn't work 100%.... > Steven Christensen Two comments: 1) Welcome to the real world - (most of what EE's do is fiqure out why things don't work). Sounds like a good project (I always hated those kind in school, too!) 2) No problem writing it up... Just figure out why it didn't work. If you can do this well, it makes a great story to tell a campus interviewer, if you decide to make a career out of this.