The Steel Guitar Forum
Pedal Steel Archive
Ideas on how to build non-magetnic pickups (Page 2)
UBBFriend: Email This Page to Someone!
profile | join | preferences | help | search
Steel Guitar Strings Strings & instruction for lap steel, Hawaiian & pedal steel guitars http://SteelGuitarShopper.com |
Ray Price Shuffles Classic country shuffle styles for Band-in-a-Box, by BIAB guru Jim Baron. http://steelguitarmusic.com |
This Forum is CLOSED. |
|
|
The Steel Guitar Forum
Pedal Steel Archive
Ideas on how to build non-magetnic pickups (Page 2)
profile | join | preferences | help | search
|
| This topic is 2 pages long: 1 2 This topic was originally posted in this forum: Pedal Steel |
| Author | Topic: Ideas on how to build non-magetnic pickups |
|
Bill Llewellyn Member Posts: 1882 |
posted 12 July 2000 07:49 AM
One of the biggest challenges in making a mechanical-to-electrical transducer like a guitar pickup is maintaining linearity:
The output of the pickup needs to correspond to the input (string displacement) very faithfully, as shown in the graph above. If the line in the graph had a curved shape to it, the sound would be distorted. In an optical system, if the reflectivity of the string varied as its angle to the sensor changed, that may contribute non-linearity. The photo sensor itself may have a variation in its sensitivity based on the intensity of the light received, i.e., a non-linear transfer function. (The LED arrangement used for MIDI systems intentionally squares-up the shape of the curve for easier digitization. If simply amplified and put to a speaker, such a characteristic sounds awful.) Linearity issues can be tough issues to get around. The good-old magnetic pickup is pretty good at these things, fortunately. But I'd sure be interested in hearing a successful, alternative solution! Another point I'd like to reinforce (made earlier) is that the tonal characteristics of the guitar would change a lot with a different pickup type. First, it would probably act more like an ideal transducer and would have a pretty flat frequency response, which I believe is quite different from the colored response we get with today's inductive pickups. Second, I believe the inductive pickups also act in a slightly microphonic way, grabbing just a bit of the guitar body vibration in their mix of sound. A pickup which gathers only string vibration would miss this. Some people strive to have their steels sound like an Emmons or whathaveyou, which may be only a slight variation away from where their guitar already is. A radical new pickup would likely sound altogether different, not at all like that golden tone they've dreamed about for years. So I think a lot of people would like the change, and a lot of people would avoid it like the plague. ------------------ [This message was edited by Bill Llewellyn on 12 July 2000 at 07:55 AM.] |
|
Rick Collins Member Posts: 3286 |
posted 12 July 2000 09:43 AM
Interesting. BTW: Since the subject is generally pickups; does anyone know if an individual is credited with inventing the magnetic pickup. If so; who is he. I have heard Les Paul is credited with inventing the electric guitar but; does that include the pickup? Rick |
|
Jack Stoner Sysop Posts: 8119 |
posted 12 July 2000 11:23 AM
Michael, I missed the part about the light causing a problem. When a thread gets long, as this one is, sometimes a point is overlooked.
|
|
jerry wallace Member Posts: 759 |
posted 12 July 2000 11:46 AM
Another question that magnetic pickups bring up in my mind is, as the magnets age do they change their properties?.If so, how does this effect the tone of the guitar. Do the magnets,change their properties,when affected by the things around them?..i.e.Other magnets,electro magnetic fields,metal,and even the Human body? In recent years,there has been a lot of supposedly interaction between the Human body and magnets?? Do our bodies have an effect on the magnets and therefore our tone?? NO GUYS ,I HAVENT BEEN DRINKING!! I just have a curious mind |
|
Bobby Lee Sysop Posts: 14849 |
posted 12 July 2000 01:58 PM
I think that the magnets in the pickups have an effect on our bodies - they make us gain weight!  |
|
Keith Hilton Member Posts: 1649 |
posted 12 July 2000 05:23 PM
If you are not carefull Bobby, these magnets can cause you to get "HOOKED" on steel. Just like taking drugs. ------------------ |
|
Jim Palenscar Member Posts: 1566 |
posted 12 July 2000 09:34 PM
I had lots of conversations with Don Lace Sr. before he died about doing a Lace Sensor Pickup for my steel. We went over specs for about 18 months (he rivaled me in taking a bit of time to accomplish a relatively simple task). After Don's death his son- Don Jr.(who then became "The Don") took over Actodyne General(manufacturer of Lace Sensor pickups as well as other neat stuff). He made me a prototype steel guitar pickup that seemed not to have the low-end that I was looking for but was crystal clear otherwise. We never continued the experiment as he was quite busy and I neglected to continue to bug him- although he is a very nice fellow and great to yak with~~ [This message was edited by Jim Palenscar on 12 July 2000 at 09:35 PM.] |
|
Keith Hilton Member Posts: 1649 |
posted 13 July 2000 07:45 AM
Jim, not asking how it was built, but would like to know the basic "THEORY" behind the Lace Sensor Pickup. What kind of sensor is it. Is it a light sensor ,or something else? Thanks. ------------------ |
|
ToneJunkie Member Posts: 245 |
posted 13 July 2000 09:12 PM
I like experimentation. It yields fascinating new things never anticipated. I think it is tremendously valuable in its own right. I also like a guitar that sounds like a guitar and one which sounds like the guitar that it is (a personal preference). The nice thing about a magnetic pickup is the immediacy of the transduction from physical vibration to electrical current. There is nothing between the vibrating string and the current but magnetic lines of flux; pure analog translation. The string passing through the flux creates the current. Transducers don't get any more immediate than that. In an optical scenario it seems to me you would first be modulating light, and then secondarily manipulating current (or some other control force) as a consequence of the light modulation. This removes the transducer's response from its stimulus by a degree. Almost every alternative transducer scenario I can imagine does this, by one or more additional degrees. And from my limited experience, what happens when you add stages of interpretation or transformation between one thing and another is you get an average of, or a distorted or incomplete picture of the stimulus. Something is lost in each stage of translation. You see it in transformers, digital sample rate converters, attenuation through multiple optical lenses, propogation delay through added circuitry, you get the idea. Voltage slew rates cannot match their analog stimuli, and attenuation and propogation delay further distort the representation of the stimulus. So, (and I'm going with b0b here on the engineering and requirements bent) if your objective is to get a clearer image of the fundamental and harmonic vibrations of a vibrating string, I am not encouraged by transducer ideas that distance the stimulus and its representationt. On the other hand, if you are interested in getting a reasonably good representation of the fundamental pitch of the string, there are probably many experiments that could be done to retrieve that fundamental frequency and to convert it however you like, e.g., pitch-to-MIDI conversion. This would be useful for players who are interested in having their guitar sound like something other than their guitar. I do not believe it is reasonable or cost effective with modern or near-future technology to modulate the frequncy content (i.e., overtones) at the instrument itself, apart from some fairly mundane spectral equalization. In order to mess with the spectral content of a vibrating string, you would first have to sample (pulse code modulate) the vibration in real time to digitize it, perform Fourier Transform analysis on the time domain signal to get to the frequency domain, and then do some mega honkin' digital signal processing on the frequency domain spectrum to determine harmonic content (it changes with each string, each pitch and the way the string is struck) and what parts of that content should be eliminated, attenuated, amplified or otherwise altered. Then, having figured it out, you have to go and do all that stuff in DSP. When you're done all that, you've got to get your signal back into the analog domain and by then, guess what, time has gone by and the note you just played is coming out your guitar milliseconds later (or worse, I was plugging mine into a Cray). So I think for now, at least, real time manipulation of the guitar's spectral content (its tone) with electronics in the guitar is probably out. If anyone has heard any sort of pitch correction studio stuff (hardware), then you know just how bad this kind of processing can sound when not fully baked. If, on the other hand you're just looking for a cool experiment, ya never know what you'll find... ...you could accidentally solve cabinet drop in the process! (Yeah, right) ------------------ |
|
Keith Hilton Member Posts: 1649 |
posted 13 July 2000 10:30 PM
Tone Junkie, you are making it sound very difficult, which it may be. ------------------ |
|
ToneJunkie Member Posts: 245 |
posted 14 July 2000 06:20 AM
Hi Keith, Yes. If you mean modifying the spectral content of the string's vibration using electronics onboard the guitar, I think that may be a very difficult proposition indeed. Cool thread. |
|
Jack Stoner Sysop Posts: 8119 |
posted 14 July 2000 07:48 AM
Tone Junkie - excellent analysis. I have to pretty much agree with you. Although Keith's "digital" devices work well, any time you have A/D or D/A conversion something is lost. An extremely high sample rate is needed to get close to true fidelity. The fundamental frequency band of a guitar is not that wide but all the harmonics (overtones and sub harmonics) that are associated with each frequency is an integral part of the charateristic tone of a guitar. I was involved with PCM Telemetry at Goddard Space Flight Center (I was a programmer on the PCM processors that was used for Manned Space in the early 70's) and getting an acceptable sample rate for critical items such as the Astronauts EKG or respiration rate - which is not as complex as a musical tone was a major NASA concern. The downlink signals were "supercommutated" (more samples over several "words" in order to get a more accurate representation) and then the D/A conversion was also over sampled. |
|
Bobby Lee Sysop Posts: 14849 |
posted 14 July 2000 11:20 AM
I think that the best way to alter a guitar's "spectral content" would be with coils and traditional analog circuitry. I like a real quick response. You're never going to get that out of any kind of DSP. |
|
ToneJunkie Member Posts: 245 |
posted 14 July 2000 11:28 AM
Bobby, I too favor the analog path and the electrical synergy between a guitar and the amplifier it is coupled with. I was responding to an earlier suggestion of altering an instrument's voice (e.g., making an MSA sound like an Emmons or a French horn) by manipulating the amplitude ratios and harmonic spacing of the string vibrations' overtone content via onboard electronics. I am trying to make a distinction here between general shaping of the power spectrum with well known and understood tone controls (equalization or 'tone') and surgical reconstruction of a a vibrating string's waveform (timbre) to make it something it never was. Cheers [This message was edited by ToneJunkie on 14 July 2000 at 11:34 AM.] [This message was edited by ToneJunkie on 14 July 2000 at 11:39 AM.] |
|
Bill Llewellyn Member Posts: 1882 |
posted 14 July 2000 12:02 PM
A-to-D conversion and DSP are getting faster all the time. Don't worry, some day it will all be fast enough that the conversion in both directions plus DSP take less time than it does for the sound to get from the speaker to your ear. I'm not much (right now) for manipulation of the PSG's waveform into a violin or train horn. I'd rather play a keyboard which does that! Maybe someday I'll want that capability in the steel. But an alternate form of pickup would be interesting. BTW, the Hall (magneto-resistive) effect is pretty direct, if you're looking to avoid conversion leaps. Do you suppose someday we'll have Digital Steel Guitars? Would anybody want one? ------------------ |
|
ToneJunkie Member Posts: 245 |
posted 14 July 2000 01:37 PM
Only if it was minimum 96KHz/24 bit! And no front end compression! I'm trying to picture fiber optic cable leaving my guitar... ------------------ |
|
Bobby Lee Sysop Posts: 14849 |
posted 15 July 2000 02:02 PM
I mentioned earlier that I thought this quest was like a solution looking for a problem. What is the design goal? Robert gave me an answer in another post. I think that one of the goals of a new pickup design should be the ability to adjust the volume of individual strings. Perhaps another design goal would be the ability to position strings in stereo sound space. To me, these goals seem worth pursuing. Many of us use two amps and/or stereo effects processors that have two inputs. It would be great if the output of the instrument itself was truly stereo (more than just a change in timbre between the two channels). ------------------ |
|
Donny Hinson Member Posts: 9192 |
posted 19 July 2000 02:26 PM
I think lasers would be the logical replacement, if there was the technology to do it reliably and cheaply. For one thing, the laser could be modulated to a precise frequency, and that would eliminate the "ambient light" problem. For another, the laser system wouldn't have to be digital! Light is quite capable of being amplitude, or complex-frequency modulated. Infrared lasers have already been used to transmit non-digital audio (in some limited aplications). I don't know what the frequency requirements are to catch all the nuances of the PSG, but if infrared lasers wouldn't handle it, UV lasers might. One thing I'll agree on, though. An all-digital system would probably be a different sound altogether. Let's stick with AM&FM. Also, I would imagine that some of the acoustical qualities of the guitar are fed back to the string itself. If so, an optical system wouldn't rob you of a specific tone (timbre). |
|
jerry wallace Member Posts: 759 |
posted 20 July 2000 04:01 PM
What type of sensor do the CD players use? could these be utilized in a pickup? ------------------ |
| This topic is 2 pages long: 1 2 All times are Pacific (US) | This is an ARCHIVED topic. You may not reply to it! |
Note: Messages not explicitly copyrighted are in the Public Domain.
Ultimate Bulletin Board 5.46
Our mailing address is:
The Steel Guitar Forum
148 South Cloverdale Blvd.
Cloverdale, CA 95425 USA
Support the Forum
Bobby Lee - email: