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From: George Jefferson on 26 Mar 2010 15:53 "�Leo�" <leo2100(a)gmail.com> wrote in message news:8ee4d776-0750-4b9a-b5ab-2c2c9ca301b1(a)33g2000yqj.googlegroups.com... > I want to make a circuit that takes a guitar input signal, and then > outputs a signal with fundamental and 2nd order harmonic with the same > level (or arbitrary levels, I want to amplify the two components at > will). > > I figured that there are various ways to do this, but I'm trying to do > it all analog if possible (since it usually produces more pleasant > sounds). Plus there are already commercial digital octave doublers, > and the ones that are analog come as ring modulators (they add more > components to the signal). The frequency range is 20hz-20khz at worst, > the available DC source is 9V. > > I'm trying to get the 2nd order harmonic by taking the input signal > through a emitter follower stage, biased so the amplification is > sufficiently non-linear to produce 2nd order harmonic distortion (and > a little 3rd). Then to isolate the 2nd harmonic, I thought of > inverting the input through another signal path and then adding the > two signals, and hope that the fundamental frequency cancels out. > While trying to do this in spice, I realized that I'm going to have to > have some kind of AGC so the two signals hace the same component of > the fundamental. Designing the AGC has been rather complicated so far. > So the idea that i had is getting a little bit complicated. > > Any help or new ideas would be appreciated. This is not a phase shifter but simply a filtering problem. You must first determine the fundamental, which is a difficult process in and of it self, then use a sharp filter and or notch filter at the appropriate frequency. With digital electronics one can do this relatively easy. Modern day digital electronics, if done right, can out-perform analog. The reason analog sounds better, in general, is because inaccuracies in analog are generally "smooth" and do not create unnatural frequencies in the original signal. IMO, if you are going to do this you should do it digitally first. The reason is that it is much much easier and may not have any of the drawbacks in quality you believe it will. You'll just need a modern 24-bit 96khz ADC with possibly oversampling and a processor(a few other bits and pieces). Then you can simply code everything in software. Using this technique will also allow you to easily extend and modify the algorithm along with doing other effects. In any case, as far as doing it in analog, the first thing you'll need is a voltage controlled filter and a frequency to voltage converter. The idea is that the frequency to voltage converter will output a voltage proportional to the fundamental which will program the voltage controlled filter. Together they represent a frequency controlled low pass filter. I.e., the frequency sets the cutoff point. This is not necessarily hard to do but it might be hard to do well. It will not work well for more than one note and you may have to design a feedback system so that the frequency to voltage converter will lock onto the fundamental and not other frequencies. There may be other tricks you can use such as squaring the signal which will emphasize the largest harmonics(which tend to be the first few harmonics) which can then be normalized again resulting in a special type of frequency controlled low pass filter.
From: Jim Thompson on 26 Mar 2010 16:50 On Fri, 26 Mar 2010 12:22:46 -0700, Charlie E. <edmondson(a)ieee.org> wrote: >On Fri, 26 Mar 2010 08:52:17 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: > >>On Fri, 26 Mar 2010 11:48:30 -0400, Rich Webb >><bbew.ar(a)mapson.nozirev.ten> wrote: >> >>>On Fri, 26 Mar 2010 08:23:12 -0700 (PDT), �Leo� <leo2100(a)gmail.com> >>>wrote: >>> >>>>I want to make a circuit that takes a guitar input signal, and then >>>>outputs a signal with fundamental and 2nd order harmonic with the same >>>>level (or arbitrary levels, I want to amplify the two components at >>>>will). >>> >>>A phase-locked loop. The CD4046 plus a divide by N is the classic "PLL >>>101" approach. TI has a pretty good app note on this and there are tons >>>of "phase locked loop" examples on the 'net. >> >>Not one that can track changing music input. >> >>But perhaps you could make an analog squaring circuit to double the >>input frequency. >> >> ...Jim Thompson > >A buffer, followed by a full wave rectifier, followed by a filter to >smooth out the bottom 'points' ? > >Charlie Yep. I was going to write that up and simulate, but I went to lunch and had a bottle of wine instead :-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: Jamie on 26 Mar 2010 18:55 �Leo� wrote: > I want to make a circuit that takes a guitar input signal, and then > outputs a signal with fundamental and 2nd order harmonic with the same > level (or arbitrary levels, I want to amplify the two components at > will). > > I figured that there are various ways to do this, but I'm trying to do > it all analog if possible (since it usually produces more pleasant > sounds). Plus there are already commercial digital octave doublers, > and the ones that are analog come as ring modulators (they add more > components to the signal). The frequency range is 20hz-20khz at worst, > the available DC source is 9V. > > I'm trying to get the 2nd order harmonic by taking the input signal > through a emitter follower stage, biased so the amplification is > sufficiently non-linear to produce 2nd order harmonic distortion (and > a little 3rd). Then to isolate the 2nd harmonic, I thought of > inverting the input through another signal path and then adding the > two signals, and hope that the fundamental frequency cancels out. > While trying to do this in spice, I realized that I'm going to have to > have some kind of AGC so the two signals hace the same component of > the fundamental. Designing the AGC has been rather complicated so far. > So the idea that i had is getting a little bit complicated. > > Any help or new ideas would be appreciated. look up the PDF file for the LM1496 chip.
From: D from BC on 26 Mar 2010 18:22 In article <8ee4d776-0750-4b9a-b5ab-2c2c9ca301b1@ 33g2000yqj.googlegroups.com>, leo2100(a)gmail.com says... > > I want to make a circuit that takes a guitar input signal, and then > outputs a signal with fundamental and 2nd order harmonic with the same > level (or arbitrary levels, I want to amplify the two components at > will). > > I figured that there are various ways to do this, but I'm trying to do > it all analog if possible (since it usually produces more pleasant > sounds). Plus there are already commercial digital octave doublers, > and the ones that are analog come as ring modulators (they add more > components to the signal). The frequency range is 20hz-20khz at worst, > the available DC source is 9V. > > I'm trying to get the 2nd order harmonic by taking the input signal > through a emitter follower stage, biased so the amplification is > sufficiently non-linear to produce 2nd order harmonic distortion (and > a little 3rd). Then to isolate the 2nd harmonic, I thought of > inverting the input through another signal path and then adding the > two signals, and hope that the fundamental frequency cancels out. > While trying to do this in spice, I realized that I'm going to have to > have some kind of AGC so the two signals hace the same component of > the fundamental. Designing the AGC has been rather complicated so far. > So the idea that i had is getting a little bit complicated. > > Any help or new ideas would be appreciated. Can a 12 string guitar be adjusted so string pairs are an octive apart?
From: Ralph Barone on 26 Mar 2010 20:23
In article <lropq5l4pm35jkm9ucq426h52eofpsqoh2(a)4ax.com>, Rich Webb <bbew.ar(a)mapson.nozirev.ten> wrote: > On Fri, 26 Mar 2010 08:52:17 -0700, Jim Thompson > <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: > > >On Fri, 26 Mar 2010 11:48:30 -0400, Rich Webb > ><bbew.ar(a)mapson.nozirev.ten> wrote: > > > >>On Fri, 26 Mar 2010 08:23:12 -0700 (PDT), �Leo� <leo2100(a)gmail.com> > >>wrote: > >> > >>>I want to make a circuit that takes a guitar input signal, and then > >>>outputs a signal with fundamental and 2nd order harmonic with the same > >>>level (or arbitrary levels, I want to amplify the two components at > >>>will). > >> > >>A phase-locked loop. The CD4046 plus a divide by N is the classic "PLL > >>101" approach. TI has a pretty good app note on this and there are tons > >>of "phase locked loop" examples on the 'net. > > > >Not one that can track changing music input. > > True enough. I assumed he was looking for a tuning gizmo rather than a > real-time doublers. Please note that the signal out of an electric guitar may contain up to six separate notes being played at the same time. Since the OP didn't say otherwise, I would say that advanced DSP is his only hope without having all sorts of weird spurious self-heterodyne signals popping up all over the place. |