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From: «Leo» on 27 Mar 2010 13:00 On 26 mar, 12:23, «Leo» <leo2...(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). > > 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. In response to all: Thanks for the ideas. Some of them are much too complicated or expensive for the scope I was aiming at. The simple techniques with spurious frequencys are already implemented, and the circuits are available on the web, so I don't think I would try reinventing the wheel. I was just trying to implement my original idea, but it doesn't seem to be an easy task and I don't think it would be reliable in the end. So, could I arrive to the conclusion that getting a 2nd order harmonic from an audio source is not a trivial task (with as little distortion as possible)?
From: Tony on 27 Mar 2010 21:00 On Fri, 26 Mar 2010 15:22:20 -0700, D from BC <myrealaddress(a)comic.com> wrote: >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? In conventional 12 string tuning, the bottom 4 pairs are an octave apart, but the G is then pretty much at the tension limit for current string technology, so the higher B and E are instead tuned in unison. But thanks for the 12 string reference - that's the ONLY way to get the OP's original request for an analog solution. All the other analog ideas presented here are reasonable until you factor in the OP's "guitar" reference, which absolutely demands either a 12 string guitar or a DSP-based pitch-shifter (there are lots around, but the technology is way beyond an amateur DIY project). Cheers, Tony
From: BobW on 27 Mar 2010 21:43 "Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote in message news:4e7qq5h2m1v7uuh32h6ih2qlnsddpt03nt(a)4ax.com... > 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 See alt.binaries.schematics.electronic. I just posted a schematic for a guitar pedal called an "Octave" made by Boss. I had this one. It works pretty well. Bob -- == All google group posts are automatically deleted due to spam ==
From: markp on 28 Mar 2010 14:05 "�Leo�" <leo2100(a)gmail.com> wrote in message news:307f95c4-a330-43b9-a98a-bc2a033e7ead(a)g10g2000yqh.googlegroups.com... On 26 mar, 12:23, �Leo� <leo2...(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). >> >> 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. >> In response to all: >Thanks for the ideas. Some of them are much too complicated or >expensive for the scope I was aiming at. >The simple techniques with spurious frequencys are already >implemented, and the circuits are available on the web, so I don't >think I would try reinventing the wheel. >I was just trying to implement my original idea, but it doesn't seem >to be an easy task and I don't think it would be reliable in the end. >So, could I arrive to the conclusion that getting a 2nd order harmonic >from an audio source is not a trivial task (with as little distortion >as possible)? I think the best solution would be to do what another poster suggested, use an A2D on a processor, sample into a buffer and play the buffer back through a D2A at twice the sampled rate. This would of cource last 1/2 the time, so you would need to 'repeat' sections. To get the distortion down you'd choose zero crossing points in the waveform and repeat small sections. It's going to add some distortion but that's the best I can come up with. Mark.
From: markp on 28 Mar 2010 14:15
"Martin Brown" <|||newspam|||@nezumi.demon.co.uk> wrote in message news:EE6rn.109131$Ye4.12859(a)newsfe11.iad... > Tim Wescott wrote: >> �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. >> >> Whatever you do will, I think, give you tremendous distortion but may not >> make the thing sound a higher tone -- I suspect that at best you'll take >> out the fundamental, but leave the odd-order harmonics. >> >> Nay-saying aside, a squaring circuit would be the first thing to try -- >> my knee jerk reaction would be to use an analog multiplier (goodness >> those things are expensive now!) with both inputs connected to your >> signal. Perhaps a _really fast_ AGC on _one_ channel, so that the output >> envelope is proportional to the input. > > An aggressive low pass filter before the multiplier so that only the > fundamental is used would help things a lot. A variant of a ring modulator > circuit based on the good old MC1496 ought to do it. > > One digital way that would work and preserve most of the guitar waveform > characteristics is to sample it with a moderately fast ADC into a large > circular buffer and play back the waveform between rising zero crossings > stepping odd samples on pass 1 and even on pass 2. The devil is in the > details of the implementation. There may be novelty voice doubler chips > that will do something like this out of the box. > > Regards, > Martin Brown That sounds a neat way of doing it, I suggested repeating blocks between zero crossing points but your odd/even sample approach may be better to reduce overall distortion. Choosing the sample repeating block size could be a parameterisable thing, I think that will be the difficult bit... Mark. |