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From: Jan Panteltje on 26 Mar 2010 12:50 On a sunny day (Fri, 26 Mar 2010 09:11:57 -0700) it happened Tim Wescott <tim(a)seemywebsite.now> wrote in <gqCdnS7j-ItCQTHWnZ2dnUVZ_oGdnZ2d(a)web-ster.com>: >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 -- I think 'double phase rectifier on small audio transformer' needs no battery at all... The distortion will sound like real good old analog hehe. |\| ---- ----| |--------- )||( |/| | f )||(________ 2f ___| )||( | )||( |\| | ---- ----| |--------- |/| LOL
From: Martin Brown on 26 Mar 2010 14:02 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
From: Richard Henry on 26 Mar 2010 14:17 On Mar 26, 8:23 am, «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. http://en.wikipedia.org/wiki/Auto-Tune
From: osr on 26 Mar 2010 14:33 AD633 has a bounceless doubler in the app notes in the data sheet. Steve
From: Charlie E. on 26 Mar 2010 15:22
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 |