simulation of rolled neck pick up

[sergiomr706]

http://www.madbeanpedals.com/projects/LowRider/docs/Lowrider2015.pdf

Hallo, i was looking at the simulation of rolled neck pick up, and I m thinking about lowering it a little,but I dont get the filtering part, in the lowrider 2015 pdf, that i ll refer to, R42 (22k) and c18(10n) form a lpf at 720hz, right?
But what abot r43/c19 and r44/c20? If using a passive bass (pb or jb), would it benefit from having the low pass filter at  400hz? And what about adding a little hpf before? A 22n with a 120k to ground or something like this? Thank you

[Mark Hammer]

There are really two filtering goals in monophonic analog octave dividers.

1) As you correctly note, filtering the input signal, both at the guitar and subsequent levels, to restrict the input signal to the divider to primarily, and ideally only, the note fundamentals.  Strong harmonics can all-too-easily result in inconsistent triggering and mis-tracking of notes.  As I noted, recently in response to kipper4/rich's thread/query, heavier-gauge flatwounds can help in this regard.  Lighter, looser, brighter strings that easily bend make the divider circuit go "Wait, was that a B or a B-flat?".

2) Filtering of the product of octave division.  Some units, like the MXR Blue Box, use the direct output of a 4013 flip-flop, which is basically an all-or-none square-wave.  Making it sound more like a bass guitar would require some additional filtering of that wave-form.  The Blue Box does include a single stage of such filtering on the output, but not really so you'd notice.  The Lowrider, like its kin the Boss OC-2, uses a different approach.  Here the flip-flop effectively gates an FET that controls the passage of the actual analog input signal.  Gating it at half the frequency yields the illusion of octave division.  It's a little more natural-sounding than the all-or-none output of the 4013 itself, since it preserves some of the dynamics and timbre of the original signal.  But one really needs to think of it as a sort of extreme form of crossover distortion.  The input MUST be suprathreshold to trigger the flip-flop.  So until the threshold is met, the gating essentially "clips" the sides of the waveform.  The result is not nearly as square as the direct output of a 4013 chip or discrete flip-flop, but it isn't exactly a nice smooth sine-wave either. 

As such, the ideal octave-divider for those not especially interested in nasty erratic buzz-saw tones, is one where the input signal is filtered enough at some point to reliably result in the octave down from where you were fretting, and subsequently filtered enough to sound like a plucked bass string, or simply like a guitar that sounds "fuller".

[sergiomr706]

Thanks a lot Mark, so filtering is the way to go! I havent tried with my flatwound pbass,just my roundwound jazz. I ll check it that way