[sdiy] Scanner Chorus pcb interest?

[David Brown]

I was always thinking of just buying a Hammond scanner and making an outboard box.  You see them from time to time on eBay.  It's been a while since I looked in the back of my Hammond, but I'm guessing all the inductors were external to the scanner and mounted somewhere else.

Looking forward to the future MOTM-like module.  My other mechanical project that is still sitting on the workbench as parts is a Raymond Scott Circle Machine.  I have the stepper motor, controller, and AVR all ready to program.  Just never quite started the bearings and mechanism.  Seems like you need at least one mechanical module for a synth.

Dave

-----Original Message-----
>From: "JH." <jhaible at debitel.net>
>Sent: Jul 6, 2007 3:01 PM
>To: synth-diy at dropmix.xs4all.nl, analog heaven <analogue at hyperreal.org>, MOTM List <motm at yahoogroups.com>
>Subject: [sdiy] Scanner Chorus pcb interest?
>
> Thinking about future pcb projects ...
>
>One thing I wanted to do for a long time is a stereo chorus based on my 
>electronic emulation of the Hammond Scanner Vibrato.
>
>I've built something like that a few years ago:
>
>http://jhaible.heim.at/scanner_vibrato/jh_scanner_vibrato.html
>
>This was purely intended to be an emulation of the Hammond Chorus/Vibrato 
>effect, but I always thought it would also make an interesting, more 
>general, and stereo, chorus device.
>
>That would be a "true analogue" chorus in a different sense than the 
>BBD-based effects, because the signal is not sampled.
>
>It's not free of side effects, thou. It has a somewhat rough modulation 
>waveform, as instead of changing a delay time continuously, it interpolates 
>between 9 taps of a 1ms analogue delay line. It's a linear interpolation, 
>not a switching - best thing is you listen to the sound samples and decide 
>for yourself. It's very rough (in a Hammond-ish way!) for vibrato, and 
>increasingly smoother when the dry signal is mixed in for chorus.
>
>It's a quite complicated method to crate a simple chorus, compared to a BBD 
>circuit. It requires a 50-pole (fifty!) low pass filter, but that can easily 
>be built from 25 cheap inductors (less than a dollar per piece at Mouser) 
>and 25 capacitors.
>
>On the positive side, it's a lot more "direct" sounding than a BBD-based (or 
>digital delay based) chorus, as the maximum delay time thru the whole 
>circuit is only 1ms. (Speak of latency ...)
>
>If there's enough interest, this could be a project for a future PCB 
>development. I wouldn't restrict this to Hammond emulation, but make a 
>mono-in / stereo out device in the fashion of many Roland / Boss dual-BBD 
>chorus circuits. Just without BBD. Let me know what you think ...
>
>JH.
>
>PS: this is not to be confused with my Interpolating Scanner, which is 
>planned to be a future MOTM module. 
>
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