This is a nice chorus. This circuit uses the MN3008. I was lucky enough to find them on smallbear and bought 2, but they were close to $20 a piece. It also will not work with any of the substitutes. If you plan to build your own I would make sure you are able to procure the parts before you order.
From the build docs:
The Choral Reef finds its roots in the EHX Small Clone™, but goes far beyond. Its design a bit unusual (although not unique) in that it utilizes an MN3008 instead of an MN3007 BBD. Peter explains his choice based on the available headroom of the MN3008 (it does have a slightly better S/N ratio than the MN3007). This choice also affords different clocking options to get faux-flanger as well as chorus type tones by switching through different timing caps. Rounding out the design is a simple buffered feedback path and delay control. All this adds up to a really unique and great sounding chorus with a ridiculous number of settings!
From the VFE website:
The CHORAL REEF analog chorus pedal took 2 years and many failed attempts to perfect. The result was a no-compromise design built upon the MN3008 bucket brigade chip to satisfy VFE’s high standards for noise, headroom, and versatility. A whole host of chorus tones are available, including flanger and vibrato. The unique feedback circuitry lets you add a touch of resonance or dive into deep modulated chaos that rings on after you stop playing.
Controls
MIX: Blends between the wet, modulated signal and the dry signal. Crank it up to the max with shorter delay times for a vibrato effect, or set it around 9:00 with longer, spacier modulation settings for a dripping, watery chorus.
DEPTH: Sets the depth of the modulation. There’s more than enough depth here to get you seasick, but turning this control all the way down removes the modulation for some unique doubling or uber-short delay effects.
SPEED: Sets the speed of the modulation, from rapid warble all the way down to super-slow, sweeping pitch-modulation.
FEED: At short delay times, this adds resonance and/or brightness to the modulation. At longer delay times, this increases the number of echo repeats.
WIDTH: Sets the delay time of the modulated signal. Shorter delay times yield flanger-esque tones, while the longest times can conjure quick slapback echos. NOTE: longer delay times = more clock noise
RANGE: Sets the range of the WIDTH control. The middle position has the shortest range, for flanger style tones. The right position is for the medium range, great for chorus. The left position is for the longest delay times, pushing the MN3008 to its absolute limits.
LEVEL: Sets the total output volume (internal trimmer). Note: I labeled this VOL on the schematic.
BBD: Sets the input bias of the MN3008 (internal trimmer).
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