This one-of-a-kind Shepherd's Crook Drive will be available in the shop on November 9, 2019 at 10:00 AM MST --> Here <--.  

The origin of the One-Off Shepherd’s Crook Drive started with a simple question.  A customer asked me what the Yellow Spiral Drive circuit would sound like with a NOS vintage precision high-speed, low noise, Burr-Brown Op Amp?  Instead of the beloved, yet notoriously slow slew-rate LM741 used in the Yellow Spiral Drive. 

There is a lot of debate among guitarists whether or not Op Amps contribute much to the sound of drive circuits.  I have experimented with many different Op Amps in this circuit, and while I can hear differences, I will freely admit that they are minuscule.  I wouldn’t classify any of them as “better,” just slightly “different.”  I went into this Incubator project with expectations that the OPA111 would probably sound a little brighter, cleaner, and feel like it has a quicker transient response.  I think I was right on all counts. 

With these sonic characteristics in mind I decided to add a 3-way Shape Toggle that would either roll-off the highs (position 1), preserve these tones (position 2), or accentuate the mids (position 3).  I also went with LED’s, Silicon diodes, and the Nanolog N2 molecular junction for clipping options: Texture position 1 = Red LED’s, Nanolog N2 in position 2 to preserve the “Hi-Fi” tonality, and in position 3 = Si 1N4735A Zener’s.  These controls in combination with the Girth Control allow you to dial-in a HUGE variety of tones to compliment your guitar, pickups, amp, gain, and task.  However, unlike the Yellow Spiral Drive, the Shepherd's Crook is not mixing the N2 with the other diodes, they are all discrete selections. 

If you run a single-channel clean amp, you can use the Shepherd’s Crook to be your dirty channel.  Just choose the Shape Toggle’s #1 setting, find the gain sweet-spot, crank up the Girth (position 4-5), and use your guitar volume to clean-up.  If you run your amp dirty, you can use the Shepherd’s Crook to focus your leads with a mild mid-boost:  Shape Toggle in the #3 position, and the Girth in position 2-3.  Or drive your dirty amp into fuzz territory without getting smeary or losing note definition:  Shape in position 1, Texture position 3, Girth position 4 or 5.

Like the Yellow Spiral Drive, the Shepherd’s Crook really shines with a dirty amp.  The various Girth/Shape/Texture positions are powerful gain-shaping tools that compliment a dirty amp channel well by adding a little extra oomph at very useful frequencies. 

 

• NOS Tin-Can Burr-Brown DiFet OPA111 With Heatsink

• Girth Control Rotary Capacitor Network

• Amber Amp LED Jewel

• Handmade Silver Sparkle Knobs, With Laser Engraved Labels

• Textured Laser-Engraved “Golden Fleece” Top

• Zebra Wood Box W/Goodies

 

Shape Toggle:

1.  Gentle High-Freq roll-off

2.  Stock (bright)

3.  Upper-Mid Emphasis

 

Texture Toggle (Discrete, not mixed):

1.  Red LED’s

2.  Nanolog N2 Molecular Junction

3.  Silicon 1N4735A Zeners in Shottky Configuration

Demo of the Shepherd's Crook Drive highlighting the Shape Toggle: