A Modern Take on the Classic Rockman Headphone Amp from the 80s
Stands on its Own
Shockman is not a clone of any particular Rockman® product. It incorporates ideas from several Rockman models, as well as a great deal of original design. It's closest to an X100 without Echo (would that be an Ultralight?), with some nice features brought in from the Soloist (soft clipping, Doubler/Stereo mode, ability to turn off the Chorus), Ace series (9V power), and even a tiny bit of Sustainor. The active mixer with independent Aux In and Line Out, the headphone amp and the specific 9V power supply arrangement are all my original designs.
The rest of the design, while derivative, is heavily modified from the original schematics. I paid particular attention to noise optimizations, while also minimizing power consumption. I achieved this by carefully choosing the most appropriate modern op amps for each stage, and also by optimizing resistor values throughout the circuit to reduce their individual contribution to overall noise. Shockman has lower Equivalent Input Noise (EIN) than the typical self noise of an electric guitar, which becomes the limiting factor for the overall noise floor. It achieves this while drawing only 8mA of idle current from 9V -- almost an order of magnitude less than a Rockman X100 (~ 55mA from 12V).
Shockman contains around 160 components distributed on both sides of the 4-layer PCB. It uses seventeen op amps, an analog chorus chip (BBD) and a couple more supporting chips.
Fits in a tin of Altoids!
Fits with room to spare in a small stompbox enclosure
Fits onboard a guitar (this is its true calling)
Pluggable form factor: the "brain" can quickly be moved between different enclosures
Watch It in Action
Make Your Own
A few words before you start: it's a LOT of work, most of the op amps I picked are only available in surface mount packages, and they're a bit pricey. Also, the pinchoff voltage of Q1 is rather critical to the correct operation of the compressor.