Mad Professor Hand-Wired Amber Overdrive

The Mad Professor Hand-Wired Amber Overdrive is a hand-wired overdrive pedal from Mad Professor. Under the hood it is something unusual for an overdrive: independent circuit analysis identifies it as a modified Big Muff with JFET transistors doing the clipping, which pulls its sound toward fat, smooth, fuzz-tinged territory rather than raspy distortion¹. Guitar Pedal X's Stefan Karlsson grouped it among his favorite fuzzy-drive pedals².

What it does to your sound

The circuit analysis on Guitar FX Layouts characterizes the Amber as producing a very thick sound whether playing chords or single notes, fat and juicy with just a hint of fuzz¹. It is also described there as offering a wide range of dynamics and expressive touch sensitivity¹.

Stefan Karlsson, writing on Guitar Pedal X, called it:

Controls

The pedal keeps things simple with three controls, which Karlsson describes as the 3 classic controls and really easy to dial in². Builder reports on the published DIY layout indicate the pedal runs loud: one builder who used 2SK117 JFETs as the clipping elements noted it is very loud, with volume and gain set at 9:00 for unity gain¹.

Where it goes in the chain

Players who like a brighter, more cutting character can exploit that interaction; players who want the intended smoothness should keep it first in line, ahead of any buffers¹.

The circuit: a Big Muff that does not sound like one

The Amber's lineage is a surprise given its name. The independent analysis identifies it as a modified Big Muff, though one that does not really sound like one¹. The key modification is in the clipping stage: instead of silicon diodes, it uses 2N3819 JFET transistors as clipping diodes at positions D1 and D2, with JFET clipping in stage 2 of the Muff gain structure¹. JFETs clip more softly than ordinary silicon diodes, which is consistent with the fat, smooth, slightly fuzzy descriptions the pedal attracts¹.

The same analysis places the Amber within a small family of related Mad Professor circuits:

• The Fire Red Fuzz is almost identical to the Amber except for the tone stack¹.
• The Sky Blue Overdrive also uses 2N3819s as clipping diodes¹.

Versions and editions

A vero (stripboard) DIY layout for the circuit has been published on the Guitar FX Layouts blog, tagged to the BJF/Mad Professor circuit family, which is where much of the technical detail about the circuit comes from¹.

In May 2020, gearnews.com reported a limited run of modded Mad Professor pedals that included an Amber Overdrive with a Midas Touch mod⁵.

For builders: substitutions and biasing

The DIY community around the published layout has worked out several practical substitutions:

Builder reports on the layout have been positive. One wrote "Its verified and sounds awesome"¹, and another: "Sounds great this. Used BF245As for D1 & 2. Its nice and loud."¹. A third, who built it with 2SK117 JFETs as the clipping elements, preferred it to the Skreddy P19, citing more range to the dirt and a more vocal tone¹.

Amber Overdrive versus the Skreddy P19

Both pedals are Big Muff variants, so they are similar in broad family terms, but they differ in transistors and component values¹. The one head-to-head opinion available is the builder quoted above, who found the Amber had more range and a more vocal tone than the P19¹. That is a single DIY builder's impression rather than a published review, but it lines up with the general picture of the Amber as a smoother, more touch-responsive take on the Muff topology¹.

Videos

Click to load

Click to load

Click to load

Questions