Ross Compressor

Somehow I've not laid this classic out already, so here's the Ross Compressor. One of the most highly thought of (and therefore copied) compressors of all time. Should be an easy fit in a 1590B.

Earthquaker Devices Disaster Transport Jr.

Here's EQD's take on PT2399 delay. The most unique thing about it probably the use of a Big Muff-like tone stack. It will definitely fit best in a 125B with the board mounted pots, but if you use long leg board mounted pots and populate them from the component side it should fit in a 1590B. Schematic can be found here.

Rockett Animal

Another fun overdrive from Rockett, this time going for a Plexi sound. Think of it as the first half of a buffer-less Tube Screamer with an AMZ Stupidly Wonderful Tone Control 2. Here's the schematic for reference. Should be an easy fit in a 1590B.

Devi Ever Ruiner

Another brutal fuzz machine from Devi, and sounds great on bass and guitar. Pretty straight forward design–two cascaded transistor amplifier stages with a pre-gain control (intensity) and standard volume control. Pots are board mounted and it shouldn't take all that long to throw together.

EarthQuaker Devices Erupter

Merry Fuzz Friday, everyone! Here's EQD's latest fuzz offering, the Erupter. Essentially it's a JFET buffer into a pickup sim (the transformer) into a Fuzz Face-esque circuit. The Bias control controls the amount of voltage going to Q3 and is a center detent pot (though a regular B10k pot will work just fine). This one might benefit by adding a volume control to the output. Should fit in a 1590B just fine. The 2N497 transistor might be hard to source, but other low gain transistors should work. Schematic can be found here.

SoulSonic FX Chalice

Here's an other heavy one. This one was designed by Martin (aka soulsonic) and is basically 3 transistor stages and a tone stack into a JFET gain recovery stage. The toggle switch selects between distortion and fuzz.

The tone in Distortion mode is a big heavy, "Doom-y" sort of thing with alot of sustain. In Fuzz mode, it's a fart-y ripping sawtooth fuzz that's good for single-note lines and possibly bass, but it can do chords without totally falling apart.

The Contour control adjusts from a dark, low-mid-heavy tone when counterclockwise, to a scooped tone when clockwise. Around 12 o'clock it has a bit of a mid-peak.

 Schematic and demo can be found here. I added a trimmer to bias Q4 (J201 or 2N5457 would be good subs). Should fit nicely in a 1590B.

Wampler Paisley Drive

Got a request for this one. Another take on the classic Tube Screamer built for Brad Paisley. The traditional input/output buffers have been swapped out for JFET-based buffers, and there are two toggles for Presence and EQ (mids). Should be able to squeeze it into a 1590B.