Here’s a simple overdrive circuit adapted from the National Semiconductor “Ultra High Gain Audio Amplifier” and Jack Orman’s “Minibooster” by Andrew Carrell (Dragonfly). It should easily fit in a 1590a.
Golden Dragon Overdrive
Tools, Tones and Toys for Guitarists
Here’s a simple overdrive circuit adapted from the National Semiconductor “Ultra High Gain Audio Amplifier” and Jack Orman’s “Minibooster” by Andrew Carrell (Dragonfly). It should easily fit in a 1590a.