TONE STACK: James

The James tone stack is one of the more common bass/treble tone controls. You most often see it in hi-fi equipment, or in guitar amps that sit outside the usual Fender and Marshall mould - although both Fender and Marshall did use similar circuits on rare occasions.

Probably the best-known guitar amp examples are Orange amplifiers and some Ampegs.  Closer to home, Australian builders, such as Goldentone and Vadis used this style of tone control.  Marshall used it in the Artiste, and Fender used a related bass/treble arrangement in the blonde Twin, model 6G8.

It’s hard to mention the James circuit without mentioning Baxandall - same same, but different, so I won’t get too bogged down in that here.  The original Baxandall circuit was an active hi-fi tone control, incorporated into a gain stage.  The James circuit came a few years earlier and is passive: 1949 for James, compared with 1952 for Baxandall.

The James is a simple and useful design. It mostly leaves the midrange alone, while giving reasonably independent control over bass and treble. Think of it as two tone controls working in parallel, rather than a Fender-style tone stack where the controls interact heavily.

For this example, ignore RIN and RL. These simply represent the source and load connected either side of the tone control.

ORANGE, GRAPHIC MKII

link to TSC for frequency response

FILMOSOUND 385

Despite the impossibly difficult to read schematic with dual 3meg pots on a single tone control, this is actually a James eq.    You probably can't find 3m dual gang pots anymore, but you can adjust values to a 1m dual pretty easily - just divide the resistance by 3, and multiply the capacitance by 3.  

Link to TCS

AMPEG B15

FENDER TWIN, 6G8

note: this uses a tapped pot.  i.e. it has fourth lug - good luck finding one of those.

MARSHALL ARTISTE