Cardinal Tremolo

The Cardinal Tremolo v1 is a tremolo effect evocative of the harmonic tremolo effect that was available from certain Fender amps, from 1960 to 1963. These amps include:

• The Fender Concert,
• The Fender Pro,
• The Fender Showman,
• The Fender Super, and
• The Fender Twin

Thermionic Studios has purchased this PCB and sourced the parts necessary to build this pedal. We are in the process of building the pedal and will have more to report upon completion.

Per the build notes document, this is a circuit by Jon Patton and was extensively influenced by previous tremolo pedal designs. In the build notes, Jon credits:

This circuit is based in part on RG Keen's Pro-Vibrato schematic. The LFO was adapted from CultureJam's Shoot the Moon Tremolo, which in turn adapted from Dann Green's Tremulus Lune. Thanks to Jimi Photon for the inspiration and samhay, ~arph, and duck_arse for discussions and suggestions on DIYStompboxes.

Controls

• Knob 1 - "Depth": Sets the depth of the volume swell of the tremolo. Clockwise turning increases the depth of the swell.
• Knob 2 - "Rate": Sets the speed of the swell of the tremolo. Clockwise turning increases the rapidity of the period of the swell.
• Switch 1 - "Select": Allows selection between Harmonic and Standard Tremolo functions.

General Information

The Cardinal Tremolo makes available both the amplike "Harmonic" tremolo, as well as a standard volume-swell tremolo effect.

http://1776effects.com/wp-content/uploads/2015/03/Cardinal-Tremolo.pdf

We currently only have Version 1 of the Cardinal Tremolo pcb. 1776 Effects has also released a Version 2. A quick look at both the schematics for v1 and v2 suggests that the only meaningful difference between the two is that the Version 2 board takes what are trimpots (set-em and forget-em) on the board and exposes them as full potentiometers.

Pedal Manual

As of this time, 1776effects.com has not issued a separate manual on how to use the pedal. The best current references that we're aware of are this wiki page, or the build manual linked here to the 1776 Effects website which describes the architecture of, and how to build the pedal.

Phase Inversion

From our examination of the schematic below, the Cardinal Tremolo, v1 appears to not invert phase on the output as compared with the signal that goes into the pedal.

Electronic Part	Action	Phase State
Q1	Inverts	Inverted
Q2*	Inverts	Reverted - see note
Q3	Inverts	Reverted
IC1a*	Does not Invert	Unaffected - see note
IC1b	Does not Invert	Unaffected

• NOTE: The Harmonic/Standard switch splits the audio signal coming from Q1. The signal is then directed either to Q2, or Q3, but not both. The end result is a phase that is inverted, and then reverted to the original phase. IC1 doesn't appear to invert phase through either portion of the integrated circuit. Its purpose is to modify the speed and depth controls; the current going through IC1 never touches the audio signal.

As with all schematic observations, this will need to be born out by testing of the actual pedal.

Schematic

© Copyright 2016, JRM/1776Effects.com

Artists

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Additional Sources

• Build Instructions Cardinal Tremolo, v.2