Silvertone & Jackson Audio Twin Trem

The Silvertone & Jackson Audio Twin Trem is a dual analog tremolo pedal that puts two different tremolo circuits in one box: an optical tremolo on the left and a harmonic tremolo on the right. Jackson Audio describes it simply as a pedal where "Harmonic and optical tremolo meet in one pedal."¹

The two circuits are parallel rather than series copies of the same effect. The harmonic side splits high and low frequency bands and volume-attenuates them out of phase from each other, which gives it a shifting, phase-like character; the optical side gives the deep, smooth pulse associated with vintage amplifier tremolo. Each side can be used alone, or the two can be stacked for more complex LFO (low frequency oscillator) interaction.²

What it does: optical and harmonic tremolo in one pedal

The two halves of the pedal behave differently, and that difference is the point of the design³⁴¹.

Premier Guitar's reviewer explained how the harmonic circuit works: in a harmonic tremolo circuit, high and low frequency bands are split and volume-attenuated out of phase from each other, rather than the whole signal being raised and lowered together as in a standard amplitude tremolo.⁴

The reviewer also noted a practical character of the optical side: its modulation speeds run slower than amplifier tremolo equivalents, and at its slowest setting the optical circuit cycles through minimum and maximum volume in just a little under a full second.⁴

RockBoard's PedalPedia entry describes the harmonic side as delivering lush, swirling modulations, while the optical side provides the more familiar vintage pulse.³

The controls and routing

Each circuit is operated by its own three-knob array: Speed, Depth, and a smaller Volume knob that can boost or cut the output of that individual circuit.⁴ Both tremolos therefore have fully independent Speed, Depth and Volume controls.³

The routing is where the Twin Trem separates itself from a standard single-circuit tremolo pedal²¹⁵:

• Each tremolo circuit has its own input and output, so the two can be used completely independently.⁵
• Independent inputs and outputs allow stereo configurations or split-chain routing.²
• The two tremolos can be separated, with another effect placed between them. Jackson Audio's own example is putting a reverb between the harmonic and optical circuits.¹
• Run together, the circuits stack for more complex LFOs.²

The LED on the pedal doubles as a status display for which circuits are engaged: blue when the optical circuit is on, red for the harmonic circuit, and purple when both are stacked.²

History: a Silvertone and Jackson Audio collaboration

The Twin Trem is the second collaboration between the two makers. It follows the 1484 Twin Twelve, a tremolo and amp combo pedal that Silvertone and Jackson Audio released after the original partnership, and it uses the same format and enclosure as that earlier pedal, with the same distinctive knobs.⁵

The 1484 Twin Twelve pedal itself was based on a piece of Silvertone history: Silvertone Guitars produced the 1484 Twin Twelve amplifier between 1963 and 1967, and the pedal recreated that amp in stompbox form. It also marked Silvertone Guitars' first foray into the pedal market.⁶ Brad Jackson, President of Jackson Audio, was quoted at the time on the pedal's authenticity.⁶

On That Pedal Show, the Jackson Audio Twin Twelve was featured in a gain pedal episode, with an introduction at 4:47 and sounds from 6:50.⁷

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