TK Audio Transformer Harmonic Generator & Color Box

The TK Audio Transformer is a two-section stereo harmonic generator and color box designed to add analog character, warmth, and tone-shaping to recorded or mixed material. The first section provides three discrete harmonic circuits in series—transformer saturation, passive saturation/clipping, and an active germanium stage—each generating a different blend of odd and even harmonics with its own tonal character; a Blend control continuously mixes the processed signal with the dry input for precise control over harmonic density. The second section is a selectable transformer-coupled Class-A stage voiced after British Class-A console designs from the early 1970s, adding a fat, punchy midrange character and smooth high-end independent of the harmonic section. An M/S function allows the mid and side channels to be processed separately through the harmonic stages—useful for applying different character to the center and the stereo field in a single pass.

Key Features

• TX Drive — transformer saturation stage — single control varies transformer saturation while maintaining a consistent output level; generates approximately 1% harmonic distortion in the low-end and a 2dB bump around 30Hz; as drive increases, the low-end bump and higher harmonics decrease while low-end harmonics remain consistent
• Gain control — up to +20dB of gain after TX Drive; used to drive the Sat and Ge stages harder for increased harmonic density
• Sat — passive saturation stage — passive clipping circuit that adds predominantly odd harmonics; activating the Even switch adds even harmonics to the character; harmonic amount is gain-dependent
• Ge — active germanium stage — germanium circuit that produces more even harmonics than odd; vintage tonal character with a soft, rounded high end; harmonic amount is gain-dependent
• Output trim — –20dB to 0dB trim control after the Sat and Ge stages; used to fine-adjust level before the Blend control
• Blend control — continuously mixes the harmonic stages output with the dry signal; allows precise dialing of harmonic density without committing to full wet processing
• M/S function — encodes the stereo signal into mid and side for independent processing through the TX Drive, Sat, and Ge stages; for example, TX Drive can be applied to the mid channel for low-end density while Sat and Ge are applied to the side for additional harmonic texture; note: the Class-A stage is placed after the M/S encoder/decoder and processes the full stereo signal, not mid and side independently
• Class-A stage — transformer coupled — selectable; British-inspired Class-A circuit voiced after early 1970s console designs; adds fat, punchy midrange character and silky high-end; HF Boost switch adds a subtle air enhancement when engaged
• Detented potentiometers — 41-click detented pots throughout for reliable session recall
• Illuminated switches — all switches are illuminated for easy status identification in low-light environments
• Per-channel in/out switching — independent bypass switches for TX Drive, Sat stage, Even harmonics, Ge stage, Class-A stage, HF Boost, and M/S function; full channel in/out bypass also provided

Specifications

• Input Impedance: 20kΩ
• Max Input Level: +26dBu
• Max Output Level: +26dBu
• S/N Ratio @ 0dBu: 89dB (varies by active stages)
• Dynamic Range: 115dB
• Gain (Gain Control): Up to +20dB
• Output Trim Range: –20dB to 0dB
• Blend: Continuous (dry to fully wet)
• Power Consumption: 13VA
• Power Requirement: 115V or 230V (internally selectable)