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The Bingham tone control (sometimes also called the Baxandall–Bingham network) was a refinement of the classic Baxandall tone control circuit developed in the 1950s. It was implemented in some Quad preamplifiers (notably the Quad 22 and its successors) because Peter Walker and Quad were looking for tone controls that:
1. Altered the frequency response gently and musically rather than with sharp steps.
2. Kept phase distortion low compared with many competing hi-fi tone controls of the period.
3. Allowed for true “flat” response when the controls were set to zero.
Background
• Peter Baxandall published in 1952 his famous active bass/treble tone control network, which became the de facto standard worldwide.
• Around the same time, R.N. (Ronald) Bingham contributed refinements to tone-control networks, which emphasized smooth turnover frequencies and symmetrical action.
• Quad adopted this Bingham variant because it better suited their design philosophy: high fidelity with minimal coloration.
In Quad preamps
• The Quad 22 preamplifier (1959) featured this network. The bass and treble controls adjusted shelving curves around chosen turnover frequencies, but the slopes were shallow, intended to compensate for room acoustics and speaker deficiencies, not to “EQ” in the modern sense.
• The action was deliberately restrained: ±10 dB or so at the extremes, with gradual curves.
• This was different from the crude “tilt” controls or stepped EQs used in other amps at the time.
Why it mattered
The Bingham control in Quad units became an audiophile reference point because:
• The frequency response returned precisely to flat at the detent (“zero”) position.
• Adjustments were gentle and broad, perceived as natural corrections rather than tonal coloration.
• It aligned with Quad’s ethos: to reproduce the original program material as faithfully as possible.
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