Schematic PDF of 2.29 MB for a tone control circuit with low, mid and high adjustment plus a sub-woofer section, according to the name. No author, model or component list is stated. Circuits of this kind are usually op-amp based active filters placed in a preamplifier stage. A builder or repairer can use it to check component values, trace signal flow through each band and the sub output, and compare against a faulty board. Confirm supply voltage and op-amp type in the drawing before building.
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