Tone control circuit intended for a 2.1 channel audio system, in a 159 KB PDF. It shows the bass and treble adjustment network that sits between the source or preamp and…

PDF circuit diagram of a mono tone control stage built around two transistors, as the name indicates.

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.

Schematic in PDF form for a tone control board labelled NEWGEN TA2411B, where TC most likely stands for tone control.

Datasheet for the MC145436A, a Motorola DTMF receiver that decodes telephone touch-tone dual-frequency signals into 4-bit codes.

Datasheet for the MT8870, a widely used DTMF receiver that decodes telephone keypad tones into a 4-bit code with a strobe output.

Romanian-labelled schematic of a preamplifier with tone corrector, meaning a bass and treble tone control section, provided as a 330 KB PDF.

PDF datasheet covering the MT8880C, an integrated DTMF transceiver with a microprocessor bus interface, able both to decode and to generate dual-tone signalling.

Equalizer circuit diagram supplied as a 263 KB PDF. The file name only says equalizer and gives no brand, model or board reference, so it cannot be tied to a particular…

PDF for the KA4558, a dual operational amplifier in the KA series, equivalent in function to the familiar 4558 dual op amp, size 121 KB.

Schematic for a mosque mixer, the Indonesian name Mixer Masjid, model Master Box X6, provided as a 585 KB PDF despite the doubled extension in the original name.

Schematic in PDF form for a stereo preamplifier with a loudness control, a common DIY audio circuit that boosts bass and treble at low listening volume.