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Paraphase Tone Control

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Published in issue 356, July 2006

As opposed to the widespread Baxandall circuit (dating back to 1952!) a ‘paraphrase’ tone control supplies a straight frequency response as long as the bass and treble controls are in the same position. This unique property makes the ‘paraphase’ configuration of interest if only treble or bass needs to be adjusted — it is not possible to adjust both at the same time!

Components

Resistors

R1-R4 = 10k

R5,R7 = 1k

R6 = 7k15

R8 = 6k80

R9,R10,R11 = 8k2

R12,R13,R14 = 2k2

R15 = 1M

R16 = 100Ω

R17 = 100k

P1,P2 = 100k preset or chassis-mount control potentiometer, linear law

Capacitors

C1,C2,C3 = 47nF MKT, lead pitch 5mm

C4 = 68nF MKT, lead pitch 5mm

C5,C6,C7 = 10nF MKT, lead pitch 5mm

C8,C10,C11 = 100nF MKT, lead pitch 5mm

C9 = 2µF2 MKT, lead pitch 5mm or 7.5mm

Semiconductors

IC1 = TL074

Miscellaneous

K1,K2 = line socket, PCB mount, e.g. T-709G (Monacor/Monarch)

PCB, ref. 060015-1 from The PCBShop