Perfectly Balanced

Noise-free volume control for Hifi amplifiers

Decent potentiometers for setting the volume in amplifiers are still quite expensive. However, there is a cheaper alternative, and it’s better too! The PGA2311 made by Texas Instruments can be used to make an almost perfect volume control. A simple circuit using an 8-pin Freescale microcontroller and a linear potentiometer are all you need to control this IC.

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Component list

Resistors
R1,R2 = 100ohm
R3 = 220ohm
R4 = 10k
R5 = 1k
P1,P2 = 1kohm linear
Capacitors
C1-C6,C9,C10 = 100nF
C7,C8,C11 = 100uF 16V
Semiconductors
D1,D2 = 1N4148
D3 = LED, free choice
IC1 = HC9S08QG4CDNE (Freescale)*
IC2 = PGA2311 (Texas Instruments)
IC3 = MAX660 (Maxim)**
IC4 = 78x05**
IC5 = 79x05**
Miscellaneous
pinheader 2x3
pinheader 2x6
flatcable 2x3
flatcable 2x6
mute switch, single on/off
symmetry switch, single pole on/off
PCB available via www.breem.nl
* available ready-programmed via www.breem.nl
** whichever applies