Article

Digital volume control

for Elektor’s Audio DAC 2000

This circuit is especially designed for those who are not satisfied with a single, fixed volume level for their Audio DAC 2000. Minimal modifications to the DAC circuit board and a simple processor circuit are all that are needed to add a de luxe pushbutton volume and balance control. An adjustable preset is even included!In part 2 of the description of the Audio DAC 2000 (Elektor Electronics, December 1999), we already briefly mentioned that the DF1704 digital interpolation filter includes a digital attenuator that can be adjusted under software control. We more or less suggested that this feature could be used very well in combination with an external processor to realise a digital volume control.

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Materials

990080-PCB.pdf

990080-11.zip

Component list

Resistors:
R1 = 8k?2
R2 = 47?*
Capacitors:
C1 = 10µF 63V axial
C2,C3 = 22pF
C4 = 220µF 25V radial*
C5-C8,C10,C11 = 100nF ceramic
C9 = 10µF 63V radial
C12 = 470µF 25V radial
C13-C16 = 22nF ceramic
Semiconductors:
B1 = B80C1500 (rectangular case)
IC1 = 80C32-16
IC2 = 74HC573
IC3 = 27C256 (programmed, order code 006506-1)
IC4 = 6264
IC5 = SFH506-36*
IC6 = 7805
Miscellaneous:
K1,K2 = 10-way boxheader
K3 = 10-way PCB connector for flatcable
K4 = 2-way PCB terminal block
S1-S5 = pushbutton, 1 make contact, e.g., ITT/Schadow D6-QBK + D6Q-BK-CAP
S6 = 5- or 6-way DIP-switch
X1 = 16MHz quartz crystal
PCB, order code 990080-1