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Volume Control for RPi Audio DAC

loud and quiet in high quality

Volume Control for RPi Audio DAC
To the delight of many, the previous issue of Elektor had a high-quality network audio player based on the Raspberry Pi/Volumio combination, which however was not provided with a 'real' volume control. Although it is possible to control the volume via Volumio (what’s in a name), but this method seriously affects the high-end characteristics of the DAC for the worse. That is why we now describe a volume control especially developed for the network audio player.
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Products
Relevant websites
Extra info, Update
* High-end volume control
* Suitable for Raspberry Pi + audio DAC
* Compact sandwich construction
* Uses an RC5 remote control
* Also suitable as stand-alone volume control
Component list
From the Store
160321-1 Bare printed circuit board
160321-91 Assembled module (headers supplied separately — DIY soldering)
160198-91 Assembled Audio DAC module (headers supplied separately — DIY soldering)
SKU 17631 Raspberry Pi 3 (model B


Component List
Resistors
R1,R2,R3,R4,R5,R6,R7,R8,R11 = 47Ohm, 125mW, 1%, SMD 0805
R9,R10 = 2.2kOhm, 100mW, 5%, SMD 0805
R12 = 10kOhm, 100mW, 5%, SMD 0805
R13,R14,R15,R16,R17,R18 = 470Ohm, 100mW, 5%, SMD 0805
Capacitors
C1,C2 = 22pF, 50V, 5%, C0G/NP0, SMD 0805
C3,C4,C5,C13,C14,C17,C18 = 100nF, 50V, 10%, X7R, SMD 0805
C6,C8 = 100nF, 25V, 5%, C0G/NP0, SMD 1206
C7,C9,C10,C15,C16 = 10µF, 35 V, 0.04Ohm, 6.3mm max. diam., pitch 2mm or 2.5mm, Würth Elektronik 870055673001 (WCAP-PTHR Series)
C11,C12 = 4.7µF 25V, 20%, X5R, SMD 0805
Inductors
L1,L2,L3,L4,L5,L7 = 600Ohm @ 100MHz, 0.15Ohm, 1.3A, SMD 0603, Murata BLM18KG601SN1D
L6 = ACM4520-231-2P-T (TDK), 2 x 0.05Ohm, 230Ohm @ 100MHz, 2.6 A, SMD
Semoconductors
LED1 = red, T-1, 3mm
LED2 = green, low-power, SMD 0805
IC1 = ATtiny861A-SU, SOIC-20, programmed with firmware # 160321-11 (or 160321-12)
IC2 = PGA2311UA, SOIC-16
IC3 = TSOP34436, 3-pin epoxy package
IC4 = M74VHC14DG, SMD SOIC-14 (ON Semiconductor only)
Miscellaneous
K1 = 40-way (2x20) GPIO stacking socket (female), extra long
K2,K3,K7 = 3-way bus strip, vertical, 0.1’’ pitch (mounted on the bottom side of the board), with long stack-through pins
K4,K5 = 3-way stereo jack, 3.5mm, PCB mount, e.g. Lumberg KLBR 4
K6 = 6-way (2x3) boxheader, vertical, 0.1’’ pitch
K8 = 3-way PCB screw terminal block, 0.2’’ pitch, 630V
JP1 = 3-pin pinheader, vertical, 0.1’’ pitch
LED1 = 2-pin pinheader, vertical, 0.1’’ pitch
JP1 = jumper, 0.1’’ pitch
S1,S2,S3,S4,S5,S6 = pushbutton, right angle, SPST, FSMRA4JH TE Connectivity
S7 = pushbutton, SPST, FSM4JRT TE Connectivity
X1 = 12MHz miniature quartz crystal, 5x3.2mm, SMD, Cload 18pF
4 pcs 17mm M2.5 spacer (05.12.173 Ettinger)
4 pcs 6mm M2.5 bolt
4 pcs M2.5 nut
PCB 160321-1 v1.1
Optional
To support the LC display (instead of 4 bolts): 4 pcs 14mm M2.5 spacer (Ettinger 05.12.143)
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