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DIR9001
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DIR9001 SPDIF decoder

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Introduction

Circuit
description

Schematics
diagram

Assembling

Component
view

Printed
circuit board

Settings

Photo
gallery

Parts

Links

End

Updates

Introduction

For transfer of digital audio between devices is standardized S/PDIF
interface (electrical) and TOSLINK (optical) for commercial use, or AES3 for
professional use. S/PDIF decoder module is used for converting of this interface
to I2S interface, which is usually used on audio DACs. For conversion we can use
for example integrated circuit CS8416 or DIR9001. In building of DAC in past I
had troubles with resetting circuit CS8416 in hardware mode. Now I select
DIR9001 which works perfectly and he has lower jitter than CS8416.

Circuit description

In supply section after bridge rectifier and smoothing capacitor I use
LOW-DROP voltage regulators IC4 LE50CZ and IC5 LE33CZ. On optical input is used
optical receiver OX1 Toshiba TORX173 with TTL output. On electrical input due to
galvanic isolation is used pulse transformer TR1 and after him RS485 transceiver
IC2 75176 with TTL output. I had better signal shape with termination resistor
75R connected before transformer. For isolation is possible to use transformer
Lundahl LL1572, Newava S22083 or similar. Circuit board is prepared for both
usual pinouts. When we doesn't need both types of input interface, we can wire
in only one which we want. Components from second input we don't need. Circuit
DIR9001 requires external reset circuit. I used available MCP120T-300. Circuit
DIR9001 can use clocks from crystal or from input signal. I used circuit with
internal PLL without external clocks which accept input signal with sample
frequency 32, 44.1, 48, 88.2 and 96kHz. Internal PLL requires external filter
composed from R2, C14 and C15. Output signals GND, SCK, LRCK, BCK, DATA and +5V
goes to six pin connector which is dedicated for connecting of DAC board. POWER
LED lights when power voltage is present. ERROR LED lights when S/PDIF signal is
not present or when error is detected. _AUDIO LED lights when received S/PDIF
signal doesn't contains RAW PCM audio data. For example when AC3 or DTS encoded
signal is received.

Schematics diagram

version
1.2 schematics in Eagle 5

version 1.1
schematics in PNG

version
1.1 schematics in Eagle 5

Assembling

We must place components on board from smaller to bigger. First we must place
IC1 which is really small. First I soldered two end pins and check the right
position of circuit. Next I solder all pins with soldering iron and pipe tin.
Almost all pins was now shorted. Next I exhaust superfluous tin with solder
wick which is perfect for this work. I visually check PCB connection on my
reading-lamp. Next I continued with placing of SMD resistors, capacitors,
diodes and IC2. I continued with wire connections and components from a top
side. When we doesn't need optical input, we doesn't place OX1 and C12. When we
don't want electrical input, we don't place X1, R1, TR1, IC2 and C13.

Component view

Printed circuit board

Printed circuit board is designed with only one side and two wire
connections. It allows to create him in amateur conditions.

version
1.2 in PDF

version
1.2 in Eagle5

version 1.1
in PNG

version 1.1
in PDF

version
1.1 in Eagle5

Settings

Output data format is selected by jumpers JP1-1 and JP1-2 connected to FMT0
and FMT1 pins. Next two jumpers JP2-1 and JP2-2 connected to PSCK0 and PSCK1
pins are for selecting of System clock. This is needed in respect to
possibilities of DAC with oversampling. Circuit has internal pull-down
resistors 51k. When jumper is not connected there is logical level L. When is
connected, there is logical level H. We must set right output format in respect
to used DAC. Next tables presents settings overview.

Output format selection

FMT[1:0] settings

Audio data output format

FMT1

FMT0

L

L

16-bit, MSB-first, right-justified

L

H

24-bit, MSB-first, right-justified

H

L

24-bit, MSB-first, left-justified

H

H

24-bit, MSB-first, I2S

System clock settings

PSCK[1:0] settings

Output clock from PLL

PSCK1

PSCK0

SCKO

BCKO

LRCKO

L

L

128fs

64fs

fs

L

H

256fs

64fs

fs

H

L

384fs

64fs

fs

H

H

512fs

64fs

fs

Photo gallery

Parts

Part list

name

value and type

quantity

R1

75R SMD1206

1x

R2

680R SMD1206

1x

R3-R5

1k5 SMD1206

3x

R6-R9

33R SMD1206

4x

C1

4700uF/25V electrolytic

1x

C2-C5

10uF/10V SMD tantal size B

4x

C6-C13

100nF SMD1206 ceramic

8x

C14

68nF SMD1206 ceramic

1x

C15

4n7 SMD1206 ceramic

1x

IC1

DIR9001 TSSOP28

1x

IC2

75176 SMD SO-08

1x

IC3

MCP120T-300 SOT23

1x

IC4

LE50CZ

1x

IC5

LE33CZ

1x

JP1-JP2

JP2QE jumper

2x

L1

47uH axial

1x

LED1

LED red 2mA

1x

LED2

LED yellow 2mA

1x

LED3

LED green 2mA

1x

B1

Bridge rectifier 1.5A/100V

1x

OX1

TORX173 Toshiba - board 1.0

1x

OX1

TORX177 Toshiba or GP1FAV50RK0F Sharp - board 1.2

1x

SV1

jumper ribbon 6 pins

1x

TR1

LL1572 or S22083 or PE-65612 or DA102C

1x

X1

cinch female to PCB TOBU3

1x

X2

frame terminal AK300/2

1x

Links

http://www.ti.com/lit/gpn/dir9001
DIR9001 datasheet

http://www.ti.com/lit/gpn/sn75176b
75176B datasheet

http://cz.farnell.com/ Shop which
have DIR9001 in Czech Republic

End

I hope that circuit doesn't have difficulties. We can have troubles with
finding of circuit DIR9001 or pulse transformer which are not usually present
in local store. Circuit works perfect for me and provides much variability in
DAC bulding.

Updates

March 8 2010 - Update of PCB for changing of SMD components with size 0805
to components with size 1206.

June 25 2010 - Update of board version 1.1 photos and partlist with
PE-65612 transformer.

February 26 2011 - Update of schematics and PCB to version 1.2 because
replace of discontinued optical receiver TORX173 with new and faster TORX177
from TOSHIBA or GP1FAV50RK0F from SHARP.

March 29 2011 - Update of PCB to version 1.2a because I2S connector was
moved for 0.635mm.

©2010-2011 pavouk[at]pavouk.org