Difference between revisions of "How to build an optical SPDIF bracket"

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WARNING:
+
'''WARNING:'''
  
 
Creating, testing and using home built electrical circuits and connecting these to your computer's motherboard may pose the following risks:
 
Creating, testing and using home built electrical circuits and connecting these to your computer's motherboard may pose the following risks:
Line 8: Line 8:
 
..however that being said, this procedure should be feasible with average technical skills and little tools and equipment
 
..however that being said, this procedure should be feasible with average technical skills and little tools and equipment
  
Introduction
+
'''Introduction'''
  
 
Most MythTV systems these days are built using a motherboard with integrated audio and video.  However, the SPDIF signal is unfit to be wired directly to a SPDIF compatible digital audio receiver.  The reason is that the signal is a TTL signal, while it should be a signal swinging between -0.5V and +0.5V.  This requires that a simple circuit be built, using some resistors and a capacitor, but the signal can not be used to drive a long cable and thus additional components like a 74HCT04 are needed to amplify this signal to acceptable levels.
 
Most MythTV systems these days are built using a motherboard with integrated audio and video.  However, the SPDIF signal is unfit to be wired directly to a SPDIF compatible digital audio receiver.  The reason is that the signal is a TTL signal, while it should be a signal swinging between -0.5V and +0.5V.  This requires that a simple circuit be built, using some resistors and a capacitor, but the signal can not be used to drive a long cable and thus additional components like a 74HCT04 are needed to amplify this signal to acceptable levels.
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This article describes how you can build a SPDIF TOSlink transmitter circuit, using just two components.
 
This article describes how you can build a SPDIF TOSlink transmitter circuit, using just two components.
  
Advantages:
+
'''Advantages'''
 
- Optical link means no GND loops, total isolation can be achieved with your receiver (however, your DVI cable will contain a GND connection to your TV, and if these share connections, there will be at least a common GND signal anyway)
 
- Optical link means no GND loops, total isolation can be achieved with your receiver (however, your DVI cable will contain a GND connection to your TV, and if these share connections, there will be at least a common GND signal anyway)
 
- no electrical interference possible
 
- no electrical interference possible
 
- cheap, simple
 
- cheap, simple
 
+
'''
Disadvantages:
+
Disadvantages'''
 
- optical TOSlink cable needed
 
- optical TOSlink cable needed
 
- receiver needs to have a optical TOSlink input (most modern ones have that)
 
- receiver needs to have a optical TOSlink input (most modern ones have that)
  
Requirements:
+
'''Requirements'''
 
- Motherboard must have a SPDIF header
 
- Motherboard must have a SPDIF header
 
- SPDIF should be unmuted (see other articles about the software setup)
 
- SPDIF should be unmuted (see other articles about the software setup)
  
Hardware needed:
+
'''Hardware needed'''
- 1 SPDIF optical transmitter unit, like the Toshiba TOTX173
+
- 1 SPDIF optical transmitter unit, this article describes the Toshiba TOTX173
 
- 1 8.2K ohm resistor, 1/4 watt 20% tolerance
 
- 1 8.2K ohm resistor, 1/4 watt 20% tolerance
 
- 4 pin header, commonly supplied with the motherboard for interconnection of SPDIF to DVI
 
- 4 pin header, commonly supplied with the motherboard for interconnection of SPDIF to DVI
 +
- heat shrink isolating sleeve 3mm diameter
 +
- thin solid core copper wire
 
- soldering iron
 
- soldering iron
 
- soldering tin for use in electronic (resin core, not acid core)
 
- soldering tin for use in electronic (resin core, not acid core)
  
 
Literature needed:
 
Literature needed:
- Application sheet from Toshiba for the TOTX173
+
- Application sheet from Toshiba for the TOTX173, download it here [http://www.toshiba.com/taec/components/Datasheet/TOTX173.pdf]
 
- manual for your mothernboard showing the pin layout for the SPDIF.  This one is important, don't guess which pin is which, it may damage your motherboard)
 
- manual for your mothernboard showing the pin layout for the SPDIF.  This one is important, don't guess which pin is which, it may damage your motherboard)
  
 
Procedure:
 
Procedure:
 
-
 
-

Revision as of 14:13, 13 January 2008

WARNING:

Creating, testing and using home built electrical circuits and connecting these to your computer's motherboard may pose the following risks: - electrical fire - toxious fume inhalation - burning of skin or face by using a soldering iron - damaging perfectly working parts of youyr motherboard or audio equipment ..however that being said, this procedure should be feasible with average technical skills and little tools and equipment

Introduction

Most MythTV systems these days are built using a motherboard with integrated audio and video. However, the SPDIF signal is unfit to be wired directly to a SPDIF compatible digital audio receiver. The reason is that the signal is a TTL signal, while it should be a signal swinging between -0.5V and +0.5V. This requires that a simple circuit be built, using some resistors and a capacitor, but the signal can not be used to drive a long cable and thus additional components like a 74HCT04 are needed to amplify this signal to acceptable levels.

This article describes how you can build a SPDIF TOSlink transmitter circuit, using just two components.

Advantages - Optical link means no GND loops, total isolation can be achieved with your receiver (however, your DVI cable will contain a GND connection to your TV, and if these share connections, there will be at least a common GND signal anyway) - no electrical interference possible - cheap, simple Disadvantages - optical TOSlink cable needed - receiver needs to have a optical TOSlink input (most modern ones have that)

Requirements - Motherboard must have a SPDIF header - SPDIF should be unmuted (see other articles about the software setup)

Hardware needed - 1 SPDIF optical transmitter unit, this article describes the Toshiba TOTX173 - 1 8.2K ohm resistor, 1/4 watt 20% tolerance - 4 pin header, commonly supplied with the motherboard for interconnection of SPDIF to DVI - heat shrink isolating sleeve 3mm diameter - thin solid core copper wire - soldering iron - soldering tin for use in electronic (resin core, not acid core)

Literature needed: - Application sheet from Toshiba for the TOTX173, download it here [1] - manual for your mothernboard showing the pin layout for the SPDIF. This one is important, don't guess which pin is which, it may damage your motherboard)

Procedure: -