General Information Sources
- Texas Instruments offer the TI Precision Labs - Op Amps educational materials. See also the TI web page Analog Engineer's Circuit Cookbooks with links to: Operational Amplifiers (Op Amps); Analog Engineer's Pocket Reference; and TI Precision Labs with online videos and hands-on labs.
- The op-amp information from Linear Technology.
- Search google for high quality op-amp based audio amplifier design.
- Sources: device selection at Texas Instruments Amplifiers and Linear, Maxim Integrated Operational Amplifiers.
High quality headphone amplifiers (DIY kits)
- NwAvGuy emphasises quantitative testing and dislikes snake oil:
- The Objective2 low noise headphone amplifier features the low-noise high-output-current NJM4556A op-amp in a circuit that uses a controlled power supply (dual battery or AC input). DIY or prebuilt options are available.
- Access o2-details → The Resources, to see circuit diagrams, printed circuit layouts, etc. (all open source). Some google docs files are no longer available but enthusiasts have copies available at
- The Objective2 (O2) Headphone Amp DIY Project (still active 10 years after the initial design was published)
- O2-amp
- Google search for NJM4556A pdf datasheet
- The ODAC is based on a ESS Sabre ES9023. Commerical implementations are available e.g. from the UK-based Epiphany Acoustics E-DAC.
- 2020 update: the public designs have been taken up by manufacturers in east Asia and I am enjoying this approx. A$25 derivative with low power audio amp. At the higher end, there are nicely packaged versions such as this o2 sdac dac amp from drop.com. References:
- Google search for SA9023 ES9018K2M audio DAC
- Google search for SA9023 module
High quality power amplifiers (DIY kits)
- Elektor magazine has a history of (mostly) successful amplifier design e.g. the Q-Watt Audio Power Amplifier http://www.elektor.com/Uploads/2013/11/UK2013090101.pdf (2013) offers extremely low distortion and high power output. It uses the Texas Instruments LME49811 power amp input stage and discrete output devices, with an OPA177 opamp handling DC offset correction. Search Elektor site for amplifiers.
- Professional-Grade Audio Amp on the (sort of) cheap (appears in IEEE Spectrum October 2018, and DIY Pro Audio November 2018).
- 2020/2021 update: I am a fan of signal processing devices from Texas Instruments and am currently enjoying a DIY stereo system based on TI's TPA3116D2 IC (50W stereo/100W mono 4.5V-to-26V supply class D) attached to an SA9023 based audio DAC. A typical 3116D2 based audio amp module can be sourced for <A$20 and a Meanwell switched power supply can be obtained for <A$30. TI have now released a more advanced class D chipset in the form of the TPA3255. References:
- TI data on TPA3116D2 and TPA3255
- Google searches: TPA3116D2 module, TPA3255 module, TPA3116D2 bluetooth module
High quality media centres (DIY)
- The Raspberry Pi computer can be loaded with a number of AV software tools but then needs a quality DAC. The Raspyfi project started as a central focus of this effort by volunteers. Later, this group added support for other compact computer boards and became the volumio project.
- Raspyfi article on choosing a USB DAC for your Raspberry Pi.
- Raspyfi article on building your own DAC (uses a Sabre ES9023).
- The volumio project website with the latest software builds for target platforms Raspberry Pi, Beaglebone black, Cubox, Udoo, etc.
- The Raspbmc project offers another option for single board computers such as the Raspberry Pi and custom media processing systems. It has now evolved into the Kodi project with a flagship hardware platform to be called Vero.
- Lifehacker articles tagged Raspberry Pi and site search http://www.lifehacker.com.au/?s=raspberry+pi (mentions cases, AirPlay receiver, etc.).
- Sainsmart is now offering an Audiophonics Sabre ES9023 DAC for the Raspberry Pi. Alternatively, check this ebay search for Audiophonics+DAC+Sabre+ES9023+I2S.
High Quality Components
Open Source Projects
- The ES9023 DAC is highly recommended and quite a few Asian manufacturers implement open source designs. See this search on ebay for ES9023.
- JDS Labs produce DIY and pre-built versions of some open source projects (Collinsville, USA).
- NwAvGuy has also developed an open source USB-connected DAC called ODAC. Both Yoyodyne Consulting and JDS Labs, plus a small number of other companies, provide components, kits and/or fully assembled versions.
- Trevor Marshall web site has links at the bottom of the main page on topics such as Precision HiFi Loudspeakers: 'Ground Effect Omnidirectional' and
Speaker wire selection (an old favourite)
