The Zen Headphone Amplifier

I’ve built a scaled-down version of Nelson Pass’ Zen power amplifier to feed my Grado headphones. For this use, the Zen topology is perfect: excellent sound quality, simplicity, linearity and no multi-stage feedback. It is a single stage class A MOSFET design with the right gain and a low output impedance. Here we don’t have the limitations of the Zen amps (at least in the single-stage implementations) regarding speaker compatibility. A single stage topology with correct interfacing values misses very few things in the original music message.

The gain device in the original Zen amplifier is biased by fixed current source. For this amp, I employed an active current source described in Pass’ patent no. 5,710,522 (see Zen Variations Part 2). The benefits of an active source include higher output current, lower distortion and 50% theoretical operating efficiency (compared to the 25% efficiency from a fixed source). This type of current source is featured in the Aleph power amplifiers from Pass Labs.

I designed this circuit to obtain the best sound from my Grado SR-325 headphones. Portability here was not imperative, so the high power consumption of a real class A amp was not a big drawback. I developed this project at the beginning of 2002 and it was first presented at in February 2002. Since the intellectual property belongs to Pass Labs, this circuit is intended only for not–for–profit use, unless the current source topology is altered. I wish to thank Nelson Pass for his open-mindedness and involvement in the DIY audio world; the DIYer community will be always grateful to him!

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Installing Subversion (SVN) & Trac on CentOS 5.X with Apache

Here’s how to install SVN + Trac with Apache on CentOS 5.x, before you do this you need to login as root.

run the following command to install SVN, SVN Support for Apache, PHP, Apache, MySQL (if your using MySQL with Trac) gcc, Python and Python for Apache and Sqlite (Defualt DB manager for Trac)

yum install subversion mod_dav_svn php httpd mysql gcc python mod_python sqlite
python ./
easy_install babel
easy_install Genshi
easy_install Pygments
easy_install docutils
easy_install textile

above will install the basic stuff to get SVN + Trac running on Apache.

now lets install Python support for MySQL if your using Trac with MySQL go to download MySQL-python-x.x.tar.gz

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How to turn your PS2 (Play Station 2) into a Media Center

[සිංහලෙන් කියවන්න]

When i got my PS2 some time back was thinking how to use this to Play MP3/DivX etc files and convert it in to a Media Center, so i start to read and find out how to do this with a Slim SP2, then i found there is a player call SMS for PS2, but found that you need to have your PS2 MOD’ed  (MOD Chip) so you can boot CD-R, if not the PS2 will not allow you to boot from any backup CD’s

so lets see how you can turn your PS2 SLIM in to a Media Center,

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Step by Step Guide to Installing Virtualbox on Windows Vista and Linux as a Guest OS

[සිංහලෙන් කියවන්න]

Today I’m taking about Virtualbox software and using it to install other OS on top of Windows Vista. this can be use full for people who use deferent OS for testing and presontations. the best part is this is a Free software, given Free for personal usage. Virtualbox was originaly done by Innotek, a German software company and now Sun Microsystems devolop this as an Open Source project.

Virtualbox curruntly run on Windows, Linux, MAC OS and (Open)Solaris and you can install lot of Guest OS’s, here you will find the full list.

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