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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 DIYaudio.com 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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Daddy’s Log – Kid date 6 | Burps, Feeding, NO SLEEP!

Day 6 and Daddy is still alive!, well partly thanks to redbull! (yes its bad for your health) people think its bad and lot of sleepless nights. its not true or false. its 50% 50%, the during the first few weeks, you need to feed the kid in regular intervals, has to be mommy’s milk and nothing else, every 2 hours or so. (you need to straggle 1 hour to feed her) at a given time the baby drinks around 60 ml of milk 😀 yes that much, less than 5 tablespoons. after that baby sleeps. but you MUST burp her, and never leave the baby on her back, always leaver her side ways, else if she vomits milk, she will drown on her own mink and something bad can happen. also you need to keep the baby warm. since she was use to saying at 36c in mommy’s tummy. what i call gift wrapping the baby 😀

since this daddy is bit paranoid, daddy keep the baby in a baby basket near daddy’s bed and watch her all night. why ? she is bit playful and mess with her wrapping cloths and cover her face with it. so we need to keep a proper eye on her. during the 1st week, if the mommy’s had the baby with a c-section, you need to take car of the mommy’s as well, cos she cant do anything on her own, even to lift the baby. so you need to take care of the mommy’s too, so you basically have 2 baby’s at home.

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Daddy’s Log – Kid date 3

When I got to know my wife was pregnant, it was kind of a mixed feeling, as I was happy and scared and didn’t know what to expect. but I always like kids, and i guess in a way they liked me too. it was not easy, wife being pregnant. unlike most women, she vomited till the day of delivery. during that time, we never cooked at home, always eating outside food, but we had good friend like SU, who send food from here place every day for my wife. that made our life much easier. my wife’s question of the day is, “monda kanne” and she never can make her mine up on what she wanted to eat. only good thing for us was she worked from home, so less issues. unlike most, we never went to a famous Dr.  but we went to someone who has experience and who has time for us. that made things much simpler, going to the hospital few times prove it was the best thing we did as he was always there when we needed, plus he was not out to make money, made our life much simpler as even when she was admitted due to a food poisoning, he didn’t want to keep us even a minute more at the hospital, same goes for the delivery,  she was up to the last day asking us if we want to have a normal delivery or not, and when we told him, its 50% 50% he simply told, lets do a test and see, after the test, simply told us that best we do a c-section then to do a normal delivery. He always took his time explaining everything, he jokes with us, even during the operation. ask to bring a camera, pushing me to video the full thing. explaining every step of the way.

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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
wget http://peak.telecommunity.com/dist/ez_setup.py
python ./ez_setup.py
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 http://sourceforge.net/projects/mysql-python/files/ download MySQL-python-x.x.tar.gz

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Edifier R1900T III review

Few days a go i went to  Unity Plaza get USB speakers for a friend of mine and after testing the speakers i found them to have this bit rich sound then compare to other computer speakers witch are small. this speakers was  form a company call Edifier witch i never heard of.  USB speakers are called the Edifier M1250. M1250 sound better then most small USB speakers i have seen, for Rs1000 (US$9) this was a deal, they do look stylish as well. normally most small PC speakers comes with set of bad speakers that can only do the mind range, but when i open the front cover of this speakers found that it has an oval shape speakers that you normally see in TV’s. this got me thinking, Edifier is in to sound.

Edfire 1250 i remember seeing set of speakers that look like book shelf speakers. once i got  home i went to the Edifier web site and found they had a range of bookshelf  size speakers.  i went back to Unity Plaza and ask whats the model of  this speakers and they told me its the R1900T III, witch was Edifiers top of the  range ones in there Studio seres. this was Rs.8500 (US$80) witch was at a  resonabl price range but not for a China made set of speakers. but i thought what  the heck and bought the speakers.

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HTPC – Intel Atom Media Center Inside a CD Player

[සිංහලෙන් කියවන්න]

Today I’m gonna talk about how to building your self a nice Home Theater System ruining Windows 7 Media Center. I wanted build one for some time now. mainly for listening to music and to play video podcasts, this is NOT a HD media center since its running on the Intel Atom 230 CPU. but you can always get an good motherboard and make this to run as a HD Media Center.

I wanted this to be unique as possible and be a more hands on job, any one can buy a HTPC case and put stuff inside the box and build a Media Center PC but i wanted this to look less then a PC  more like a HiFi device like my DVD or CD-Player and operate the same way with out worrying about keyboards and mouse. This will fit nicely on your HiFi rack and look sexy at the same time 😀

Lest see the hardware and parts i have used for this project, that don’t mean you have to use the same.

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Music, Me & My Neighbors

I always count my fingers till the weekend come, guess every one do 😀 it’s not that I don’t like to work, but my work place is not like where you guys work (if you do actually work :P), bit hard to concentrate as people keep on coming and bother me or give me some thing else to do, then I have to stop every thing I was doing and attend to that. Well, with my line of work with out concentration it’s hard to work, but its challenging and the strange thing is I LOVE what I do.
I have been a music lover since the day’s of Audio tapes of rather Cassettes, and AM radio (I know half u you guys don’t know what that is), Tube (Valve) radios, use to recode songs off the AM radio to cassettes and make mix tapes.  Then came CityFM, the 1st FM Stereo Channel in Sri Lanka, this was a multi lingual channel, with Sinhala, Tamil and English. Use to start at 7PM and I still can remember how happy I was to see the “Stereo” LED lights up on the RADIO.  it sound heavenly to me when comparison to AM radio.
We didn’t have a BIG HiFI system. Only a Stereo cassette player made by Sanyo. I grove up with Nanda Malanee, T.M Jayarathne, Jim Reeves, ABBA playing.  We moved to a new place and its no Colombo, I was the only one who was listening to English music when I came there. and even the kids use to ask “What the heck are you listening to”, when I started to doing O/L, I was so in to music and sounds, I built my own speakers, amplifiers and even the cassette players. Do you believe my dream back in the days was to get a CD player? I use to dream about it, I know other kids at my age use to dream about other stuff, my dream was to have a CD Player :D, when I think about electronics, I didn’t have money to buy a soldering ion, so what I did was took a copper coin and hammered it around a bicycle spoke and put it over the kerosene cookers and solder with that 🙂 I never wanted to bother my parents with stuff. I always try to buy things my self even when I was little.
from Modern Talking, MC Hammer I turn my music love to R. Kelly, Led Zeppelin, AC&DC and 2PAC, one day when I was playing 2pac my mom came and ask me “Do you understand what they are saying ?” and I was like “yeah, filthy words” and after that she never ask me that question 😀 but I know my nabors, even my friends thought of me as a nut case for listening to those kind a music, you have to understand this is NO Colombo, even in Colombo people was scared to listen to them 😛 those days I can name any song by heart, I should say thanks to stations like TNL Radio for player Rick Dees Weekly Top 40. TNL use to have this request show at 12pm. I use to call them and request “How do you want it” by 2pac, 😀 those days radios hardly played RAP.
yes, my dream did come true one day, my 1st CD Player was a Sony CDP-350, it was a used one but i was a happy camper 🙂 its hard to explain the feeling you get when you listen to music with the stuff you made your self, speakers boxes made out of cardboard tubes, AMPS built on top of a table.
Now things have changed a lot, my Nabors now listen to RAP :D, not the good kind, the dumb kind sing by Sri Lankans, well not saying all the Sri Lankan rap are bad, but 99.9% of them are. what they says don’t mean a SHIT, rapping is saying what you feel and getting your word out, not blabbering some random words or making dumb faces and finger/hand gesture. People like Kasun Kalhara have real talent, take Sirasa Suppers Stars or any other copy cat shows like that and American Idol, you can really feel the talent deference. Take Kamal who host Super starts, how dumb is he to be or rather copy Ryan SeaCrest, why cant he be more like them some one else, In Sri Lanka you call singers as talented when they can sing like the original singer, Eg: if one can sing like Amaradewa, he’s talented, in other part of the world people call them impersonators or doubles.  i think as Sri Lankan we have a long long way to go when it comes to music.
Music always make me happy, now I hardly get a chance to enjoy music the way I want to, with a good system with my work and I come home late, cant blast music at that time, but today I really got a chance to enjoy some good music. from a boy with a home made tape player and cardboard tube speakers, I have some a long way, Yamaha Amplifiers, Bose speakers, 7.1 Surround sound, drams do come true…. all you have to do is dream…

I always count my fingers till the weekend come, guess every one do 😀 it’s not that I don’t like to work, but my work place is not like where you guys work (if you do actually work :P), bit hard to concentrate as people keep on coming and bother me or give me some thing else to do, then I have to stop every thing I was doing and attend to that. Well, with my line of work with out concentration it’s hard to work, but its challenging and the strange thing is I LOVE what I do.

I have been a music lover since the day’s of Audio tapes of rather Cassettes, and AM radio (I know half u you guys don’t know what that is), Tube (Valve) radios, use to recode songs off the AM radio to cassettes and make mix tapes.  Then came CityFM, the 1st FM Stereo Channel in Sri Lanka, this was a multi lingual channel, with Sinhala, Tamil and English. Use to start at 7PM and I still can remember how happy I was to see the “Stereo” LED lights up on the RADIO.  it sound heavenly to me when comparison to AM radio.

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iPhone OS 3.1 and Battery Life, iTunes 9

I mostly blog in Sinhala, I first started as a Sinhala blogger and I kept this English blog to put some of my Sinhala blog posts in English translation, with the time limitations, feeling lazy to write the same blog post again, it didn’t work out the way i hope it would. then thought to write this blog as an independent blog from my Sinhala blog, so here goes…  oh FYI: I’m bit dyslectic so, if you do see a mistake in my writing or rather SPELLINGS,  do POINT them out

When the iPhone OS 3.1 and iTunes 9 came out I upgraded with in few hours of it release! thinking it might have fixed the issues the OS 3.0.1 had, oh I got the iPhone 3G not the 3GS, my hardware might not have the horse power needed to run the OS3.1 smoothly. OS 3.X is optimized for the iPhone 3GS, but it runs quite well on the 3G. do you know I simply hated the iPhone ? 😀 well… do I still ? hmm…. thats a question for next time 😉 if you read my Sinhala blog you can see that I got this phone as a gift from some one who is trying to prove me wrong !

The gaming experience was really improved with the new OpenGL ES, can say better then a PSP ! 😀 but you might have to get use to the slow responsive touch screen at times while trying to hold on to the phone ! yeap its a slippery bugger ! well I did kind a felt its hard to play some games on it where you need multi touch, maybe be coz I’m OLD 😛 well cant call me a teenager any more right 😀 even the kids on the road call me “අංකල්” now ! dam you 😀 i really felt this when i was playing the Terminator game on the iPhone.

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Post Removed

As per the original post that was here, there was a friendly
discussion here about a software program that consists of technical
analysis and findings. How ever some people have used that information
to attack Dr. Sameera De Alwis personal and professional life, this
post never intended to be used in that manner, it was a technical
analysis rather then an attempt to insult any one. Few days ago I had
email communications with Dr. Sameera De Alwis and he explained
the personal and professional hardship he had to face due to the fact
people are using the information that was posted here as a weapon to
attack his personal and professional life.

As per the original post that was here, there was a friendly discussion here about a software program that consists of technical analysis and findings. How ever some people have used that information to attack Dr. Sameera De Alwis personal and professional life, this post never intended to be used in that manner, it was a technical analysis rather then an attempt to insult any one. Few days ago I had email communications with Dr. Sameera De Alwis and he explained the personal and professional hardship he had to face due to the fact people are using the information that was posted here as a weapon to attack his personal and professional life.

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Queen’s Hotel Kandy Sri Lanka Hangs by a thread (Hotel Revew)

[සිංහලෙන් කියවන්න]

Recently (Aug – 2008) me and few friends went to Kandy and was looking for a place to stay in Kandy, thought that Queen’s Hotel Kandy is a good place to stay, since its a 3 Star rated hotel.

but i was disappointed how bad condition the rooms are in this so call “3 Star” Queen’s Hotel Kandy,

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Bloggers’ Rights at EFF

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