Friday, November 07, 2008

Metallica, Pepsi Center, Denver

S. called and told me about Metallica playing in Denver, and he got to know pre-release. I didn't even have to think twice, so he got what turned out to be floor tickets! Took a day off work on Tuesday to go down to see them.

We got there way early, at 3:00, for a concert that started at 7:00. Not a minute too soon, either, since the crowd started piling up. Unlike my last three concerts, I noticed that we tended to be on the older side of the crowd :) We waited till 6:00 when they finally opened the doors. A quick scan of my ticket, the usual security clearance... but then they gave us this wrist-band, which I assume was to identify us on the floor. We pretty much ran from the doors to the stage, to get a better vantage... and boy were we amazed! Mere FEET from the stage, I couldn't believe my eyes! I called D., and while talking to her, this security guard points to a yellow line and says I need to be on the OTHER side :-D The stage was right in the middle of the floor, people all around.

There were two opening acts, the first group was The Sword. They were tight, especially the drummer. Trouble was, the sound system (or perhaps our location) meant we couldn't hear the vocals at all. I could see the guy ten feet away, though, screaming into the mike!

The second opening band was Down. These guys scared the crap out of me... I'm not exactly used to sludge metal. The sound system suffered the same problems, and I was hoping they'd fix it before Metallica played. I'll never forget Anselmo hitting himself on the forehead with a microphone so hard he started to bleed.

About 45 minutes and several false alarms later, Metallica finally took the stage. The stage went dark, and the effects from That was just your life started to play... then all of a sudden, LASERS... hundreds of them, formed a cage all around the stage! They went on to play The End of the Line, and then surprised us all by playing Ride the Lightning :) Mebbe Hetfield was a bit surprised too, saying "Whoa, it seems you know that song, yeah?"



The lights were up on these coffin-shaped fixtures, just like the album cover. Didn't think much of them until in the middle of the solo for Ride the Lightning, they tilted way down over the band:



Was a great show, the new bassist Robert Trujillo did a great job with both the new songs as well as classics like For Whom The Bell Tolls. Kirk Hammett did his solos right up in our faces, I could see each note he played. He scorched effortlessly through every song, and threw in two solos to boot. Lars Ulrich looked like he was thoroughly enjoying himself, thrashing away on his kit. There was a group of Lars fans nearby, who had a Danish flag, so our side of the stage became his favourite :D Hetfield was... being a bit weird, saying his daughter disapproves of his too-short hair! Oh well...

My favourite song was, by far, Master of Puppets, the crowd singing along, the solos, ah, awesome! The set was pretty good, I just wished they played Battery, Blackened or Sanitarium. Of course, there was this moment during Enter Sandman where I'm sure Hetfield was looking right at me screaming out the song, wondering "what the heck is this desi kid doing in the audience?" :D

It would seem like the band is really trying hard to make amends for the whole Napster fiasco, they gave away a copy of the audio CD for Death Magnetic to everyone who bought a concert ticket, and I could download a copy of the entire concert as MP3s :) My very own bootleg!

Set List:
  1. That Was Just Your Life
  2. The End of The Line
  3. Ride the Lightning
  4. The Memory Remains

  5. One
  6. Broken Beat and Scarred
  7. Cyanide
  8. Sad But True
  9. Wherever I May Roam
  10. For Whom The Bell Tolls

  11. Kirk Hammett Solo
  12. The Day That Never Comes
  13. Master of Puppets
  14. Damage, Inc

  15. Kirk Hammett Solo 2
  16. Nothing Else Matters
  17. Enter Sandman
  18. Last Caress
  19. Hit The Lights

  20. Seek and Destroy


I just noticed that way at the end of the concert, they threw in a bit of Waste my Hate...


"Hail to the King"

Wednesday, September 17, 2008

Inspiration, the HP way

I once had the pleasure of reading Analog Circuit Design: Art, Science and Personalities, where Jim Williams talks about how his mentor at MIT had him fix broken test equipment to get a better understanding of practical electronics. I dimly recalled that as I wrestled a 50-pound HP 8673 Synthesized Microwave generator onto my workbench today. No, they don't build 'em like they used to.

The unit started behaving oddly, would put out a signal with a frequency offset. Strange... so I thought I'd give it a shot, got the service manual and opened 'er up. It's not every day that you get to crawl in to the mind of a genius, but man, this thing's built like a tank and had such detailed instructions on what was going on inside. I followed the service manual, isolated the fault to a malfunctioning YIG-tuned oscillator (YTO). I pulled out the YTO boards one by one, and marvelled at the elegance of the designs. Then I found a burned-out capacitor, and figured I'd swap it out for another one. Oddly, I hesitated quite a bit before applying a soldering iron to the board, I felt like I was violating some sacred artefact, the work of a true engineer, the kind that wears a pocket protector. Anyway, after replacing the cap, the synth came up perfectly, and has been working since.

While I didn't learn a whole lot directly, it did help to see how things were built by HP.

Brilliant(e)?

Looks like Miss Grafx tagged me Brilliante. Hey, I take what I can, so here goes:

The Rules:

  • When you receive the prize you must write a post showing it, together with the name of who has given it to you, and link them back

  • Choose a minimum of 7 blogs (or even more) that you find brilliant in their content or design.

  • Show their names and links and leave them a comment informing they were prized with ‘Brilliant Weblog’

  • Show a picture of those who awarded you and those you give the prize (optional).



I'll relax the seven blog rule, since I don't really follow that many active, non-tech blogs.

V (not for Vendetta), I do all my dining out through her. Virtual dining. How about that...

Jo Kart, the travel freak. I visit other places through his eyes... er, camera.

Silverine, the perfect cure for a dull morning.

Karthik, just coz it's fun to keep in touch!

DJK. No link, she'd rather not people visit her blog that's not updated any more. I liked the vitriol.

Grafx, for the pretty graphics and rollercoaster rides :)

Wednesday, July 16, 2008

Saturday, May 17, 2008

DNS updates with tinydns

I administer a small network (~30 hosts), and I've set up a router running DJ Bernstien's tinydns and a DHCP server. I wanted to have tinydns update itself each time a new host connects to the network and announces its host name to the DHCP server. Fortunately, Michael Stella had written a handy Perl script to do just this, called djb_update.pl. I had this set up, and everything seemed to work, except that new DHCP clients only appear in the DNS system after a day or so. Strange.

It turned out the problem lay in the fact that I'm using the dnscache part of tinydns in addition to the regular dns server. The usual approach with most of DJ Bernstien's programs is to call the "svc" program with a "-h", which ends up restarting it to reload configuration files. The djb_update.pl script periodically checks the DHCP leases file to detect changes. These changes are then written to the tinydns configuration files and tinydns is restarted. This is done using a Makefile in /etc/tinydns/root, but the Makefile does not restart the dnscache. The dnscache updates itself once a day or so, hence the delay.

So I modified the Makefile to add this line after the tinydns restart line:

/usr/local/bin/svc -h /etc/dnscache

Mystery solved...

Sunday, March 16, 2008

Tube amp - design

Months away from a soldering iron gave me the itch to start working on something. In my "past life", I had a hobby of building audio amplifiers and speakers, and I never got a chance to work on a tube project back at home. Now, I figured, is a good time to start.

Hi-fi tube designs are necessarily expensive, the tubes involved can cost quite a bit, and the designs aren't exactly for the beginner. The next best thing, IMO, is a guitar amp, so that's what I'm going to try. Given that I don't play (oh the irony!), I enlisted the help of a friend, S., who will also be building the speaker cab in addition to providing guitar input :)

So anyway, I started off by hunting for existing guitar amp designs, and there are literally thousands to find. I settled on the VOX AC-15, since it's a well-known and proven design. It's also relatively low-powered, which is good, since S. plans to play in his apartment, not a stadium. Also, the output tubes are EL84s, which are not terribly expensive. Finally, it is a push-pull design, which means that the output transformer isn't too expensive, and won't saturate easily.

I did do some tinkering with the design, though. First, I took out the tremolo and reverb parts of the AC-15. These are a bit difficult for me, as a beginner, to work with. Besides, S. has a bunch of fancy effects pedals which would do the job. I also decided to do away with the rectifier tube of the classic AC-15, and use silicon diodes instead, with a series resistor to allow the supply to sag a little when heavily loaded. Caps across the diodes kill some of the switching noise. There's also the usual filter cap and bleeder resistor.

There were several variants of the AC-15 design floating around. I'm using two 12AX7 dual-triode tubes as pre-amps, since they're cheap and plentiful. I might also try an EF86 input stage later. There's two sets of channels, a "normal" and "brilliant" channel, the difference being the "brilliant" channel uses smaller coupling caps between stages, which decreases bass response. Also, the tone controls only affect the "brilliant" channel. A third 12AX7 acts as a phase splitter to drive the power tubes. The power tubes are EL84 beam power tetrodes. Given the relatively low power involved, there is no power tube bias control.

Another change from the AC-15 design is the inclusion of a switchable 12-dB attenuator. This will permit S. to drive the amp really hard without too many complaints from the neighbors :)

Some more hunting around lead me to TubesAndMore, a nice online store that lets you buy, as the name suggests, tubes and a lot more stuff that you can use to build hi-fi and guitar amps.

So anyway, that's what I'm going to try. I'll post here when I get some results. Anyone with tube experience, feel free to give this beginner a hand :)

Monday, February 18, 2008

Free!

Well then, looks like I finally made it. The path I struck out on over a year ago is finally at it's end. Not being very good with words, I'll go with Jorge Cham's gems:

After some amount of general fooling around and getting busy with other things, it finally got down to this:


... six months later...


After some back and forth...

... I finally got close enough to defend.



Worked hard on doing the following to make up a "good" presentation:


Fortunately, it didn't turn into this:


In the end, besides a couple of crafty questions, I made it! I graduate!!! I get to... go back to doing exactly what I've been doing for 4 years now. sigh Oh well, it's not all bad. At least I won't technically be a student any more.

Sunday, December 16, 2007

For Mom

Yeah, it's been a while since I've posted anything, it's been a trying time for me, working on my thesis. Anyway, I'm writing because it's my mom's birthday, and I suddenly remembered something she did for me that for some reason I'll never forget.

I was in third standard, and the school I was in was not really known for being very forgiving towards, um, rule-breakers. It was probably the second week of school, we had our new books, and like everybody else, they were covered in brown paper. The class teacher, however, makes up this rule that the brown paper must be the kind that has the shiny plastic on it, the supposedly water-proof kind. Unfortunately, it's also the expensive kind, and all my books are covered with the ordinary brown paper. My teacher gives us a warning, no, an ultimatum, that by the end of the week, we all had have the shiny plastic covers. I come home and tell my mom about it, she doesn't believe me. She thought that I was making a fuss for no reason, and that no teacher in her right mind would have such strange requirements (and she'd be right, too). The end of the week grew closer, and my books were still covered in the ordinary brown paper. That Thursday, I get pulled up in front of the class and made fun of, since my books apparently looked "shabby". I came home, and told mom about it, but she didn't believe me. I panicked, hid away and started crying. My dad wasn't at home (he was away on duty), and it was late, past the time all the shops closed when she found me crying my eyes out. She asked me what was wrong, and I told her. Then she did something I'll never forget. She found some plastic sheeting, which she cut, and folded to form covers for my books. The only stapler in the house was with my dad, who wasn't home, so she sewed the book covers in place with a needle and thread. She made sure I saw the books had a plastic cover before I went to bed, which was when I finally stopped crying.

Thanks, mom, I don't think I ever thanked you for that. And happy birthday! :-)