Time for another post on....MY AMP!

LOL... Righto so this is yet another post on my amp. Well after my amp has been completed and weeks of running in, i decided that something is missing in the sound. Compared to the previous amp that i DIYed, it lacked that musicality i would say. I don't get moved when i listen to this amp although the soundstage and details are alot more better. I thought that it could be my opamp that is different cause i used the AD826 i my previous amp and now im using OPA2134. They are in the different league in terms of pricing. The AD826 costs 9 bucks a piece and the OPA2134 costs 4 bucks a piece. Thats more than 2 times the price. I decided to go for OPA2134 this time around because of design constraints. I wanted my amp to have a high input impedance and by doing calculations, i had to use a opamp that had low input current which lead me to use the OPA2134. Okay so anw, i tried swapping the opamps but cannot la, my DC offset jump to over 20mV which i don't feel all right with. So decided to change back and instead do some biasing for the opamp. Yan recommended me to use LM317L to do the biasing as it "takes out the guess work and works much better than using discrete transistors and gates". So went to get the components from SLS and off i started soldering. Solder solder solder solder... and TADA!
Standing up on my circuit board. Point to point wiring. Art work.

So test was up next and boy was it disappointing. It distorted. Crap. Think think think, then suspect is my power supply to my opamp cause i had this circuit to limit the initial surge to the filter caps for the opamp. It actually also limit the maximum current. Removed it and YAY! good sound. Installed it for both sides and done. Did not listen to it but will do so tomorrow.

Teacher's Day

(: the new implementation works for ACFM (: So glad.

Righto, todays teachers day performance. I was on board and quite stressful la. Everything was quite smooth except for the transition from the normal performances to the band performances. For some stupid reason, until noe i still don't know, the setup for the bass guitar did not work well. So in the end Kee Ann and Zhong Xian decided to mic it up, which is a good move. Choir was not very good too because of the way the mics were aiming at. I could not do much on the board cause if i pushed the gaine even more, it will feed. Actually if u hear closely, it feed a few times but they are minor feeds. I think i pumped the volume a little too loud for dance? But how leh, dance always want loud loud music-_- Then the music of the dance start playing only ahh, Miss Tay SMS me tell me to lower the front left amp because the sound very sharp. I AGREE! The dancers told me to cut bass and boost treble?! hmm. But anw, i think MRC did quite a good job this time round ba. The emcees had a part to play too cause i was giving them commands to tell them when we are ready to go or not so a BIG thank you to them. Last but not least, THANK YOU STUDENTS COUCIL FOR ORGANISING TEACHER'S DAY!!

Bowling + ACFM

Okay its been very long since i last updated, so here is something.

Today we went bowling! Okay we includes vivian, kai yuan, jaymond, cynthia and me. Five people went to play bowling! Woah!... We started off with making the trip to the bowling alley. It was funny for us to be in such a rushing mode because of Vivian. She had to get back to school before 4.30 for her Chinese Orchestra. So we walked really quick and ran after a 196 bus-_-. Eventually we reached West Bowl and then started discussing about how many games to buy. We settled for 2 games each.

We started bowling and oh my, Jaymond is super pro! His highest being 140. I was just having fun with the first game and i think i scored terribly. All the random shots which totally required skills that are next to none. Vivian started off with a winning streak which had 2 strikes. (Notes: strikes in here mean this sign "-" and not "X") She was busy washing the gutters. Haha. She was laughing at herself too but then she soon became busy with sulking at herself la. But overall, she improved throughout the 2 games. In fact, she is the 4th one to get a strike cause i did not-_-. But hey! i managed to get a strike in my very last game.

Okay so bowling game came and went. Now on to ACFM.

For this week, the ACJC students council would be having ACFM where students can dedicate songs to their beloved teachers to thank them for their hardwork and effort in nurturing students into bright young talents. Main point. MRC had to support. They had this very odd request. The ACFM they wanted was very different from the previous ACFMs as they wanted the sound to come out from the hall and outdoor system. This would mean that they are not using the school's horns. Crap. More work for us. Even Mrs Sharon Loh made that comment. We had to find a solution to channeling the audio feed into the hall system as it was non existent. I thought of one and decided to go ahead with it. It used speakon cables as it seems that that is the only cable that is long enough to travel from the hall to the lobby. I soldered this speakon to XLR converter and on Firday, Kang De, Kee Ann and me started to lay the long speakon cable. We flew the cable from the third floor and let it down to the first floor all the way to the concourse. From the third floor, the cable entered the side door and went all the way into the cage. The length required was very long that we had to get another speakon cable to extend the 1st speakon cable0_0. So all was laid and we decided to do a test first before we duct tape everything down.

The source was a creative mp3 player. AMAZINGLY, the sound was just super clean and clear. I was rather surprised to hear such clean sound as i did not expect that. I was expecting to hear some buzzing sound because speakons are not balanced cables which means that they are more prone to noise pickup. But anw it worked. So we started to duct tape everything down.

So this week came and we have to support ACFM everyday for this whole week. First day no major problem. The transmission was quite okay except that there was some buzzing sound which was not really loud. Second day, MAJOR buzzing sound. So major that i had to rethink about how i transmit the signal. Well i thought of it and im going to try it out tomorrow to see if will it work. So wish me luck for tmmrs new implementation.

Stupid Actions

Today i did something stupid. Very stupid.

It started of with me walking with Joe to the MRT. Then we got onto the MRT. Then in the MRT, somehow we started talking about chinese teacher. He mentioned about his chinese teacher who used to be a reporter for Mediacorp News. Then i was like who? He replied saying that it was the one who was the chief invigilator for the chinese mock exam. Then i went. OHH!!! THAT ONE WHO ALWAYS DID THIS ACTION AHH? And stupidly, i did the vulgar hand signal which means no d***. ZZZ. The people around me were like trying to walk away from me after that la. Crap, so embarassing.

A trip to City Harvest Church

Yesterday, i had a chance to visit City Harvest Church. Mr Foo said i could go there and see him operate the board during their services so i decided to just go take a look. I reached quite early so i entered the hall like halfway through a service. The service was for children i guess? Cause everyone there were pretty young.

The place is quite impressive and the main hall is situated underground. I went into the hall and first thing i saw was the BIG LED screen. Yes they don't use projectors, they use LED screens. Then i saw the board in the middle of the hall so i went to it. Met Mr Foo there and started to admire at the equipments. The board was a 48 channel, Series Five Spirit mixer by Soundcraft. Its quite old already. The previous mixer that was in this position was a MIDAS Heritage 3000 but it got shifted over to Singapore Expo Hall. Still i had a wonderful time at just looking at the equipments. The speakers were those hanging from the ceiling array speakers. I felt that the volume was very loud cause i could feel my ear drums ringing after the first service. Clearly not very good for the ears. The board was around 3 metres long? Not very sure but im very sure that i must run from one end to the other to control it. They confirgured it such that one side was for the singers and one side is for the band. Mr Foo was on board and he did it himself. The impressive thing was the amplifiers they used. From the mixing desk, i could not see any amplifier cause the amps were in a different room. So if it was in a different room, how am i going to control it? There is this computer at the side of the mixer and a software was running. Then i realised that that software actually controls the amps! You could adjust the gain the volume from it and everything is connected through fibre optics.

So after the first service, Mr Foo took me around the whole hall to show me all the equipments. I went to the amp room and it looked like a server room to me with all the racks and stuff. Then he brought me to the light room which was super cold. Then he showed me the subwoofers which are like hidden. Then we went to their "own" room and before we entered that room, I saw another mixer as big as the main mixer in the centre of the hall. It was used JUST for controlling all the stage minitors! It was another Spirit Mixer but it was much older than the main mixer. It was a Spirit Viena. Not just that, beside it was a MIDAS Venice mixer to accompany it. Below that mixer was all their wireless mics receiver. Awesome stuff.

Their setup would sure cost ALOT. Everyt channel in use had a compressor and a gate. Thats like 0_0. Wah if only my school had such equipments......

scared

Scared. A word that that describes fear. I felt it. Today.

During chemistry tutorial, it was suddenly jolted into my brain that this term is going to be over. Promos is just 45 days away and im still struggling away with my maths and physics. Somebody save me! The kind of fear that got into me, is really something that i do not want to feel. So fast the june holidays ended. So fast the term is going to be over. So fast will the promos end. And eventually it will be, so fast did my college days end.

I just cant believe it. I better start studying.

One ACS National Day

Today, all 6 schools of the ACS family gather at Queenstown stadium to celebrate One ACS National Day. Well other people may have found it boring but i found it fun. Not because of the parade by itself but more of because i was doing Roving DV on it. All of the Roving DV crew were suppose to meet at 6.30am and i made it there at 6.05am. I even went to school at around 5.50am to get extension cord. BUT holy crap, everyone reached at 7. -_-. 7 leh! omg thats like 30 mins late la.

So anw, started to take videos. We had on hand 2 cameras so we took almost anything we could see. Kellop (is this how u spell it?), Geraldine's cousin was our reporter. So we started off trying to record an intro, which was almost impossible because of the super duper loud speakers behind us but we eventually manage to get the timing right.

Then we interviewed our GOH. He was very friendly and answered our question with very elaborated details. Well he was once an ACS boy too (: So after the interview, we had to take a wrap up shot. We took like 4 shots before we got it right. Quite fun i would say but i won't want to do the script.

My New Amp!

All righty, my new amp is up and running. Whats left is just some fine tunning. So here are some pictures for you:



Pretty Blue Light







Cause im on a budget, i had to recycle parts from my old amp



Last shot of it before it is disected :(



So this is what i took out to recycle. Reconditioned it and its ready to be used again.



Getting everything ready to do a mock up with everything inside.



Got those ellen key screws to hold everything in place.



Bare back.



Started soldering all the wires together. Its hell of a mess...Like my hair!



Messy right?!











The largest and smallest heatsink i used in this amp.







Then came the time to spray my casing. I had to sand everything before i could spray. Luckily, i had this adapter thing to sand for the drill and it really helped alot!



Managed to sand it till it reflected evenly but its not very shiny.



The power of aluminium dust...!



Then the spraying started off. I had to do it at the condo's staircase shaft so that no one could smell the smell of spray paint.



Sprayed a total of 3 coats of paint and i think it looks quite nice (:







Final product without the top cover.



And my workspace (Bedroom)



Really learned alot this time round from my father and the people online. Want to really thank my father for being so surpportive this time round. I was seriously shocked when he was so supportive of it but really, he teached me alot of things that i don't think normal schools would teach. So thanks to all those who helped and suggested idea for my project!

away?

You may be wondering where have i been after that random post? Well im just here and there and everywhere? haha. Nah, i have been bust with my amp and im so excited cause i can predict that if nothing goes wrong, it will be ready by tonight! I have loads of pictures which i would really wish to show, but due to time constraint, its hard. So look out for the space above this post to see my new amp :P

random

This shall be a rather random post. Here goes.

I am pretty sure that many of us have heard before of the story about a 1/4 filled water bottle and the many different ways in which a person can look at it. One such way is that you can think of the bottle as " Hey there is 1/4 of water in the bootle! Thats great!" and alternatively you can think of it as "Oh dear, something is not right cause 3/4 of the bottle is not filled!". It really depends on how you want to think of it and how you want to accept it.

Well, many a times this story is used to encourage people to look on the bright side of things and its not really the end but ever thought of "you" being the one trying to tell the story, know of this story and truly follow it yourself? We keep telling such stories to friends and such, but when it comes down to performance indicators, do we ever see that the 1/4 of the bottle is filled? I am rather sure that most of the time, most, but not all, of us only can see that the 3/4 of the bottle is empty , little will we realise that there is actually this 1/4 of the bottle being filled. In fact, I feel that demands and expectation actually minimises the 1/4 such that it almost appear negligible to oneself. Isn't it such an irony for such a story which is suppose to be encouraging to not be accpeted in the eye of the performance analyser?

Amp Update

Today i went to my father's office to build the chasis for my amp. Since a picture speaks a thousand words, i shall just use pictures (:
My present, wraped in newspaper. Hmm, whats inside the wrapping paper. Aluminium sheets! Precut somemore... (okay that sounds lame)

Mock up of the whole thing. Shall eventually spray it black.

Then we began drilling 15mm deep holes using the bench press.Look at that! So long!

For the tapping part, we used a portable drill, set it to low speed and tap.

Thats about all for today. Only managed to do the tapping for the top and bottom of the heatsinks, the front and back have to wait till later. It sure is hell lot of work!

MRC handover day

Today was MRC handover day. The new comittee members are as follow:

President: Kang De
Vice President: Zhen Ning (yar thats me)
Secretary: Zhong Xian
Treasurer: Shermaine
Quarter Comittee: Colin, Xiang Jun, Joe, Kee Ann

So there it is. I felt rather sad that the seniors are leaving us. All seems just so fast. Well, have to accept it ba.

Together, this new comm shall lead MRC to great success!

Council Investiture 2007

Great work they got there. Very very grand in my honest opinion. I was up there in the cage on the mixer. Stress level not as high as before, like chinese new year which i totally screwed up. But anyway, the whole investiture was quite well done except for the start where the cue was given to play the music and i played but then the council people didn't walk out. A few seconds later, we had a council rush into the cage telling us the people haven even reach the door!! Okay okay, i faded out the music and then Miss Annie came out and repeated "I present to you, the student councillors. Again." It was really quite funny but then all went on quite smooth after that.

I was rather touched by maggie's speach. Not just because of she thanking us MRC but it was an overall thing. The way she phrased everything and stuff, was just meant to touch peeple. The first CCA she thanked was MRC, and indeed it touched me to know that someone out there actually still knows that we are always around, suporting various events "secretly".

Through this investiture, i learned that council is quite a fun thing. I stayed on for their recession and really saw the other side of council. They were actually giving out presents to teachers and councils. The councils first gave the 5 teacher in charge presents and they were very very creative presents in my opinion. There was one for this teacher called: eeker tanial?! Don't really know how to spell it but its pronounced it this way. So the first present was this card showing a new kind of evolution from ET to 一个大牛 to Tuna. I couldn't really get the tuna part but it was just funny la. So after that card, the council people gave him a back massager with a cow head soft toy on its tip. Then came the fun part. He was given 2 custom shirt. The first one was a white shirt with the words, 一个大(a cow head). The next T-shirt was one with the words tuna. But it was designed to look like the Puma style. So instead of the words Puma, it was replaced with the words TUNA and instead of a leopard, it was replaced with a flying tuna -_-. Quite lame but it was hilarious!

Ahh its just so sad that half a year has gone and various CCA leaders are stepping down already. What have i done this half year? I don't really know. Its like i just closed my eyes and half a year is gone.

Oh ya. From council investiture, i learned one thing too! Old teacher does not necessarily mean naggy. Trust me on that. I learned that FIRST HAND. Haha!

Amp Update

Righto. Reached home at like 8+, then took a shower and started working on my amp before dinner came. What i had to do was to remove the parallel resistor so that i would have a effective resistance of 1.2Ohms along the output stage in order to decrease my bias current
Instead of 2 resistors, now there is only one. so its 1.2ohms

Each channel has its own heatsink.

Everything needed to run the whole thing.

Now some maths. With voltage of 0.739V and a resistor of 1.2Ohm, we have:

0.739=(I)(1.2)
I=0.616A
Power that is continuously dissipated.
P=VI
P=(32)(0.616)
P=~20watts

Thats alot of heat considering im not using it to cook anything. It works already and there is sound. I would really wish to borrow my father's office oscilloscope and check for oscillations here and there. But anw, theres sound already. I have yet to do a proper listening test so cant really comment on the sound. Must wait till it gets fitted into a box, which will be my aluminium casing (:

Jia Qian's Mum

She passed away, while giving birth to twins. Its really a sad case. Her mother went under the operating knife to deliver the twins but after the operation, she could not stop bleeding. Her wound was oozing with blood that could not clot. The hospital, R*ff*e* hospital, told them that they could not give her anymore blood because they have already hit the quota and their blood supply is running low. Indeed she was given 20packets of blood which is 10 litres of blood. Thats alot. The family made a agreement with the doctors there that if they found people to donate blood, the hospital would release more blood. So the next day many of us received smses asking us for help. Most of us went to help, i wanted to but i could not because i just donated my blood not long ago. The blood bank had more blood but after that, im unsure of what happened. I suppose she got more blood. I heard that her mum was in stable condition soon after but the next day, she passed away.

The newspapers reported on this and its a very hot news now. Sadly and annoyingly, the hospital is actually claiming that they were willing to provide as much blood as they could to her mother. It is just super annoying. Shying away from responsibility? It has not been the first time i seen such cases already. Last year, my grandma passed away also under the surgeons knife. She was admitted to the hospital just to undergo a simple surgery to change her broken bone to an artificial one. The chance of survival as claimed by the doctor was 90%. 90% mind you. My cousin, who was a doctor too, encouraged my grandma to undergo this operation. Who knew what happened? The incision was made, and immediately, my grandma went into cardiac arrest. She had a heart attack in the middle of the operation? I don't know. But what i knew was that when my uncles and parents probed the hospital for the reason behind my grandma's death, they were wishy washy and very very inefficient. Excuses were that the doctors was on leave. Very "efficient" i must say.

I feel very sorry for Jia Qian and her family. Just hope that her father will stay strong. Not easy to bring up 4 children now. Pray that they would not meet with any big problems. To end it off, i will quote what her father said

"Does Saving A Life Require Approval?"

Chinese Orals

Gone. Screwed. Quite badly done im my opinion. I had difficulty reading the passage and smoked through 4-5 words. Confirm the examiners would have picked it out. Then came conversation. The question was something like: Nowadays there are alot of people posting their photos online to share, do you think this hould be encouraged? And i went: yes it should be encouraged but there are the negative sides of it too. Did i answer the question?!?! hmm. Then i only said like a few points and started err err erring until the examiner could not take my errs anymore and said: you have said quite alot already so let me ask you another question. Dead. Towards the end, i was very nervous already and it was pretty obvious that the examiner wanted me to be gone. Okay dead.

0_0?!

Wat the! Another cap went kaput again! But then this time i was pretty darn sure i did not wire it wrongly! I guessed that it was a surge problem cause my cap bank is like 30000uF which draws a very very high current momentarily when just turned on. I suspect it could be due to that problem and then somewhat confirmed it after hearing from my dad that Tantalum caps cant really withstand surges in power.

This time the blowing up was even more POWERFUL! I was wiring everything up on my second channel and decided to turn it up after checking the wiring. So i turned the power on and POP! Saw a damn big spark and then saw the cap actually shoot out of the circuit board?! So scary la! Very lucky again cause i wasn't sitting in the "firing range". I think im going to change all the tantalum caps on my circuit to either ceramic caps or just use the electrolytic cap la.

A trip to my father's office

After countless tries of drilling with a simple hand drill, i decided that the quality sucks big time and decided to ask for my father's help. He was really open about me building another amp this time round:)

I was super excited cause i got to use this machine:
Its a heck of a drilling machine and the good thing is, its precise. I was rather surprised when i got to know of the price tag of this machine, around 100+. Wah such a precise machine and it costs less than a Black and Decker hand drill?! WOOTS!

Pop goes the capacitor!

Yikes! So scary! I hooked everything up to a speaker and turned it on. It seemed normal but then there was no sound although there was an incoming source. So i thought that it was just a matter of loose connection but upon checking it wasn't. The thing was powered down and i checked for problems. Then i realised something. Something very very very strange that i could not explain initially but after consulting the simulator i managed to figure it out. I actually soldered the +ve supply for the opamp to ground. So it effectively was a short circuit. That explains why there was this pop sound when i first powered up the whole circuit. What puzzles me is that how come even with the +ve side missing, due to the short, why can it still bias itself right? Quite strange

But anyway, the scary thing was this. I happily resoldered back the +ve supply to the opamp's +ve input and turned that thing on again. "PIACK" and black smoke arose. WTF HAPPENED?!?!?!

I was stunned to see that but quickly switched off the whole thing and waited for the large caps to discharge. Honestly speaking, i was pretty lucky cause i took safety precaution before turning it on if not that cap would have exploded in front of me! I went to the look at the circuit board and guess what i saw? This ---->

Looks allright right?

Hmm whats that line along the side of this cap?WTF!The black marks are the results of the cap blowing with great velocity.

Im seriously not sure what happened. Its a tantalum cap and it is a polar cap. Im pretty sure that i did not connect it wrongly. So what happened?

Its Alive!

Yes my amp is alive! This morning i worked on the power supply and after lunch, i decided to connect it all up! Yay it works! Haha but at the start i connected one wire wrongly. Its the Base and Emitter of the transistor that i connected wrongly and i just swapped them around and there was magic! Here are some pictures:

Power supply in the making. Cap bank of 30000uF per rail. +/-16V, full wave DC rectification.Mounted the amp onto the heatsink

Connected everything up togetherTurned it on and it works after repairing one fault.

Now time for some maths. As you can see, the multimeter is reading 734mV. So in other words its 0.734V. The yellow and green crocodile clips are measuring the potential difference between this 0.6Ohm resistor.

V=IR

0.734V = (I)(0.6Ohm)

I = 1.22A

Thats a reasonable quiescent current. But after letting it idle for awhile, its current quiescent current is around 1.21A which is still a reasonable value. Most probably i would bias it even higher to around 1.5A cause my heatsink is like damn big and now the heat emiting from it is quite low.

Now gonna hook a speaker to it and have a listen. See ya!