Saturday, October 27, 2007

Feedforward Shunt Regulator again

I redid the Shunt Regulator again. One channel seem to "runaway" when switched on for a while. This caused some speaker cone movements even when no source is playing.

Measuring the incoming supply, the voltage between the two 10M45S, and the output voltage, it seems that only one of the chip is giving this problem. Looks like the small heatsinks are not enough to dissipate the heat, resulting in thermal runaway... i think this what it is called.

So, i did it using plain old point to point wiring on a spare heatsink that i have. This new version will be muncho mancho enough to take the heat, else nothing would. ;)

During testing, the voltage did not fluctuate much. No runaway this time. Cathode resistors measured spot on at around 2.98v. The 10M45S are sourcing around 10mA per chip as per specification. It's just that the 10% coffin resistors are not accurate enough to produce equi-voltage between L and R. I may have to measure for a pair that fits the bill.

Maybe I should start digging for my 2k2 vishay power resistor somewhere in my box...

Thursday, October 25, 2007

Mozzy Mozzy Bite Me!

I'm sure lots of people heard of the mosquito ring tone being used by teens in schools so that the teachers are none the wiser when their phones ring.

Well... i took the mozzy test just now... It's supposed to be at 17kHz. Try it here in mp3 format.

And let the result be out... I am 17kHz deaf.

Now tell me about those audiophiles that swear by the super tweeters... Are they crossing them too low?

And tell me that my Diatones do not reproduce highs... Well... it does not bother me if they start rolling off at 18kHz or so.

Bite me, but the mozzy ringtone just proved me right... that i do not need a speaker that goes from 20hz to 20kHz, nor super tweeters.

Saturday, October 13, 2007

John Broskie's B+ feedforward shunt regulator

i've actually got this board done up before i shifted. that must have been 3 or 4 weeks ago. i was even comtemplating putting it into my 5687 preamp the day before NoiSing07 so that i can demo the preamp with the regulator.

good thing that i did not... it took many attempts before i got it to work. most of the time, i burnt resistors as i forgot where the ground of the board is cos it was sooo long and i did not mark the board with symbols.

i also killed quite a couple of 10M45S chips. it seems that even though it is sourcing 10mA, heatsinks are still required on the chips.

it seems that the regulator added a sense of scale and resolution to my soundstage. it is easy to pick out details... very resolving. also, the bass seems to have benefitted by being more controlled and detailed. not quite sure how to put it, but i would say that this is worth the effort.

perhaps other HV regulator designs would produce the same effect?

the circuit is based on Jon's feedforward shunt regulator.

parts are swapped below as mentioned:
1. first dropping resistor after B+ as 1k2 10W instead of 309R
2. second dropping resistor after B+ as 2k2 10W instead of 614R
3. B+ is 290V, between dropping resistors is 228V and 136V (L channel)/140V (R channel)

Sunday, October 7, 2007

A trip to Chek Jawa

It was raining on and off. We left home when it stopped raining and the sun was out.

A boat ride from Changi Village to Pulau Ubin is $2 per person, regardless of age. Another $2 per bicycle.

Upon reaching Pulau Ubin, a van ride to Chek Jawa itself is $2 per person, regardless of age. It's a 10 minute ride. I am guessing a walk would take an hour odd because of terrain.

The van does not go all the way in. We have to continue on foot to the Chek Java Visitor Center, which is a less than 5 mins walk. We started the trail around Chek Jawa starting from the Forest boardwalk. This will lead us to the Coastal boardwalk, then to the Chek Jawa Visitor Center.

Some of the resident lifeforms were not spotted, but i guess not everyone spots everything at the first go. Heard from my wife that her friend did not see anything in the few times she was there.

I find the place a little over-hyped, but nonetheless, it is still a good idea to have a wild life preserve. At least Lucas's generation will have some nature to see when they are older.

Some pics here.

Tuesday, October 2, 2007

Poem for a lost child

We had a miscarriage 2 weeks ago. The operation was on 28th September.

My wife wrote a poem that moved me to some tears. I was in the middle of a partner hosted lunch when I saw it on my Blackberry.

I asked if she was ok, and if I should put in on my blog.

Here it is, something for us to remember her (she was sure it was a girl) by.

You Left

I knew it was you
I knew your name
I could feel your presence
Long before you came

I wanted to hold you tight
I wanted to keep you safe
Embrace you with love
Nurture you with faith

You did not stay
You did not wait
I did not know you left
Was I just too late?

So many questions unanswered
Appointment you had to keep?
Had you something real urgent?
That you left me here to weep?

Had I known, had I known
If only a farewell bade
I did not know you left
I was just too late