What high source output impedance meets uneven load impedance sounds like

This has been sitting on my desktop for a while so I uploaded it before deleting it.

I did do this with an MS-1 last time, but MS-1's impedance is fairly flat so there isn't much to be heard. This one is more extreme.

Klipsch X10 Xonar DX recorded vs original (original from 01m29s onwards).mp3 - MediaFire

A quick look at three laptop power adapters

So due to some circumstances, I have three laptop adapters, and a lapdesktop to power. Might as well see which is the most efficient.

Xonar DX output impedance

~86Ω @ ?V into 33Ω load
~108Ω @ 0.15V into 16Ω load

Update 23/03/12: I remeasured again with a 16Ω load @ -22.7dB into a 16Ω load and got 108Ω. I will try to remeasure when I get another 33Ω load working, but I'm expecting both figures to be correct. I'll post the possible explanation once I confirmed the numbers.

Well you don't have to read the rest of my blabbering, but if you want to,

Diminishing returns

"As with all audiophile products, diminishing return rule indeed..." - quoted from somewhere

But, there is another camp that believes the opposite - the higher you go, the more something affects.

How about the third camp -

It is possible to have both decreasing and increasing returns.

Because placebo effect doesn't care if you think the returns are increasing or decreasing - that is how you interpret the improvements... that don't exist.

[Review] Zalman Shenzhen Ice Dragon II (冰龙II) CH-90A-06 Heatsink

My sentiments too!

Too many cars in Singapore

I mean, look at how crowded this carpark is!

It's a black world

Black laptop bottom, black laptop sleeve, black phone, black PSP, black calculator, black camera pouch with a black camera inside, black wallet, black mouse, black keyboard, black pencil case, black cables, black power adapter, black speakers, black USB hub, black monitor base (the monitor itself is dark purple, well mostly black), even the memory cards at the bottom right are black.

Remember the time when everything was beige? Well now's the black age.

Why the basic CMoy's simple resister divider virtual ground is not a good idea

I was thinking about why the simple resister divider virtual ground in a simple CMoy is inferior to active solutions, say, an active rail-splitter or a buffered resister divider. The usual answer would be "drifting of the virtual ground voltage as the amplifier pushes current into the load", or (over)simply said, "uneven splitting".

But, how much?

I need to reconsider the practice of installing cables without using my eyes

This ability is acquirable through practice, from installing computers and televisions many times. With little working room available, being able to connect the cables after a glimpse of the connectors' positions is very useful.

But at the same time, this practice can be dangerous.

So I was connecting my speakers to one of my amplifiers. I saw the black connector of the cable was already in. So I took the red one, inserted it, then turned on the amp.

Nothing.

Random thought: Watching Ikoku Meiro no Croisée...

HOW CAN ANYONE HATE CHEESE???

I mean, I hate it for killing my arteries and for being overly-expensive, but if I were immortal and rich, I would add cheese onto everything.

Cheese between bread + ketchup makes for a quick and nice snack.

Oh, ketchup, the wonder condiment. The brands available in Southeast Asia are mostly nasty though. Including Maggi. Maggi ketchup sucks. Sinsin and Kimball are also nice, but I find myself going for Heinz most of the time for both tomato and chili sauces.

Sinsin's garlic chili (the one McDonald's uses) is also a winner and also easily found, but don't buy the bottle version if you don't use it often. Something happens when it is left for a while.

How to avoid buying fake or overpriced products

The audiophile market is filled with unscrupulous sellers, people who take something worth very little and sell it for a lot more than it should be.

This happens in some industries (not just audio) because it is very difficult to verify the product's performance. You can't tell if that that hair-growth formula really works, if that toothpaste really whitens, if that weight-loss pill is not poison, or if this exercise machine is not actually a... wtf.

A seller can simply take a mediocre component, relabel it as something that costs more, and sell it to unsuspecting buyers who are too (insert adjective here) to verify its authenticity. Or he can put a high price tag on a worthless design and sell it to unsuspecting buyers who are too (insert adjective here) to verify its performance. Or, the seller claims he "made improvements" to the original design and sells it for twice as much.

Fortunately, there is a way around this.

Amplifier output power vesus load impedance

Amplifiers have their own rated output powers. Typically consumer products only show one set of numbers, for example, 30W @ 8 ohm.

This often leads to confusion when speakers of impedances other than 8 ohm are used. Statements like: "4 (or 8) ohms gives more power", and "2 (or 16) ohms will spoil the amplifier".

The correct answer would be: it depends.

Understanding sarcasm

"Understanding the subtlety of this usage requires second-order interpretation of the speaker's intentions. This sophisticated understanding can be lacking in some people with certain forms of brain damage, dementia and autism, (although not always)^[11] and this perception has been located by MRI in the right parahippocampal gyrus.^[12][13]"

Sarcasm - Wikipedia, the free encyclopedia

Oh, k......?

ASUS Xonar Essence One Review

Class 4 SD

The Kingston is class-less, while the Sandisk is class 4.

A reminder that not having a rating or certification does not necessarily mean it is bad. OEM PSUs with >>80% efficiency and without 80Plus certification, speakers without THX certification.

I am so going to buy a car

[Flipside] The male protagonist's situation is troublesome

Many people write stories or play games to transform into the main character, someone that they wish they were.

Being chased after by a bunch of pretty girls.

And they (the male protagonist) always think it is troublesome.

Well, what if we apply reality check.

The typical real woman is not pretty.

The typical highschool girl may or may not be pretty, depending on which group you hang out with.

So what if you are being chased around by a bunch of ugly ones? This is more likely to happen.

Troublesome indeed.

Gaming ruins lives

I just had two full days worth of productivity wasted because I got a GTX 560. Two full days can mean a lot of progress.

But in GTX 560's defense, I completed Crysis 2.

Quote of the day: Audio snakeoils are like ghosts - they only come out if you believe in them, and they never appear when you want to show them to other people.

Compaq Presario Casing Review

Because reviews don't have to be always of the newest things that you can buy.

CaseFail

[Flipside Week] The internet as a source of truth

Did you enjoy the week of alternative opinions? Some of them are logical fallacies, many are incomplete truth such that if you know the entire picture, the current practices will be explained. It is all troll logic, so don't message me about your intellectual superiority.

But it gets you thinking. Why are some things done some way. It need not always follow logic, or more specifically, layman's logic. Common sense differs between people with different amounts of knowledge. What is logical to a child may not be logical to a scientist.

I decided to finish up the week with a big topic that affects all of us: the internet.

[Flipside Week] A government that keeps quarreling and gets nothing done is bad?

An argument against too much opposition in the government is that people will quarrel the whole day and get nothing done.

Taiwan and USA are cited as examples.

But, is getting nothing done bad?

[Flipside Week] People who get sexposed the most are the ones who get elected

[Flipside Week] Strong national currency is bad? Yea rite.

A strong currency is said to hurt the nation's competitiveness. The reason given is that the exports are now more expensive to other countries.

So there will be less demand for the nation's exports. So less jobs for the people.

Is that a bad thing?

[Flipside Week] Are you really being smart?

People in some jobs, some majors, we consider them smart.

But, are they really being smart?

[Flipside Week] Another view of what the Earth thinks about us

[Flipside Week] School exams grades are not useless for measuring the capabilities of employees

[Flipside Week] Being retrenched is good

Welcome to Flipside Week!

Flipside week is another of my themed weeks. This time, I will be looking at things from a different angle and giving interpretations that are opposite of the norm, yet still makes logical sense. This begs the question - by how much have our beliefs been shaped by the common view of others, instead of logic.

So here is the first one -

Truth hurts

That's why scams based on the target's beliefs work.

[Audio] Why good engineering never wins

Engineering is not just about building something - a monkey can do that

Building something that performs well.

And building the best while working within limits.

And cost is always one of the limits.

If a product of a specific performance is required, a well-designed product would be cheaper for the same performance.

Cheap parts can be used to achieve same or better performance than a design using expensive parts.

This translate to lower costs. And if the market is perfectly competitive, lower prices. Consumers are happy. Designers incapable of reducing the cost die off.

This is practiced almost everywhere.

But, when it comes to audiophile equipment, things can be different.

An amplifier with NE5532 and electrolytic caps for output, versus an amplifier with (insert discrete op-amp here) and PIO caps for output, which one would you think performs better?

Majority of fanatics would choose the latter.

Even though it may not be. Remember that engineering is about building the best for the least.

Or heck, say the two amps perform identically, but one uses cheaper parts through good design, the other uses a design from the 80's. The cheaper parts one is priced cheaper while the more expensive one is priced more expensive.

Which would people think performs better?

More expensive, more expensive parts, no doubt.

Even if the well-designed one is priced the same, people will look at it, and go for the more expensive-looking one. And then claim it is value-for-money because of the more expensive parts for the same price.

So a well-designed product is being penalized for being cost-effective.

And that is why people pay so much for wood.

Taiyo Yuden YUDEN000 T02 DVD+R: Surviving fine after five years

So my PC's soundcard is less noisy when the CPU is under load? - An investigation on computer activity and audio noise

A while back I discovered that my laptop's onboard audio's RMAA-measured performance was better when the CPU was under load. However I could not reproduce it on my desktop (it is still completely reproducible on the laptop) so I took it as a one-time affair and let it rest.

I was reminded of this topic again, with all those low-power CPUs, minimalistic OS builds, and SSDs, as well as linear power supplies and power filters for HDDs and fans running around. But this time, I can measure down to -120dB.

Repairing a Yamaha keyboard

So my family's keyboard had a few keys that didn't make sound when pressed. It is not a good keyboard in the first place (though it did accompany me or mostly my bro to various performances and competitions) and very old (>10 years), so I didn't want to repair it. But my mom was asking me to.

So on a free day, I took it apart to try my luck.

Whistling away at 600rpm...

Back to being silentpcreview.com-approved.

I had to do some things to the HD5670 to achieve this though:

 

HD5670, 92mm fan edition.

And then undervolt the HD5670 to 1.0V @ 700MHz. The HD4770 could do 0.9V @ 675MHz.

Quote of the day:

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." --Floyd Toole

NZXT Havik 140 CPU cooler - User review - Special pseudo-fanless edition

I never thought I would get my hands on an NZXT product. NZXT is famous for its chassis and case fans, typically aimed at the silent computing enthusiasts. I also am a silent computing enthusiast, but I never spend on expensive casings and fans. I have never spent on CPU heatsinks either since I got the Ninja in early 2006.

And it happened that I won a contest (or is it more of a lucky draw?) and got myself a NZXT Havik 140 CPU cooler. And being a number-hunter, I promptly proceeded to test it.

Muse M20 EX3 TA2021 amp - User review

Measurements

I finally got around to measuring this amp. And building the contraptions needed to measure amplifiers.

ATi/AMD AVIVO Video Converter - GPU "hardware-accelerated" encoder: June 2011 update

It is July, but I typed June, because I tested the June drivers and the July drivers were not out yet.

Random thought: Why is an extra op-amp in the chain always bad, but an extra (any of the 101 unrequired things you can put in a system) always good?

Two terms created this time while I was in the army:

All the F - the response to what the F, e.g. "WTF does this thing do?" "ATF."

Ohsnoesis - the movement of ohs noes from a region of higher concentration to a region of lower concentration

Quote of the day: "Be a messenger of truth, not a creator of lies"

Quote of the day: "The value of a product is inversely proportional to the amount of marketing speak you see on its webpage."

What you can get for SGD$50 nowadays

Nokia 1800. Got it for $50.

Getting the power indicator LED(s) working on Muse M20 EX3

At first I was cursing about how the Muse M20 EX3 does not have a power indicator LED. Turns out I was wrong.

There is, but it is so faint, it might as well don't be there.

I only noticed it because I saw a faint blue glow coming from the bottom side of the volume knob when the room is dark. In fact, even with the lights off, the light is so dim it cannot be captured on my camera.

So there is light behind the knob. So I pulled the knob out.

Four LEDs do the job of lighting up the blue glow.


But the light is blocked by the knob which is too fitting.

So pull the knob out until you get the amount of light you want.


How it should look like.

I don't know if this is a design flaw, problem during transport, or intentional. But easily adjustable power LED indicator is useful for me. You know how the newer monitors can set the power indicator light to off, so that you can enjoy the movie in total darkness?

Muse M20 EX3 TA2021 amp - a pictorial

Around the interwebs

"2) 1 pair Ultimate Bybee rca filters with 4 small Bybees slipstream purifiers. Connectors are Eichmann Silver bullet plugs. $300

These are meant to be connected to your interconnects, near the destination of your interconnect. For example, from your source to amp/preamp, then these are to be installed near your amp/preamp side.

The Ultimate version has a slipstream purifier on BOTH the signal AND ground connection. Excellent results o for digital audio data transmission (SPDIF from your DVD to your processor)."

I hate stories where there is only one lead guy and many girls

But, I like Anime adapted from Visual Novels because the stories are generally good. By that, I mean most of the Visual Novels (or text adventure games, some of them don't count as Visual Novel, but the idea... you get it) that get adapted into Anime have generally good stories, although exceptions do happen. (Because I can safely say that, for each good one that are 99 rubbishes in the industry) Note: Does not apply for Anime based on games like strategy, action, RPG, SRPG, ARPG, even if they have any amount of dating sim or sex inside. You already know the usual outcome for those. Disaster.

The good story generally outweighs the pimp-master setting, or actually in many games, it's really ultimately 1 guy 1 girl per story, just that there are many stories for the protagonist to choose. Or the ultimate style of needing to go through all or at least half of the stories to know what is going on. Think mystery/suspense adventure games, but I've seen this being used for romance stories, multiple times.

So when I see a romance story with multiple guys and multiple girls and multiple relationships, I get interested. Not the first time I've seen, and not limited to Visual Novels, but is still rare.

This may have something to do with some Anime that I may be giving my views on, because I think it is not getting the appreciation it deserves (as with every time I post my views on an Anime).

Random

Improve your ATi / AMD graphics card's video playback quality by DISABLING all the enhancements

It happened one day (a long time ago actually), I acquired Nanatsuiro Drop's DVD creditless opening video, so when I got home I played it on my main PC with a HD5670 and SyncMaster 913V.

What I saw, was a putrid mush of ****.

It should be noted, at that point in time, my 913V was not calibrated. But that only makes the problem even more obvious.

I've seen the TV version of that video so I know what it looks like. My experience from comparing different encodes tells me how some fluctuation in color is normal, due to different tuner and tuning settings (more an analogue problem than a digital one nowadays), different broadcasted and subsequently captured raws, encoder and filter colorspace issue, and any enhancement the encoder (person) wants to add.

But even if you haven't seen the original video before, you can tell which one looks the most and least s**tty -





Four photos, with AMD video enhancements on and off, and display calibration on and off, in various combinations. +5 brightness and +25 contrast added in Photoshop as a noobish attempt to compensate for camera color response.

I'd expect some fight between 2 and 4, but 4 is closer to the original video, and 2 looks worse when big (click for 800x600). Photo 4 is with display calibration on and video enhancements off. As you can see this screen is fairly inaccurate while uncalibrated (photo 3), it is one of the earliest 19-inchers and only has a VGA input.

With an uncalibrated screen and enhancements on by default, I was greeted with the oversaturated POS of photo 1.

Fortunately I already knew that ATi / AMD cards have video enhancements on by default all along, and that it only works with MPEG2 (now also H.264 and VC-1 as long as you are using DXVA), so for all the MPEG4 ASP and AVC videos it didn't have any effect so I ignored it. But this video is MPEG2.

Speaking of oversaturation, this is what can happen with enhancements on, at least with an uncalibrated screen -



You know something is wrong when dark hair turns from being a light absorber to a light emitter.

Enhancements can be good sometimes, but they can be very bad many other times. So it should be left off by default unless the user wants it. However this is not the case with consumer video products, where upscalers, more vibrant colors, sharper edges, and motion-enhancement-whatever flood the market.

Xonar DX RMAA

My new measurement card.

SGD$128 for this kind of performance. Some manufacturers should be ashamed.

The D2X is rated almost twice as good at twice the price. That is the card to go for if you have a bit extra moolah. For now, this is enough to help weed out the bad products.

List of the amplifier chips used in some studio monitor speakers - thoughts

List of the amplifier chips used in some studio monitor speakers

Pro-audio is one place I expect to find balance of component performance. Because with so many competitors as well as using measured numbers to reflect performance, it is about the best performance for the same money, at least on paper. And to do that, bottlenecks must be minimized, and the performance of each part matches the performance of the rest.

With so many gainclones being used, this makes me wonder about the performance of T-amps and such.

Gainclones aren't bad, in fact they perform very well for the price.

And that is actually the problem. Look at the number of LM3886 being used. And usually two of them are used for a bi-amp configuration.

And take a look at the amplifiers themselves:

(Source: Everywhere on the internet, I just visited webpages that were given to me by Google Image Search, if you demand credit or need it removed just inform me)

M-Audio BM5A


Mackie HR824

Yamaha HS80M

ESI nEar05

Tannoy Reveal 5A

Genelec 8050A

Behringer B2031A

I could go on forever, but you should get the idea already. Even if we ignore the complicated preamp section, looking at the power amp sections themselves, well they are not fancy with multi-colored components and "magic materials" or what the ****s, but they certainly are no slouch either. Well you can see some amps being bigger than others due to price differences of the speakers, and some amps more worth the money than others, but in general, a 2xLM3886 amp, complete with parts of those size, costs quite a bit already materials alone.

I don't expect cheap gainclone kits to do any better. Or even the same, those cheap kits using cheaper or fake chips and tiny capacitors.

And that is the problem. If pro-audio designers are using this quality of gainclones with their $300-1000 active speakers, then passives speakers in the $300-1000 range should demand even better amplifiers.

And Creative T20 Series II and T40 using TPA3123D2 and TDA8932 respectively tells more about the value of these amps.

Now I'm doubting that <$100 amps are sufficient.

Random thought: Hearing loss and frequency range

Since I was doing a frequency sweep might as well check my hearing.

Reliable detection - 18kHz. Don't know at how many dB down. Not bad considering my ailment. Might have dropped I dunno, I can't remember my 18kHz loudness from last time, and it can be due to equipment. (The Atom's 18kHz is rather high compared to the Diamond 8.2's)

Just to make sure I also did all the way till 14kHz in 1kHz intervals. I'll never understand how the ear interprets these high frequencies.

But one thing in common as I listened to all those tones.

They all sound like ****.

They are meant to be a screech alright. But the similarity...

That is when this struck me. A basic concept in music and acoustics that had escaped me. (Well because nobody mentions this during discussions involving hearing range, because hearing range translates into phallus size.)

The octave.

The ear differentiates tones by their relative differences.

An octave = doubling of frequency
A semitone - 1.059463 times frequency

So, if we take 15kHz as the reference,

A person with an over-perfect upper limit of 22.5kHz can hear 7 semitones higher, also equals to a fifth (e.g., C to G), or 1.5x frequency
+6 semitones = 21.2kHz
+5 = 20.0
+4 = 18.9
+3 = 17.8
+2 = 16.8
+1 = 15.9
0 = 15.0
-1 = 14.2
-2 = 13.4
-3 = 12.6
-4 = 11.9
-5 = 11.2
-6 = 10.6 = 1 octave lower than 21.2

So even if your hearing range has deteriorated until the seemingly bad 10.6kHz, you have only lost 1 octave compared to a small child.

And human hearing range has 20 to 20.5kHz = 11 octaves to start with.

So you would've lost 1 octave out of the original 11.

Big deal.

This argument supports the phenomenon that musicians and old listeners, although their hearing range could have deteriorated to below 10kHz, it is a relatively minor handicap and their experience more than makes up for it to make them better listeners.

(Note: This is partial bullsh!t. Yes the maths make sense, but you can try the effect of a high-pass filter via a parametric equalizer and cut the highs at different frequencies and see the result. It is not unnoticeable.)

Lord praise the guy who invented Li-ion

...Or we would still be using 3 NiMh cells and getting two hours of runtime out of hand-held gaming consoles.

Now if only someone can standardize the form-factor of Li-ion cells, may lord praise him too.

List of the amplifier chips used in some studio monitor speakers

Got this from here, now to make a copy before it disappears
http://toki.2ch.net/test/read.cgi/av/1245925463/l50

Alesis M1Active / M1Active 620 - LM3886 x2 - National Semiconductor
Behringer B2030A / B2031A - LM3886 x2
Dynaudio Acoustic BM5A / BM5A Compact - LM3886 x2
Fostex NF1A - LM3886 x2
Event - PS、TRシリーズ LM3886 x2 / ASP6 ASP8 (LM3886 x2) x2
ESI nEar05 eXperience - TDA2052 + ？？ - STMicro
Genelec 1029A - LM3886 x2
Genelec 1030A - STK4036V x2 - Sanyo
Genelec 1031A - STK4241V - Sanyo
Genelec 8030A - LM4780 - National Semiconductor
Genelec 8050A - STK442-130 - Sanyo
KRK V4 V6 V8 Series2 / VXT6 - LM3886 + ？？
KRK Rokit Powered RP5 RP6 RP8 - TDA7294(LF) + TDA2052(HF) - STMicro
M-Audio EX66 - TDA8927 (Class-D) - NXP
Roland DS-5 - LM3886 + ？？
SONY SMS-1P - UPC2505 - NEC
Tannoy Reveal 5A 6D - LM3886 x2
Yamaha HS50M HS80M - LM3886 x2
Yamaha MSP7 Studio - STK415-130A - Sanyo

Go gainclones.

Energy conservation

As I read this topic, cost savings and ROI keep coming up.

Use less electricity = lower electricity bill.

And if the whole world uses less electricity, demand goes down, price per unit goes down also, because it is cheaper to generate.

Right?

My ass.

Cost-based pricing is never used in the real world.

And if OPEC realizes they are selling less oil, they will simply increase the price instead so they earn the same amount of money.

And locally we have good examples too.

When oil prices increase, electricity and transport prices go up.

When oil prices drop back, electricity and transport prices go up, citing "other costs".

That's why you can't trust the system.

I just discovered I can tell the difference of 3cm of head positioning

I've been feeling that my left speaker's a bit louder than the right. Thinking it could be either due to room acoustic, supported by the fact that the perceived bass is stronger on the left even though the subwoofer is on the right, I ignored it.

Today I was thinking that the left/right volume can be altered by the positioning of the head, so I decided to shift my head towards the right to get the perfect balance. When I got the balance I want, I looked at my head's position...

...to find it right in the middle of the two satellites.

You see, due to some strange situation of my table, my monitor is placed 6cm closer to the left satellite than the right. And I always make sure my head is at the middle of the screen. Which resulted in my head being 3cm off the sweet spot.

But what's a concept without testing.

Test methodology

Music is played through the speakers. Subwoofer volume turned to zero to prevent it from influencing the balance. The room lighting and computer screen are turned off (it's night btw). Eyes remained closed throughout each test until each measurement is taken.

1. Stand up from the chair, pulling it a short distance away from the original position.
2. Walk a metre or two away and back, pulling back the chair and sitting down at a random position. The direction to face is decided by the chest feeling against the table edge (my table is fairly large enough to do this).
3. The positioning of the head is shifted left right forward backward while facing the same direction as much as possible as the center position is attempted to be found.
4. After deciding position of head, a torchlight, one end placed against the chin and the other end pointing at and close to the table is switched on. There is a piece of paper fixed onto the table and where the torchlight is pointing at (the brightest part at the center) is marked.
5. Repeat from step 1 for next measurement.

A total of 6 readings were taken with the speakers at the original positions untouched. Then the left speaker is shifted 6cm to the left such that the distance between each satellite and the screen is both approximately 9.5±0.5cm. (Originally the left speaker is approximately 3.5cm away) This results in the sweet spot shifting left by 3cm. Another set of 7 readings was taken.

The screen is 53cm wide, so the original distance between the speakers is 66cm while the new distance is 72cm - an increase of 9.1%. The speakers are approximately 65cm from the edge of the table. The resulting change in distance between speaker and "sweet spot" - taken to be the edge of the table, equidistance from each speaker, is 1.9%, and resulting increase in angle is 7.7%.

Results


The first set of readings are those directly above the horizontal line while that of the second set are indicated by a circle.

It is not a lot of readings and variance is fairly huge. However, two important observations - the average distance (from the left side of the paper) of each set of readings differed by approximately 3cm, while the differences between both maximums and both minimums are both 3.5cm. The difference between max and min values of each set is 4cm, resulting in a 0.5cm overlap.

Which means that it is fairly possible for the human ear(s) to detect changes in sound due to the sweet spot shifting by 3cm. 5cm would be a safe estimate.

Note that this little test does not reveal which position is the more accurate one, since there are other factors that affect balance of both channels - channel imbalance of equipment, room acoustics, hearing loss etc, but the main objective is to see if audible differences in perceived sound can result from small shifts in the positioning of the head relative to the speakers.

Granted, I used some sort of averaging technique to increase my precision - I shifted my head left and right to find the positions at which one channel is a certain degree louder than the other, and took the center. Like the way you tune the TV and focus the camera. But my head only moved by a few cm in the process (although it feels like a lot). This adds more weight to the idea that our hearing is precise to a few cm.

I'm not really surprised by the result - animals are able to pinpoint the location of predators and preys that are far away by just hearing, and some are even able to use them to navigate and eat prey. This would require even better precision. Way, way better. If I go and search I believe I would find better technical articles on the precision of human hearing.

This has implications on speaker positioning and how subjective listening tests are being carried out. I already know that some instruments in a particular song sound relatively louder and softer depending on the position and angle of my head, but having numbers puts things in perspective. We would need to be accurate to a few cm and a few degrees when positioning our speakers, and in subjective listening tests you may be hearing differences that are not actually there due to the head not being in the same position. And how many people actually make sure their heads are in the same position throughout the test? It also questions the credibility of auditions carried out simultaneously by a group of people, for no two heads can be in the same position at the same time, although subjective bias caused by the first guy to open his big mouth is more likely to cause everybody to "hear the same thing".

Looks like we may need, as it is jokingly mentioned on some forums, a vice clamp for our heads.

[Update] JDS Labs cMoyBB v2.03 OPA2604 measurements

I noticed some peculiarity with the OPA2604's distortion graph. This is a chip that is used in some high-end designs achieving lower than -100dB THD+N, so the graph I had wasn't reflective of its true performance. And I was checking this blog's stats on a hunch, and found many traffic sources from Google image search, with the search term OPA2604.

People may get the wrong idea reading that graph, so to reduce the amount of rubbish on the internet, I decided to do a retest with a 12V power adapter this time.

Results are shocking.


The EMU wasn't cooperative that day, and I was in a rush, so I didn't bother getting 0.001% THD. But this is good enough to show the previous measured performance of the OPA2604, which was shocking bad as >0.01%.

The first thing to notice is the numbers for THD dropped by an order of magnitude.


Now it measures okay. Most of the spikes are EMU's "noise floor" (for the lack of a better term that I know).

And yup, this is with 9V battery. So the issue wasn't insufficient voltage. This is an example of why control measurements are important, for if I had measured only 12V scenario, I would had gotten a different and wrong conclusion.

The main difference is the greatly-reduced even harmonics.

My guess for the cause? Is not going to be something groundbreaking - probably a bad contact.

Other graphs are similar, 12V and/or 33Ω load, so I won't go into that. Into 33Ω for both cases THD is 0.005+% but how much of it would be due the the EMU? Even-order harmonics did increase with current draw as with the case of OPA2132. Speaking of which, now I wonder how accurate are the measurements for OPA2132, particularly the 0.015% reading.

So here I declare the previous OPA2604 measurements invalid. Some others might also be questionable.

Boston Acoustics HPS 10HO subwoofer repair - Day 2

Day 2 start - got my fuses, lets go.

The symptoms on day 1 got me feeling that it is the power amp section that is spoilt. So I have to disconnect just the power amp section. A good way is via removing the rectifier. But before I do that, lets look at a strange thing I saw on day 1:


Yes, one leg of the rectifier is missing. In replacement a wire is soldered on half that leg and the solder pad on the underside of the board. Why would anyone do that is out of my comprehension.

This does hint of something wrong with this portion of the circuit, or maybe the rectifier. Unfortunately the rectifier measures fine out of circuit and unpowered, plus the humming when turned on (after the capacitors get their power before the fuse blew) indicates something wrong further downstream. There is also a previously unnoticed burn mark on one of the connector pins for the wire from the transformer, which further hints that the power amp section is the problematic part.

The 20W of my Goot iron really shows its inadequacy here, I am unable to desolder the bridge. Thick leads and traces conducted heat away too fast. I had to cut the legs off to remove the rectifier then desolder the remaining sections of the legs.



The right side of the board, the blue capacitors and the parts below it, is the power supply for the pre section. This tested working fine, and nothing blew up with the pre board connected either. Now I just need a way to tap the pre-out to ensure it is working, then I'll stuff an amp inside and finish it up. But this is enough for the day.

Bugger has 50VAC x 2, wooorr. But that is also a problem because I don't remember any chipamp that can handle ±70VDC. (Erm yes those big capacitors are 6800uF 80V)

God I want one

For some reason this lab also has many Audio Precision - the early 2700 series units. Many faulty ones - burning smell when power on - all lined up on the shelf.

Also has Neutrik audio analyzers. Just what does this lab do?

Juvenile

One day I heard lots of mynah chirping (as in a lot of the chirping, not mynahs). I looked to the source thinking it was another mynah fight. But no, all I saw was four mynahs standing close to each other. Two of them were slightly smaller than the other pair. Upon close look I realized they were juveniles.

They can already fly and are walking around pecking at things, but following close to their parent and chirping incessantly. Probably learning how to hunt.

On first look they can be easily mistaken for adult mynahs, since they can already fly and such. But they are not adult yet and probably still stay in the same nest as their parents. Isn't it the same for humans; some of us appear to have reached adulthood, but are missing one critical step to really becoming one. That includes NSFs, uni students, businessmen, investors, inventors and entrepreneurs - those who stay with their parents and throw their savings away via their businesses because they can't do real jobs.