Random thought of the day

Analogies - for people who can't understand the actual thing

Random thought: Rephrasing

You have a device running on 115V.

When you use it with a step-down transformer, you worry about the negative impact of the step-down transformer.

But when you use it with an isolation transformer that also does 230V -> 115V, you start hearing the improvements.

Note that some step-down transformers are autotransformers which do not offer isolation. However the step-down transformer inside your consumer equipment is almost always isolated.

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.

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.

[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 -

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?

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."

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.

Random thought: Amplifier output power ratings, 4Ω vs 8Ω

Typing the Ω symbol reminded me that I have a lab report to complete. It's week 9 yet I feel like zero hour.

Many if not most amplifiers specify max output power ratings at 4Ω or 6Ω for those that cannot handle the high current, rarely 8Ω. Amplifiers and limited by both the voltage their power supplies provide and the current their output stage can put out. However, in marketing speak amplifiers are always be able to source or sink 1000A of current for a nanosecond. Hence current is not a problem and output power is limited by voltage instead. Since V²/R, the smaller the R, the bigger the power.

Hence the Tripath TP2050 power stage chip is a peculiarity. It is highly current-limited such that it is rated at 8Ω in the datasheet (although it is also mentioned that the minimum it can go is 6Ω).

However, there is something interesting about this chip - in stereo mode, it is a pair of bridged amplifiers. Change some resistors and switch it to mono mode, the two bridged outputs combine together to form a 100W into 4Ω amp that is capable of twice the current. Hooray for FET output stage. These numbers also suggest that the max power into 8Ω in this mode is still 50W, but hey extra headroom is always nice.

Now, this thing has my interest because some completed product amp manufacturers misuse those numbers, dunno if it is by their marketing department, or a careless designer. 100W and 50W output powers were quoted with different combinations of number of amp chips and load impedance. You can see that some combinations don't work.

Official specs for this chip is 50W into 8Ω in stereo mode and 100Ω into 4Ω in mono mode. But nothing was mentioned about power into 4Ω in stereo mode.

So a few calculations using Ohm's Law later,

Current limited = fixed current = power proportional to resistance = half of power into 8Ω = 25W

Well, that is veryyyyyyyy small compared to 50W.

For a few seconds it didn't make sense, until I remember the other form of the formula P = I²R. In paralleled mode it has twice the current capacity. Hence four times the power.

Well, the amount of thinking that was carried out would take just a few seconds, but this reminded me that a good amplifier should never be current-limited. And amplifier power ratings are screwed up.

What's the difference between a programmer and a manga artist?

The manga artist chose to torture himself for fun and pride.