Fake audiophile opamps: OPA627 (AD744?)

http://zeptobars.ru/en/read/OPA627-AD744-real-vs-fake-china-ebay

by atomlib • 12 years ago

149 67 12 years ago

joosters2• 12 years ago

If you can't tell the difference without dissolving the chip in acid... perhaps then there is no difference?

atomlib2• 12 years ago

According to the blog post fake opamp has higher noise levels and higher offset voltage. But I would love to see it tested on audiophiles, I'm sure they can't hear the difference.

gcommer• 12 years ago

From the article:

On the other hand AD744 has higher noise (3x) and higher offset voltage (0.5mV vs 0.1mV).

joosters2• 12 years ago

I was being facetious; but my point was that for audiophiles, you shouldn't need to be disassembling components in order to tell the difference between systems.

Sure, if you can notice a difference, then go ahead and track down where it is coming from. But if you start from the wrong end (i.e. the 'AD744 has higher noise and higher offset voltage') then you should stop and question your actions, IMO.

analog31• 12 years ago

The difference in noise is readily measurable. I've done op amp based design for commercial products, including an audio product for my side business. (n.b., it's not targeted at the "audiophile" market). I've measured the noise of dozens of op amp types for a specialized application. Impressively, the measured noise performance typically doesn't stray very far from datasheet values. You can measure it with a few dollars worth of parts, and the audio input of your PC.

Now, it's not a slam dunk that every application should use the quietest chip. Noise trades against some other factors such as current consumption. And of course from an engineering standpoint, cost matters too.

josh-wrale• 12 years ago

Small parts in complex systems may make drastic outcomes (e.g. Heartbleed bug). In many cases there are so many small components that perceiving such a "difference" is a non-trivial task. Thus, not being able to identify from whence the difference sprang in the context of a complete circuit does not entail a lack of any difference. tl:dr: Difference is difference: a tautology; or rather: no difference != difference

icegreentea• 12 years ago

Remember that these aren't made -for- audiophiles. Audiophiles might like using these, but they are used for other uses where it would matter.

stinos2• 12 years ago

exactly. We use them e.g. for amplifying signals where low noise matters. Never compared against the AD device but did compare them once against your standard 741 and the difference is obvious, eben simply by looking at the signal on an oscilloscope.

Serow225• 12 years ago

Exactly, I believe they were designed for instrumentation amplifier duty, hence the wide bandwidth and low noise.

nate_meurer• 12 years ago

stinos and Serow225, I accidentally downvoted your comments. Sorry, I need to abstain from HN when I haven't had enough sleep.

If someone would upvote these comments to compensate for my carelessness, I would be much obliged.

vonmoltke• 12 years ago

In addition to what has already been stated, components have additional concerns about environmental tolerance and long-term reliability. If two chips test the same on a test bench, that just means there is no difference at this point in time and under the conditions of the test bench. It says nothing about vibration susceptibility, moisture susceptibility, EMI susceptibility, ESD sensitivity, operational and non-operational temperature ranges, or a host of other factors that affect reliability and manufacturability.

HeyLaughingBoy• 12 years ago

Exactly this. There are many cheap (I mean cheap, not merely inexpensive) versions of "industrial" electronics on eBay. Most of them will probably work just fine in an office environment at room temperature. But put them in a factory where the temperature near the doors in winter can be below freezing and up near the roof in the middle of summer it's well over 100F, then your cheap eBay-purchased sequencing timer starts having hiccups, dumping hot asphalt on the floor.

thrownaway24244• 12 years ago

The interesting thing here is that the part has been substituted with another part that's comparable in quality and only slightly less expensive. The margins for counterfeiting this part can't have been very good.

It's pretty common to counterfeit electronic parts. I've come across counterfeit op-amps, exotic transistors, power transistors, ordinary transistors, capacitors, and even fake resistors which is amazing. It always just makes me wonder what is wrong, collectively and institutionally, with China? Making counterfeit goods of all kinds is apparently a common line of business in China. Is it just because _everything_ is made there so counterfeiting has proportionately shifted there as well?

mschuster91• 12 years ago

Fake resistors? How is one supposed to fake a resistor? There are no manufacturer markings on them, just (easily testable) resistance/precision indicators...

midas007• 12 years ago

In China, pulling a fast one is de rigueur.

So it might be just a typical business "f u, because we can."

hammock2• 12 years ago

The margins for counterfeiting this part can't have been very good.

Unless they were stolen, and repackaged in order to hide their origin. Like a chop shop, only no chopping

kaptain• 12 years ago

While most of the discussion here is technical from engineering and business perspectives, your question digs more at the root of the problem: this is a cultural and institutional problem.

I live in China: people pinch pennies (or mao) here without taking into account the overall cost. This is why you have a large market for imported goods; even amongst the most nationalistic Chinese consumer, there is an assumption that imported goods are better because domestic products are made by cutting corners.

There's a strong suspicion of things that are priced cheaply but, bizarrely, people still buy cheap goods but are resigned to the product failing rather quickly. This just doesn't apply to electronics, but also to clothes, vehicles, etc.

There's a very strong tension between value-pricing and product quality. That is, there is a demand low prices but assume that the product quality is poor. On the other side of the spectrum there is a demand for high-quality "luxury" goods too. Thus pricing your product too low, even though it may be a quality product, basically indicates that it is a low-quality product.

Part of the myopia here is that people will cut corners without figuring out the benefit/risk ratio. That is, is it worth losing a contract to improve your bottom-line by a negligible percentage? Culturally (and I'm speaking in a broad generalization here) there's a desire to "win" at a contract... to make the contract be better for yourself than what's on paper. So even if the contract spells out your profit margin, it's a matter of pride to be able to improve on it (aka, "sticking it to the man"). With China's large population and widening gap between rich and everyone else, there's a perception that you have to get rich or die trying; no one else is going to help you... certainly not the government.

China's future could be a lot brighter than it is; the problems aren't technical.

fnordfnordfnord2• 12 years ago

Obviously someone noticed a problem. It was confirmed by looking directly at the silicon.

marcosdumay2• 12 years ago

He didn't test it. He suspect the chips were fake because of the price.

That said, the very small difference is very important on laboratory applications. It's completely irrelevant for audio.

natejenkins2• 12 years ago

Can someone point out where are the laser trimmed resistors in the photos, and maybe explain some more of the components?

atomlib2• 12 years ago

Here is image Mikhail Svarichevsky (author of that blog post) posted as answer to this question in comments on Habrahabr http://i.imgur.com/vC5VkH0.jpg

ableal2• 12 years ago

The trimmed resistors are the four brown rectangles with notches (one is shown in atomlib's pic).

The silvery surfaces are aluminum - seems a single layer of metal process. Some large plates may be capacitors.

In analog circuits, MOS transistors are often fairly big, to carry larger currents, sometimes in the tens or hundreds of milliamps. There are a few such large devices, where you can see an interdigitated structure: think two hands open flat with the fingers interpenetrating but not touching. One hand is the MOS source terminal, the other is the drain terminal, the space between is the gate that controls current flow in the channel between the two first terminals.

(Layout diagram picture: http://pages.cs.wisc.edu/~butts/icons/ex2.gif - blue is metal drain and source, red is poly gate, green squares are contacts to silicon below.)

cc_• 12 years ago

If you're interested in this sort of thing, there is a great class at RPI which has its lecture slides available:

http://security.cs.rpi.edu/courses/hwre-spring2014/

The slides for lecture 4 (http://security.cs.rpi.edu/courses/hwre-spring2014/Lecture4_...) shows what various types of components (such as laser-trimmed resistors) look like on a die.

natejenkins2• 12 years ago

I am and this looks awesome. Thank you!

morcheeba• 12 years ago

Here: http://i.imgur.com/Fk5f69k.jpg

You can see the laser has cut the resistive material, increasing the resistance.

darksim905• 12 years ago

How do they get such high resolution? An electron microscope or something? Such a cool blog, I've seen it featured on HaD a few times.

rdl• 12 years ago

Decent optical microscope is more than adequate for photos like that; electron microscope is for gate-level.

Zac Brown and Adam Laurie are doing awesome stuff (with cheap equipment, relatively) in chip teardowns; basically the stuff Chris Tarnovsky (flylogic, now ioactive) does with $5mm stuff, they do 90% with $5-10k.

ableal2• 12 years ago

Analog circuits are fairly big, this is taken with a regular microscope. You can see that the chip is a few millimeters square.

Besides, electron microscope pictures are monochromatic.

BarsMonster• 12 years ago

This is optical microscope with 5mp digital camera. Multiple shots (from 4 to 800 for large chips) are stitched in 1 big panorama.

njharman• 12 years ago

til; that resistors are trimmed with lasers http://en.wikipedia.org/wiki/Laser_trimming

Terr_• 12 years ago

They also may use lasers to trim and tune the mostly-crystal oscillators used in timing circuits, such as the small quartz "tuning fork" found in many digital watches.

http://en.wikipedia.org/wiki/File:Inside_QuartzCrystal-Tunin...

leephillips3• 12 years ago

Counterfeiting of chips is such a big problem that the US DARPA has a major program to develop tiny cryptographic chips that can be embedded inside chip packages to prove their authenticity. It's called the SHIELD program (solicitation number DARPA-BAA-14-16 if you want to ask for money).

AJ007• 12 years ago

Its not just counterfeiting that is a problem, but also recycling. Real product, but used: http://spectrum.ieee.org/semiconductors/processors/the-hidde...

wyager• 12 years ago

the US DARPA has a major program to develop tiny cryptographic chips that can be embedded inside chip packages

Seems legit.

http://www-rohan.sdsu.edu/faculty/vinge/hotchips/security.ht...

logicallee• 12 years ago

I wouldn't have believed that wasn't a cover story 5 years ago - today?

malandrew• 12 years ago

I'm not an EE, but I imagine that a much better solution would be a universal device where you can connect a chip and run a publicly available test suite against the chip to confirm that is performs as expected.

Like @wyager, I'm extremely skeptical of a program like SHIELD.

leephillips3• 12 years ago

They think that the embedded chip (which they call a dielet), which responds to a crytographic challenge from a handheld device on an assembly line, can avoid testing, which is much more time consuming and complicated. To test, you need to connect the device's pins to something and power it on. These devices are for military systems: you'll need to test lifespan and performance under a variety of environmental conditions. I don't know if the dielet idea will work out, but it's specifically to verify authenticity without having to test.

michaelt• 12 years ago

A public test suite wouldn't reveal features introduced by a hostile foreign government, such as a security backdoor that only activated in response to a secret key too long to brute force. Presumably for DARPA this is a worry.

Agree a public test suite would be good for other fake component risks though.

hammock2• 12 years ago

Is that for counterfeiting, or security

leephillips3• 12 years ago

Both. Counterfeiting, or substituting recycled parts, can be for economic reasons, or can be a hostile government that managed to substitute its hardware into the supply chain, for sabotage or to create backdoors.

boise• 12 years ago

Best to only buy from TI franchised suppliers. Can't find any that go down to $16 though

http://octopart.com/opa627au-texas+instruments-420817

GFK_of_xmaspast• 12 years ago

"Hey! This is lizard oil, not snake oil!"

Johan-bjareholt• 12 years ago

I have previously bought two of these chips and they sound pretty good, sad that they are fake though.

Will buy the genuine one for comparison, will see if I can hear any sound quality difference

Fake audiophile opamps: OPA627 (AD744?)

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