7 ms·
Fake audiophile opamps: OPA627 (AD744?)
- joosters 12y agoIf you can't tell the difference without dissolving the chip in acid... perhaps then there is no difference?
- atomlib 12y agoAccording 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 12y agoFrom the article: > On the other hand AD744 has higher noise (3x) and higher offset voltage (0.5mV vs 0.1mV).
- joosters 12y agoI 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.
- nawitus 12y agoThere's no reason for an audiophile to test if the part is genuine. They would need to buy a "genuine" part to compare against, but that presumes knowledge about the original part being fake.
- swimfar 12y agoExcept that it's only one component of many in a system. I doubt there would be a measurable performance difference between a standard formula 1 car, and one which has had it's carbon fiber steering wheel swapped out for an aluminum one. But making a lot of small, nearly immeasurable changes can result in noticeable differences. Certainly, in the case of racecars if two components differ only in weight, we can infer in what ways this should affect the performance. With audio it's not quite as clear (to me). Is there a measurable difference in the signal between using copper and silver wire? I don't know. But if we know that one component has measurably higher noise, that seems like it has the potential to result in a "cleaner" signal. However, without going too far down the rabbit hole, I generally agree that in the end the important question is, "does system A sound better than system B".
- marcosdumay 12y agoNope, we are talking about replacing the engine for one of a completely different model. Those amps and a very small number of resistors and capacitors are the first stage of amplification of an equipment. They are the biggest source of noise, by a couple orders of magnitude. If you can't tell the difference once you change them, it's because the difference is not relevant (and for audio systems, it's completely irrelevant).
- Dylan16807 12y agoIt's hard to notice subtle things without an A/B test, it might just be that quiet parts of certain songs just don't sound as good. For something like this you would want to measure the noise levels, not make assumptions about audiophiles being wrong; they're only wrong a significant fraction of the time.
- jff 12y agoAny true audiophile will notice the warmer sound of proper laser-trimmed resistors
- al2o3cr 12y agoYou could probably convince most "audiophiles" that the color of sneakers worn by the production line employees changes the sound of opamps.
- analog31 12y agoThe 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 12y agoSmall 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 12y agoRemember that these aren't made -for- audiophiles. Audiophiles might like using these, but they are used for other uses where it would matter.
- deleted 12y ago[deleted]
- stinos 12y agoexactly. 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 12y agoExactly, I believe they were designed for instrumentation amplifier duty, hence the wide bandwidth and low noise.
- nate_meurer 12y agostinos 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.
- stinos 12y agohey no problem, after all the buttons are quite close together (I always wonder how touchscreen users deal with them?)
- vonmoltke 12y agoIn 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 12y agoExactly 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.
- thrownaway2424 12y agoThe 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 12y agoFake resistors? How is one supposed to fake a resistor? There are no manufacturer markings on them, just (easily testable) resistance/precision indicators...
- mhb 12y agoTemperature coefficient perhaps?
- thrownaway2424 12y agoAnything people pay more for, including tempco, tolerance, power rating, whatever. I once got counterfeit models of these[1] from ebay. http://www.vishaypg.com/docs/63066/e102.pdf http://www.vishaypg.com/docs/63066/e102.pdf
- yitchelle 12y agoResistor is more than resistance. There is also other characteristics like power capacity, accuracy, tolerance, frequency responses, temperature coefficient etc. The cheaper resistors are typically very loose for most of these characteristics. A tight characteristics means a high level of quality control at manufacturing, and this is usually lacking for the fakes. For Op-Amps, the interesting spec is their frequency response as the op amps are not typically used in DC situations.
- fnordfnordfnord 12y agoObviously someone noticed a problem. It was confirmed by looking directly at the silicon.
- marcosdumay 12y agoHe 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.
- Qantourisc 12y agoFor audio yes. For the stability of your circuit it can cause mayhem if you are doing wonky things. Often can be solved by adding extra capacitance, but can be quite tricky to do (no room on PCB, capacitance was already large, ...)
- natejenkins 12y agoCan someone point out where are the laser trimmed resistors in the photos, and maybe explain some more of the components?
- atomlib 12y agoHere 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 http://i.imgur.com/vC5VkH0.jpg
- ableal 12y agoThe 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 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_ 12y agoIf 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/ http://security.cs.rpi.edu/courses/hwre-spring2014/ The slides for lecture 4 (http://security.cs.rpi.edu/courses/hwre-spring2014/Lecture4_Layout.pdf 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.
- natejenkins 12y agoI am and this looks awesome. Thank you!
- darksim905 12y agoHow 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 12y agoDecent 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.
- ableal 12y agoAnalog 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 12y agoThis is optical microscope with 5mp digital camera. Multiple shots (from 4 to 800 for large chips) are stitched in 1 big panorama.
- njharman 12y agotil; that resistors are trimmed with lasers http://en.wikipedia.org/wiki/Laser_trimming http://en.wikipedia.org/wiki/Laser_trimming
- Terr_ 12y agoThey 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-Tuningfork.jpg http://en.wikipedia.org/wiki/File:Inside_QuartzCrystal-Tunin...
- leephillips 12y agoCounterfeiting 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 12y agoIts not just counterfeiting that is a problem, but also recycling. Real product, but used: http://spectrum.ieee.org/semiconductors/processors/the-hidden-dangers-of-chopshop-electronics http://spectrum.ieee.org/semiconductors/processors/the-hidde...
- deleted 12y ago[deleted]
- wyager 12y 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.htm http://www-rohan.sdsu.edu/faculty/vinge/hotchips/security.ht...
- logicallee 12y agoI wouldn't have believed that wasn't a cover story 5 years ago - today?
- malandrew 12y agoI'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.
- leephillips 12y agoThey 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.
- boise 12y agoBest to only buy from TI franchised suppliers. Can't find any that go down to $16 though http://octopart.com/opa627au-texas+instruments-420817 http://octopart.com/opa627au-texas+instruments-420817
- GFK_of_xmaspast 12y ago"Hey! This is lizard oil, not snake oil!"
- Johan-bjareholt 12y agoI 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
- Johan-bjareholt 12y agoI 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