Are all AD8610/20 on eBay fake?

Just get a set from an authorized distributor such as Newark.

Cimarron Technology, Inc. - Pre-Mounted Components
Here is on adapter pre mounted AD8620 for 15,95$, they ship worldwide, shipping was about $10, if I remember correctly.

I bet they're all fake, or people abusing sample programs. Just order from a reputable dealer.

Yeah, not a single original AD8610/20 around there...

Or?

I bought a set of now unobtainium toshiba transistors from ebay, they are indistiguishable from my NOS from Newark. I think a lot of the ebay " fake " chips is paranoria.

You should buy the ones on ebay and another from Newark and listen for differences or run Audiotester. My guess is there will be no difference.

Any chip that costs more than $5 retail is pretty likely to be a fake in my opinion. Think about it logically. What is the incentive to sell you two ad8610s that cost $7.50 each when they can easily rebrand some chips that cost $.50 each.
In order to confirm they are fake generally you need some pretty serious equipment and electronics knowledge.

they pull them from used equipment for pennies a piece, its cheaper to pull authetic used chips than it is to setup some grand counterfieting scheme. Profit is almost 100% on used chip pulls.

Its ashame we don't have electronic junkyards in the US like they do in China.

When counterfeiting opamps, how do they do it? All dual opamps and most of the singles have the same pinouts, so it's not easy to tell if they're fake or not, and they could easily be counterfeit. Some singles like LT1028, AD797 and OPA627 have unique pinouts, and I have a hard time to see how they could be rebranded cheap-o's. It should be very costly do design and manufacture copies, shouldn't it? I've bought AD797's from Ebay and they have the correct pinout, have bias currents matching the data sheet, sounds good and measures exceptionally well as expected from AD797.

I don't think many of the opamps for sale at Ebay are used parts. Besides, there can't be many products with AD8610/20 in a junkyard.

No, they just get an opamp with the same package and pinout (there are countless opamps to choose from) remove the stamp (acetone probably does the trick), and stamp it with the stamp of the desired opamp.
The biggest cost involved is making the stamp and that's a pretty minor cost.

This is probably far more prevalent than you think:
U.S. Government Finds Thousands Of Counterfeit Electronics From China In Avionics Weapon Supply Chain

http://spectrum.ieee.org/computing/hardware/bogus

There are tons more articles if you wish do further research.

pinout, bias current, "sounds good" are all very easy to fake.

How did you measure it exactly?

There may be some counterfieting going on, but I think we as a group should support the recycling of used chips that we are seeing being done in the orient instead of dismissing them all as counterfeit.

I've gotten a few chips that are just about impossible to economically counterfeit and impossible to find NOS . I support chip recycling and think it is good for the hobby.

You mean this:
"Uncontrolled burning, disassembly, and disposal can cause a variety of environmental problems such as groundwater contamination, atmospheric pollution, or even water pollution either by immediate discharge or due to surface runoff (especially near coastal areas), as well as health problems including occupational safety and health effects among those directly involved, due to the methods of processing the waste. Thousands of men, women, and children are employed in highly polluting, primitive recycling technologies, extracting the metals, toners, and plastics from computers and other electronic waste.
...An expedient and prevalent method is simply to toss equipment onto an open fire, in order to melt plastics and to burn away unvaluable metals. This releases carcinogens and neurotoxins into the air, contributing to an acrid, lingering smog. These noxious fumes include dioxins and furans.[19] Bonfire refuse can be disposed of quickly into drainage ditches or waterways feeding the ocean or local water supplies.[16][20]
["Electronic waste" - Wikipedia]

On top of that there is nothing good about "recycling" that worthless and possibly no longer to spec op-amp.

When it comes to actual recycling of things like LCD monitors I think people should embrace that.

But if you want to find out if these parts have been pulled just ask the vendor if they are new parts. I have a feeling I know what the answer is. Also if you look at the chips that people here are buying they are obviously new.