how about measuring Ibias... => uA or pA ...JFET opamp?
how about measuring Vnoise (g=1000)=> 6nV/sqrt(hz) ?
How about measuring BW (g=1000)=> 10KHz?
shouldn't take you more than 1 hour o-great-brainy ...
oopps sorry, you didn't care anymore....i guess you care more about starting a hype about fake opa627s... yeh that would be a great idea!
how about measuring Vnoise (g=1000)=> 6nV/sqrt(hz) ?
How about measuring BW (g=1000)=> 10KHz?
shouldn't take you more than 1 hour o-great-brainy ...
oopps sorry, you didn't care anymore....i guess you care more about starting a hype about fake opa627s... yeh that would be a great idea!
tschrama said:
oopps sorry, you didn't care anymore....i guess you care more about starting a hype about fake opa627s... yeh that would be a great idea!
Actually, this thread was started because a diyaudio member asked a simple question, and was concerned that he may have some fake chips. That's a legitimate concern, especially when you see the variation in the package that has been presented in this thread. I also had some doubts that have been thankfully addressed.
Whilst I'm sure making those measurements would verify the chips once and for all, I doubt many of us have the equipment and know-how to do it.
This is a useful thread for those of us without prior knowledge and/or testing capabilities. Please don't turn it into a flamefest.
Thanks,
Michael
bbakota2000 said:
Yes, but DIYers are smarter than the average guy. There is no equivalent part that would meet OPA627 specs or even be a look alike electricaly. One thing almost anyone could look at would be the large signal frequncy response, there are little anomolies particular to each amplifier just like a fingerprint.
tmblack said:
You really have no idea how to do that, or are you just being irri..?
I especially choose parameters that are easely measured with just that: a millivolt meter and a soundcard/PC....
If you cann't figure that out yourself, I suggest you read a datasheet or buy an introduction analog electronics book...by al means don't expect me to teach you...
tschrama, please keep it to technical discussion and drop the personal stuff.
That would have been me. I remain disturbed by what I saw. And although it was at a bit of a distance, they did look like 8 pin DIL. This was just at the time there was a thread running about fake power transistors. Heck, the transistor fakers hardly seem to care if the part explosively fails some time later. So a fake 627 could be almost any fet op-amp. A 627 must be a very tempting target. Most will be used in circuits where a much lesser performing op-amp will still work, just perhaps not especially well. Maybe just rebadge an opa134, that would probably work really quite well. I suspect many would be hard pressed to realise that they had been duped. And the price differential is pretty breathtaking. Sure you could tell if you went looking. But if you had a 134 in circuit, how many would be able to realise that something was intrisically wrong, wrong enough to start measuring the op-amp for the tell tale signs of a fake? How many might just ascribe it to a bad chip anyway?
Not to say that what I saw was a group faking 627s, but it is very hard to believe that these guys were not faking something.
Actually one shouldn't forget how small a niche the high end audio biz is. Serious users don't pay premium prices unless they need to and most instruments using these parts (if fake) would fail some QC test. The returns then go to the real maker and the fakes are discovered, ask me how I know. 
Actually there has been less faking with power erasers since the bubble burst in high tech.
As I mentioned, starting on page 11 of the data sheet there are large signal frequncy response anomolies mentioned that would appear on very few (if any) other parts. See pic for one.
Actually there has been less faking with power erasers since the bubble burst in high tech.As I mentioned, starting on page 11 of the data sheet there are large signal frequncy response anomolies mentioned that would appear on very few (if any) other parts. See pic for one.
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scott:
that was a very interesting and useful tidbit.
for some reason, i always thought that characteristic was something exhibited by most FET input op amp (similar to the old phase reversal problem).
i was prompted by your comment and photo to take a QUICK look a some datasheets I happened to have handy of other products and noticed that the severity of this little quirk sure does look to be unique to OPA627.
I looked at OPA606, OPA604, LT1122, LF411, and (of course ) AD8610. I think(?) all of these are less $ than OPA627.
interesting ...
and, i can sympathize about the returns/FMA experiences.
mlloyd1
that was a very interesting and useful tidbit.
for some reason, i always thought that characteristic was something exhibited by most FET input op amp (similar to the old phase reversal problem).
i was prompted by your comment and photo to take a QUICK look a some datasheets I happened to have handy of other products and noticed that the severity of this little quirk sure does look to be unique to OPA627.
I looked at OPA606, OPA604, LT1122, LF411, and (of course ) AD8610. I think(?) all of these are less $ than OPA627.interesting ...
and, i can sympathize about the returns/FMA experiences.
mlloyd1
scott wurcer said:... The returns then go to the real maker and the fakes are discovered, ask me how I know.
large signal frequncy response anomolies ... appear on very few (if any) other parts...
tmblack said:
I would just like to expand on Scott’s comments and I am sure I am saying something he knows already.
A lot of datasheets contain information (clues) about design specifications and performance.
Typically terms include,
1) Guaranteed by design.
2) Sample tested.
3) Batch tested
4) Fully tested to meet all AC, DC specifications etc.
Maybe Scott you can expand or illuminate on that.
One thing I can say for sure is that apart from testing the OPA627 it's sonic attributes in a revealing system are obviously different (better to my ears) to an OPA134 or any other op-amp I have ever heard. That maybe a benefit to those without test equipment and known authentic OPA627s as a reference.
CB
Hi Scott,scott wurcer said:
Maybe old, but AD is now moving to a dielectrically isolated process too while TI is moving away from it. Though for some mysterious reason AD has +/-13 V max.
Hot nitric acid is not for the layman. But interesting to see how you study the competition. I advice to stay away from hot agressive chemicals if you want to keep your sighting.....
I think the simple answer is:Elso Kwak said:
1 They can't manage higher technically. If you may have read, they have GHz transistors, one of the reasons to extremely good performance.
2 Customers don't demand higher voltage than +-5 to +-12 V. Mention one industrial application that nowadays demands +- 15 V!
Elso Kwak said:
High voltage and high speed are generally incompatible for some very fundamental reasons. The DI process that the OPA627 is made on is fairly slow by modern standards and, I think, still on 4" wafers, making it quite uneconomical these days. Also as others have observed, +- 15v amplifiers are a rapidly shrinking slice of the market. Actually the last time I looked at an OPA627 they were in those little metal cans, very easy to open, like tuna.
SOIC fake?
How about these? I couldn't get OPA627 from digikey or mouser, so I tried eBay.
Couldn't comment on the sound because I soldered them into adapters then plugged them in reverse polarity after not enough sleep and fried them.
The SOIC ones that I received didn't have a pin 1 marking.
Topside marking:
BBOPA
627AU
0322
Bottom marking:
TWN
How about these? I couldn't get OPA627 from digikey or mouser, so I tried eBay.
Couldn't comment on the sound because I soldered them into adapters then plugged them in reverse polarity after not enough sleep and fried them.
The SOIC ones that I received didn't have a pin 1 marking.
Topside marking:
BBOPA
627AU
0322
Bottom marking:
TWN
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