Searched high and low, there is no mention of anybody else reporting any fakes. Can you point to anybody else who has? I don't think that there are enough AD844 on the market to be targeted and if there was... there would be reports. As for you saying they were 'oscillating' - sample variation and poor layout can also cause that.
Rather not use SOIC, but I have some OPA860/861 that are SOIC and hot-soldered onto adaptors, but a bit of a pain.
I note that somebody in China, probably Hong Kong, with 99% plus rating selling AD844AN for a bit more than AUD $3 and also there is PayPal to protect you. Let's say they are not real AD844, but AD811. Most people buying AD844 will use them as current-feedback opamps and insert them into a circuit and chances are that they would not really know they are using AD811 re-badged as AD844, so they, the seller, gets away with it. That would explain what happened to George, because he would have found a zero feedback AD811 going completely out of control when no feedback applied. But of course, put a resistor on pin 5 on the AD844 and it should behave without any loop feedback.
But then I look at the range of prices AD811 fetch, and current-feedback opamps in general, why would anybody rebadge something unless there is money in it and they get as much from an AD811 as AD844 etc.
I may order a handful from that HK supplier and just find out - then report back here whether they behave as an AD844 should or if they are just current-feedback opamps rebadged (George could have checked that before he put his in the bin). I see that RS and Element14 prices have hit the roof - they are just asking to much, so if they are available at a decent price, why waste money?
Finally, as I said before, there doesn't seem to be any report flying around that there are fake AD844, so...?
Cheers, Joe
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You're right Joe - the fear and myths about faking exceed the reality by an order of magnitude or more. Since I've been in China (been buying parts fairly regularly here for about five years, mostly on Taobao) I've so far only encountered one fake batch of ICs which were TDA7294s posing as 7493s.
There look to be lots of AD844 in various guises available 2nd-hand on Taobao which is a fairly good sign. Even ones with /883 qualification (these look to go for $8 and up). I'd guess these would be the ones to fake. Ceramic cased chips look more difficult to fake as the markings on the top look more difficult to erase - anyone know if its possible or have examples of it being done?
There look to be lots of AD844 in various guises available 2nd-hand on Taobao which is a fairly good sign. Even ones with /883 qualification (these look to go for $8 and up). I'd guess these would be the ones to fake. Ceramic cased chips look more difficult to fake as the markings on the top look more difficult to erase - anyone know if its possible or have examples of it being done?
Like I said the fakes were directly sub'd for ones bought from RS and no problems. So the fakes were bin'ed, BTW they came from Asia.
Cheers George
Member
Joined 2006
Member
Joined 2006
OPA861 & OPA660 are pins compatible, but I don't know if the swap of each others change something else than higher output ! Transconductance is better (higher) with the 660, at least this is my poor understanding !
Not sure the use of 660 change something in the audioband in relation to the 861, that's why I asked to Joe Rasmusen who have an understanding of the way it works...
pfff i have a channel totally dead and certainly one of the two dead on the other channel (the buffer : bzzzzzzzbbzbbzzzzzbbzbzzbzz
)
And think I also breaked the I2StoPCM board for the simultaneous mode by touching the supply just after the first problem ! An horror never comes alone !
! Well I have a spare but it was planned for an AD1862 DAC !
Are you sure your Florida shop sells genuine items ?! Heard there are some crocodiles in those aera and if this one doesn't bite you the Pythons do the job !
pffffffffffffff !
Not sure the use of 660 change something in the audioband in relation to the 861, that's why I asked to Joe Rasmusen who have an understanding of the way it works...
pfff i have a channel totally dead and certainly one of the two dead on the other channel (the buffer : bzzzzzzzbbzbbzzzzzbbzbzzbzz
)And think I also breaked the I2StoPCM board for the simultaneous mode by touching the supply just after the first problem ! An horror never comes alone !
! Well I have a spare but it was planned for an AD1862 DAC ! Are you sure your Florida shop sells genuine items ?! Heard there are some crocodiles in those aera and if this one doesn't bite you the Pythons do the job !
pffffffffffffff !
Member
Joined 2006
...
Are you sure your Florida shop sells genuine items ?! Heard there are some crocodiles in those aera and if this one doesn't bite you the Pythons do the job !
pffffffffffffff !
Yikes,
Not sure how old u r but, think Crocodile Dundee -- 'Aussie', therefore Alligator = Florida!
:duck:
Sorry to hear that..hope you could get things fixed soon ...
Perhaps you could try both OTAs.for.fun and report it.back
Money is missing, I spent too much with diy !
I sold my R2R DAM1021 as I feeled it will cost a lot for uncertain result to save money for Ian's device !
So I have to make a choice : opa660 or opa861 ! Ah, wisdom says "stays on the opa861"... but as I'm a fan of tda1541 I know Pedja begann with 844, then found better the opa660 but swaped to 861 because the 660 was discontinued !
So it pushes to me to think if 660 is same same but different
!hello ADL,
you know it's like dromadaires & camel : in the action you run and looks not too much the teeths ! Hey I read somewhere the anacondas in The Kees are winning the battle against the Caimans... which is for me more the car I 'd like to have though I will have no utility to it ( all those animals are too fast for a Wookie !)Ah ! Australian Saltwater Crocodiles - Pictures And Facts About The Saltwater Crocodile
look at the first picture : and focus on the two big teeth : this crocodile is from Roumania ! Run....Don't ask him if he prefers to be called crocodile, caiman or hand-bag.... run instead !
I can't believe it, some have anaconda at home as new pet : BBC News - Australia: Snake eats crocodile after battle ! I believe the keys of The Kees is Dexter !
>Forgett : better the opa660 or the 861 ?
look at the first picture : and focus on the two big teeth : this crocodile is from Roumania ! Run....Don't ask him if he prefers to be called crocodile, caiman or hand-bag.... run instead !
I can't believe it, some have anaconda at home as new pet : BBC News - Australia: Snake eats crocodile after battle ! I believe the keys of The Kees is Dexter !
>Forgett : better the opa660 or the 861 ?
..back to purchasing AD844 from China, does anyone know which of these print styles is more likely to deliver genuine chips?
brown printing:
white printing:
brown printing:
An externally hosted image should be here but it was not working when we last tested it.
white printing:
Just a comment or question about using the AD844 and it's layout. I am using 2 stacked 844s on the same location of the previous opamps, the same analog ground plane as the PCM1704s. I use pin 5 as output to my 250k input of the amps with a 1k resistor and 2000pf styrene cap as reconstruction filter. I recently decided to try it without the cap as was done by Georgehifi a while back. I also got a slightly softer sound, not quite as focused sound stage. I also had noticed that the ground placement location of these component in relation to pin 3(grd of 844) was not symmetrical . I relocated the grounding position of pin 5 resistor from across the length of the chip to next to pin 3 on both channels. This produced a perfectly centered soundstage. Is the softer sound due to removal of the cap which may introduce ground bounce from the ground plane? I believe that abraxalito had previously brought up something about the location of components in past posts(sorry if I'm wrong). I see that the analog ground plane has all the decouple caps for the ps, pin 3, pin 5 resistor and the ground of the output signal. The decouple connection are fixed as is pin 3, but where should the rest be located if there is a continuous ground plane? Still more to do......