Opamp fakes vs real vs audiophile

[Sokel]

I am temped to bride my nephew so to get me a bunch of those (I don't get to Ali, young ones do and get crazy stuff from there, last time he got mechanical insects! ) .

I suspect we will have a lot of fun measuring those "OPA2134" and "TI1656", etc.

But I do have a note, at some thread I can't find right now I described how one of these cheapo preamps was outputting a glorious 15VDC right out of the box (one of the traces didn't make it to their destination) .

So it might be a good idea to always check them, at least for DC, etc, first.

 

[0bs3rv3r]

I am temped to bride my nephew so to get me a bunch of those (I don't get to Ali, young ones do and get crazy stuff from there, last time he got mechanical insects! ) .

I suspect we will have a lot of fun measuring those "OPA2134" and "TI1656", etc.

But I do have a note, at some thread I can't find right now I described how one of these cheapo preamps was outputting a glorious 15VDC right out of the box (one of the traces didn't make it to their destination) .

So it might be a good idea to always check them, at least for DC, etc, first.

Agreed. The line preamp version has coupling capacitors, and provided they are wired in circuit, should avoid this. I tend to build my own equipment with input caps, so even if the device puts out DC, it won't get into downstream equipment.

I have two of those minimal AD828 preamp boards on the way right now, to try them out.

 

[torgeirs]

The pictures show really small size SMD caps and resistors. Distortion on such board may just as well originate from those small passives as from the opamp. I have seen this in DAC boards. The passive output filter is way more unlinear than the dac chip.
(I have even bought boards with opamps that don`t work with the 5 volt single supply on the board, and that is great opamps. So the bad engeneering know no limits and actually be worse than fake components)

 

[Sokel]

The pictures show really small size SMD caps and resistors. Distortion on such board may just as well originate from those small passives as from the opamp. I have seen this in DAC boards. The passive output filter is way more unlinear than the dac chip.
(I have even bought boards with opamps that don`t work with the 5 volt single supply on the board, and that is great opamps. So the bad engeneering know no limits and actually be worse than fake components)

Some sure are all over the place.
The OPA's I measured though was bad on their own, I have comparison with real one at the linked thread.

If anyone wants pictures of these "OPA2134" let me know, they even miss the pin 1 dot!

 

[wwenze]

Just thinking today, while looking at Asian markets selling opamps and opamp based preamp boards, about the prevalence of fakes, or likely fakes, in the market. Then I recall the various tests that show opamp rolling might not make much difference.

So, does it matter that my OPA2134 might be a 5532, or something obscure? My experience is that these preamp boards almost invariably work, and work quite well. I have also never bought an opamp that didn't work, although, yes, there are reports of that happening. Lately you can buy nearly anything, even discrete opamps, video opamps (like AD828), etc etc being sold as audiophile opamps.

But, if the tests are right, there is not enough difference to really matter, and if you like what you hear, so does it matter if the 2134 is a 5532 or a TL072?

It does matter because they need to use different values for the resistors around them. One is FET input the other is bipolar.

In fact this is one way to tell if some old DAC chips like TDA1543 are real or not, since the circuit will have values designed around the fake which would not work with the real.

 

[wwenze]

No idea why they put an AD828 into this board. It is a video opamp per Analog Devices (i.e. for video signal applications). It is not particularly cheap at $4.12 each at 1,000 pieces.

https://www.analog.com/en/products/AD828.html

Well, it has a high bandwidth, high slew rate, low power, single supply, etc., it also makes an excellent audio preamp. I have a couple in one preamp and they work very well indeed. Video is just high bandwidth audio in a sense. It is becoming popuar in audio uses, judging by what Asian markets are selling.

The question answered itself.

 

[NTK]

No idea why they put an AD828 into this board. It is a video opamp per Analog Devices (i.e. for video signal applications). It is not particularly cheap at $4.12 each at 1,000 pieces.

https://www.analog.com/en/products/AD828.html

Well, it has a high bandwidth, high slew rate, low power, single supply, etc., it also makes an excellent audio preamp. I have a couple in one preamp and they work very well indeed. Video is just high bandwidth audio in a sense. It is becoming popuar in audio uses, judging by what Asian markets are selling.

The question answered itself.

If that's the case, these Asian manufacturers must be much more technical knowledgable than the Analog Devices engineers who designed this AD828 thingy. Then, my question is, why don't they go the extra step and design their own opamps which will undoubtedly be superior to the AD ones.

Those AD engineers, after all, when they started out to design a video opamp, seemingly by accident made an audio opamp that is better than their audio offerings. And they didn't knew about it and have to wait for the Asians to find out. Doesn't sound like these AD folks really know what they are doing. Obviously these Asian manufacturers are able to do much better.
/S

 

[0bs3rv3r]

If that's the case, these Asian manufacturers must be much more technical knowledgable than the Analog Devices engineers who designed this AD828 thingy. Then, my question is, why don't they go the extra step and design their own opamps which will undoubtedly be superior to the AD ones.

Those AD engineers, after all, when they started out to design a video opamp, seemingly by accident made an audio opamp that is better than their audio offerings. And they didn't knew about it and have to wait for the Asians to find out. Doesn't sound like these AD folks really know what they are doing. Obviously these Asian manufacturers are able to do much better.
/S

Perhaps the parameters are not mutally exclusive. Consider the needs for a video opamp to be a superset of those of an audio opamp and you'll realise how a video opamp MIGHT make a good audio opamp.

 

[0bs3rv3r]

It does matter because they need to use different values for the resistors around them. One is FET input the other is bipolar.

In fact this is one way to tell if some old DAC chips like TDA1543 are real or not, since the circuit will have values designed around the fake which would not work with the real.

A design for a DAC is a very different situation. Opamp circuits are largely designed around viewing an opamp as a blackbox circuit element (theoretical infinite gain and infinite input impedance) and so this is why people get away with rolling nearly any opamp in place of any similar opamp position with the same pinout.

 

[antcollinet]

Perhaps the parameters are not mutally exclusive. Consider the needs for a video opamp to be a superset of those of an audio opamp and you'll realise how a video opamp MIGHT make a good audio opamp.

Or it could be a superset in some areas - a subset in others.

Video op amps need to be much faster than audio op amps, by orders of magnitude. They don't have the same requirements for noise and distortion, however.

 

[0bs3rv3r]

Or it could be a superset in some areas - a subset in others.

Video op amps need to be much faster than audio op amps, by orders of magnitude. They don't have the same requirements for noise and distortion, however.

Agreed. But maybe the asian audio world has discovered that this one does have other good features low noise and distortion. It's use in low level microphone preamps might indicate that. I was surprised just a week or so ago (I had never seen it before), to see how common it has become, to the extent that advertisements for other opamps (like discrete opamps) that they are selling, have a list of opamps that their item can replace, and it includes the AD828 along with all the usual suspects, 5532, 2134, etc etc.

To head back a little to the initial topic, as someone said, why use a more expensive opamp if a 5532 would do? If they are fake, then why would they fake and use an AD828 opamp, if it isn't considered desirable by the audiophile world.

 

[antcollinet]

But maybe the asian audio world has discovered that this one does have other good features low noise and distortion.

If they have - they should demonstrate it with good measurements.

why use a more expensive opamp if a 5532 would do? If they are fake, then why would they fake and use an AD828 opamp, if it isn't considered desirable by the audiophile world.

No-one here can tell you why they have done it. All you can do is ask them directly.

 

[Sokel]

To head back a little to the initial topic, as someone said, why use a more expensive opamp if a 5532 would do? If they are fake, then why would they fake and use an AD828 opamp, if it isn't considered desirable by the audiophile world.

Just a note, there's ALSO fake and rejected (by the thousands) 5532 out there selling for good and original.
As odd as it sounds.

Perhaps a joke for the extra cautious who think "why would they fake even that? "

 

[Ifrit]

maybe the asian audio world has discovered that this one does have other good features low noise and distortion. It's use in low level microphone preamps might indicate that.

Quite the opposite: distinct sound of mic preamps is mostly due to the specific set of noise and distortion, characteristic to that particular cuircitry. So low noise and distortion are only needed if want to make 'clean' preamp without sonic signature. And there are lots of those already, why bother creating another one?

 

[mhardy6647]

My guess is that "they" use the video opamp chips in a mic preamp for the same reason "they" use, e.g., the Chinese 6C1 (roughly equivalent to the Russian 6C1P, a sharp cutoff pentode tube for high frequency RF or IF amplifier use) in (e.g.,) the FX Audio "Tube-01" preamplifier (or whatever it is)!
Spoiler alert: there is absolutely no reason to use such a tube type, except that there were apparently zillions of surplus 6C1 available for extremely low prices (in China) when the amplifier was designed and built.



The cool kids who bought these devices (original price $31 USD) like to replace the more or less generic, Chinese-sourced tubes with a variety of other sharp-cutoff pentodes (e.g., the a member of the 6AK5/EF95/5664 EDIT 5654 family) because... you know... tube rolling. They also replace lots of other stuff in them (mostly capacitors) and it probably goes without saying that the results are jaw-dropping...

 

[mhardy6647]

Postscript: It is only a matter of time before one of the - ahem - second tier audio companies realizes they can build vacuum tube op amps... and then we'll be off to the races with those!

 

[wwenze]

If that's the case, these Asian manufacturers must be much more technical knowledgable than the Analog Devices engineers who designed this AD828 thingy. Then, my question is, why don't they go the extra step and design their own opamps which will undoubtedly be superior to the AD ones.

Those AD engineers, after all, when they started out to design a video opamp, seemingly by accident made an audio opamp that is better than their audio offerings. And they didn't knew about it and have to wait for the Asians to find out. Doesn't sound like these AD folks really know what they are doing. Obviously these Asian manufacturers are able to do much better.
/S

The question answered itself because the Asian manufacturers know how to sell tubes and fake opamps labelled as an expensive product at higher prices than a NE5532-based products, evident by the buyer's reply.

 

[torgeirs]

https://www.analog.com/media/en/technical-documentation/data-sheets/ad828.pdf AD828 is from 2002 and AD has moved on.
The thing with video opsmps is that they are very fast, so more skill in cirquit design is required. Or the circuit easily gets unstable.
A slow fake one is much easier to use

 

[mhardy6647]

... so more skill in cirquit design is required.

or not.

 

[torgeirs]

I have two of those minimal AD828 preamp boards on the way right now, to try them out.

A genuine AD828 have very good cable drive capability. So it should drive a hf square wave through a long cable with not to much overshoot. If you have access to a scope or ADC