Sorry guys no prize.
These were fitted to circuit boards that I had bought before I knew that fakes existed.
What has made me think these are fakes are the caps supplied on the boards are 10000uF 105c usr Rubycons that are definitely fake, as they were only available as 85c.
I have replaced all the chips with genuine LM3886 and noticed an improvement in the sound. Could be psychoacoustic but I don't think so.
I've sent a message off to National semiconductors to see if they can tell whether or not they are fake.
But I thought I would ask here too.
Thanks.
These were fitted to circuit boards that I had bought before I knew that fakes existed.
What has made me think these are fakes are the caps supplied on the boards are 10000uF 105c usr Rubycons that are definitely fake, as they were only available as 85c.
I have replaced all the chips with genuine LM3886 and noticed an improvement in the sound. Could be psychoacoustic but I don't think so.
I've sent a message off to National semiconductors to see if they can tell whether or not they are fake.
But I thought I would ask here too.
Thanks.
Hi,
the JM46AD looks smudged.
The "N" symbol seems to vary in thickness with the others.
Should the labeling be painted on or lasered on?
Does it depend on age? Did national change during production?
Send them back to National for confirmation.
They may just send you genuine samples in return.
the JM46AD looks smudged.
The "N" symbol seems to vary in thickness with the others.
Should the labeling be painted on or lasered on?
Does it depend on age? Did national change during production?
Send them back to National for confirmation.
They may just send you genuine samples in return.
These were purchased from a ebay seller based in Hong Kong.
It would be good to know if they are fake, as it can serve as a warning to other unsuspecting buyers.
I will only be buying my components from authorised dealers from now on, as it looks like there is no bargains to be had.
Lots of people are buying these components from ebay thinking they are getting the real McCoy.
I feel the manufacturers should be doing more to identify this problem and make consumers aware that the problem exists.
Thanks.
It would be good to know if they are fake, as it can serve as a warning to other unsuspecting buyers.
I will only be buying my components from authorised dealers from now on, as it looks like there is no bargains to be had.
Lots of people are buying these components from ebay thinking they are getting the real McCoy.
I feel the manufacturers should be doing more to identify this problem and make consumers aware that the problem exists.
Thanks.
In my experience, there are REAL gems at ebay chinese sellers. Among these are my dared amp, Nikon DSLR, Ninja brake pads, etc.
The trick is to do bit of research/question before buying. In this case I was also considering to buy those "I wanne buy" GC, because they cost $12/channel including parts and PCB. No messy point-to-point work okay. Quick check at this forum someone else posted his review which was unsatisfactionary.
Now, I wonder whether $12 is worth the price for PCB alone he..he..
The trick is to do bit of research/question before buying. In this case I was also considering to buy those "I wanne buy" GC, because they cost $12/channel including parts and PCB. No messy point-to-point work okay. Quick check at this forum someone else posted his review which was unsatisfactionary.
Now, I wonder whether $12 is worth the price for PCB alone he..he..
Gopher said:
Thanks for the smart comment. A lot of help there.
The chips came on a pcb and a fair number had been sold with no neg. feedback. Like I said, it was before I realised these fake chips and caps were being made.
At the end of the day they have been reasonably priced circuit boards.
I guess if we can't work out if they fake or not, then how will anyone else know.
I am sure there are fakes, I used to see a lot of fakes back when I was building STK amps ( 439 ..459 etc) ..they were easier to fake I think . A LM3886 might be a bit difficult to fake , but can't be sure of their capabilities. Anything as popular as an LM3886 is bound to be faked... Toshiba output devices for example, but these were transistors so faking is real easy just rebadging the case . If your LM3886 is working with a circuit matching national's reference I doubt whether your chips are fake...at the most they might be a cheaper chip that is pin compatible with LM3886 ..which I doubt is possible.
Why risk getting fakes?
You can get up to 5 pieces of LM3886's (or any of the other GC chips) for FREE direct from NS! They have a link on their website to allow you to request free samples of many of their semiconductor products. If you have a ham license just list your call sign as your company name in the request form (they must have a soft spot for hams). Just don't over do it and limit your requests to a few a year. The parts you get might be marked as "Engineering Sample", but they will simply be cosmetic defects that couldn't be sold as 'new'.
Analog Devices, Microchip, and Maxim are other semiconductor makes that will send you free samples for the asking. (Low noise op amps anybody?).
You can get up to 5 pieces of LM3886's (or any of the other GC chips) for FREE direct from NS! They have a link on their website to allow you to request free samples of many of their semiconductor products. If you have a ham license just list your call sign as your company name in the request form (they must have a soft spot for hams). Just don't over do it and limit your requests to a few a year. The parts you get might be marked as "Engineering Sample", but they will simply be cosmetic defects that couldn't be sold as 'new'.
Analog Devices, Microchip, and Maxim are other semiconductor makes that will send you free samples for the asking. (Low noise op amps anybody?).
..and lot of other people too...I recently purchased one of the 3x3886 inverted paralelled units from "I wanne Buy"and the markings look legit like the pics mjf posted.However in preliminary testing I was only getting about 50 watts into 4 ohms with +-30 volts DC .What kind of power should I expect to get from them into 4 ohms?Aswell the response dropped off above 10k.One of the small caps must be acting as a low pass filter.gainphile said:
Operation into 4 ohms at 30v is actually outside the operation envelope, max. voltage at 4 ohms should be limited to +/-28v, and the chips will run cooler at 25v for 4 ohms. If you measured 50w output at less than .1% IMD, I'd say that was good. The LM3886 is spec'd to give 68w output into 4 ohms at 28v, but at over 1% IMD (which sucks). IMHO, I wouldn't publish a power spec that was over .1% IMD.F1 FAN said:
If your response was dropping off above 10khz I'd wonder if the chips weren't fallout parts, or maybe the circuit has an added rolloff filter in the feedback circuit (an extra 50pf cap in series with a 20k resistor placed in parallel with the existing Rf). Some variations of the classic circuit add this extra element to insure stability at HF, but that might be to correct a bad PC layout.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.