Great point Sangram. 1W measurements are quite important and telling. Especially the spectral harmonic distortions at 1W.
The Multi-tone IMD measurement differences between the XY design, LM3886-DR and Modulus-86 are quite illuminating but the measurements were done at high output power levels. Of course, the Modulus-86 was the rockstar here but the LM3886-DR was clearly better than the XY design as well. But I wonder how they are different at a 1W level with respect to Multi-tone IMD. As long as it is higher than the noise floor of the APx 525 itself!
Best,
Anand.
The Multi-tone IMD measurement differences between the XY design, LM3886-DR and Modulus-86 are quite illuminating but the measurements were done at high output power levels. Of course, the Modulus-86 was the rockstar here but the LM3886-DR was clearly better than the XY design as well. But I wonder how they are different at a 1W level with respect to Multi-tone IMD. As long as it is higher than the noise floor of the APx 525 itself!
Best,
Anand.
In Jeff Rowland lm amp... not a 11 dollar amp
Those look the real deal. The lettering is aligned to the left and the case design is quite different from the TF, which is as it should be.
All the TF versions I have ever bought had laser etching, never the white paint in my memory. This was even true for (some) Chinese sellers, which was the only option for 3rd world-ers like us.
Ignore the PCB. It's part of my past sins, which I keep as a reminder of how not to do things. At least it has nothing connected to it...
And the quality of the photograph, which was taken by the camera module of a Chinese phone. So it's not just amplifier PCBs...
Attachments
How much money can you make copying parts that you can buy in bulk for $6-7? I don't get it, but people must be making money if they're doing it.
I bet it doesn't have SPIKE or SOA protection. I would test for that. I know for a fact that you can trigger SPIKE and SOA protection on a 3886 if you try hard enough.
I like my stuff to WORK so I buy from Digikey and Mouser. Every single part I've bought from them still works, except an electrolytic capacitor I installed backwards. And that was worth the price of admission to see it melt down on the prototype.
I bet it doesn't have SPIKE or SOA protection. I would test for that. I know for a fact that you can trigger SPIKE and SOA protection on a 3886 if you try hard enough.
I like my stuff to WORK so I buy from Digikey and Mouser. Every single part I've bought from them still works, except an electrolytic capacitor I installed backwards.
And that was worth the price of admission to see it melt down on the prototype.
I bought the XY Kit fair and square as any DIYer would do. I populated it and tested it. I then compared its performance to that of my LM3886DR, which you can buy fair and square. The difference is that I point you to Mouser as the source for genuine parts, whereas XY delivers fake parts. To the average DIYer the parts look genuine or at least genuine enough. That's pretty clear from the sheer number of "is this part fake" threads here. All I'm doing here is giving the buyer more information so that he can make an informed choice of what to buy.
I did consider writing up a long post on how to address the various issues in the XY board. The post would basically explain how to change the XY layout into the LM3886DR layout. If that's what you want, I think you're far better off buying my LM3886DR board or building the circuit point-to-point as that's essentially what you'll end up with.
I'll see if I can squeeze those in. I really need to make progress on other projects.
True. Then you end up with rising THD above a few hundred Hz due to the wiring inductance that you introduce. Been there. Measured that.
Tom
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It's not just a matter left/right alignment and ink/laser. Please read Post #1 and check out the websites I link to there for the lot code details. That's not to say that the copycats can't copy the lot code, but at least in case of the LM3886 I received from XY, they just made up one.
I know, right? They must be selling *A LOT* of fakes.
Tom
So are you going to blow it up, Tom?
And will you be offering a board only option with your new 3886 kit? I prototyped a circuit on perfboard and I knew that this chip has a lot of potential. And I hate making boards, and I don't have the modern technology to do it either. I've made them the same way for 50 years, like a caveman. At this point I'd rather buy somebody else's boards if they're good. I'm almost completely blind now.
And will you be offering a board only option with your new 3886 kit? I prototyped a circuit on perfboard and I knew that this chip has a lot of potential. And I hate making boards, and I don't have the modern technology to do it either. I've made them the same way for 50 years, like a caveman. At this point I'd rather buy somebody else's boards if they're good. I'm almost completely blind now.
I bought a pair of the XY kits from one of the Chinese ebay sellers, planning to install them in an old Crown D60 chassis. The plan was to ditch the output resistor, add Zobel and Theile networks, input RF filter, replace all the capacitors with my own parts of known provenance, move the feedback resistor, fix the grounding issues, and happily carry on.
Tom succinctly addressed the sanity of that approach in post #25.
Now, I think I'll just get a couple 3886DR boards to play with, and relegate the XY's to a speaker test jig or other test bench amp.
The LM3886TF that came with the kits looked good- nice clean mold and leadout, left-justified clean laser etched labeling. Looks authentic for sure. Except, the lot#/date code ID is: 3BA2NRUE3
That doesn't jive with any manufacturing code format I could find on the TI website. They might as well have silk-screened "LM3886FAKE" in fluorescent green ink.
-Peter
Tom succinctly addressed the sanity of that approach in post #25.
Now, I think I'll just get a couple 3886DR boards to play with, and relegate the XY's to a speaker test jig or other test bench amp.
The LM3886TF that came with the kits looked good- nice clean mold and leadout, left-justified clean laser etched labeling. Looks authentic for sure. Except, the lot#/date code ID is: 3BA2NRUE3
That doesn't jive with any manufacturing code format I could find on the TI website. They might as well have silk-screened "LM3886FAKE" in fluorescent green ink.
-Peter
So are you going to blow it up, Tom?
Nope. I'll de-solder the chip and send it to a friend at TI to get it opened up. I'm interested in seeing which die is actually inside.
Bare board, no parts is actually my default option. I provide a link to a project set up with Mouser. Click the link, enter the number of projects (= boards) you'd like to order, and hit "add to cart". A few days later a box of goodies show up on your doorstep. Mouser are so much better at putting little parts into little bags than I am.
For those who prefer an actual kit, I'll be happy to order the parts from Mouser and ship them to you with the board. I charge a very reasonable markup for that service.
That's how I look at it. If your time is worth anything, it is usually way more cost-effective to buy a good board and be done than it is to create your own board. With my boards you also know what you're getting as I post the full measurements of it.
I'm almost completely blind now.
Man. Sorry to hear.
Tom
Thanks man, but I'm still working and still making and fixing stuff. I haven't been able to get a legit job since 2009 (they laugh at me when I apply the bastards) but I do1099 stuff; mostly consulting, planning, and supervision of residential rehabs and additions. People like me, I know how to make it get done right. It's the "new economy" where most people have to become uber drivers and charge each other the same $30 to drive each other to the airport.
At least I'm luckier than that.
It's the "new economy" where most people have to become uber drivers and charge each other the same $30 to drive each other to the airport.
Yeah... I suspect the pendulum will swing back eventually. Sooner or later enough people will have gotten burnt on cheap products or labour that they will recognize the value of quality again. Hopefully they will also realize that quality does have a higher price tag than cheap.
Tom
With all due respect Tom (and I do have a lot of respect for you!), that is not the point.
Are you an Engineer or a Shop Keeper?
If you are a shop keeper then simply comparing product A with product B, as you have done is valid, although a bit pointless given the price difference!
However, I suspect that you will always have your engineer hat on, and that what you are really doing is comparing your pcb design with XYs. That can only be done by populating both boards with genuine components and correct (recomended) values.
And why does the XY perform so well around 1W????
I can understand the bad full power performance and the bad hi-frequency performance of it. I also understand the idea of the comparison between the "China u get what you get" and the "Done Right, u also get what u get".
If the XY was rebuilt with the real deal components and adequate bypassing at the chips power terminals, what then?
How does the XY perform with the real parts,
and how does the DR perform with the China?
Labor has been globally commoditized, and the only parameter considered relevant is price. So when people say you're competing with workers in China for a job, they're correct. And this is exactly how the money powers want it.
A lot has to happen before it gets back to normal, and it's already started happening. Here in the US we have paid a dear price for this new global economic infrastructure. The Canadian government has done a much better job of keeping the wolves away, while the Swiss just laugh at all of us.
Eddie: Sitting next to me at work is one of the visual studio devs on the team. Only 10% vision in his good working eye. Great guy, hard worker, and we get a dog in the office. I am thankful my employer bases decisions on hires based on whether they can do the job not where they are on a bell curve of normal.
Ref global economy, would love to debate that with you from a non-American view on the world, but its against the rules sadly and well, I've derailed enough of Tom's threads in the past.
But I hope Tom is in touch with some of the 3886 design team which is probably scattered to the 3 winds now so he can tell them how much a small group of enthusiasts and bodgers love what they did.
Ref global economy, would love to debate that with you from a non-American view on the world, but its against the rules sadly and well, I've derailed enough of Tom's threads in the past.
But I hope Tom is in touch with some of the 3886 design team which is probably scattered to the 3 winds now so he can tell them how much a small group of enthusiasts and bodgers love what they did.