Hello everyone,
I have just finished putting together an LM3886 build from Neurochrome audio. It went together great, measures fine in terms of DC offset/gain, has no static/distortion etc however I am quite skeptical on the LM3886's that I had ordered from eBay.
As they were not in stock on Mouser or DigiKey at the time of purchasing the other parts, I decided to take my chances and look for a North-American based seller with good recent feedback thus purchacing a pair for 16-17ish dollars. They came in 3 days and looked good to me, checking for any poor QC/Cloning or obvious fake markings like the use of ink or right-skewed text.
I attached an image here (I have 2, both matched pairs supposedly) :
I have just finished putting together an LM3886 build from Neurochrome audio. It went together great, measures fine in terms of DC offset/gain, has no static/distortion etc however I am quite skeptical on the LM3886's that I had ordered from eBay.
As they were not in stock on Mouser or DigiKey at the time of purchasing the other parts, I decided to take my chances and look for a North-American based seller with good recent feedback thus purchacing a pair for 16-17ish dollars. They came in 3 days and looked good to me, checking for any poor QC/Cloning or obvious fake markings like the use of ink or right-skewed text.
I attached an image here (I have 2, both matched pairs supposedly) :
Good looks help but are not definitive.
But like they say: "the proof of the pudding lies in the eating" or here in Argentina, the Gaucho saying "en la cancha se ven los pingos" (the racetrack tells you which is the best horse), meaning:just use them (what else?) , but be cautious:
1) turn amp ON with bulb limiter without load (a good precaution always) and check DC voltages, offset, etc.
2) apply audio and drive it to clipping, still same conditions as before, scope out.
I was burnt by a lot of TDA2050 which measured "right" on DC but upper sinewave half abruptly clipped showing a leading edge, 5V below +V rail (lower half clipped normal) which in my view shows internal transistors did NOT stand rated +/-22V ; yet they work perfectly with +/-14V ,TDA2030 spec.
Meaning EBay parts often work, sort of, so seller gets good ratings ... but they don´t last long.
3) repeat without lightbulb , so it gets full mains voltage
4) repeat driving a load.
Or play it loud into your speakers, scoping output.
Peaks should clip symmetrically reaching within 3-4V of rails.
This is a "muscle" type test, and separates Men from weaklings 🙂
But like they say: "the proof of the pudding lies in the eating" or here in Argentina, the Gaucho saying "en la cancha se ven los pingos" (the racetrack tells you which is the best horse), meaning:just use them (what else?) , but be cautious:
1) turn amp ON with bulb limiter without load (a good precaution always) and check DC voltages, offset, etc.
2) apply audio and drive it to clipping, still same conditions as before, scope out.
I was burnt by a lot of TDA2050 which measured "right" on DC but upper sinewave half abruptly clipped showing a leading edge, 5V below +V rail (lower half clipped normal) which in my view shows internal transistors did NOT stand rated +/-22V ; yet they work perfectly with +/-14V ,TDA2030 spec.
Meaning EBay parts often work, sort of, so seller gets good ratings ... but they don´t last long.
3) repeat without lightbulb , so it gets full mains voltage
4) repeat driving a load.
Or play it loud into your speakers, scoping output.
Peaks should clip symmetrically reaching within 3-4V of rails.
This is a "muscle" type test, and separates Men from weaklings 🙂
"Ordered from EBAY" == FAKE.
The top marking is one of a chinese packaking plant (forgot the name, many use them), the logo is wrong, it should be saying TEXAS INSTRUMENTS, national is deader than a doornail. They killed the brand and culture alike.
The only reasonable monolithic speaker OpAmp I'm aware of, that remains, is STA540, I mean, made by a reputable company that you can find at distributors easily. Of course, if the LM3886 counts, it will be found with TI branding, most likely. See on their website how these are supposed to look like. But here, I could be wrong, and these could be great.
The top marking is one of a chinese packaking plant (forgot the name, many use them), the logo is wrong, it should be saying TEXAS INSTRUMENTS, national is deader than a doornail. They killed the brand and culture alike.
The only reasonable monolithic speaker OpAmp I'm aware of, that remains, is STA540, I mean, made by a reputable company that you can find at distributors easily. Of course, if the LM3886 counts, it will be found with TI branding, most likely. See on their website how these are supposed to look like. But here, I could be wrong, and these could be great.
Funny that I had visited the page some long time ago, and do not even remember! But I have something to add, the JM stands for the packaging plant! An example of several plant markings are W, J, JC. I do not have the location of JM at the moment.
Example here: https://www.onsemi.com/pcn/public/final-document/tMbf3uyVo83vVT_BBbt7Tw
I would be putting a dc blocking capacitor on the output in case they die and take out the speakers too.
