eBay mono LM1875 kit

hi
i am impatient...i did it!:D
i set the chip on 20V rail and it worked fine. so now its a TDA2040.
correct?

i let the amp run on its clipping border = 500mVrms with my sweep 5 minutes at 8R and its survived. the chip has 59°C then i stopped and cooled with fan.


pic 1 is the consumption during 500mVrms 1khz on 8R
pic 2 is the scope probe ...its about 11,1V rms = 15,5 Watt


chris
good night
 

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good morning kurtvisti


yes the pcb is ok. the components are maybe not the best but using +/-26V per rail is not recommended to any of these chips. TDA2030,2040, 2050 not more then 25V- datasheet .....the lm1875 is ok with +/- 30V at 8R and not at 4R!
actually my TDA2040?- fake 1875 is running since 90minutes with 20V per rail with a sweep of 10hz-35khz with 100mVrms. and the temp is on the chip 48°C. this is fine....don´t forget that no genuine TDA2030,2040,2050 is active or will be produces - so we have to expect a fake.
as i wrote i am surprised with the amazon kit that this chip can handle 25V per rail and give the recommended 20WAtt at 8R

so its definitive no TDA2030 - know i believe its a better one. its important to check because my transformer is a 18 -0 -18V AC = 25V DC.



chris
 
25V rail ... no smoke

Hi


i did it !....25V per rail and no smoke


pic 1 idle
pic 2 +3 1khz with 100mVrms at 8R
pic 4+5 1khz with 600mVrms at 8R near clipping

13,1 Vrms on the scope give me 21,4Watt at 8R calculated...


so my chip is fine :cool:
chris
 

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Good morning.



+/- 26V is out of specifications, so magic smoke is a logical consequence.

I know that TDA have been off the production line for years but I don´t know another chip that has similar characteristics to LM1875. In all the websites I have consulted they talk about TDA models.


The good news for all (thanks to Chris's tests) is that the fake chip is good enough. How much? I do not know
 
Sure, you are right. What I mean is that to be a fake (a TDAXXXX), the chip does its job in an acceptable way.

As I said before, the cost of the kit is about 2€ or 3€ for me the PCB is the important thing, the rest of the components is simply a gift.

However, although I have original LM1875, I am curious to know what chip they have used for counterfeiting.


Jose
 
As for the audio quality, I can tell you that so far, the differences I have found have been greater "brightness" in the LM1875. The fake has a "warmer" profile.

If you mean pure measurements, both were quite linear in a sweep of 20Hz to 20Khz although I only used a voltage of +/- 15vDC and +/- 18vDC for these tests, so take this with tweezers.

Chermann has a better laboratory tools so maybe he can provide more data.
 
Hi again


so 4 hours test of the fake...i will say tda2050is done. 70mVrms input with my sweep let the chip run at 40°C with this heat sink configuration.
additionally to this i let this chip run at 5 minutes full power= 600mVrms sweep , 25V rail and 8R load. its about 13,5Vrms = 22,7Watt calculated.
the chip gets after 2 min about 73 °C then its stable up to 5 min...then i cooled it with fan.
i do all this effort like my class D chip projects. my amps had to run very long before i go to my good speakers. :) now i tested just the amp board and i have to check the other chips i have got....


yes you are right - the power says nothing about the sound. my first step must be to check the rail voltage i can handle because of my trani. so this is done.;)



i am not able to measure THD so i will try with rectangle or square to find some "ringing/oscillation"...i am not an expert guys;)
and yes this kit give me a lot of fun and much learning headache :D


BTW....my son is 11years and he finished a kit well...:)

chris
 
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Hi rabbitz


thanks for your hint but i go for 18-0-18 and these transformers are on my bench,;)


i did a 6 hours test with my aliexpress kit with 100mVrms sweep , 25Vrail 8R load ....its about 2,3Vrms output....0,7Watt......the chip gets stable with 46°C all the time....so for me this fake is a TDA2050.


now i test the second ali kit (from my son) and it worked with 25V per rail too.:)
test is ongoing.....running at 46°C stable...
DC offset is 0,1mV !!!

chris
 
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