Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

eBay mono LM1875 kit
eBay mono LM1875 kit
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 17th September 2019, 08:22 AM   #131
kurtvisti is offline kurtvisti  Denmark
diyAudio Member
 
Join Date: Oct 2017
Location: Sorø
Quote:
Originally Posted by blackdod View Post
Good morning.

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

My ebay kit chips says LM1875 so therefore not out of specifications.
I don’t want a TDA20xx or a TDA20xx lookalike in my LM1875 amp.
Decent quality components bought instead....for me life is to short for fakes and poor quality.
  Reply With Quote
Old 17th September 2019, 08:39 AM   #132
blackdod is offline blackdod  Europe
diyAudio Member
 
Join Date: Jun 2011
Location: Spain
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
  Reply With Quote
Old 17th September 2019, 08:49 AM   #133
kurtvisti is offline kurtvisti  Denmark
diyAudio Member
 
Join Date: Oct 2017
Location: Sorø
Yes, and you are right too....it would be fun to find out which chip is used.
But I wonder if it’s possible by measuring only supply voltage and RMS output?
It might still be a cheaply made clone with bad sound quality specs.....
  Reply With Quote
Old 17th September 2019, 09:13 AM   #134
blackdod is offline blackdod  Europe
diyAudio Member
 
Join Date: Jun 2011
Location: Spain
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.
  Reply With Quote
Old 17th September 2019, 10:41 AM   #135
chermann is online now chermann  Austria
diyAudio Member
 
Join Date: Jan 2017
Location: Vienna
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


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

chris

Last edited by chermann; 17th September 2019 at 10:54 AM.
  Reply With Quote
Old 17th September 2019, 10:50 AM   #136
chermann is online now chermann  Austria
diyAudio Member
 
Join Date: Jan 2017
Location: Vienna
Default error in post 120

pic 4+5 are with 1450mVrms 1khz into 8R - before clipping = its about 12Watt rms


typo !!!

pic 4+5 are with 450mVrms 1khz into 8R - before clipping = its about 12Watt rms
  Reply With Quote
Old 17th September 2019, 11:19 AM   #137
blackdod is offline blackdod  Europe
diyAudio Member
 
Join Date: Jun 2011
Location: Spain
Quote:
Originally Posted by chermann View Post


...and yes this kit give me a lot of fun and much learning headache


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

This is one of the best parts of this hobby.
  Reply With Quote
Old 17th September 2019, 01:48 PM   #138
rabbitz is offline rabbitz  Australia
diyAudio Member
 
rabbitz's Avatar
 
Join Date: Jul 2003
Location: Newcastle, Australia
Good information Chris and thanks for sharing.

Probably best if you use the chip that comes with the kit is to use 15-0-15 transformer (21VDC rails) and if using a genuine TI LM1875, then 18-0-18 transformer (25VDC rails) is fine.
__________________
If there are no dogs in Heaven, then when I die I want to go where they went - Will Rogers
  Reply With Quote
Old 17th September 2019, 05:34 PM   #139
chermann is online now chermann  Austria
diyAudio Member
 
Join Date: Jan 2017
Location: Vienna
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

Last edited by chermann; 17th September 2019 at 05:44 PM.
  Reply With Quote
Old 17th September 2019, 05:37 PM   #140
chermann is online now chermann  Austria
diyAudio Member
 
Join Date: Jan 2017
Location: Vienna
So lets do some math to calculate the gain of the kits.if i remember right...
Gain = 20 *log (Uout/Uin) - 20*log (2,3V/0,1V) = 27,23 dB


chris

Last edited by chermann; 17th September 2019 at 05:39 PM.
  Reply With Quote

Reply


eBay mono LM1875 kitHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
LM1875 Ebay dual channel pcb question nenad88 Chip Amps 11 29th August 2018 11:21 PM
Chinese Mono LM1875 Board Twil Chip Amps 54 23rd April 2018 08:04 AM
ebay lm1875 pcb asuslover Chip Amps 7 27th August 2016 03:58 AM
Running two LM1875 mono amp from single psu si82 Chip Amps 21 2nd June 2014 03:32 PM
Just fired up my new dual mono lm1875 Gainclone. Shoog Chip Amps 5 19th January 2004 06:09 PM


New To Site? Need Help?

All times are GMT. The time now is 06:09 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki