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Class D Switching Power Amplifiers and Power D/A conversion

TPA3250 somebody is listening?
TPA3250 somebody is listening?
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Old 7th January 2019, 11:14 PM   #751
Wiliks is offline Wiliks  Slovakia
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What is the value of FREQ_ADJ resistor in that FX-audio amp board? it should be pin #15 i think.
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Old 8th January 2019, 06:27 AM   #752
chermann is offline chermann  Austria
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Quote:
Originally Posted by Wiliks View Post
What is the value of FREQ_ADJ resistor in that FX-audio amp board? it should be pin #15 i think.
yes it is pin 15. datasheet 10.2.1.2.4..do you want to change the working frequency? i remember the setup at the fx is about 450khz.
if you want to change look at table 12 and table 13.

Last edited by chermann; 8th January 2019 at 06:37 AM.
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Old 8th January 2019, 12:54 PM   #753
chermann is offline chermann  Austria
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Quote:
Originally Posted by chermann View Post
luckly I planed to use this for my tpa3255 YJ boards...


its really tight !




SQ compare between both amps not done. same opamp (4562) same input caps (elna silmic 2) but now different coils


chris
Questions to the experts here...

should i solder the 3rd pad of the coils (würht 7443631000) together and connected to ground?

what happend? Better SQ?


thanks you in advance
chris
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Old 8th January 2019, 01:01 PM   #754
Wiliks is offline Wiliks  Slovakia
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yes I was thinking about more ways of improvement and this one looks interesting. Its just about changing one resistor to get it working at 600kHz (oscilating at 3,6MHz according to datasheet) I am surprised that noone tried it yet, and i would be very curious if that brings further sound improvements or just more heat, dont know...

I am still waiting to get my amp, so once it will arrive i will definitely test that
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Old 10th January 2019, 08:32 PM   #755
chermann is offline chermann  Austria
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Default Sound check with different opamps

Good evening
After changing the the fat coils in both amps i did the SQ check for my DIL opamp i bought:
LM4562, LM49720, BB2134
at post 440 and 575 i did some compare tests.

TPA3250 somebody is listening?


the distance get closer but its the same as i have described. all opamps made the job better than the fake opamps which come with the fx502spro.


slightly difference:
4562 is my favorite , this amps is darker and give me all natural sound i like, deep stage and no real mistakes.
lm49720 is closed to the 4562 but is not so dynamic and dark.
BB2134 is not as bad as i described. he is very present in the middle of the speaker, analytic and is concentrating his force in the middle of the speakers...it feels like the sound comes through a big 3m magnifier glass, less sound from the back ground--> ideal for headphones


pic shows my listening examples

chris
Attached Images
File Type: jpg fx502spro coil compare3.JPG (34.8 KB, 124 views)

Last edited by chermann; 10th January 2019 at 08:38 PM.
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Old 10th January 2019, 08:36 PM   #756
chermann is offline chermann  Austria
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to test my soic opamps to dil8 i bought this
10 PCS SOP8 SO8 SOIC8 SMD to DIP8 Adapter PCB Board Convertor Double Sides: Amazon.de: Beleuchtung


any idea where i get some correct pins to solder in that fits into the DIl-8 socket of the fx502spro???




thank you in advance
chris
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Old 10th January 2019, 08:38 PM   #757
doctormord is offline doctormord  Germany
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I wonder when you came to the conclusion that the original opamps are/where fake? Am i getting old?
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Old 10th January 2019, 09:16 PM   #758
chermann is offline chermann  Austria
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Originally Posted by doctormord View Post
I wonder when you came to the conclusion that the original opamps are/where fake? Am i getting old?

because of:


post 333
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Old 11th January 2019, 06:40 AM   #759
chermann is offline chermann  Austria
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maybe thats the reason why the LM49720 and LM4562 are sounding different

http://www.waynekirkwood.com/images/...dio_Op_Amp.pdf
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Old 11th January 2019, 11:49 AM   #760
LC1979 is offline LC1979
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So I just swapped out the (fake?) opamps from my FX502spro and put in LME49720NA.

The problem now is that I have a significant crackling sound in my right channel that I'm fairly certain wasn't there before

Is there any chance that I broke something when I opened the amp, maybe by pressing too hard on the board when inserting the opamps?

Or what else is it likely to be?
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