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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 11th January 2019, 03:18 PM   #761
chermann is offline chermann  Austria
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Quote:
Originally Posted by LC1979 View Post
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?



sorry for you...
did you really check the direction of the opamps...pin 1....pin 8 orientation!!!!
TPA3250 somebody is listening?


check visually if every pin is in the socket correctly
and no...there is not a really chance that you push sooo hard that the pcb is broken....i guess


put them out and the fake in-.....is the crack still here?

Last edited by chermann; 11th January 2019 at 03:21 PM.
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Old 11th January 2019, 03:53 PM   #762
LC1979 is offline LC1979
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Quote:
Originally Posted by chermann View Post
put them out and the fake in-.....is the crack still here?
Great idea, thanks! Did this and the crackle is gone, phew!

Got the new opamps from a reputable store, faulty I guess?!
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Old 11th January 2019, 04:31 PM   #763
chermann is offline chermann  Austria
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Originally Posted by LC1979 View Post
Great idea, thanks! Did this and the crackle is gone, phew!

Got the new opamps from a reputable store, faulty I guess?!



very very seldom that a repudiate store send you cracked chip...

but ok...crack is gone and the amp is playing music



but -->go ahead find the failure !...


mark your new opamps and change one after the other into the board.
e.g.
socket 1 old opamp
socket 2 new opamp1 - new opamp2



socket 1 new opamp1 - new opamp2
socket 2 old opamp


chris
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Old 12th January 2019, 05:05 PM   #764
LC1979 is offline LC1979
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Quote:
Originally Posted by chermann View Post
but -->go ahead find the failure !...
Replacement on its way
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Old 12th January 2019, 07:27 PM   #765
chermann is offline chermann  Austria
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Fine......😁
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Old 12th January 2019, 09:40 PM   #766
chermann is offline chermann  Austria
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Exclamation ..Wrong datasheet TPA3250...april2016

i want ot look at the implementation of a bigger cap e.g. 470µF at AVDD


i found that the chapter 6 and the chapter 10.2 show different pin layouts!!!


pic 1 is the correct pin layout of tpa3250
pic 2 is the wrong BTL-application it shows the TPA3251

TPA3250 and TPA3251 are mirrored at pin 8 9 and 14 15 !!! (irribeo told me that a long time ago..


chris
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Old 16th January 2019, 07:10 AM   #767
chermann is offline chermann  Austria
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Hi

yesterday night i go ahead with something light...


...are the FX doing some additional gain?....yes the implementation with volume knob do this!

yesterday night i did some short quick measurments with my diff probe of the scope
the input into the amp was set with 100mVrms / 1khz and at the pin 1 (outA) give me different voltages depending of the position the volume knob. this is logical and this is why we have a volume knob
the position with no gain is about 1 o clock. here i measure exactly what i set as input. 100mVrms/1khz
What i realize is if you set the volume knob more than 1 o clock, eg 2 o´clock position, i get "ringing" = the top of the sine is smeared and peaky, starting at 580mVrms/1khz rms input.
at 24V i got clear clipping at 690mvrms -46,7Vpp at 8R (34Watt)


additionally
yes i can confirm that the LM317 power up just the opamps.
the LM2596S is pushing 11,53V to the ams1117-3.3V for the logic chip (on off chip)


chris
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Old 16th January 2019, 07:28 AM   #768
chermann is offline chermann  Austria
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Hi again

according to the upper study . the input of the tpa 3250 chip can handle max + - 3,9V input at all INPT_X entry so no trouble with additionally gain from the opamps to the chip....ok no problem at that point (datasheet table 6 for BTL)


my question is about gain up or down at the opamps soundwise? could that be that if we change with the volume knob the gain that some opamp chip do something "different" soundwise????
can i measure this with scope? or just with THD equipment?



chris

Last edited by chermann; 16th January 2019 at 07:34 AM.
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Old 16th January 2019, 08:18 AM   #769
voltwide is offline voltwide  Ireland
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Maybe you measure some high frequency ringing that is above the audio band and thus inaudible. Sometimes you see inaudible things on the scope, sometimes you hear distortions your scope does not show you. Could you show a screenshot of your ringing?
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Old 16th January 2019, 09:29 AM   #770
chermann is offline chermann  Austria
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Maybe you measure some high frequency ringing that is above the audio band and thus inaudible. Sometimes you see inaudible things on the scope, sometimes you hear distortions your scope does not show you. Could you show a screenshot of your ringing?

yes i will...evening..
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