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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 1st December 2018, 02:12 PM   #711
forestsgump is offline forestsgump
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Join Date: Dec 2017
Quote:
Originally Posted by chermann View Post
changing caps is not need now.just add a caps in parallel.


pic 2..the smal red capsTPA3250 somebody is listening?
Chris ~ just curious, have you done any mod for removal of speaker-pop during power-down?
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Old 1st December 2018, 03:25 PM   #712
chermann is offline chermann  Austria
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Quote:
Originally Posted by forestsgump View Post
Chris ~ just curious, have you done any mod for removal of speaker-pop during power-down?

as i wrote pages before...i do not have this issue....
and...


if i am ready with my YJTPA3255 mods i restart the FX502spro journey...
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Old 3rd December 2018, 12:30 PM   #713
Overeem is offline Overeem  Netherlands
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Join Date: Mar 2008
Hi,
My first post in this thread.

I bought the FX502spro and trying to find out how much sound I can squeeze out of it.
Changed all electrolytics for better Q and 50V. Opamps 4562. filter the noise on the LM317. exchanged the 33uH for 150mH after the buck regulator. Exchanged the air coils for shielded types (lot of work as in these where glued...) and took filter caps out and smaller value polyprop. 470 uF on AVDD.
Bought 32V adapter, so its running on 32 V now. (much better than 24V)

The sound has improved dramatically. And it is really interesting to see what can be squeezed out. Generally I like the sound of this class-D, it is still not perfect. Sound stage is wide and high, but lacking real depth.

After exchanging the 33uH after the Buckregulator the hum with volume turned down has gone. With my ear at the speaker I hear still some noise.

But the strange thing is, when I turn up the volume, at a certain point the hum is back. But turning it further (last quarter or so) the hum disappears again. Ofcourse the hum is in the range I would listen to.
Someone any idea how this can happen? And how to resolve?

Many thanks.
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Old 3rd December 2018, 01:35 PM   #714
chermann is offline chermann  Austria
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Join Date: Jan 2017
Location: Vienna
Quote:
Originally Posted by Overeem View Post
Hi,
My first post in this thread.

I bought the FX502spro and trying to find out how much sound I can squeeze out of it.
Changed all electrolytics for better Q and 50V. Opamps 4562. filter the noise on the LM317. exchanged the 33uH for 150mH after the buck regulator. Exchanged the air coils for shielded types (lot of work as in these where glued...) and took filter caps out and smaller value polyprop. 470 uF on AVDD.
Bought 32V adapter, so its running on 32 V now. (much better than 24V)

The sound has improved dramatically. And it is really interesting to see what can be squeezed out. Generally I like the sound of this class-D, it is still not perfect. Sound stage is wide and high, but lacking real depth.

After exchanging the 33uH after the Buckregulator the hum with volume turned down has gone. With my ear at the speaker I hear still some noise.

But the strange thing is, when I turn up the volume, at a certain point the hum is back. But turning it further (last quarter or so) the hum disappears again. Ofcourse the hum is in the range I would listen to.
Someone any idea how this can happen? And how to resolve?

Many thanks.
Hi

oh....nice that you did a lot of changes...do you have some pics for us.

@hum
hum like 50Hz-100Hz...or e.g. pink noise over the speakers?


lg
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Old 3rd December 2018, 01:49 PM   #715
chermann is offline chermann  Austria
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Join Date: Jan 2017
Location: Vienna
Quote:
Originally Posted by Overeem View Post
Hi,
My first post in this thread.

I bought the FX502spro and trying to find out how much sound I can squeeze out of it.
Changed all electrolytics for better Q and 50V. Opamps 4562. filter the noise on the LM317. ........

Many thanks.
Do you have no thermal problems with the LM317. originally it is set for 24V output...but if you push 32V you should have at least 1 Watt Dissipation.
e.g.

8V different , 160mA drawn by all elements (post #222)= 1.28Watt
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Old 3rd December 2018, 02:27 PM   #716
Overeem is offline Overeem  Netherlands
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Join Date: Mar 2008
No, everything stays pretty cool.
I read about more heat with different voltage than 24V, but that is not my experience..

I think only the 2 opamps are after the LM317.

Last edited by Overeem; 3rd December 2018 at 02:41 PM.
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Old 3rd December 2018, 02:38 PM   #717
Overeem is offline Overeem  Netherlands
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Join Date: Mar 2008
No, not noise. But indeed like 50..100Hz. Only higher, I think.
Attached Images
File Type: jpg WP_20181203_15_29_10_Pro.jpg (986.2 KB, 92 views)
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Old 3rd December 2018, 04:21 PM   #718
Overeem is offline Overeem  Netherlands
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Join Date: Mar 2008
Quote:
Originally Posted by forestsgump View Post
10% safety factor for capacitor, Oh~Ye - thks fr confirm, now i have peace of mind supply FX502spro with meanwell configured 31V.

You have a point on heat problem, my thoughts of using 31V beyond 24V:
~ TPA3250 Power output depends on voltage -- was hoping 31V provides more for any transient music peak.
~ 24V from LM317~1.5A if undergood dissipation
Rough estimate: This 24V supplies NE5332 Op-Amp (datasheet 16mA) , to LM2596HVS gives 12V for TPA3250 Logic/Gate control (datasheet 40mA), to AMS1117 to provide 3.3V for 8bit MCU ST S003F3P6 (datasheet 100mA) ~ total max approx 0.16A
LDO LM317 ~ 7V drop gives 1.2W heat.

What else did i missed?

2 items unsure:
~ International Rectifer IRF9530N -- what function on FX amp?
~ Does FX TPA3250 back-stage driven by whatever voltage from DC Supply voltage (OR being internally regulated by LM317 - i highly doubt, but not sure what jigglebones is implying)?
from post#222

I checked again, but the lm2596 is fed directly from powersupply, not from LM317. So only the 2 opamps are behind the LM317.

Rectifiers are there to prevent wrong polarization of power.
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