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Old 15th January 2017, 09:38 AM   #1
diyAudio Member
Join Date: Dec 2016
Default Noise issue from bluetooth source or TDA7498, Help me find.


I connected 2 amps (TPA3116 for speakers and TDA7498 for sub-woofer) to one bluetooth receiver headphone out, which is creating the continuous hissing noise along with a mild whistle noise throughout. If I disconnect the TDA7498, the noise totally goes away, OR if I disconnect the bluetooth module and connect to my phone out, the noise goes away. I tried to make a common ground, which did not worked well Or may be I did not do it correctly.

both TPA3116 and TDA7498 is connected to 24V power from battery.
for the Bluetooth module, I am using a step down converter to 12V. I also tried connecting the bluetooth to a direct 12V battery terminals without stepdown just to make sure the noise is not from the stepdown converter, but that did not worked, I still have the hissing noise.

So this combination produces Noise
Bluetooth Out + TPA3116 + Sub-Woofer TDA7498 = Noise

and in this combination, there is no noise
Phone Out + TPA3116 + Sub-Woofer TDA7498 = No Noise
Bluetooth Out + TPA3116 = No Noise

Can you please help me find if the issue is with the TDA7498 or Bluetooth module? or something else?


Amp stereo input cables are soldered to the bluetooth headphone output cable.

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Old 15th January 2017, 11:03 AM   #2
diyAudio Member
Join Date: Jan 2017
Location: Spain
Maybe you should check ground connections, they can generate a lot of noise.
You can add a ground loop isolator or something, wish i can help more
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Old 19th January 2017, 03:16 AM   #3
diyAudio Member
Join Date: Oct 2014
which BT module are you used?
besides Ground connection,the BT module will be the source of niose
diff output with Cap coupling?any filter on the signal line?
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Old 31st January 2017, 12:00 PM   #4
diyAudio Member
Join Date: Dec 2016
thanks for the response guys!,
yes, noise was coming from the bluetooth, I was using this bluetooth module, Bluetooth 4.0 PAM8610 taking the headphone out from that board, that caused the noise, now replaced with Bluetooth module output op amp with NE5532 and works good, the noise is gone,

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