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Class D Switching Power Amplifiers and Power D/A conversion

Problems with amp and Bluetooth module.
Problems with amp and Bluetooth module.
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Old 9th November 2017, 01:39 AM   #11
cfaye is offline cfaye
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I just tested the same board. Suffers from the ground loop hissing endemic to these all-in-one bluetooth/amplifier boards. To its credit - if you pause your bluetooth playback, it shuts off the amp a split second later to cut the hiss. The heatsinks are just glued on, so one of mine had fallen off. Otherwise the components are pretty good and the amp is very nice sounding - although there is no auxiliary input.

I was able to get it quite loud at 18v. It sounds silly - but check the volume of your bluetooth source. I was disappointed in the output until I noticed that the volume on my iPhone was at two bars. Once I turned the iPhone up, I had no problem making a lot of noise.

The controls provide good flexibility to tune to your speakers. If you don't mind the hiss, this is probably one of the best all-in-ones. There is only a mild beep with "on" and bluetooth connect - there is no loud voice about status, nor is there a super loud beep. I also didn't find any loud on/off popping, although I didn't try every combination.

I am going to ditch the all-in-one concept and go to a separate bluetooth module and amp. That way you can use an isolated power supply for the bluetooth and/or use isolating transformers for the bluetooth audio signal line to the amp and eliminate the ground loop hiss.
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Old 10th November 2017, 12:43 AM   #12
Bustedparts is offline Bustedparts  United States
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Ok. I did some measuring with my fluke while I am at work. In from the bluetooth module is .950 volts. Then i took a mesurment at the output with the speakers hooked up. Turned the volume to max. 2.975 is the max A/C voltage mesured. The speakers mesure 3.2 ohms from the neg to pos. I am running it on a better 19.8 volt 3 amp power supply. The speakers do not distort at all at full volume. And it isnt really that loud. So i am not sure what couks be wrong.
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Old 10th November 2017, 06:32 PM   #13
millstonemike is offline millstonemike  United States
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Quote:
Originally Posted by Bustedparts View Post
Ok. I did some measuring with my fluke while I am at work. In from the bluetooth module is .950 volts. Then i took a mesurment at the output with the speakers hooked up. Turned the volume to max. 2.975 is the max A/C voltage mesured. The speakers mesure 3.2 ohms from the neg to pos. I am running it on a better 19.8 volt 3 amp power supply. The speakers do not distort at all at full volume. And it isnt really that loud. So i am not sure what couks be wrong.
I presume you used a sine wave to measure RMS voltage with the fluke. If so, your only getting about 3:1 gain between the BT output and the amp chip output.

I wonder if some resistors in the op amp circuits are mis-populated reducing the BT signal level because the minimum gain the chip supports is 19 dB (9x gain) and most all TPA311X implementations are set to 26 dB gain (~20x gain). You could measure the voltage at the TPA3116 inputs to verify.
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Old 11th November 2017, 04:23 AM   #14
Bustedparts is offline Bustedparts  United States
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I did not use a sine wave. I didn't know that that was a standard practice . I am new at this . Is there a phone app I can get to input it to bluetooth? I will get a data sheet on the chip so I can check the voltage level at the chips. Also sending a sine wave through the bt will be somewhat annoying . What kind of resistor would be suitable to put in the speaker's place for testing.
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Old 11th November 2017, 07:32 AM   #15
Mooly is offline Mooly  United Kingdom
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Problems with amp and Bluetooth module.
You can create a sinewave test tone using Audacity and save it as an MP3:


Installing and using Audacity. A get you started guide.

Here is a 440Hz (less annoying than 1kHz) sine wave test tone (64kbs MP3 file) to get you started.
Attached Files
File Type: zip 440 Hz Sine.zip (433.0 KB, 2 views)
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Old 10th July 2018, 09:18 AM   #16
Rude1 is offline Rude1  India
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I have a similar board, with dual TPA3116D2 chips, 3 channels, citing 2x50W and 1x100W. The issue I'm facing is that with amplifier volume set to 70-75% range, any increase in the Source (a DAC) beyond 60% of it's volume, the speakers stop momentarily during the playback like for a fraction of second. This keeps happening unless I turn down either the source volume or the amplifier volume. What could be the problem here? Source giving too much high powered signal, beyond the input sensitivity of the amplifier or the amplifier not powerful enough to handle the load?
The amplifier is connected to the source using RCA cables. It's being powered by the 90W Dell laptop PSU. I did try to swap it with a 24V 10A Switching PSU but the problem persisted.
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Old 10th July 2018, 11:02 AM   #17
doctormord is offline doctormord  Germany
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Does this happens on all 3 output channels?
The TPA have an OC/OT protection build in (overcurrent/overtemp) which can be wired to self clear after about a second. But this involves some heat/time constant to occur.If there's a opamp based xover between BT and TPA the opamp might get overdriven into saturation which may get you in trouble if these aren't rail2rail and do some fancy amplitude folding at the output which result in something like you describe. Do the speaker cones "stay" in/out for that second?
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Old 10th July 2018, 11:30 AM   #18
Rude1 is offline Rude1  India
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The board I have, doesn't have Bluetooth module, just RCA input. It happens on all the 3 channels, mainly seen during bass heavy songs and yes the moment this happens, the diaphragms stay put at rest, neither in, nor out.
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Old 10th July 2018, 03:48 PM   #19
doctormord is offline doctormord  Germany
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Then i would guess that the over-current protection is kicking in. If this occurs for all 3 channels, they must have wired the FAULTZ pins altogether.
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Old 10th July 2018, 03:58 PM   #20
Rude1 is offline Rude1  India
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So, is there any way to fix it.
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