LM1875 (TDA2030 2.1) grounding issue - diyAudio
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Old 20th November 2013, 03:35 AM   #1
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Default LM1875 (TDA2030 2.1) grounding issue

This is my first project like this...so please be patient with me as I'm a total newbie. I'm trying to build my own Bluetooth stereo, and I'm actually very close. I'm using a 12v 150w switching power supply, and connecting it to the TDA2030 2.1 amplifier board. I need to power the A2DP Bluetooth module with 5v, so I built a small voltage regulator board to step the power down from 12v to 5v. Then I'm running the left and right channel outputs from the Bluetooth module back to the amplifier board.

I'm happy to report that I can connect to the Bluetooth module from my iPhone, and can even start playing music through the speakers. The problem is, the music is very "choppy", and then just stops playing after about 30 seconds. I can repeat after unplugging the power, with the same results.

From what I've read so far, it seems like a ground issue. I should note that the audio only works when I leave the audio output ground cable unplugged from the audio input on the amplifier board. If I plug it in, I get no audio.

I'll be honest, I don't really understand electrical circuitry. I've attached a picture of my project. One of the things I don't really understand: I run 3 wires from the power supply to the amplifier board, -v, +v, and ground. But the Bluetooth module only has two connections, one for power and one for ground. The only way to get 12v was to run the -v and + wires to the Bluetooth module (through the voltage regulator). But the how is it grounded? Is this what they call a "floating ground", and is this my issue? If so, how to fix it.

Any help would be greatly appreciated!
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Old 20th November 2013, 06:16 AM   #2
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Use +12 and ground from PSU to blue tooth module, do not use -12V, do not interconnect blue tooth ground to amplifier ground.
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Old 20th November 2013, 04:41 PM   #3
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Thanks Sivan. That's one thing I haven't tried yet. I'll run power directly from the power supply to the Bluetooth module (through the regulator board), instead of pulling the power from the amplifier board. I'll try it when I get home from work. Thanks again.
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Old 23rd November 2013, 04:43 AM   #4
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I ran power from the PSU to the Bluetooth module (through the regulator board), but I'm still having the same issue. Also, I tried using +12 and ground from the PSU, but it only measured at 4.45v and when I connected to the Bluetooth module, it dropped to 1.3v. It seems I can only get 12v by using the -v and +v.

From what I've read online, it sounds like I have a ground loop issue going on, but I don't know how to fix it. I'm attaching a new picture of my current configuration.
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Old 23rd November 2013, 05:38 AM   #5
Art M is offline Art M  United States
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GND is not a power supply output line, it is just connected to the Chassis and protective ground.
The only output terminals are +, +, -, -. This looks to be a Single output power supply, not a dual. even though it is showing 4 output terminals.
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Old 23rd November 2013, 01:53 PM   #6
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You may shorten the wires from/to BT-module and even your regulator board. Next thing will be checking for the output capacitor at the regulator. Get some 47uF with 100n in parallel. You may also try to improve the filtering in front of your regulator by adding a 10 ohms 0.1W resistor in your wire coming from the power-supply.

Does the BT-module work with a different amp attached?

There also might a be an interference coming from the power-supply which distors your 2.4GHz signal.
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Old 13th January 2014, 01:32 AM   #7
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I'm happy to report that the Murata mee1s1205sc DC-DC converter took care of the buzz caused by the ground loop issue. But now I'm having other issues. The speakers are distorted, and if I hook them all up, the amplifier "shuts down". I'm pretty sure it's a power supply issue. I've got two 3-1/2" 20 watt RMS drivers at 8 ohms, and a 6-1/2" 60 watt RMS sub at 4 ohms. I was trying to use a 12v 150w 10a power supply (12-0-12), but the amp would shut down immediately. My cousin said that 10 amps was too much for this amplifier, so I bought a 12v 60w 5a power supply, and it has been better, but there's something still wrong. I can play the sub and one driver. Although distorted, it will play and not shut down. The LM1875 chips don't even get hot. But when I hook up the second driver, then the amp shuts down. I tried just hooking up the 2 drivers without the sub, and it still shuts down. But the chips still don't get hot.

I don't really understand the power supply. I don't know if I'm giving the amp too much power, or if I'm not supplying enough power. I figure if the power supply wasn't keeping up with the speakers/amp, that the LM1875 chips would at least be getting hot, but they're aren't. I do have a heat sink attached.

My next attempt was going to buy an 18v 5a power supply.

Any suggestions?
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Old 9th February 2014, 08:32 PM   #8
bknabe is offline bknabe  United States
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Default groundloop fix

Can you post a pic on how you wired the Murata converter? I am having a similar groundloop issue. Thanks,
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