Hello,
I've recently got a 5V bluetooth receiver audio board to play music remotly to my speakers, before I soldered the power I tested it via a 5V phone charger and it worked fine..
When plugged into the DC-DC step down board the BT receiver board is making first high frequency noises and then it's just buzzing.
Any ideas how I could fix that problem?
Bluetooth board:VHM 314 Bluetooth Audio Receiver board Bluetooth 5.0 mp3 lossless decoder board Wireless Stereo Music Module-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group
Wiring diagram:
I've recently got a 5V bluetooth receiver audio board to play music remotly to my speakers, before I soldered the power I tested it via a 5V phone charger and it worked fine..
When plugged into the DC-DC step down board the BT receiver board is making first high frequency noises and then it's just buzzing.
Any ideas how I could fix that problem?
Bluetooth board:VHM 314 Bluetooth Audio Receiver board Bluetooth 5.0 mp3 lossless decoder board Wireless Stereo Music Module-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group
Wiring diagram:
Last edited:
It's due to a ground loop - the Bluetooth chip draws current in short bursts and this also affects the signal ground (as they are connected together), causing the noise you're hearing.
There's four possible solutions, one of them you already tried...
1. A very oversized ground connection. I'm not convinced this will work but it may be worth a try.
2. A 5v - 5v isolated supply. This will break the ground connection on the power feed side so the signal ground "floats" on the noise along with the signal hot. I've tried this with good success, the chips are cheap enough, eg
AliExpress
3. 1:1 audio transformer on the signal side. Results may vary but this should also address the problem.
4. Seperate power supply altogether for Bluetooth module and amplifier.
I've tried bypassing the noise with all manner of capacitors and chokes, with very limited success. In the end I found option 2. a straightforward and effective solution.
There's four possible solutions, one of them you already tried...
1. A very oversized ground connection. I'm not convinced this will work but it may be worth a try.
2. A 5v - 5v isolated supply. This will break the ground connection on the power feed side so the signal ground "floats" on the noise along with the signal hot. I've tried this with good success, the chips are cheap enough, eg
AliExpress
3. 1:1 audio transformer on the signal side. Results may vary but this should also address the problem.
4. Seperate power supply altogether for Bluetooth module and amplifier.
I've tried bypassing the noise with all manner of capacitors and chokes, with very limited success. In the end I found option 2. a straightforward and effective solution.
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I've read this thread with interest, as I have recently bought an all-in-one board with amp and blue-tooth system together...
This one
It has a similar issue where there is some Bluetooth noise getting through into the amp. I have not resolved the issue on my board, but I've read that that the bluetooth signal is being fed through from the bluetooth RF circuit being too close to the headphone jack location, and the headphone jack is fed directly to the amp. I also read that someone else fixed the issue by running the full double-ended audio signals from the bluetooth chip to the amp, as my original board has an op-amp to convert the double-ended audio signals to single-ended.
Currently, your signal is coming off the bluetooth board as three lines - a ground line, a left signal and a right signal. If you can find a left+/left-, and right+/right- signal, and take these four lines through to the amplifier, this might help. It's a lot of work to figure this out and test it, and it will change your whole volume control setup, working with a differential signal.
I'm still working through possibilities to resolve my board, but I'll be interested to watch how you go with yours. It's interesting to know that your first board didn't have the issue, but your subsequent boards do have the problem.
This one
It has a similar issue where there is some Bluetooth noise getting through into the amp. I have not resolved the issue on my board, but I've read that that the bluetooth signal is being fed through from the bluetooth RF circuit being too close to the headphone jack location, and the headphone jack is fed directly to the amp. I also read that someone else fixed the issue by running the full double-ended audio signals from the bluetooth chip to the amp, as my original board has an op-amp to convert the double-ended audio signals to single-ended.
Currently, your signal is coming off the bluetooth board as three lines - a ground line, a left signal and a right signal. If you can find a left+/left-, and right+/right- signal, and take these four lines through to the amplifier, this might help. It's a lot of work to figure this out and test it, and it will change your whole volume control setup, working with a differential signal.
I'm still working through possibilities to resolve my board, but I'll be interested to watch how you go with yours. It's interesting to know that your first board didn't have the issue, but your subsequent boards do have the problem.
.. because they have been properly designed, with fewer corners cut to reduce cost.
Cheers
Disappointing results
I've just tested one of these modules with a clean power supply and can hear the noise on the headphone jack (with headphones). I was able to reduce the noise a bit by adding a 1000uF cap at the power terminals, but the results were still not acceptable.
Without even measuring, it is clear that it doesn't come close to the published spec of 90dB s/n.
I suspect they just copied the numbers from the chip datasheet.
I've just tested one of these modules with a clean power supply and can hear the noise on the headphone jack (with headphones). I was able to reduce the noise a bit by adding a 1000uF cap at the power terminals, but the results were still not acceptable.
Without even measuring, it is clear that it doesn't come close to the published spec of 90dB s/n.
I suspect they just copied the numbers from the chip datasheet.
I just replaced linear converter with B1205S to power a bluetooth module I added in my car. The hiss is gone! Thank you very much for this tip.
I am facing this same noise issue in my diy stereo system.
In my case I am using a 24v 4A SMPS power supply for amplifier board and LM7805 voltage regulator ic for 5v Bluetooth decoder board.
And the Bluetooth board produces too much noise, also I observed that the noise reduces when I touch the metallic parts in the board. But I don't know where I can take a common ground point to earth the board metal parts.
I am also using the same power supply for the speaker protection board and gain board (regulated 12v).
My question is, If I use a separate power supply using 12-0-12v transformer for the speaker protection board, gain board and Bluetooth board, the noise issue will get solved? Also I can use the transformer center tap to ground the body parts!!
24V is too much for 7805.
Try a drop resistor in series, so the regulator sees about 9V input.
Same for 12V, drop the input to about 15V.
See what happens.
And proper grounding of course.
And put small value caps (pF / nF) as filters in parallel with the large smoothing caps, that might help.
Never mind if it is a SMPS, put extra caps.
Try a drop resistor in series, so the regulator sees about 9V input.
Same for 12V, drop the input to about 15V.
See what happens.
And proper grounding of course.
And put small value caps (pF / nF) as filters in parallel with the large smoothing caps, that might help.
Never mind if it is a SMPS, put extra caps.
The transformer secondary center tap needs to be grounded (usually), but does not provide grounding. A useful Ground usually comes from the power line Earth. But anytime you can touch part of the circuit and reduce an objectionable noise, insufficient grounding is a likely place to start. Adding in another whole linear supply (implied by the 12-0-12V mention) isn't likely to solve the problem -- you'll still need Earth Grounding. The 24V 4A SMPS is probably 'floated / double-insulated' (has a 2-wire mains plug) so your gear has no Earth whatsoever.
Remedy the lack of Earth, then address possible Conducted Noise.
Cheers
Remedy the lack of Earth, then address possible Conducted Noise.
Cheers
I can add a three pin socket for smps input supply
But to where I should connect ground? To 3pin earth grounding or to transformer center tap (or to negative pins of power supply!!)
And also, is it required to ground the ground wire of audio signal?
Here is the funny thing.
When I setup my system it was working fine of days. Crystal clear sound.
Then some wire shorted as its all in pieces on the speaker now.
doing a dry run before I move it all into a cabinet. This short triggered my safety lamp.
After this I got a nasty hum.
And the only way I could get rid of it was to power the bluetooth off a 12 volt car bat. That when the system is on powers the blue tooth and when the system is off charges the bat.
My doubt is what blew and created this problem.
Another thing you need to know upfront is if the grounds on multiple coils are shorted or kept separate.
i.e. is the 0 from the 15-0-15 also the same zero from your 24-0-24
I have also heard people say do not run a ground in your signal out. Just connect the two signal wires. Ground is anyway shared via the power supply pins.
My module has an Agnd for all the audio inputs and outputs. And a simple Gnd for the power.
But when it check with my meter it shows that agnd and gnd are shorted. i.e. the same.
When I setup my system it was working fine of days. Crystal clear sound.
Then some wire shorted as its all in pieces on the speaker now.
doing a dry run before I move it all into a cabinet. This short triggered my safety lamp.
After this I got a nasty hum.
And the only way I could get rid of it was to power the bluetooth off a 12 volt car bat. That when the system is on powers the blue tooth and when the system is off charges the bat.
My doubt is what blew and created this problem.
Another thing you need to know upfront is if the grounds on multiple coils are shorted or kept separate.
i.e. is the 0 from the 15-0-15 also the same zero from your 24-0-24
I have also heard people say do not run a ground in your signal out. Just connect the two signal wires. Ground is anyway shared via the power supply pins.
My module has an Agnd for all the audio inputs and outputs. And a simple Gnd for the power.
But when it check with my meter it shows that agnd and gnd are shorted. i.e. the same.