If the mute is active low, couldn't you use a resistor and capacitor to add a suitable delay on startup? You may have trouble depending on the input impedance of the mute pin. If it is less than the resistor in your RC circuit it would.discharge the capacitor faster than the other R can charge it so maybe add another resistor between RC circuit and mute. V+ ---> 1M2 R ---> 1uF C ---> 2M0 R ---> Mute Pin
The ST data sheet for the TDA7492P shows a 2.2uF cap to ground with a 30K-33K resistor in series with the control line. www.st.com/content/ccc/resource/technical/document/datasheet/35/01/97/6b/20/ce/40/6f/CD00211320.pdf/files/CD00211320.pdf/jcr:content/translations/en.CD00211320.pdf
Have you considered routing the mute through the input detect pins on your earphone jack? It looks to me like the two pins at the bottom right of the connector would be shorted with the connector in, and open circuit without it. That doesn't help for when you turn on the amplifier with an input plugged in, but it seems like it's probably a reasonable compromise.
The suggested resistor capacitor delay should work fine, but might be an idea to place a diode in parallel with the resistor to discharge the capacitor quickly at switch off.
Why not to use some simple delayed latching circuit, hook it up to the power switch of the whole board? It would be much more convenient than a second switch to power this thing on. Either that or replacing the push button with a 3 state lever switch that will have 3 positions in that order: OFF / ON / ON and resistor closed.
The audio (power) jacks have a middle connector which is normally not used. You might be able to place that resistor on its path to be bypassed, every time you insert the audio input jack. Which will bypass the resistor.
Can you not put a small Capacitor in line with that 10K to delay the Mute when it powers up ? I would guess the bigger the cap, the longer it takes to charge it to 3.3V before it unmutes and once it reaches 3.3, it unmutes when the Umphf is over
Is there a way that you could tie into the microcontroller to perhaps reprogram it? I mean it just occurs to me something like that might be possible with some bodge wires and a little patients. Provided that is, that they haven't scrubbed the numbers off the chip or used something that doesn't come up with any kind of schematic when you search for it. I think that might be something worth looking into because if you can just add the code to unmute it after the 3 second key-press that would make more sense to me than having to fit a switch into your project. I mean why make it more complicated than it has to be. And yes I do quite thoroughly realize the irony of that last statement considering the context...
Could you not utilise the minijack port to do the muting for you in some way when a jack is plugged in? And unmute when unplugged? Even change the jack port for something that could do this?
Julian, why don't you just add an override switch with a resistor and capacitor to override the bluetooth module just enough to delay the module power on? (Oh wait you already said that.)
it would be cool if you showed replacing the aux jack with one that has a normally open switch for detecting when a plug is inserted. that would make the speakers pop only if you start it up with a plug in, minor improvements, but allows the Bluetooth to work fully as designed
You must have a different firmware version on the amplifier, mine plays "line in" with no bluetooth connection and no bridging resistor but it does "pop" a little when I turn it on. There is a version identifier on the top right of the board, mine reads "SW - HF01 V3.2" and under that it reads "150419"
Maybe you could modify your board with a different aux jack. Like the ones that have a little switch in it to determine if there's a jack in it or not. With no plug connected, it goes to bluetooth. With a plug, the aux.
Cant you do a lil delay circuit between the power button and the resistor with a transistor and a cap limited by a resistor to make it charge up in 2-3 seconds then triggering the transistor to then put the resistor in series ? This might not work with the power off doh but by the looks of things the power on was the most extreme.
You could use a transistor with a short delay (a capacitor??), to mute the output for a second, before it switches on (or off) thus presenting a suitable resistance in lieu of that 10k Ohm one. The old fashioned way, which still turns up occasionally, would be to add a delay relay to the amp output or to the 'unmute' resistor connections. One DP relay would switch both channels.
You don't need a switch to mute the amplifier when switching on. Leave the 10k resistor connected, and connect an electrolytic or tantalum capacitor between the mute terminal and 0V. (Perhaps you can increase the resistor value to 100k and use a 10 uF tantalum capacitor to give a 1 second time constant). You might need to connect a diode across the resistor to discharge the capacitor when switching off.
That's what I was going to ask. Is there a way to disable the Bluetooth? Maybe with the Bluetooth off, it will unmute the sound and allow the 3.5mm jack to work.
Add a NPN transistor in series (CE) with the resistor. Add a cap from base to ground. Add high value resistor from the high side of the mute circuit to base. When powered down cap will discharge via BE diode of transistor. When powered on transistor will be off. As cap charges transistor will turn on. Possibly consider a Darlington configuration.
@Jeff Merlin it says "Published 27.06.2017" under the video and i checked Julian's channel yesterday evening and it was not yet uploaded at that moment. Uploaded maybe but not published.
Yes, I'm experimenting with early access for Patreon subscribers. It's the least I can do, in return for their generosity. Unfortunately, it seems to have put an end to the "first comment" shenanigans ;)
Got same (well, it looks the same, but as we know that means nothing :-)) board that I've not played with yet. Just wondering how bluetooth security works. If my bluetooth source isn't connected, can my neighbour randomly connect? Was kinda hoping you have to put the thing in pairing mode but the video seems to suggest that's not the case :-( Anyone know?
Hey Julian I was wondering how this project was coming along. (How you plan to charge the completed project.) I was wanting to do a similar project. Perhaps not that specific bt amp but something around 15w per chan. And a USB charging circuit for an iPod / phone
I'm still waiting for the second speaker (which the seller promised to send). The remaining two supercapacitors won't be coming - they've been refunded. So it's just a waiting game at the moment :(
Im surprised that you are messing around with this amp when there are soo many little boards out there.. Though you would have tried a few different ones.
So why did I watch this? Was it to remind us you have a bluetooth amp module and 1 speaker still connected by loose wires? Why would you even upload a failed test of the 3 second mute thing.
ya if you don't have close to 24v the gain all the way up is terrible and I have had a couple of those boards mostly without the power switch or the 3.5 in but the one I did have with the 3.5 in it was seeming just in parallel but I don't know
Hmm, I noticed that when you boosted the speaker volume it interfered with the focusing on your camera. Possibly the force of the sound waves was moving the camera slightly? Maybe you could do some testing of that?
An RC coupling would do it. If you need/want a digital ON/OFF signal, you could go for a RC coupled Schmitt trigger. You can get them in single small packages. Last one i used was an CD74HC14 which is an hex inverted schmitt trigger IC. only need two external components. Mabe something like this : www.ti.com/lit/ds/symlink/sn74lvc1g17-q1.pdf
why not use a aux connector with switch inside so when you connect aux it overwrites the mute.. then just dont have a aux connected when the unit is switched on
on a side note, i found a similar listing for the exact same board and it says Note: If you use external audio, you need connect 3.5mm audio line; Auto detection for AUX input, the Bluetooth will disconnect after AUX input.
You can buy an FT232RL USB to SERIAL converter to program the bluetooth chip and change the device name. Drivers: github.com/lorf/csr-spi-ftdi Bluetooth pinout: github.com/lorf/csr-spi-ftdi/issues/11
Welcome to the world of Chinese class D Bluetooth amplifier boards. If you are lucky enough to find a fix, the next one you buy (even if you go back to the same seller and see the same photos) could very well be a different version, or a bad reverse engineering job built by a different factory that has a different set of issues. The sellers don't care if the amplifier makes weird noises. If it works and looks somewhat similar they think you should be happy. It's always the same story: "Oh no, I did not mislead you. This is the new version". If you bought it on the bay and want to jump through the hoops for 10 days or so at the resolution center, you have a fair chance of getting a return label and/or a refund. If you bought on AE you will be lucky to get 50-60% of your money back. Just my two cents...
If the mute is active low, couldn't you use a resistor and capacitor to add a suitable delay on startup? You may have trouble depending on the input impedance of the mute pin. If it is less than the resistor in your RC circuit it would.discharge the capacitor faster than the other R can charge it so maybe add another resistor between RC circuit and mute.
V+ ---> 1M2 R ---> 1uF C ---> 2M0 R ---> Mute Pin
This is exactly what I've done and it works perfectly.
I was thinking about the same idea while watching this video. XD
I was going to suggest trying a cap as well, so be interested to see if it helps.
Was thinking the same thing. RC delay.
The ST data sheet for the TDA7492P shows a 2.2uF cap to ground with a 30K-33K resistor in series with the control line. www.st.com/content/ccc/resource/technical/document/datasheet/35/01/97/6b/20/ce/40/6f/CD00211320.pdf/files/CD00211320.pdf/jcr:content/translations/en.CD00211320.pdf
I wonder if the bt module has a wired auxillary in it seems like it would.
Have you considered routing the mute through the input detect pins on your earphone jack? It looks to me like the two pins at the bottom right of the connector would be shorted with the connector in, and open circuit without it. That doesn't help for when you turn on the amplifier with an input plugged in, but it seems like it's probably a reasonable compromise.
Does the input have switched contact?
Was going to say the same thing. And if it doesn't have a switched socket, he could always swap it out for one that does.
Adam Egan many do, and it looks to me like this one does.
The suggested resistor capacitor delay should work fine, but might be an idea to place a diode in parallel with the resistor to discharge the capacitor quickly at switch off.
Why not to use some simple delayed latching circuit, hook it up to the power switch of the whole board? It would be much more convenient than a second switch to power this thing on. Either that or replacing the push button with a 3 state lever switch that will have 3 positions in that order: OFF / ON / ON and resistor closed.
i think the same. maybe a cap charging trough a resistor and then switching a transistor.. i dont know..
90msg90 - Like an off, an on bluetooth, and an on aux
maybe you can use a minijack socket with a switch in it to enable the resistor?
I ordered my pair of these speakers after your last video with them in. You will be ecstatic to know that I received 2. As ordered.
Ecstatic and a little envious :)
Why not add a little circuit to the red / flashing LED and the mute override. As it is only on / flashing when BT is not used which is what you want.
Maybe build a little 555 timing circuit to switch the mute odd after a reasonable amount of time
The audio (power) jacks have a middle connector which is normally not used. You might be able to place that resistor on its path to be bypassed, every time you insert the audio input jack. Which will bypass the resistor.
stick a cap in series with the speaker to get rid of that DC when you power it on or off.
It's not DC, it's a transient.
Work out the mute function is the way forth.
cap would act as high pass filter
I believe there already is a cap in series - but it has to charge before it can block the DC.
Adding the caps at output stage does work, just tested it on mine which is the same model
The caps placed on the board are just for the input voltage to the amplifier there is no output capacitors
Could you not pull the mute pin on BT module to low (or high depending on its wiring) or even direct feed the audio into the amp?
Can you not put a small Capacitor in line with that 10K to delay the Mute when it powers up ?
I would guess the bigger the cap, the longer it takes to charge it to 3.3V before it unmutes and once it reaches 3.3, it unmutes when the Umphf is over
Is there a way that you could tie into the microcontroller to perhaps reprogram it? I mean it just occurs to me something like that might be possible with some bodge wires and a little patients. Provided that is, that they haven't scrubbed the numbers off the chip or used something that doesn't come up with any kind of schematic when you search for it. I think that might be something worth looking into because if you can just add the code to unmute it after the 3 second key-press that would make more sense to me than having to fit a switch into your project. I mean why make it more complicated than it has to be. And yes I do quite thoroughly realize the irony of that last statement considering the context...
Maybe if the cap doesn't give the delay needed, just a three position switch with mute in the middle position, so off-mute-on.
Could you not utilise the minijack port to do the muting for you in some way when a jack is plugged in? And unmute when unplugged? Even change the jack port for something that could do this?
Julian, why don't you just add an override switch with a resistor and capacitor to override the bluetooth module just enough to delay the module power on? (Oh wait you already said that.)
it would be cool if you showed replacing the aux jack with one that has a normally open switch for detecting when a plug is inserted. that would make the speakers pop only if you start it up with a plug in, minor improvements, but allows the Bluetooth to work fully as designed
You must have a different firmware version on the amplifier, mine plays "line in" with no bluetooth connection and no bridging resistor but it does "pop" a little when I turn it on. There is a version identifier on the top right of the board, mine reads "SW - HF01 V3.2" and under that it reads "150419"
Maybe you could modify your board with a different aux jack. Like the ones that have a little switch in it to determine if there's a jack in it or not. With no plug connected, it goes to bluetooth. With a plug, the aux.
Cant you do a lil delay circuit between the power button and the resistor with a transistor and a cap limited by a resistor to make it charge up in 2-3 seconds then triggering the transistor to then put the resistor in series ?
This might not work with the power off doh but by the looks of things the power on was the most extreme.
What is the output impedance of your audio source? It might be too high for the amp to detect that there is an Aux input plugged in and un-mute.
You could use a transistor with a short delay (a capacitor??), to mute the output for a second, before it switches on (or off) thus presenting a suitable resistance in lieu of that 10k Ohm one. The old fashioned way, which still turns up occasionally, would be to add a delay relay to the amp output or to the 'unmute' resistor connections. One DP relay would switch both channels.
You don't need a switch to mute the amplifier when switching on. Leave the 10k resistor connected, and connect an electrolytic or tantalum capacitor between the mute terminal and 0V. (Perhaps you can increase the resistor value to 100k and use a 10 uF tantalum capacitor to give a 1 second time constant).
You might need to connect a diode across the resistor to discharge the capacitor when switching off.
How about a small choke in place of (or in series with) the resistor.
I wonder what would happen if you just switched the blue tooth circuit off...saving a few milliamps too
That's what I was going to ask. Is there a way to disable the Bluetooth? Maybe with the Bluetooth off, it will unmute the sound and allow the 3.5mm jack to work.
Add a NPN transistor in series (CE) with the resistor. Add a cap from base to ground. Add high value resistor from the high side of the mute circuit to base. When powered down cap will discharge via BE diode of transistor. When powered on transistor will be off. As cap charges transistor will turn on. Possibly consider a Darlington configuration.
Have you tried connecting the 3.5 audio in plug after the unit is switched on in case that auto switches it .
Looking forward to seeing it fully built and see how long it lasts on your capacitors.
Have you time traveled to the future? This video was posted a today!
Jo-Bob Bubba That's because Patreons get to see it 1st before the non Patreons i thinks it's 24hrs sooner but I could be wrong. ..
Steve Jones is correct, I am a Patreon supporter and sometimes we get to see the videos a day or two before general release.
How can there be 2day old comments? This video is up for 2 mins. ?
Scorpiaa_ | YT: ScorpiaDev The video has been up for 2 days. :-)
it went up on patreon 2 days early.
@Jeff Merlin it says "Published 27.06.2017" under the video and i checked Julian's channel yesterday evening and it was not yet uploaded at that moment. Uploaded maybe but not published.
Maybe patreon or private.
Yes, I'm experimenting with early access for Patreon subscribers. It's the least I can do, in return for their generosity. Unfortunately, it seems to have put an end to the "first comment" shenanigans ;)
Maybe add a cap so it will stay low for a few seconds while the cap charges..
have you tried any resistor rating.? may be it would work in less resistance
julian, what about putting a capacitor in series with the output?
Does the aux plug have a switch in it like most jacks do?
My BT amplifierboard does the same thing as yours. and i have not even modified it...
muh1h1 mine too but mine plays from aux if Bluetooth is not connected.
there's a pretty easy 2 component mod you can do to these to eliminate that thump; I've uploaded a video recently on that
Good thing you kept talking during the music or I would've thought I was watching 2001: A Space Odyssey ;)
Got same (well, it looks the same, but as we know that means nothing :-)) board that I've not played with yet. Just wondering how bluetooth security works. If my bluetooth source isn't connected, can my neighbour randomly connect? Was kinda hoping you have to put the thing in pairing mode but the video seems to suggest that's not the case :-(
Anyone know?
Hey Julian I was wondering how this project was coming along. (How you plan to charge the completed project.) I was wanting to do a similar project. Perhaps not that specific bt amp but something around 15w per chan. And a USB charging circuit for an iPod / phone
I'm still waiting for the second speaker (which the seller promised to send). The remaining two supercapacitors won't be coming - they've been refunded. So it's just a waiting game at the moment :(
Im surprised that you are messing around with this amp when there are soo many little boards out there.. Though you would have tried a few different ones.
So why did I watch this? Was it to remind us you have a bluetooth amp module and 1 speaker still connected by loose wires?
Why would you even upload a failed test of the 3 second mute thing.
Mine dose this and i have not modified it
good luck if you are mounting in a case then the switch will be easy to connect up
What about latency? Is that good?
Some of these 6 pin 3.5mm connectors has internal switches
ya if you don't have close to 24v the gain all the way up is terrible and I have had a couple of those boards mostly without the power switch or the 3.5 in but the one I did have with the 3.5 in it was seeming just in parallel but I don't know
Maybe use a NE555 delay switch. Then the caps will be full as the resistor comes on. Only a couple bucks on Ebay.
rather than a switch use a relay and a capacitor so the relay closes a couple of seconds after switch on?
or a mosfet resistor and a capacitor. So after a short period of time the capacitors voltage rises above gate threshold and the Mofet turns on.
Old school dethump relay required. Funny how many old solutions still hold.
Geoffrey Keane Haha! Student: "how can I mute a speaker?" Zen prof: "don't connect it". Enlightenment!
Reminds me of docking with a space station on Elite.
A dangerous entry into a circle of reminders
Hmm, I noticed that when you boosted the speaker volume it interfered with the focusing on your camera.
Possibly the force of the sound waves was moving the camera slightly?
Maybe you could do some testing of that?
the bt chip has programable flash memory with its fw on it, it should be possible to reprogram the io
Only issue i would see is finding suitable firmware to reflash it with.
An RC coupling would do it. If you need/want a digital ON/OFF signal, you could go for a RC coupled Schmitt trigger. You can get them in single small packages. Last one i used was an CD74HC14 which is an hex inverted schmitt trigger IC. only need two external components.
Mabe something like this : www.ti.com/lit/ds/symlink/sn74lvc1g17-q1.pdf
Put a 555 timer on it. Use the old power on, reset circuit.
Still no second speaker!!!
why not use a aux connector with switch inside so when you connect aux it overwrites the mute.. then just dont have a aux connected when the unit is switched on
Berta, das Ei ist hart! Das Ei ist hart!
leave the mute hooked up and put a speaker protection board on it. less than 4 dollars US on ebay.
Ok my play pause idea didnt work with this module, worth a try
on a side note, i found a similar listing for the exact same board and it says Note:
If you use external audio, you need connect 3.5mm audio line;
Auto detection for AUX input, the Bluetooth will disconnect after AUX input.
You can buy an FT232RL USB to SERIAL converter to program the bluetooth chip and change the device name.
Drivers: github.com/lorf/csr-spi-ftdi
Bluetooth pinout: github.com/lorf/csr-spi-ftdi/issues/11
Nice Nexus 4!
Welcome to the world of Chinese class D Bluetooth amplifier boards. If you are lucky enough to find a fix, the next one you buy (even if you go back to the same seller and see the same photos) could very well be a different version, or a bad reverse engineering job built by a different factory that has a different set of issues. The sellers don't care if the amplifier makes weird noises. If it works and looks somewhat similar they think you should be happy. It's always the same story: "Oh no, I did not mislead you. This is the new version". If you bought it on the bay and want to jump through the hoops for 10 days or so at the resolution center, you have a fair chance of getting a return label and/or a refund. If you bought on AE you will be lucky to get 50-60% of your money back. Just my two cents...
Glenn C make a dispute then step it up to aliexpress if need
It's fun when things don't work out of the box. :-)
True. What's not fun is ordering two things and receiving one :)
I love your videos julien but you've begun to extend them by repeating yourself quite a bit.
julian please make longer videos like mr carlson and continue to repeat because it helps to make the info stick. great vids
Just add a switch to disable the mute
before the notification =)
Seems like a lot work for a cheap piece of shit amp.