Hi, new member here. I'm finally starting some diy project so here I am, having some troubles already 😀
Anyway, I want to make a bluetooth speaker so I purchased this TDA7492P bluetooth amp from ebay.
It's not bad for 10 bucks. The only thing that concerns me is popping when turning on, actually it's not popping as much as it is pushing the cones outwords for at least half a second and it doesn't look safe, so i'm thinking if there is a way to connect something on output before speakers to limit this sudden flow of power. The last thing I would like to put is volume because I would have to turn it down every time I'm turning on the speakers...
Anyway, I want to make a bluetooth speaker so I purchased this TDA7492P bluetooth amp from ebay.
It's not bad for 10 bucks. The only thing that concerns me is popping when turning on, actually it's not popping as much as it is pushing the cones outwords for at least half a second and it doesn't look safe, so i'm thinking if there is a way to connect something on output before speakers to limit this sudden flow of power. The last thing I would like to put is volume because I would have to turn it down every time I'm turning on the speakers...
Does it pop without pre amp connected ?
It might need a resistor across input to discharge any volts on coupling capacitors.
It might need a resistor across input to discharge any volts on coupling capacitors.
They're only connected to this amp, nothing else is there. Wireless input --->amp ---> speakers. Thats all.
Maybe build a mute switch in the speaker leads? A couple of big 8-16ohm resistors and a nice big stereo switch?
Well, the BT module should take care on this by utilizing one of its PIOs to drive the Mute of the amp.
From the DS here:
http://www2.st.com/content/ccc/reso...df/jcr:content/translations/en.CD00211320.pdf
Page 18/27 Figure 21
A "crude" softstart or longer startup mute time can be accomplished by changing R4 to a high value of i.e. 810k for the case, they implemented it like that. If not (would guess) it needs to implemented from scratch. 3v3 should be avail at the BT module. (Mute Pin is 3v6 max)
From the DS here:
http://www2.st.com/content/ccc/reso...df/jcr:content/translations/en.CD00211320.pdf
Page 18/27 Figure 21
A "crude" softstart or longer startup mute time can be accomplished by changing R4 to a high value of i.e. 810k for the case, they implemented it like that. If not (would guess) it needs to implemented from scratch. 3v3 should be avail at the BT module. (Mute Pin is 3v6 max)
Looks like I'll have to put a mute switch on output then :/ Damn chinese, almost perfect for the price, product 😛
Nah, if it's just on power up, an RC filter at the Mute pin will do. like 810k + 1-2uF. Exact values can easily be simulated.
Sorry, i am new to this, but I am willing to learn. You mean I should solder RC filter to the mute pin of the amp? I mean, what side would I need to connect to the pin?
First you need to indent If the pin from the datasheet. Then check what external circuitry is connected to that pin. If there's nothing, solder 2u2 from this pin to ground and 820k in front of this pin with the other end to a valid 3v3-3v6 source.
Here's the pics with and without bckg light:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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Seems like a design/implementation problem. Change this 100k for 750k-1MEG and see if it's properly muted then.
Hi Doctormord,
thanks a lot for your advice to change the resistor. I even had an older version of the bluetooth TDA7492P module with two 39 kOhm resistors. After replacing R21 by an 1 MOhm version the evil popping noises are gone now.
Wish you a nice weekend,
Thomas
Many thanks all of you for posting this information and the follow up confirmation. I had written this amp off because of this problem but will now see about changing out R21 and give it another try. For those who don't want to fool with changing SMD resistors, the similar Sanwu TPA3116 bluetooth board that xrk971 recommends in this thread does not exhibit the problem.
http://www.diyaudio.com/forums/class-d/275961-30-tpa3116-bluetooth-speaker-protection-eq-any-good.html
Doctormord, would you be willing to create instructions for us plain folks on how to reprogram the bluetooth module to eliminate or reduce the beeping sounds? I am using the TPA3116 version at the moment but I assume the process is the same for most of the CSR chips? If we could also rename the device that would be icing on the cake.
I'm curious if anyone has compared the Sanwu TPA3116 BT amp to the Sanwu TDA7492P BT amp with respect to sound quality.
http://www.diyaudio.com/forums/class-d/275961-30-tpa3116-bluetooth-speaker-protection-eq-any-good.html
Doctormord, would you be willing to create instructions for us plain folks on how to reprogram the bluetooth module to eliminate or reduce the beeping sounds? I am using the TPA3116 version at the moment but I assume the process is the same for most of the CSR chips? If we could also rename the device that would be icing on the cake.
I'm curious if anyone has compared the Sanwu TPA3116 BT amp to the Sanwu TDA7492P BT amp with respect to sound quality.
I compared both boards and actually would only recommend the TPA3116 version, board revision 2.2 and up.
Reprogramming the CSR modules needs an SPI programmer and some CSR tools, but will check if its possible to reprogramm the EEProm with a simple I2S programmer, which are avail from China for cheap (CH341 based).
Reprogramming the CSR modules needs an SPI programmer and some CSR tools, but will check if its possible to reprogramm the EEProm with a simple I2S programmer, which are avail from China for cheap (CH341 based).
Fixing the power-on-plop is as follows:
R21 = 820k
R22 = 680k
If you don't care for the line in, it's also possible to implement an automatic power-down when no bt transmitter is connected.
R21 = 820k
R22 = 680k
If you don't care for the line in, it's also possible to implement an automatic power-down when no bt transmitter is connected.
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