Newbie on Class D, TDA7492, Help!

[nastorrent]

Hello,

I have this amplifier board for a project I'm starting. It's a TDA7492.

I'm more an 'speaker guy' and with Class D I'm a total newbie.

I've tested it with a 19v 4.75A and a variable 12-24v 3A Laptop power supply, with and without 5000 to 20000 uF capacitors.

It sounds very good, strong sound especially with 20000 uF, BUT... it makes a big POP when I connect/disconnect the amplifier or the phone to Bluetooth.

Can any of those Class D Masters around this forum help me to correct this? or Should I choose another amplifier?

Thanks.

 

[HumbleDeer]

Hello,

I have this amplifier board for a project I'm starting. It's a TDA7492.

I'm more an 'speaker guy' and with Class D I'm a total newbie.

I've tested it with a 19v 4.75A and a variable 12-24v 3A Laptop power supply, with and without 5000 to 20000 uF capacitors.

It sounds very good, strong sound especially with 20000 uF, BUT... it makes a big POP when I connect/disconnect the amplifier or the phone to Bluetooth.

Can any of those Class D Masters around this forum help me to correct this? or Should I choose another amplifier?

Thanks.

Its not really related to the amplifier chip, actually. Rather because they didn't wire it up all correctly.

Check if the amplifier and preamplifiers reference signal ground are connected to your input ground from both BT and your plug.

For the pin out you might need to Google around a bit or ask the seller for a pin out of the BT module 🙂

Cheers,
Anna

 

[nastorrent]

I'll try contacting the seller, but I don't hope too much from my "chinese friend" 😉 (the price is very low, as the support 😕).

I'll stand here for more ideas.

Thanks.

 

[nastorrent]

Hi,

I have contacted the seller, but it's holidays season on China.

While I'm waiting for the seller... Anyone knows any similar board that doesn't show this problem?

I prefer TPA3116 or TDA7492 for the wide power supply voltage range.

It will be used probably under 4 ohms. Bluetooth with Apt-X preferred but not exclusive.

Thanks

 

[ravels]

So it not only makes a pop when you turn it on/off, but also when you switch between AUX and BT?

 

[ravels]

I see a 5532 between the BT module and the TDA7492. It takes the differential signals coming out of the BT module, converts them to single ended and feeds them as such to the differential inputs of the TDA7492. My guess is that the aux is also being muxed in somewhere around there.

If you are only going to use the BT input, you can bypass the 5532 and wire the diff outputs of the BT module directly to the 7492. There's probably an enable signal that also needs to be hard wired to BT mode.

Here is a link to doctormod's website that describes this mod on a different (but similar) board.

BTW, I had one of the SANWU TDA7492+CSR8625 boards and it got busted when using it with a 24V supply. You may want to stick to the 19V supply to be safe.

 

[nastorrent]

Thanks to all!

ravels, can you post again that link to doctormod's website?


I saw other user that made the mod on the photos, but I think it's more related to static problems that the Popping problems.

What do you think?

 

[doctormord]

It sounds very good, strong sound especially with 20000 uF, BUT... it makes a big POP when I connect/disconnect the amplifier or the phone to Bluetooth.

Differential connection between BT module and amp ic might/will fix this. (With loose of AUX if muxed behind the Diff2SE opamp. If they managed to use the internal AUX input of the CSR86XX, then you wont loose it.)

Does it also pops when using the AUX wired connection? If it only does on BT link, then it's a "feature" of the CSR firmware, which disables the outputs without link.

Btw. the CSR8635 does not support APT-X. Most likey they also forgot to enable MP3/AAC direct stream like on the other chinese boards.

(This all can be fixed with a programmer)

 

[nastorrent]

Hi again and thanks for all the replies.

I'll do more tests to identify the exact situations where it Pops to try to get a solution, but first I need to get a pair of cheap speakers for testing purposes. It's stupid to continue putting at risk expensive tweeters with a chinese board with problems.

Meanwhile, I'll be looking this post beacuse I'm open to suggestions of other similar boards that skip the popping problem (or bluetooth module + amplifier), TDA7492 and TPA3116 preferred. This board was dirt cheap and I can use it for other projects.

By the way, the project I'm starting is a very small portable bluetooth speaker, battery powered, +105dB and good bass response. The only part I need to get working is the amplifier.

Thanks to all for help and suggestions.

 

[doctormord]

+105dB sensitivity?

 

[nastorrent]

105dB SPL or more of output, depending on amplifier, not the sensitivity of the speaker, of course. 😉

 

[doctormord]

At 40W i'd guess?

So 89dB 1W/m.

 

[nastorrent]

Yes, something like that. Depending on crossover.

It has 4 positions, 2 positions for woofer and 2 for tweeter.
Tweeter is about 95 dB (I'm still in doubt between 2 models) with 0 and -6dB Lpad and crossed about 4kHz 6dB/oct.
Woofer is about 89dB (I'm still in doubt too, woofer or fullrange) with 2 positions too, about 4kHz crossover 6dB/oct. or fullrange.

Depending on the conbination of the crossover positions and final driver selection it should go to 105 to 108 dB easy.

 

[doctormord]

Is it used in tuned br?

 

[nastorrent]

I plan to do 2 same size. 1 sealed and other sealed + Passive Radiator.

 

[doctormord]

Okay. I'd try tuned reflex to get more spl at the lower end. For small enclosure tuning in the 100-150hz range.

 

[nastorrent]

I'd try tuned reflex to get more spl at the lower end. For small enclosure tuning in the 100-150hz range

Nice suggestion. I had tried all types of arrangements over the years (BR, 4th and 6th order bandpass, horns, ...), sometimes with weird tuning frequencies and box materials but, at this moment, I prefer the "naturalness" of sealed wood boxes after a right driver selection, but this is a matter of taste.


What about the amplifier board suggestions? due the cheap prices of some boards, I could test 2 or 3 alternatives without killing my budget...

Thanks.

 

[doctormord]

Which one you suggested?

For APT-X you'll need a CSR8645 minimum (or 8670 or the new CSRA64XXX)

Without you get away with a CSR8635+TPA3116 Sanwu if you patch the BT-Amp interconnect for differential and change the output inductors to some with higher saturation current.

If all gets stuffed in one enclosure you might try to remove the output filter and go for Ferrite+C filter like shown in the datasheet. (Haven't tried, might reduce BT range)

 

[nastorrent]

Hi again,

after doing several test with a pair of cheap behringer speakers I think I will discard this board for this project.

Now I'm planning to choose a Sure Bluetooth module with Apt-X with a separate amplifier board (or 2 mono boards).

I'm looking at these ones, which one would you choose?

The links are only for visual reference, don't know where I'll buy them, maybe at ebay.

1 - https://www.yuan-jing.com/ClassD-T/...ard-anti-pop?sort=p.price&order=ASC&limit=100
2 - https://www.yuan-jing.com/ClassD-T/...oard-50w-50w?sort=p.price&order=ASC&limit=100
3 - https://www.yuan-jing.com/ClassD-T/...oard-50w-50w?sort=p.price&order=ASC&limit=100
4 - https://es.aliexpress.com/item/XH-M...32752811302.html?spm=2114.13010308.0.0.rTwYIc
5 - https://es.aliexpress.com/item/TPA3...32616198446.html?spm=2114.13010308.0.0.rTwYIc

Thanks

 

[Yatsushiro]

I think I've tried maybe 7/8 different TAP3116 amps in my system; the one I keep coming back to (and the only one where I've bought a second) is this one:

https://www.yuan-jing.com/ClassD-T/tpa3116-class-d-2-0-stereo-amplifier-board-anti-pop?sort=p.price&order=ASC&limit=100