Class D amplifier without output chokes

[Janux]

I found this micro amplifier with TPA3116D2 on Amazon, two boards for about $14.00!

Given the size and low cost it could be useful to replace the internal amplifier in an active subwoofer, but I have a couple of questions:

1. the first thing that catches the eye is that it has no inductors, no LC filter on the output, so I wonder how the modulation signal does not reach the speakers?
2. To use it as a mono amplifier you have to modify the chip configuration as per the datasheet for the PBTL mode I guess, can't I simply bridge the two channels? (It would be too easy! 😆)
3. Without a heatsink up to what voltage can it be powered?

Thanks

 

[jean-paul]

Ask the seller as the seller earns the money. Check the datasheet of the IC too.

Normally these have LC filters otherwise they emit pollution. This one is too simple.

 

[theAnonymous1]

G

Thread 'Are cheap tpa3116d2 boards without output lc filter or snubber usable?'

2018-06-28 2:34 am

Hello all, this is my second post, the first one led me to choose popular tpa3116d2 amplifiers for my new speaker build.

I know there is a monster thread on tpa3116d2 amplifiers, but i wasn't able to find information regarding this particular board design through the forum search function.

Here is the amplifier i'm talking about, it is dirt cheap($2.30 is almost what the chip itself is), has minimum number of components, but lacks heatsink, output lc filter and output snubber.

There is also an image of the board in question in attachments, just in case you dont want to click...

• gezzer
• Replies: 10
• Forum: Class D

 

[uriy-ch]

so I wonder how the modulation signal does not reach the speakers?

You can apply a PWM signal to the LF speaker, nothing will happen to it. If the amplifier is located next to the speaker, the EMI from the connecting twisted wires will not be very large.

 

[Janux]

If it is necessary to add 4 toroidal inductors of 10µH with associated 4 polyester capacitors of 680nF and two electrolytic capacitors of 2200µF then the costs and the size increase, at that point it is better to orient oneself on a board already designed for the PBTL mode that already has LC filters and snubbers integrated.

 

[Janux]

I still have a question for the experts.
Using two separate boards with TPA3116D2, one stereo and one mono in BTL mode, to create a stereo amplifier with subwoofer is it necessary to connect the Sync pins of the two TPA3116D2 together using a 10K resistor or is it not necessary?

 

[Mark Tillotson]

If you don't sync them there will be a beat-frequency imposed on the power rails which may be audible. If running off separate supplies I think you can get away with this, but on the same supply don't risk it. Check the datasheet to be sure...

 

[Janux]

Thanks Mark, on the datasheet Texas Instruments simply says that the Sync pin is an output when the device is configured as master and an input when it is configured as Slave. Now, I don't think that the mono cards sold to drive a subwoofer are configured as Slave, so in addition to connecting the sync pins of the two cards together, it is necessary to modify gain resistors on pin 8 GAIN/SLV.

The problem is that no one indicates this information in the specifications, they are "sellers" not technicians.
Especially in China, they sell both sneakers and electronic cards with the same little information 😆