Leaving one output channel disconnected on TPA3116

[robskillz]

Hi all,

I'm planning on using a stereo TPA3116 amp board to drive a single full range speaker. This particular board can't be bridged, so assuming the same mono signal is going to both input channels will it damage the amp to leave one output disconnected? Or could it cause electrical noise? I could also connect a dummy load, either to match the driver on the other channel or high impedance so as not to 'waste' power as heat.

Thanks! Rob

 

[Bone]

Short the unused channel input to ground, via a capacitor if there isnt one on the input, then terminate the output in a dummy load of say 16 ohms 2 watt or greater.

 

[nigelwright7557]

I know with irs2092 based class d amps you shouldn't leave output disconnected.
The output filter starts to ring at high volts and can take out output filter capacitor if it isn't rated high enough to take the extra high volts.
I usually put a high voltage capacitor in output filter just in case.

Simplest solutions as message 1 with input shorted to ground and 16 ohms on output.

 

[robskillz]

Thanks! As the board in question has built-in Bluetooth it will be difficult to pull one input to ground. I'll put a 16 ohm load on the unused output channel however.

 

[Bone]

If you just put a dummy load on the unused channel, it must be rated at the full power output of the chip, and you will lose a lot of power. It will get hot, very hot.

 

[theAnonymous1]

The TPA3116 can easily be put into PBTL (mono) mode with a few board mods.

 

[doctormord]

If you just put a dummy load on the unused channel, it must be rated at the full power output of the chip, and you will lose a lot of power. It will get hot, very hot.

With the input grounded, there will be no output signal. The dummy load is just there to dampen the output filter. No power is lost, except some HF switching noise.

(Or go PBTL)

 

[robskillz]

I don't think that grounding one input channel will be that straightforward as the board will be used with its integrated Bluetooth receiver as the two-channel input to the TPA3116. If the load on the output channel is quite high impedance - say a 100 ohm, 1k-ohm or 10k-ohm resistor, it shouldn't get too hot but will that be enough to satisfy the output stage on that channel? Or will the voltage rise too high and blow the cap?

The board in question is this one. The blurb says that the manufacturer can make it in PBTL mode for bulk purchases but they won't supply instructions or circuit diagram for customers to do it themselves 🙁
Sure Electronics' webstore 2 x 50 Watt 4 Ohm Class D Audio Amplifier with Bluetooth 4.0 APT-X - JAB2-50

 

[robskillz]

Clearer close-ups of the board can be seen on Parts Express website here with zoom:
Wondom AA-AC11161 2x30W 4-8 Ohm Class D Audio Amplifier Board BT4.0 with Functional Cables

This is the 30W version with no heatsink. I'd be happy to do a mod to disconnect one channel's input and ground it. Close-up view:
http://www.parts-express.com/Data/Default/Images/Catalog/Original/320-3519_ALT_1.jpg

 

[robskillz]

@doctormord I enjoyed reading your post about the SANWU + CSR noise fix. Do you think a mod on the board above ^ (see .jpg link) to disconnect one input channel to the TPA chip (maybe by removing a coupling cap) and tying it to ground might be possible? I appreciate that you can't really see the PCB tracks on the photo! It's all probably running single-ended. I would then be interested in combining the two input signals onto the one remaining channel.

This Sure board is clearly more complicated than the SANWU board, due to the aux-in and other extra features (analogue volume pot, etc.)

Thanks!

 

[doctormord]

Will look into this.