Tpa3118/tda7498 Ground loop

[godslayer]

Hi,

I have a simple transformer based supply from 16 and 22v center tapped transformer.

16v for tpa3118 and 22v for tda7498.

The common ground is taken at center tap.

Each rail has 10000uf capacitors.

The amps have very slight interference which goes away when you connect either of them to the output and it becomes dead silent.

However as soon as soon as i connect their inputs to output on the same soundcard(soundblaster x-fi pro 5.1 on l/r and c/sub) on different ports, there is a very loud persistent hum on the speakers. This remains once usb is disconnected completely or connected. Somehow something inside the sound card is causing hum between the two amps.


I have tried adding diodes to ground but doesnt work.

Can someone enlighten please?

 

[DUG]

Could you draw a schematic of your hookup?

I am not sure why you need a centre tap because neither amplifier needs a negative supply.

 

[godslayer]

Could you draw a schematic of your hookup?

I am not sure why you need a centre tap because neither amplifier needs a negative supply.

Hi dug,

I am using it as it had it with me.

Here is the schematic.

EDIT- **NOTICED THE WRONG POLARITY OF THE LOWER CAP, ITS OK IN THE CIRCUIT**

 

[DUG]

The transformer seems strange...a centre tap with different voltages on each side.

You have half-wave rectified the AC, using basically two diodes in series.

This will produce a lot of ripple in the supply.

It would have been better if the 16V and 22V windings were separate.

 

[godslayer]

The transformer seems strange...a centre tap with different voltages on each side.

You have half-wave rectified the AC, using basically two diodes in series.

This will produce a lot of ripple in the supply.

It would have been better if the 16V and 22V windings were separate.

I have tried this setup but the capacitors were heating like crazy for unknown reasons.

 

[Khron]

A photo of the actual (ie. real-life) setup might help clear up things...