Vero 4K audio noize and update problem

Help and Support Vero 4K / Vero 4K +
1

Hello,

I wanted to use my headphones by connecting them to the audio jack output on my VERO 4K. The audio is clear, but the volume is not sufficient for me. So I decided to use a headphone amplifier. The problem occurs ones I connect the VERO to my amplifier. I hear an very loud interference noise, much louder than the actual audio. If I use my amplifier without the VERO, with my phone for example, the audio is clear so I don’t think the problem is in the amplifier.

This is where it gets technical,The first thing I tried was to lower the input impedance of my amplifier since this is the mayor difference between the amp and the headphones. I did this by adding a resistor of 220 ohm to the input, both left and right. This unfortunately didn’t help, so I tried lowering the value to 56 ohms but the noise was still there and the volume of the actual sound was lowered. Therefore I changed the resistors back to 220 ohms.

I figured it might be a ground-loop somewhere, so I tried disconnecting everything like HDMI and ethernet leaving only the power supply and the audio connected. I even disconnected the signal wire of the audio, only leaving the ground of the audio connected to the amplifier but the noise didn’t disappear. This is weird considering the power supply of the amplifier is a transformer and the ground isn’t connected. There is no electrical connection between the VERO and the amplifier except for the ground of the audio jack and still the noise is there.

Can anyone help me with this problem?

Regards,
Bas

By the way, I was updating OSMC and I got this error: “rbp-userland-osmc (3.1.0-1)”. I never really tried to fix this but since I’m posting anyway I thought I’d mention it.

2

What sort of audio plug are you using? Check this:

I wouldn’t lower the input impedance - you will lose signal voltage by that.

3

Hello,

I use the analog output with a TRS plug as described in this image:

4

Are you sure it’s pushed all the way in? Maybe try another plug (say an extension lead)?

If that fails, then I think your ‘ground loop’ theory may be right. What sort of noise is it?

5

I recorded an audio sample. https://ufile.io/t02tu
The wiring are correct, I start to think the problem is with the power supply.
If I connect the ground of the supply to the ground of the amplifier, without the VERO, I can hear the noise.

6

Do you have another 5V2A supply to try? Or another supply for the HP amp? What make/model is it?

7

Hello, I just tried it out with another supply and the noise is much lower. I still hear a bit on the background but this is also there without supply to the VERO. I’ll try to add some filtering to the inputs, It might just do the trick.

8

It does look like some sort of ground loop.

image
image590×513 8.89 KB

9

Hello,

I added some filtering to the input of the amplifier. If I turn the volume all the way up I can only barely hear the noise with the original power supply. With my other supply the noise is completely gone.

For anyone having the same issues: The filter I applied consist of a resistor and capacitor parallel across the sound signal. Values are 220ohm and 10nF, witch filter around 72kHz (low pass).

See this beautiful ASCII art for the schematic :slight_smile:

VERO		      AMPLIFIER

OUT O---+-----+-----O IN
        |     |
        |    ---
       ---   | |
       ---   | |
        |    ---
        |     |
GND O---+-----+-----O GND

Thank you for the help

1 Like
10

Good to know. You might think a tighter passband might do better as long it was, say, only 1dB at 20kHz.