Hi, I'm new of the forum. I have a poor knowledge of electronics so I'll try to explain my problem as best as I can...
I play soft synths on a laptop controlled by MIDI keyboard. The laptop is connected to an external USB sound card with two 1/4'' balanced jack outputs. The problem is, when I connect the jacks to a mixer sending signal to the PA, I can hear a very high 50 Hz hum (I live in Italy).
I tried the following:
- replacing the PSU with a stock one, less noisy, the noise lowered but it's still on
- improve the SNR inside the laptop (basically turning the digital volume to the maximum possible without distortion), it worked but as soon as I need a litte more volume the noise can be heard again
- putting a jitter filter between the laptop and the USB cable, the sound is far better, all the other noises have disappeared (circuitry, mouse ecc) but the 50 Hz noise is still on place
- using a DI-box: the SNR is better, the sound is better, but the noise is still relatively loud
- running the laptop on battery only: sometimes the noise goes away, sometimes not, depending on where I am.
The problem is not always present: when I am in locations (venues, studios etc.) that I know are properly grounded, there's no noise, but in other places the noise is very high.
I don't know what else can I do: I was thinking of powering the sound card via a battery-powered USB hub which removes totally the power supplied by the laptop, maybe changing the USB cable with a better one, but honestly I am tired of experimenting and so I would like to have your opinion on this matter
thanks in advance!!
I play soft synths on a laptop controlled by MIDI keyboard. The laptop is connected to an external USB sound card with two 1/4'' balanced jack outputs. The problem is, when I connect the jacks to a mixer sending signal to the PA, I can hear a very high 50 Hz hum (I live in Italy).
I tried the following:
- replacing the PSU with a stock one, less noisy, the noise lowered but it's still on
- improve the SNR inside the laptop (basically turning the digital volume to the maximum possible without distortion), it worked but as soon as I need a litte more volume the noise can be heard again
- putting a jitter filter between the laptop and the USB cable, the sound is far better, all the other noises have disappeared (circuitry, mouse ecc) but the 50 Hz noise is still on place
- using a DI-box: the SNR is better, the sound is better, but the noise is still relatively loud
- running the laptop on battery only: sometimes the noise goes away, sometimes not, depending on where I am.
The problem is not always present: when I am in locations (venues, studios etc.) that I know are properly grounded, there's no noise, but in other places the noise is very high.
I don't know what else can I do: I was thinking of powering the sound card via a battery-powered USB hub which removes totally the power supplied by the laptop, maybe changing the USB cable with a better one, but honestly I am tired of experimenting and so I would like to have your opinion on this matter
thanks in advance!!