G1176 Hum 100 200 300 HZ europe -86 dB

[pstcho]

Hi Guys i got a Hum at 100 200 and 300 Hz with my G1176

The maximum peak at 100hz is -84.7dB then 200Hz at -86.5 300hz at- 90.6dB then 400hz -99dB

In between those frequencies, the signal goes very low like -105dB  ( i think it is the noise of my soundcard )

It happens even if No Input is plugged and depends on th input and outpout volume

Also get a nice Hum under 20Hz

At 65hz i have normal noise of -102.1dB

It happens also in By pass

Any Idea?

Thanks

 

[pstcho]

None?

Just to be sure i made the ground loop cut as adviced on the Gyraf's website

If i activate the Nuke mode, it goes to -50.6dB at 100hz and keep the same proportions for the other frequencies

 

[RuudNL]

I think the question you have to ask yourself is: "how disturbing is a hum at - 86 dB?"
Of course lower is better, but I think I could live with a signal to hum ratio of 86 dB.
Also: how accurate is your measurement?
Because I don't see where the 'hum' under 20 Hz would be coming from!

 

[pstcho]

Mesurement made with an oscilloscope hardware very acurate

not too anoying if you put a drums, but annoying on sweet voices

 

[zamproject]

I think the question you have to ask yourself is: "how disturbing is a hum at - 86 dB?"

yes and the second question is -86dB from what reference ???

 

[pstcho]

from the 0dB digital,  let's say line level 0dB

 

[gyraf]

Please use the dedicated 1176 help thread - this is where everyone goes for advice, and it's best to have all such info in one thread.

0dB digital,  let's say line level 0dB

No, 0dB digital is very rarely the same as 0dBu. You need to measure to know your reference.

And then, remember to measure with input terminated, i.e. either shorted, or shorted through a 600 Ohms resistor. Otherwise you're picking up unneeded noise.



Jakob E.

 

[mjrippe]

Did you hear this hum when you tried to use the unit, or did you just see it when taking measurements?  Chances are good that -86dB is down in the noise floor of your entire system and it will not be noticeable in use.

 

[pstcho]

only by mesurements, when i use on vocals it can be a bit disturbing on male operatic voice ( power metal ) otherwise i didnt get any problem since the week i tried it, with a snare or bass drum or guitars no issue at all, my question was more by curiosity in fact, in case it can get more quiet

 

[gswan]

Since you have the equipment to take measurements, try measuring the ripple voltage on the 30V rail.
Hum at twice mains frequency (plus harmonics) is often related to ripple from the full wave rectification.

 

[pstcho]

thanks a lot for your reply, sorry but my english is a bit lame, what / where is  ripple ?

 

[gswan]

The amount of AC voltage you have on your DC rail. It is the amount of decay of the DC rail between successive peaks from the rectifier. The large electrolytic capacitors are there to smooth this out, and the regulator will also reduce it, however there may still be some present.

 

[pstcho]

ok i got it thanks a lot i will take a look asap !!!