VR: Ground Loop with NJS NJA760

[Sylvere]

hi trolls,
Anyboby experience buzz problem with the amplifier NJS NJA760 (provided by Souri) ?
Cause I ve got buzz running in my cutterhead. When I cut without amplifier it's ok no buzz just noise surface.
MainUnit, amplifier and mixer are plugged in my black lion audio pg 1F power regulator.
Any idea to fix the ground loop ?
thx a lot
syl

[markrob]

Hi,

If you unplug the line inputs and the buzz goes away, maybe consider 1:1 isolation input transformers.

[Sylvere]

exactly when I unplug the line in buzz goes away !
thx for the tips
syl

[markrob]

Hi,

Make sure that your upstream audio path is not the cause before you go to the isolation transformer route. For example, if you are using a mixer, see if the buzz goes away if all inputs are disconnected. Is the buzz independent of the master level fader? If it moves with the fader, then the the cause is upstream someplace.

You can also try using a floating AC mains adaptor to float the safety ground on the power amp. If you lift this ground and the buzz goes away, then the transformer idea should work. I wouldn't use a floating safety ground as a final solution, just a means to see if the ground loop is broken after lifting the ground. If this stuff is in a common rack, you might have to isolate the chassis. To test this remove the amp from the rack.

Mark

[Sylvere]

Hi,
Audio path is really clean, mixer is a Palmer monicon XL
To test this remove the amp from the rack
-yes, I did but the buzz goes on...
I ordered an ART DTI 1:1 2 channels passives transformer
let u know

[Sylvere]

the buzz is only on the channel A !
B is cristal clear

[markrob]

If you swap the input connections, does the buzz move to channel B?

[Sylvere]

f you swap the input connections, does the buzz move to channel B?
No the buzz is still in A ch
I test with just with 2 SpeakOn and 1 input
the B ch is really clear with the 2 ch of cutterhead
but the input ch A is still running a small buzz
obviously when I cut the buzz is in L ch (A)
The output of Souri main unit is cristal clear.

[markrob]

Hi,

Seems odd that its only one channel. The would seem to go against it being a ground loop. Have you tried another amp? Are you running balanced or unbalanced connections?

Mark

[Sylvere]

Unbalanced connection only, cause the input of the amp is unbalanced.
I ve tryed with different cables (really short).
I will try with another amp as soon as I can !
and let u know.
Thanx a lot for your interest.
Syl

[Sylvere]

ART ATI transformer isolator 1:1 fix my problem )
cheers
syl

[markrob]

Hi,

That's great to hear!

Mark

[Tape27]

hi,

my njs nja also causes some hum when I turn it on.

think it has nothing to do with the signal path as the hum is still there when line inputs are unplugged.

anyone has any suggestions ? maybe i can build some isolator before the powercable of the amp goes to the socket?

appreciate any input

peace

[markrob]

Hi,

Any light dimmers nearby? If you float the safety ground with the inputs unplugged does the buzz go away? If you have dirty AC mains power, perhaps a good line filter would help.

Mark

[Tape27]

hey,

thanks for the fast answer,

no dimmers nearby

can you explain what you mean with floating the safety ground?

thank you!

peace

[markrob]

In the states, its the green wire ground. This is the single round contact, not the two flat ones. There are adaptors that allow you to lift this ground. They are designed for older two prong AC outlets. Not sure the equivalent exists outside of the US. This is not a long term safe thing to do. It is just to help identify the problem.