Static Noise

[antanast]

Guys, completely lost here and hopefully you can find a solution.

I have my ADI2 connected via the RCA cables to my Rotel A11, which drives my speakers. I also use the balanced output or the ADI2 , connected to my headphones tube amp TA-26S. What I notice is that there always seems to be static noise in the loop. When the RCAs are connected to the A11, and crank up the volume in my headphone amp, you can hear the noise in the headphones. If I put the wires vice versa, i.e. the RCAs connected to the headphone amp and the balanced to the A11, you can then hear the noise in the speakers of the A11. If I remove one of the two devices then the noise goes away. Both amps use a triple connection electricity wire, so I would assume they are grounded.

 

[Jimbob54]

Guys, completely lost here and hopefully you can find a solution.

I have my ADI2 connected via the RCA cables to my Rotel A11, which drives my speakers. I also use the balanced output or the ADI2 , connected to my headphones tube amp TA-26S. What I notice is that there always seems to be static noise in the loop. When the RCAs are connected to the A11, and crank up the volume in my headphone amp, you can hear the noise in the headphones. If I put the wires vice versa, i.e. the RCAs connected to the headphone amp and the balanced to the A11, you can then hear the noise in the speakers of the A11. If I remove one of the two devices then the noise goes away. Both amps use a triple connection electricity wire, so I would assume they are grounded.

What if you leave the a11 connected , disconnect the 26S but listen to the headphones on the rme headphones jack ?

 

[antanast]

What if you leave the a11 connected , disconnect the 26S but listen to the headphones on the rme headphones jack ?

no issue. The noise comes when both devices are in the loop. So lets say i remove the a11 then the headphones from the 26s will have no noise. The minute a11 is back then noise goes back to the headphones. If i put the volume up on the a11 connected speakers and have the t26s also in the loop then the noise comes in the speakers. If i disconnect it the 26s then no noise in the speakers… maybe its the dac doing something?

 

[antcollinet]

no issue. The noise comes when both devices are in the loop. So lets say i remove the a11 then the headphones from the 26s will have no noise. The minute a11 is back then noise goes back to the headphones. If i put the volume up on the a11 connected speakers and have the t26s also in the loop then the noise comes in the speakers. If i disconnect it the 26s then no noise in the speakers… maybe its the dac doing something?

What is the device inputting to the RME? A PC?

And are you sure it is always the device with the balanced connection input which is noisy? That is counterintuitive to say the least. Can you describe the complete system. for use. Even a sketch showing ALL interconnect and mains connections would help.

 

[antanast]

Maybe this video helps?

 

[Bob from Florida]

Guys, completely lost here and hopefully you can find a solution.

I have my ADI2 connected via the RCA cables to my Rotel A11, which drives my speakers. I also use the balanced output or the ADI2 , connected to my headphones tube amp TA-26S. What I notice is that there always seems to be static noise in the loop. When the RCAs are connected to the A11, and crank up the volume in my headphone amp, you can hear the noise in the headphones. If I put the wires vice versa, i.e. the RCAs connected to the headphone amp and the balanced to the A11, you can then hear the noise in the speakers of the A11. If I remove one of the two devices then the noise goes away. Both amps use a triple connection electricity wire, so I would assume they are grounded.

If I understand correctly, the Rotel A11 may be the common factor. Looking at the A11 the input AC connector is missing the ground which implies double insulated device. However, if your power cord has a ground prong there may be a ground wire inside the power cord - not connected at the amp. The internal power supply is likely a switcher since it weighs only 15 pounds. There is a possibility that noise draining into the neutral wire is coupling to the ground wire in the power cord. If so, this could be the source of the static. Use a ground cheater plug at the power plug to test for this. If the static goes away, then that's your solution - since the IEC end on the amp is missing the ground pin perfectly fine to leave it that way.
Good luck

 

[antanast]

If I understand correctly, the Rotel A11 may be the common factor. Looking at the A11 the input AC connector is missing the ground which implies double insulated device. However, if your power cord has a ground prong there may be a ground wire inside the power cord - not connected at the amp. The internal power supply is likely a switcher since it weighs only 15 pounds. There is a possibility that noise draining into the neutral wire is coupling to the ground wire in the power cord. If so, this could be the source of the static. Use a ground cheater plug at the power plug to test for this. If the static goes away, then that's your solution - since the IEC end on the amp is missing the ground pin perfectly fine to leave it that way.
Good luck

Here is how it is normally connected via a grounded three pin plug

If i understood correctly, you told me to use a non grounded plug right? So i basically did this

Still noise, and probably more

 

[Bob from Florida]

Here is how it is normally connected via a grounded three pin plug
View attachment 398699
View attachment 398700

If i understood correctly, you told me to use a non grounded plug right? So i basically did this

View attachment 398701

Still noise, and probably more

A11 rear power connector from picture on web. Does yours look different?

 

[antanast]

Here it is

 

[antcollinet]

The sounds like a classic ground loop. Do you have toslink available out of your PC? Or a USB sound card with Toslink out? If so try using this to the DAC instead of USB.

If not, probably the cheapest solution is to get a USB to toslink converter (typically around $£E20, and use toslink to the dac.

Alternatively use a balanced switch, and use balanced to both amps (if they both accept it). Or a USB isolator.

 

[Bob from Florida]

Here it is

View attachment 398727

As you can see, the Rotel does not have a ground pin at the back. So, even though you have a 3 wire power cord the ground is not connected at the amp. The scratchy type noise is almost always because of a switcher supply somewhere feeding noise back into the loop. The device you used to "eliminate" the ground pin had its own switcher supply - which is probably why it got worse. Ground isolators in the U.S. look like below. No idea what you need in your neck if the woods.

 

[antanast]

As you can see, the Rotel does not have a ground pin at the back. So, even though you have a 3 wire power cord the ground is not connected at the amp. The scratchy type noise is almost always because of a switcher supply somewhere feeding noise back into the loop. The device you used to "eliminate" the ground pin had its own switcher supply - which is probably why it got worse. Ground isolators in the U.S. look like below. No idea what you need in your neck if the woods.
View attachment 398735

Thanks Bob. But why does it happen only when I connect the second amp in the loop?

Would something like this work? https://www.digitec.ch/en/s1/produc...13-c13-adapter-plugs-24415292?supplier=406802

If not then how could i resolve this?

 

[antanast]

The sounds like a classic ground loop. Do you have toslink available out of your PC? Or a USB sound card with Toslink out? If so try using this to the DAC instead of USB.

If not, probably the cheapest solution is to get a USB to toslink converter (typically around $£E20, and use toslink to the dac.

Alternatively use a balanced switch, and use balanced to both amps (if they both accept it). Or a USB isolator.

But this happens even if the dac is not connected to the pc

 

[antcollinet]

But this happens even if the dac is not connected to the pc

That suggests the PC is not the source of the noise then - and if it is a ground loop, it is a loop around the other components. What about if the PC is switched off? Does the noise still happen?

 

[restorer-john]

The internal power supply is likely a switcher since it weighs only 15 pounds.

The A11 tribute uses a toroidal, however it has a <0.5W standby consumption which might mean there is a small SMPS in there for remote/wakeup.

 

[antanast]

That suggests the PC is not the source of the noise then - and if it is a ground loop, it is a loop around the other components. What about if the PC is switched off? Does the noise still happen?

It happens when the second headphones amp is connected

 

[antanast]

The A11 tribute uses a toroidal, however it has a <0.5W standby consumption which might mean there is a small SMPS in there for remote/wakeup.

View attachment 398750

Meaning?

 

[antcollinet]

It happens when the second headphones amp is connected

And with the PC on or off? Or it makes no difference? (I'm interested in if the PC is the source of the noise (possibly by magnetic coupling, or via mains connections) even though disconnected on USB.

 

[restorer-john]

I'm with Bob on this. The Rotel is double insulated and may contain a small switching supply for wakeup/etc. That means the chassis may be "floating" and contain some switching noise, even when the amplifier is "off" (standby). I would connect it all up as per normal and then pull the power plug of the rotel, wait 10 seconds or so and tell us if the noise is still there in the headphone amp. If the noise is still there- it's not the Rotel. If it goes away, it is the Rotel.

 

[antanast]

And with the PC on or off? Or it makes no difference? (I'm interested in if the PC is the source of the noise (possibly by magnetic coupling, or via mains connections) even though disconnected on USB.

Wow, this is a breakthrough!

So, next to me there is also a desktop that I use as my Roon server. I also have a NAS next to it.

BUT, what I noticed is that when I unplug the desktop, the noise goes down by probably 90%. Unplugging the NAS plays no role. So the main issue seems to be with the PC. I can still hear some small static sound btw, but that is when I crank up the volume 100% of the amp, which I guess it is acceptable right? And if I completely disconnect the T26S amp, noise goes almost down to 0.

So what now?

BTW, thank you all for such a great community!