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[aviorrok]

The noise appears only when the analyzer button set to post, when the button set to pre there is no noise.

[hz37]

Are you saying you can actually hear this as noise? Because it appears to be very narrow band and 20 kHz means you have exceptionally good ears. Even my 8 year old daughter can only hear up to 19 kHz.

It would be interesting to render this to disk and watch it in a spectral editor, like Izotope RX. If there is a thin line at 20 kHz, then something is creating this harmonic as an artefact. I probably wouldn't worry too much about it, because only a handful of young people might actually hear it. And dogs, cats, bats and the likes.

Hens Zimmerman

The noise appears only when the analyzer button set to post, when the button set to pre there is no noise.

[James Perrett]

The noise appears only when the analyzer button set to post, when the button set to pre there is no noise.

I'd guess that the noise is still there but you can't see it on the display as it is 25dB lower at the input. Do you really need a 25dB boost?

[aviorrok]

Are you saying you can actually hear this as noise?

I’m not hear it but is very annoying.

[Dave B]

Dude, life is too short - move on and let go.

The fact that it is not there on the input means that the eq itself is more than likely causing the issue. The stock logic eq is fine, but not the be-all and end all of eqs. TBH, even if you are recording the odd _very_ high frequency content and even if that is getting summed by the time it gets to the master bus, you'd be fine with using a filter with a very steep slope to clean it up. I was always taught to both high- and low-pass the bus before any other processing to keep things tidy anyway.

[James Perrett]

The fact that it is not there on the input means that the eq itself is more than likely causing the issue.

There's a good chance that it is real but the analysis display doesn't really go low enough to see it on the input. As far as I can see, it comes up to about -40dB on the post eq display which would mean that it was 5dB below the minimum value on the pre eq display. I find it useful to be able to see down to -120dB or lower on a frequency analysis display. In a previous post I thought the cause had been narrowed down to the Warm Audio preamp.

[aviorrok]

I discovered something new the noise sound appears only if the project set to 48Khz or more.
If I set sample rate to 44.1Khz the noise gone.

[Hugh Robjohns]

As James commented above, I thought we had narrowed the problem down to the Warm preamp and a potential ground-loop or interference issue.

I suspect the fact that this ~20kHz tone appears only at 48k and higher as sample rates is due to unfortunate beat frequencies between the digital rig and something in the Warm preamp (switched mode PSU perhaps, or unintended self-oscillation maybe). Resolving any ground-loop problems may well make the HF tone disappear permanently.

H

[aviorrok]

As James commented above, I thought we had narrowed the problem down to the Warm preamp and a potential ground-loop or interference issue.

I suspect the fact that this ~20kHz tone appears only at 48k and higher as sample rates is due to unfortunate beat frequencies between the digital rig and something in the Warm preamp (switched mode PSU perhaps, or unintended self-oscillation maybe). Resolving any ground-loop problems may well make the HF tone disappear permanently.

H

I solved the problem I switch to line input 3/4 in the UR242.
1/2 inputs is a preamp inputs, so I connected a preamp to preamp and that make the noise.

[aviorrok]

The problem is not solved but I know the cause.
When I disconnected the UPS (USB) cable from computer the noise is gone but the noise is happening only when the preamp is power on and the UPS USB cable is connected.
The UR242 connected to the preamp with TRS, how can I solve the problem?

[Hugh Robjohns]

The fact that it only happens when the preamp is powered up suggests a fault with the preamp to me... since a simple ground-loop would be present all the time regardless of powering status. Which is what I thought we identified a while ago.

Having said that, the unwanted noise (from the preamp) would appear to be getting into the system via the grounding of the control line from the UPS.

If it's not already the case, I'd start by making sure the preamp is plugged into the same power outlet as the UPS since that will minimise the group-loop area.

After that, I'd try breaking and isolating the screen connection in the balanced cable from the preamp to the interface, ideally inside the TRS plug at the interface end. That will break the ground-loop -- if there is one -- and that might well help... but it really depends on where the interference is actually getting in to your system.

H

[aviorrok]

The fact that it only happens when the preamp is powered up suggests a fault with the preamp to me... since a simple ground-loop would be present all the time regardless of powering status. Which is what I thought we identified a while ago.

Having said that, the unwanted noise (from the preamp) would appear to be getting into the system via the grounding of the control line from the UPS.

If it's not already the case, I'd start by making sure the preamp is plugged into the same power outlet as the UPS since that will minimise the group-loop area.

After that, I'd try breaking and isolating the screen connection in the balanced cable from the preamp to the interface, ideally inside the TRS plug at the interface end. That will break the ground-loop -- if there is one -- and that might well help... but it really depends on where the interference is actually getting in to your system.

H

I solved the problem
I connected the UR242 input to preamp output with XLR and not TRS and the noise is gone!
Maybe you know why?
(I tried to replace TRS cables and inputs and outputs)

[Martin Walker]

I solved the problem
I connected the UR242 input to preamp output with XLR and not TRS and the noise is gone!
Maybe you know why?

Aha - then it does sound like a ground loop issue, as by moving from TRS to XLR connections you are now balanced and have broken the loop

As Hugh said over a week ago:

As James commented above, I thought we had narrowed the problem down to the Warm preamp and a potential ground-loop or interference issue.

Resolving any ground-loop problems may well make the HF tone disappear permanently

Martin

[aviorrok]

I solved the problem
I connected the UR242 input to preamp output with XLR and not TRS and the noise is gone!
Maybe you know why?

Aha - then it does sound like a ground loop issue, as by moving from TRS to XLR connections you are now balanced and have broken the loop

As Hugh said over a week ago:

As James commented above, I thought we had narrowed the problem down to the Warm preamp and a potential ground-loop or interference issue.

Resolving any ground-loop problems may well make the HF tone disappear permanently

Martin

But th TRS is also a balanced cable am I wrong?
Also ground loop frequency is about 40-55Hz so I don’t think it’s a ground loop issue with the TRS

[Martin Walker]

But th TRS is also a balanced cable am I wrong?
Also ground loop frequency is about 40-55Hz so I don’t think it’s a ground loop issue with the TRS

You can still sometimes get ground loop problems with both TRS and XLR connections, as I described in this SOS FAQ some time ago:

https://www.soundonsound.com/sound-advi ... ound-loops

As for ground loop frequency, old fashioned analogue ground loops do indeed tend to result in mains hum (which normally include various levels of the mains harmonics, such as 50Hz, 100Hz, 150Hz, and so on in the UK, or 60Hz and higher multiples in the US).

However, now that digital devices have entered the equation, ground loops can also result in a wide range of scratches, ticking, buzzing, whistling (your problem) and other digital gremlins that are often associated with computer activities such as graphic redraws, mouse movements, and hard-drive activity.


Martin

[Hugh Robjohns]

I solved the problem I connected the UR242 input to preamp output with XLR and not TRS and the noise is gone! Maybe you know why?

Nope. Not a clue. A TRS-TRS cable is supposed to be balanced in the same way as an XLR-XLR cable.

So if changing the cable type 'solved the problem' then there must have been something 'unusual' about the original TRS-TRS cable or the connectors or something.

It could be that the screening of the TRS cable wasn't as good as that of the XLR cable, or a lack of RFI protection on the TRS input to the interface, or any number of other possibilities that would require very careful investigation to track down definitively.

The problem you have is clearly more than just a simple ground-loop hum, but a ground-loop path does appear to play a part in it. The apparent frequency of the offending noise/interference still makes me think there's something not quite right about the preamp...

H

[Wonks]

Ground loop noise can be any frequency and is often quite high pitched.

Both the TRS and XLR outputs on the WA preamp are balanced, as are the front XLR/TRS combi inputs and rear TRS inputs on the interface.

The UR242 is a slightly funny beast in that both the XLR and the TRS on the combi inputs can be mic or line.

With the front inputs used as line inputs, the pad switch is supposed to be used to drop the signal level down so the preamp can then amplify it again.

Also, the TRS input on input 1 can be selected as Hi-Z

The rear line inputs 3 and 4 are balanced TRS and software switchable between -10dBu and +4dBV (-10 is the default).

So when using a TRS cable, aviorrok,

a) Was the pad switch engaged?
b) Was it plugged into input 1?
c) if b), was the Hi-Z switch engaged?

The only possible physical difference between the TRS and XLR inputs is the Hi-Z switch on input 1 . If that was in, then the WA output may be prone to picking up more interference. Either that or the TRS cable has a fault on it and is letting in noise.

So try the TRS cable on input 1, but with the pad switch in (if not already and ensure the Hi-Z switch is out (obviously the +48v power should be off).

If you still get the noise, but when using the XLR cable on the same input you don't have it, then either there's a bad connection to the TRS socket in the UR242, but more likely there's a problem with the cable.

I'd also try the TRS cable on inputs 3 and 4 (switching the mode to +4dBV first in software) to see if that works. This should determine if its a faulty XLR socket.

Personally I'd keep the WA plugged into one of the rear sockets, leaving the front ones free for easier access.

[aviorrok]

Ground loop noise can be any frequency and is often quite high pitched.

Both the TRS and XLR outputs on the WA preamp are balanced, as are the front XLR/TRS combi inputs and rear TRS inputs on the interface.

The UR242 is a slightly funny beast in that both the XLR and the TRS on the combi inputs can be mic or line.

With the front inputs used as line inputs, the pad switch is supposed to be used to drop the signal level down so the preamp can then amplify it again.

Also, the TRS input on input 1 can be selected as Hi-Z

The rear line inputs 3 and 4 are balanced TRS and software switchable between -10dBu and +4dBV (-10 is the default).

So when using a TRS cable, aviorrok,

a) Was the pad switch engaged?
b) Was it plugged into input 1?
c) if b), was the Hi-Z switch engaged?

The only possible physical difference between the TRS and XLR inputs is the Hi-Z switch on input 1 . If that was in, then the WA output may be prone to picking up more interference. Either that or the TRS cable has a fault on it and is letting in noise.

So try the TRS cable on input 1, but with the pad switch in (if not already and ensure the Hi-Z switch is out (obviously the +48v power should be off).

If you still get the noise, but when using the XLR cable on the same input you don't have it, then either there's a bad connection to the TRS socket in the UR242, but more likely there's a problem with the cable.

I'd also try the TRS cable on inputs 3 and 4 (switching the mode to +4dBV first in software) to see if that works. This should determine if its a faulty XLR socket.

Personally I'd keep the WA plugged into one of the rear sockets, leaving the front ones free for easier access.

The noise with TRS cable occurring in all inputs 1-4 (The pad, 48V and Hi-z is off). I also try to replace TRS cables but the noise still here when I replaced to XLR the noise is gone.

[Wonks]

That would point to some issue with the TRS socket or wiring to it on the WA preamp to me.

Fire off an email to Warm Audio about it and say all the testing seems to indicate an issue with the TRS jack socket. It's strange, because I'd imagine that the connections are paralleled up at the socket end, so what's on one socket should be on the other. But the sockets may be independent and have their own driver chips, so that either a driver circuit component is faulty, or its wiring runs too close to a source of noise.

So I'd use an XLR cable for now, but the noise issue on the TRS socket should be solvable by WA.