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Can anyone help me kill computer noise and interference from usb/HDMI screens?

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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby merlyn » Sat Apr 10, 2021 11:06 am

For a long term solution it would be nice to have spade terminals crimped onto whatever cable you end up using.

Before that, though, I would try tests of concept to find out what is going to work before making up cables.

This would involve hacking up a lead. If you've got a spare guitar lead you could try cutting one end off that and screwing the bare wires (as short as possible) to the terminals to see if it reduces noise. Then put the hum eliminator in to see if that helps.

If you have a spare TRS lead cut one end off that and leave the screen off at the Orban end. If that doesn't work try leaving the screen off at the interface end. This might be best because the Orban is earthed and the Mac and interface aren't.

I notice there is a resistor across the output. What is that for?
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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby BigDeano » Sat Apr 10, 2021 10:32 pm

merlyn wrote:For a long term solution it would be nice to have spade terminals crimped onto whatever cable you end up using.

Before that, though, I would try tests of concept to find out what is going to work before making up cables.

This would involve hacking up a lead. If you've got a spare guitar lead you could try cutting one end off that and screwing the bare wires (as short as possible) to the terminals to see if it reduces noise. Then put the hum eliminator in to see if that helps.

If you have a spare TRS lead cut one end off that and leave the screen off at the Orban end. If that doesn't work try leaving the screen off at the interface end. This might be best because the Orban is earthed and the Mac and interface aren't.

I notice there is a resistor across the output. What is that for?

Cheers dude! Only just saw your reply.

I’m sure I’ve got some leads around somewhere so will give those ideas a try.

Those resistors were there when I got it. I have no idea what they’re for! Would a photo help figure out what’s going on?
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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby BigDeano » Sat Apr 10, 2021 10:46 pm

Just thought I’d have another look at the manual, and a page 2, 4th paragraph down it mentions those resistors, not that I understand what it actually means!

ftp://ftp.orban.com/111B/111B_Manual.pdf
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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby merlyn » Sun Apr 11, 2021 2:27 pm

The manual is pretty in depth. :thumbup: Yes, you should leave the resistors.

The manual mentions using a transformer on the input in 'difficult environments'.

What I'd try first is a TRS lead from the interface output to the hum eliminator, then a guitar lead suitably prepped from the hum eliminator to the terminals on the back of the Orban.

I hope that helps.
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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby BigDeano » Sun Apr 11, 2021 10:55 pm

Thanks for the replies guys! Much appreciated. Been a bit hectic with work to try any of these suggestions out yet, but will give them a go soon and let you k is how I get on!
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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby BigDeano » Tue Apr 13, 2021 12:20 am

So, I put the hum eliminator in between the output of the Interface, and input of the orban using balanced leads on both sides, and this helped a bit, but the noise was still there.

In theory shouldn’t there be no noise due to the transformer isolation?

I was doing some reading though, and thought I’d try using the extension cord for the Mac charger, which does have a ground on it, and woah!! That made a huge difference. All the horrible digital noise has gone. It’s 98% cured! Definitely enough to be using now.

There is still some ground hum there, but I haven’t tried any other leads out yet, so maybe using a spade end on a short bit of wire at the orban end will help.

Still not quite sure why the hum eliminator didn’t solve it completely though.

Out of interest, is taking the TRS cold wire off the ground terminal on the unbalanced input, the same as using a TS lead?
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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby BigDeano » Tue Apr 13, 2021 11:03 am

Ok, one last question and the. I’ll stop bugging you guys!

According to this Rane paper - https://www.ranecommercial.com/kb_artic ... ticle=2107

Electrically balanced out - unbalanced in should be wired using No.9b.

TRS Tip - TS Tip
TRS Ring - Unconnected
TRS Sleeve - TS Sleeve

My question is, what happens to the wiring when you place the hum eliminator in between that?

Should the wiring then be balanced - balanced - balanced - unbalanced, or would you still treat it the same and go with TRS (No ring) - TRS (No ring) - TS - TS?

Hopefully that makes sense! I know I can just try the different options out and see what works, but wondering what in theory is the right thing to do?
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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby James Perrett » Tue Apr 13, 2021 11:58 am

What bit of gear are you using with an electronically balanced output?

The correct wiring scheme depends on the exact design of the output so the best thing is to look at the manual for that bit of gear for recommendations.
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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby BigDeano » Tue Apr 13, 2021 1:09 pm

That would be my interface, a Focusrite Claret 2 Pre USB. Had a look and it just says electronically balanced in the manual
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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby James Perrett » Tue Apr 13, 2021 2:09 pm

The manual for the Clarett clearly shows a TS connector used for unbalanced connections which means that there is no problem with shorting the cold output to ground. So that section in the Rane website doesn't apply to the Clarett.

So in this case I would first try using an unbalanced connection between the Clarett and the hum eliminator.
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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby merlyn » Wed Apr 14, 2021 1:05 pm

The Rane link you posted is a good reference.

BigDeano wrote:So, I put the hum eliminator in between the output of the Interface, and input of the orban using balanced leads on both sides, and this helped a bit, but the noise was still there.

The Orban has an unbalanced input so this diagram from the Rane site shows how a transformer isolator goes from from balanced to unbalanced :

Image

In theory shouldn’t there be no noise due to the transformer isolation?

I would have thought so. The spanner in the works here is that the Mac and interface are floating, as you found out for yourself. I don't understand how you grounded the Mac through a DC power supply, but if it works, cool.

Out of interest, is taking the TRS cold wire off the ground terminal on the unbalanced input, the same as using a TS lead?

Not exactly. Taking the cold wire off is number 9b on the Rane website. Using a TS lead between a balanced output and an unbalanced input is equivalent to shorting cold to the shield at both ends.

Electrically balanced out - unbalanced in should be wired using No.9b.

TRS Tip - TS Tip
TRS Ring - Unconnected
TRS Sleeve - TS Sleeve

I think what the Rane website calls 'cross-coupled' you are calling 'electrically balanced'. Cross-coupled means the balanced output uses op-amps instead of a transformer. If that's what's in the Clarett then the correct cable is number 11.

Should the wiring then be balanced - balanced - balanced - unbalanced, or would you still treat it the same and go with TRS (No ring) - TRS (No ring) - TS - TS?

TRS (No ring) isn't balanced. I would use balanced where it's available as shown in the diagram of a transformer isolator above. :thumbup:
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Re: Can anyone help me kill computer noise and interference from usb/HDMI screens?

Postby Sam Spoons » Thu Apr 15, 2021 4:30 pm

merlyn wrote:
In theory shouldn’t there be no noise due to the transformer isolation?

I would have thought so. The spanner in the works here is that the Mac and interface are floating, as you found out for yourself. I don't understand how you grounded the Mac through a DC power supply, but if it works, cool.

I did a little bit of checking for another similar thread recently and discovered that the wall plug adapter for a MacBook PSU (2011/12 MagSafe and 2020 USB-C so presumably all the others too) does not have an earth connection to the metal retaining spigot, the 'extension cable' version does, This results in an earth of sorts between the mains and the MBP chassis, in the case of two of my PSUs that measured around 1kΩ. That is probably not enough to cause a significant earth loop signal but equally not enough to prevent EMI creeping in either.

If the system is more or less floating I wouldn't expect a transformer isolator to improve matters much. What is needed is a proper earth in the system, does the Orban provide this (it looks as if it should but if it's the only earth then isolating it definitely won't help).
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