Interference with new KRK setup

[Room Service]

I just bought a new pair of KRK Rokit RP5 G4, but I'm having an issue with them. There's high interference sound coming from them.

Setup: The KRK's are connected to my Focusrite Scarlett Solo Gen2 via XLR ro RCA (Since the Scarlett Solo only has RCA inputs). The Scarlett is then connected to my PC via USB.

I've tried different cables and I still get the interference. However, when I connect the KRK's to my Pioneer DDJ 400 directly using the same XLR to RCA cable there's no interference.

What is going on here?

 

[MaxwellsEq]

I just bought a new pair of KRK Rokit RP5 G4, but I'm having an issue with them. There's high interference sound coming from them.

Setup: The KRK's are connected to my Focusrite Scarlett Solo Gen2 via XLR ro RCA (Since the Scarlett Solo only has RCA inputs). The Scarlett is then connected to my PC via USB.

I've tried different cables and I still get the interference. However, when I connect the KRK's to my Pioneer DDJ 400 directly using the same XLR to RCA cable there's no interference.

What is going on here?

Nobody can be certain but it sounds like PC noise is transfering via the USB. You may have a ground loop when the PC is involved (you aren't using balanced working, so this is likely), or the PC is particularly noisy. You could experiment with a USB filter.

 

[Room Service]

Nobody can be certain but it sounds like PC noise is transfering via the USB. You may have a ground loop when the PC is involved (you aren't using balanced working, so this is likely), or the PC is particularly noisy. You could experiment with a USB filter.

Would the speakers being in the same outlet as the PC create this interference?

 

[staticV3]

Would the speakers being in the same outlet as the PC create this interference?

Not necessarily. You can experiment with connecting them to different outlets, but I wouldn't be surprised if the noise stays.

I agree with Maxwells. Try a USB isolator.
https://www.tpdz.net/productinfo/733226.html
https://hifimediy.com/product/hifime-high-speed-usb-isolator-v2/
https://aliexpress.com/item/1005001927948863.html

Also, it may be worth looking into impedance balanced RCA->XLR interconnects.

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Nice, have not seen that error thought but i dont play loud or have demanding headphones. Will wait until some ppl in this thread can confirm the update works without issue until i update. Well, I've updated and do not notice any difference. (Used windows 11, turned the DAC on and simply ran...

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Properly constructed, these will give your Scarlett Solo the same noise ceiling and ground loop breaking attributes as a native XLR interface..

 

[Room Service]

Also, it may be worth looking into impedance balanced RCA->XLR interconnects.

Properly constructed, these will give your Scarlett Solo the same noise ceiling and ground loop breaking attributes as a native XLR interface..

I'm sorry, I never heard of a USB isolator/filter before. So these would go on my PC then I'd connect the Scarlett's USB to it?

Also, an impedance balanced XLR to RCA cable would also solve the issue? Cos where I live in, sound equipment is very scarce if non-existent here. (I live in Macau btw), however there is a old shop that does custom cables. So if I went there and asked for one of these, it would stop the interference?

 

[staticV3]

I'm sorry, I never heard of a USB isolator/filter before. So these would go on my PC then I'd connect the Scarlett's USB to it?

Correct.

Also, an impedance balanced XLR to RCA cable would also solve the issue? Cos where I live in, sound equipment is very scarce if non-existent here. (I live in Macau btw), however there is a old shop that does custom cables. So if I went there and asked for one of these, it would stop the interference?

In theory, yes. I can't guarantee it.

Also, you need to find the output impedance of the Scarlett's Line out.
Focusrite doesn't specify this, so it needs to be measured.

 

[AnalogSteph]

I would have them make a RaneNote 110 #17 for starters.

It's unfortunate that output impedance is not yet specified in the Solo 2nd gen, though it's likely to be anywhere from 47 to 220 ohms. The 1st-gen 2i4 had 47 ohm unbalanced outputs, the 3rd-gen Solo 430 ohms balanced.

You could have them put in 100/120/130 ohms between RCA ground and cold as a compromise with decent impedance matching either way, or take the cable with you half-finished with 220 ohms and the ends accessible, so either a 180/200/220 ohm or a 68 ohm resistor can be held in parallel while listening which version gets rid of the noise the best.

The balancing resistor needs to go wherever the transition from unbalanced to balanced is. If the cable in shielded twisted pair, it goes at the RCA end, while if the cable is coax, it would go at the XLR end. There should not be a connection from XLR pin 1 to RCA shield - well, except for a small capacitor of no more than a few nF perhaps, but that's going into gilding the lily terrain.

 

[Room Service]

Also, you need to find the output impedance of the Scarlett's Line out.
Focusrite doesn't specify this, so it needs to be measured.

I see, so the issue is most definitely from the Scarlett's interface. I have no idea how to measure these things and being in Macau, it's very difficult to find a specialist professional that offers such services. Plus, I'm only a club DJ, not a sound engineer so I have no idea about most of these things. I could ask the sound engineers at the club I work for, but they are native Chinese speakers and their English is below basic, so communication is quite difficult.

 

[Room Service]

I would have them make a RaneNote 110 #17 for starters.

It's unfortunate that output impedance is not yet specified in the Solo 2nd gen, though it's likely to be anywhere from 47 to 220 ohms. The 1st-gen 2i4 had 47 ohm unbalanced outputs, the 3rd-gen Solo 430 ohms balanced.

You could have them put in 100/120/130 ohms between RCA ground and cold as a compromise with decent impedance matching either way, or take the cable with you half-finished with 220 ohms and the ends accessible, so either a 180/200/220 ohm or a 68 ohm resistor can be held in parallel while listening which version gets rid of the noise the best.

The balancing resistor needs to go wherever the transition from unbalanced to balanced is. If the cable in shielded twisted pair, it goes at the RCA end, while if the cable is coax, it would go at the XLR end. There should not be a connection from XLR pin 1 to RCA shield - well, except for a small capacitor of no more than a few nF perhaps, but that's going into gilding the lily terrain.

Wow, that's a lot of technical stuff that I simply do not understand

All I understood is that my gen 2 Scarlett doesn't have balanced outputs. I could show your link to the little shop I know here and get a custom cable built, however, the owner knows these things are hard to get by in Macau so he heavily overcharges for services (like 4x the actual value).

Maybe it's time I upgraded my sound interface. Would you have any suggestions for a sound interface that would offer balanced outputs at a budget? Something around 120/130 USD would be as much as I would be willing to spend.

I found something on TaoBao (it's the same company as Alibaba but it's only for people who live in China), so I'm not sure if this is exactly what's been described on this topic (USB isolator/filter) as everything is in Chinese and translation is a bit weird, I'm not sure about the quality of the items and for the price they're asking for one is too risky for me to try it out.

 

[MaxwellsEq]

I see, so the issue is most definitely from the Scarlett's interface. I have no idea how to measure these things and being in

No, that's the wrong conclusion. What @staticV3 and @AnalogSteph are saying is that if you want to make up an impedance balanced cable you need to know the output impedance of the interface, otherwise you can't match the impedance.

The thing about earth loops (assuming that's the problem here) is that they are the fault of the entire chain. You need at least "two wrongs" to have an earth loop. Studios always use balanced working to avoid the tedious task of identifying the loop mechanism.

 

[Lambda]

Setup: The KRK's are connected to my Focusrite Scarlett Solo Gen2 via XLR ro RCA (Since the Scarlett Solo only has RCA inputs). The Scarlett is then connected to my PC via USB.

Classical problem with Common mode USB noise from your PC.

Your monitor as well as the PC and its Power-supply are all reference to PE earth ground.
Since in the PC are high currents the USB GND potential can have a view mV offset and noise

Easiest way to fix this, get a USB isolator. only drawback it costs 70$

 

[Room Service]

I found this on TaoBao, the English is translated from Chinese text, but could this be a USB isolator?

 

[Wicky]

View attachment 352638I found this on TaoBao, the English is translated from Chinese text, but could this be a USB isolator?

Yes, also the products @staticV3 linked to in the post above.

 

[staticV3]

View attachment 352638I found this on TaoBao, the English is translated from Chinese text, but could this be a USB isolator?

No, it's not a USB isolator. It's a USB filter. It won't help with ground loops.

 

[Wicky]

No, it's not a USB isolator. It's a USB filter. It won't help with ground loops.

Apologies, yes keyword "galvanic isolation" ... USB filtering is not helpful

 

[Room Service]

No, it's not a USB isolator. It's a USB filter. It won't help with ground loops.

Damn. It's so hard to find things where I live Since Paypal is illegal here, eBay is out of question. Amazon delivery costs to Macau are actually insane at +55 USD even if it's something small. Hong Kong might be easier, but I rarely have time with my day time job + DJing.

I think the fastest and easier solution for me is to get a sound interface with balanced outputs. I know the Scarlett Solo gen 3 have balanced outputs, but any other suggestions that could be better around the same price?

 

[Lambda]

Apologies, yes keyword "galvanic isolation" ... USB filtering is not helpful

You don’t need "galvanic isolation"
You need a to add as muss impedance as as possible in Common mode for the frequency range of the interference.
"galvanic isolation" is per definition closes to infinite Impedance for DC so its usually good for low frequency interference.

But in theory you could have a good high impedance Common mode filter without true isolation.

sad truth is most USB filter are not this

 

[AnalogSteph]

Maybe it's time I upgraded my sound interface. Would you have any suggestions for a sound interface that would offer balanced outputs at a budget? Something around 120/130 USD would be as much as I would be willing to spend.

What would a 4th gen Scarlett Solo cost you?

 

[Room Service]

What would a 4th gen Scarlett Solo cost you?

About 180 USD after conversion. It's all good, I'm buying the Topping D10 Balanced and a USB volume knob, which is about 100 USD + 4 USD for the knob.