Keeping a balanced audio signal between two monitors and PC

[seklas]

Hello everyone, first of all I'm very sorry If a thread like this already exists (I honestly couldn't find it).

Recently I bought 2x KRK Rokit 5 G3 monitors for my desktop computer setup. I bought a RCA to 1/8 TRS cable to connect them both together. However as an unbalanced output I'm getting a lot of noise/humming if I turn the knob at the back of a speaker any higher than the minimum -30dB. When left at -30dB - no noise whatsoever.

I thought that maybe I should buy another cable (Double XLR to single 1/8 TRS), but when looking more into it, I noticed that this would also turn the signal into unbalanced and I don't understand what would solve the problem, because it's not like I can connect two different TRS 1/8 into my PC simply expecting it to recognise them as left and right speaker.

Would anyone have any advice as to what I should do? Thanks a lot in advance

 

[Kei]

Your current connection method sounds like it's unbalanced anyway. To get a balanced connection, both the output device and the receiving device need to have the necessary circuitry. You'd need to have a professional audio interface with either XLR out or two separate 1/4" TRS jacks for left and right. A proper balanced connection has 3 connections per channel. (known as Hot, Cold and Ground) In your case, I doubt that going proper balanced would actually solve the problem as it sounds a lot like a ground loop. Easiest solution would be an inline isolation transformer. (AKA, a ground loop isolator) I got around mine by using these for a while but eventually opted to use optical as there is no physical connection between the devices.

 

[seklas]

Your current connection method sounds like it's unbalanced anyway.

Well that's what I'm trying to figure out. RCA is an unbalanced connection, however what I am looking for is someone to tell me exactly how can I get a balanced connection. My point is that using XLR or 1/4 TRS alone won't make it balanced. There are only two ways to connection audio to the desktop 3.5mm audio jack or USB. If I'd use two XLR to TRS 1/8 cable it would still be unbalanced. If I'd connect each speaker individually, the desktop probably won't recognise them as left and right channels, but two individual devices instead, so in my understanding 3.5mm is not an option, however I have no idea what kind of device I could/should use so it would have to TRS 1/4 input ports and USB as an output.

 

[Marsman]

You need an audio device with balanced outputs. You won't find that on a sound card; you'll need something like an audio interface. Focusrite Scarlett 2i2 has balanced TRS outputs.

 

[james.miller]

Why wouldnt you use a 3.5mm to rca cable? Am i missing something?

 

[SupraWez]

You need an audio device with balanced outputs.

^^^ This

 

[Marsman]

Why wouldnt you use a 3.5mm to rca cable? Am i missing something?

Possible ground loop. Kei's already suggested a ground loop isolator, which is worth a shot and a heck of a lot cheaper than buying an audio interface. OP did ask how to get a balanced connection though.

 

[Kei]

The alternative method of getting a balanced connection is by using either an active matching converter like a sonifex rb-ul1 or by using a passive transformer based system. In any case, if it is a ground loop as I suspect, going balanced won't solve it. I've been and tried it as I have both a xonar st and a balanced yellotec PUC interface. Any direct copper link to my HiFi without an isolation transformer caused noise pickup, be it balanced or unbalanced analogue, aes, spdif via coax even HDMI.

 

[seklas]

Thank You everyone, but yeah I looked at the ground loop isolators and decided that I'd rather save up and get an audio interface, which will not have the problem, rather than trying to fix something at the cost of the quality of sound. Depending on the isolators I heard that it does decrease the quality :/

 

[seklas]

The alternative method of getting a balanced connection is by using either an active matching converter like a sonifex rb-ul1 or by using a passive transformer based system. In any case, if it is a ground loop as I suspect, going balanced won't solve it. I've been and tried it as I have both a xonar st and a balanced yellotec PUC interface. Any direct copper link to my HiFi without an isolation transformer caused noise pickup, be it balanced or unbalanced analogue, aes, spdif via coax even HDMI.

Seriously? Isn't the noise exactly the reason why people use balanced XLR or TRS instead of RCA, which is meant to be a cheaper alternative?

 

[Marsman]

It can certainly help, but I can't see it being rid of interference completely, if it's that much of a problem. As Kei said, it still uses copper wire, which carries electrical signal. Not just the signal you want, but the noise you don't.

Using a balanced connection via an audio interface may work. It does for some people, but not others. Every case is potentially different, so it's trial and error really. You can't know if that will be successful until you try it.

If it's that much of a problem, a DAC via optical is a more certain way of being rid of the noise, as there is no copper wire for the noise to transmit along.

 

[seklas]

If it's that much of a problem, a DAC via optical is a more certain way of being rid of the noise, as there is no copper wire for the noise to transmit along.

So what you're saying is that I would need a DAC which has TRS 1/4 input and optical output? Or would any DAC with a single 3.5mm audio jack input and an optical output do the job?

 

[Marsman]

DAC will be optical input, not output. Stands for digital to analogue converter. Takes digital data in and converts to an audio signal, which is analogue. Output is commonly RCA, although some do have 3.5mm as well.

You'll need optical out on your motherboard. If your board doesn't, then it maybe worth trying a USB audio interface; because otherwise, you'd need to add a sound card in order to have optical output, to connect a DAC to.

 

[seklas]

Okay, I have done some testing at home with what I had. First, I tried to plug in my monitors into a different power socket - it didn't help (maybe it was still on the same power grid, I'm not too sure about the installation at home). Then I found a 3.5mm male to male cable, to one side I added a TRS 1/4 head adapter, the other I plugged straight into the motherboard, honestly there is no noise whatsoever at any volume level, even +6dB, however I only tested on one monitor as I only got one cable like this and the sound wasn't working properly. It sounded mono, kind of like when you go to your Realtek audio settings and click on voice cancellation (karaoke) option to cut out half the lyrics from any song, that's what it sounded like. I assume that's more of a software problem now. So If I would get a double TRS 1/4 to 3.5mm cable, do you guys think it would actually work, even though I should probably just get an audio interface anyways...

 

[Kei]

Seriously? Isn't the noise exactly the reason why people use balanced XLR or TRS instead of RCA, which is meant to be a cheaper alternative?

It is true that the professional market use balanced connections in order to minimise noise pickup. It utilised common mode rejection, where differential amplification is used to essentially cancel out noise picked up along the cable run. The problem with a ground loop is that it essentially occurs beyond the point where the balanced interconnect would be able to reject it. You can get high quality isolation transformers, but don't expect cheap. (look up jensen, which are the best in the business)

Some good articles on ground loops, here and here.

Okay, I have done some testing at home with what I had. First, I tried to plug in my monitors into a different power socket - it didn't help (maybe it was still on the same power grid, I'm not too sure about the installation at home). Then I found a 3.5mm male to male cable, to one side I added a TRS 1/4 head adapter, the other I plugged straight into the motherboard, honestly there is no noise whatsoever at any volume level, even +6dB, however I only tested on one monitor as I only got one cable like this and the sound wasn't working properly. It sounded mono, kind of like when you go to your Realtek audio settings and click on voice cancellation (karaoke) option to cut out half the lyrics from any song, that's what it sounded like. I assume that's more of a software problem now. So If I would get a double TRS 1/4 to 3.5mm cable, do you guys think it would actually work, even though I should probably just get an audio interface anyways...

The reason it sounded weird would be that you fed an unbalanced stereo signal into the balanced input, where it expects a mono differential balanced signal.

 

[seklas]

Thank You everyone for the input. I just wanted to conclude that the problem is solved now. I've bought the Focusrite 2i2 and connected my monitors via two separate TRS 1/4 cables. No noise is coming from them now at any volume level

 

[Marsman]

That's good news. Glad there's no noise via USB.