RCA into XLR or TRS 6.35

[JasonM]

I've some Prodipe Pro 5 V3 studio monitors, the inputs on them are XLR/TRS 6.35 or RCA

http://www.prodipe.co.uk/studio-monitors/2111-pro-5-v3.html

I want to connect them to an Asus Essence ST card - so RCA output only. Tonight I connected one of the speakers just to test via the Essence ST's RCA however the noise floor was higher then I preferred.

Is there any better way of connected these speakers, I've seen RCA to TRS cables, and also RCA to XLR cables. Would these give a better solution that just using single RCA (mono) cable into each speaker.

In a perfect world I should use a DAC with XLR output, however are there any tricks I can use to improve an RCA signal into these speakers.

 

[lucid]

There's lots of angles on this, so bare with me as I run through some stuff.

In a perfect world all of our analogue connections would be balanced. It doesn't solve every issue, but as far as noise and isolation goes, it's a good solution. Whether the plug is XLR or TRS jack makes no difference. All balanced really needs is two conductors. Thse provide the signal and the inverted signal. The ground connection is there to help with cable shielding.

Connecting an RCA output - which is unbalanced - to a XLR or TRS jack doesn't imbue the signal with any of the properties of fully balanced connections. Inside the XLR or jack plug, all that's connected for an unbalanced source signal is the ground and the RCA centre pin to the Hot line on the balanced connection.

This brings us to what's behind the balanced audio connector on a bit of hardware.

Balanced connections look professional, and cool, and have a 'value added' appeal. However, not all that looks balanced really is. To get the full benefits, its not enough to simply use balanced audio in the device to device connections. The signal path has to be balanced all the way from through the source device and as far through any intermediary devices as possible. That's where a lot of gear falls down. Balanced sockets are fitted, but the signal is effectively unbalanced except for the journey via some external connection cable. The reason for that is cost. It's bloody expensive to make fully balances audio component circuit boards.

Where does this leave us?

Unbalanced RCA in to a balanced audio connector (XLR or TRS jack) is still an unbalanced signal. All things being equal, the noise floor for the signal coming in to the speaker this way versus the RCA connection should be the same unless the circuit design for each connection is different.

RCA-to-RCA cable shielding is important. It ranges from very good right the way down to utterly crap. Sadly, cost is no indicator of quality.

Analogue audio signals from a PC live in a noisy environment. Taking optical out (cable is immune to electrical noise) and then converting to analogue stereo way from the switching noise of the PC can help solve some of these problems.

Check the noise floor of the speakers with an alternative source and with the PC off. If the noise floor is still high then the speakers are not helping your cause.

 

[JasonM]

Thanks for your reply, and fully understand what your saying about balanced output needs to be all the way, including from source.

I will test these speakers on another source, however I think it's these speakers generating the noise.

I was running my Essence ST into a regular stereo amp with RCA only, and there was no noise to mention. My feeling is because these active speakers have been designed around XLR, then they don't favour RCA input very well.

To get around the problem these speakers have a gain control on the back. If I set the speaker gain to lowest level, then set maximum output level from the Asus Essence ST, noise is reduced to the point it can hardly be heard (unless listening close when there is no signal or sound output). I can't help feel these speakers will be better with a proper balanced input into them however.

 

[Mr_Sukebe]

Sounds like you've already identified a perfectly good solution, i.e. use a max output from the card, and a low input volume on the speakers. Go with that.

 

[lucid]

I will test these speakers on another source, however I think it's these speakers generating the noise.

BIB Which is what I said to do.

The reason for doing it with a source is to help with grounding the input connector on the speaker. It can change the noise floor, which should be for the better if there's any change.

I was running my Essence ST into a regular stereo amp with RCA only, and there was no noise to mention. My feeling is because these active speakers have been designed around XLR, then they don't favour RCA input very well.

That would suggest that they're not very well designed then.

To get around the problem these speakers have a gain control on the back. If I set the speaker gain to lowest level, then set maximum output level from the Asus Essence ST, noise is reduced to the point it can hardly be heard (unless listening close when there is no signal or sound output). I can't help feel these speakers will be better with a proper balanced input into them however.

A balanced signal will give double the signal level compared to unbalanced. That's because balanced carries two versions of the signal. The conversion back from balanced inverts the negative phase signal and adds it to the positive phase; hence double the signal level minus any cable noise.

The upshot of this is that the noise floor will remain the same, but because the signal level is twice as loud, the signal to noise ratio improves, but not necessarily because the balanced inputs are designed any better. It may well be that it's simply because there's a lot more signal level compared to the background noise.

You might want to have a think about adding an interface box (DI box) to convert unbalanced to balanced before feeding the speakers. That, or send the Prodipes back and buy better speakers that deal with the unbalanced input correctly.

 

[JasonM]

Just an update on this.

Luid, after your first post I looked again at sources of noise. You won't believe what the main cause was, it was the mid range Maplin RCA cable I was using!

I changed RCA cable to one that was better shielded, and it's reduced the background noise by maybe 80%.

What is strange is I thought these Maplin RCA cables were good, and used them in plenty of other hi-fi gear with no issue. I can only assume these Prodipes are really sensitive to interference.

Did not know DI box's even existing, is there any downside to using these?

I got the Prodipes really cheap second hand. I'm evaluating them, however I might end up returning to my Yamaha / Edifier sub setup that I was using previous. These Prodipes are a bit 'boring' there not very musical! The amp inside them is good quality, and the cabinet is built well, i'm just on the fence to switch out with my existing setup. I'm not a music producer, it's just music / audio for my home office / software dev setup.

 

[lucid]

Just an update on this.

Luid, after your first post I looked again at sources of noise. You won't believe what the main cause was, it was the mid range Maplin RCA cable I was using!

I changed RCA cable to one that was better shielded, and it's reduced the background noise by maybe 80%.

What is strange is I thought these Maplin RCA cables were good, and used them in plenty of other hi-fi gear with no issue. I can only assume these Prodipes are really sensitive to interference.

Did not know DI box's even existing, is there any downside to using these?

I got the Prodipes really cheap second hand. I'm evaluating them, however I might end up returning to my Yamaha / Edifier sub setup that I was using previous. These Prodipes are a bit 'boring' there not very musical! The amp inside them is good quality, and the cabinet is built well, i'm just on the fence to switch out with my existing setup. I'm not a music producer, it's just music / audio for my home office / software dev setup.

I'm not surprised about the cable shielding. I wrote as much in my first reply:

RCA-to-RCA cable shielding is important. It ranges from very good right the way down to utterly crap. Sadly, cost is no indicator of quality.

With cable shielding, its a bit like a parachute. You don't know you need it until you really need it. Then when you find out you bought a dud, it's too late.

My guess would be that the HI-FI gear was shielded well enough, and the power supply clean enough, that it never really shone a spotlight on the cable shielding. IOW, you didn't need good shielding with the HI-FI system, so the cables seemed okay.

Now you have these new speakers, probably with a switch mode power supply inside, and maybe not the cleanest of SMPS units, it's showing up as radiated interference picked up by the weak shielding in the cables.

Sad to say, but most retailers/e-tailers haven't a clue about how good or poor the shielding is in their cables. Nor do they know (or possibly don't care) that some types of shielding suits certain applications better than others. All they know is that the cable is shielded; but as you've found out, just having any shielding isn't enough. It also has to be the right shielding for the job.


As for DI Boxes, it won't come as any surprise when I say that the pros and cons depend on the application, and the quality of gear it's going in to, and the quality of the box.

A good DI box going in to a lesser quality system shouldn't cause any signal issues. But a poor box in to a good system...

If this is a home DJing set-up then you should be fine with a simple DI box to convert unbalanced to balanced.

 

[Purgatory]

Use one of these CLEANBox Pro – Dual Channel Level Converter this will fix the issues you have. I use one with my keyboards, studio gear and from an Oppo 203 that doesn't have balanced outs like the 205 and produces a clean balanced signal from unbalanced and will also work other way round too from balanced to unbalanced. You can find them for £58-£65 but buy them from a place that sells them with a UK adapter most are with Europe power plugs and a converter for uk. The link below I gave you is best place to get it from with a UK adapter and no EU converters needed. Make sure to buy some balanced cables that will go into your monitors go the xlr route and make sure the rca cables you use are good quality too from the pc to the cleanbox then xlr out to the monitors.

This will get rid of all the hiss and background hum and you have full control of the levels too and the sound quality is fantastic from RCA (unbalanced) to XLR (balanced). Fixed all the issues I was having with the same things you are saying and brought out all the fine details in the original source.

https://artproaudio.com/product/cleanbox-pro-dual-channel-level-converter/

https://www.andertons.co.uk/art-cle...MIkayV_-fD6gIVcWHmCh2gnw2hEAkYASABEgLwd_D_BwE