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how to convert balanced to unbalanced with minimal loss?

kenshone

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Hey guys,

I see a lot of products online that allow one to plug in an XLR cable at one end, and an RCA cable at the other.

I want to do this in a way that is as transparent as possible, while rejecting as much common mode noise as possible. To be more concrete, the chain I'm considering is SOURCE -> XLR -> PASSIVE CONVERTER -> RCA -> AMP, and the XLR cable run will be 20+ feet long, so there's a legit risk of picking up undesired noise.

Surely some of these options must be better than others:

- XLR -> RCA cable
- XLR -> passive converter box -> RCA
- XLR -> active converter box -> RCA

And perhaps I'm missing some options either within these choices or aside from them.

EDIT: It occurs to me that I can buy a transparent, yet relatively cheap differential amplifier to terminate the XLR connection after the long cable run, and connect via RCA to a stereo amp. But I hope there's a more efficient option out there!
 
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kenshone

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I'll add a product that caught my eye as a concrete case study: https://www.amazon.com/gp/product/B07D7P7366/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

This product gives the option of passively converting XLR to RCA. Would it be correct to conclude that since the box is passive, it will not achieve common mode rejection, implying that if my chain is SOURCE -> XLR -> PASSIVE CONVERTER -> RCA -> AMP, there would actually be no common mode rejection between the source and the amp?
 

Gorgonzola

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You might get more expert advice, but I have experienced no loss of quality using XLR female to RCA cables. Below shows the long-standing RANE advice for this sort of cable. This diagrams shows the connection depending cable type; (note that "output" refers to the source, "input" to the target) ...
RANE-Balanced-to-SE connection.jpg
 
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kenshone

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You might get more expert advice, but I have experienced no loss of quality using XLR female to RCA cables. Below shows the long-standing RANE advice for this sort of cable. This diagrams shows the connection depending cable type; (note that "output" refers to the source, "input" to the target) ...
View attachment 207373

Hey thanks for the response. I will add to the post that in addition to transparency, I want common mode rejection as close to the amplifier as possible.
 
D

Deleted member 46664

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Hey guys,

I see a lot of products online that allow one to plug in an XLR cable at one end, and an RCA cable at the other.

I want to do this in a way that is as transparent as possible.

Surely some of these options must be better than others:

- XLR -> RCA cable
- XLR -> passive converter box -> RCA
- XLR -> active converter box -> RCA

And perhaps I'm missing some options either within these choices or aside from them.

The best option is almost always the one that adds the least "junk" to a circuit.

An XLR connector carries 3 wires ... A shield, a "hot" copy of the audio signal and a "cold" copy of the signal.
The hot and cold signals are identical, except the cold signal is inverted... so when hot is going positive, cold is going negative. The shield is grounded. At the receiving end, the cold signal is inverted and added to the hot signal... this effectively cancels any noise on the cable.

You can effectively take the shield and either the hot or cold copy of the signal and use it as an unbalanced signal with little or no loss or degradation of sound quality. This can easily be accomplished with a simple Cable. The only thing you need to be careful of is that XLR standards use male connectors for outputs and females for inputs, so an XLR->RCA cable is different than an RCA->XLR cable. (But only by the connectors used)
 
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Hey thanks for the response. I will add to the post that in addition to transparency, I want common mode rejection as close to the amplifier as possible.

Are you having noise problems?
If not... it won't make any difference.

Common mode rejection is not a function of the cables ... it comes from processing at the XLR inputs, which your amplifier doesn't have.

 
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kenshone

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The best option is almost always the one that adds the least "junk" to a circuit.

An XLR connector carries 3 wires ... A shield, a "hot" copy of the audio signal and a "cold" copy of the signal.
The hot and cold signals are identical, except the cold signal is inverted... so when hot is going positive, cold is going negative. The shield is grounded. At the receiving end, the cold signal is inverted and added to the hot signal... this effectively cancels any noise on the cable.

You can effectively take the shield and either the hot or cold copy of the signal and use it as an unbalanced signal with little or no loss or degradation of sound quality. This can easily be accomplished with a simple Cable. The only thing you need to be careful of is that XLR standards use male connectors for outputs and females for inputs, so an XLR->RCA cable is different than an RCA->XLR cable. (But only by the connectors used)

Thanks for the awesome explanation! It would be ideal if I could preserve some of the CMRR of the XLR somehow.
 
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kenshone

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Are you having noise problems?
If not... it won't make any difference.

I think it could. The room that'll contain this audio signal chain has a lot of electronics, and the XLR cable run is going to span the room which is 20+ ft. If it turns out to be overkill, Amazon has free returns. :)

If nothing else, it's an interesting thought exercise for me.
 
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I think it could. The room that'll contain this audio signal chain has a lot of electronics, and the XLR cable run is going to span the room which is 20+ ft. If it turns out to be overkill, Amazon has free returns. :)

If nothing else, it's an interesting thought exercise for me.

Again ... common mode rejection is not a function of the cables themselves. They enable the amplifier to perform noise cancellation at it's inputs... but the amplifier has to be equipped for it. If your amp does not have balanced inputs, all the XLR cables in the world won't make one whit of difference.

topology.png

Noise cancellation happens at the "Balanced Input" ... not in the cables.

You can buy adapters for this, but you will either have to get power from the amplifier for them or power them externally with a small power supply. But ultimately that last few inches between adapter and amp will still be unbalanced.
 
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kenshone

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Again ... common mode rejection is not a function of the cables themselves. They enable the amplifier to perform noise cancellation at it's inputs... but the amplifier has to be equipped for it. If your amp does not have balanced inputs, all the XLR cables in the world won't make one whit of difference.

topology.png

Noise cancellation happens at the "Balanced Input" ... not in the cables.

I read you loud and clear. I've edited the original post accordingly.
 

theREALdotnet

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I read you loud and clear. I've edited the original post accordingly.

RE: your edit. @theREALdotnet is correct. Yes, you can convert externally... and it will work but check the prices on those doo-dadds... they don't tend to be cheap.... and they are rarely exactly what you want.

I'm thinking your best bet is to re-arrange things to get the preamp closer to the amplifier.
 
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