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Would increasing power minimize noise on unbalanced cables?

tifune

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When I look up the maximum recommended lengths of various cables, I typically come up with a chart like this . While i understand that chart is a bit of an oversimplification, it did make me wonder if a higher line level output would permit longer runs of unbalanced signals?

For example, in my case I have multiple rooms with 16gauge runs through the walls almost all of which are over 100ft. It was definitely designed with the intention of using a power amp with a switch box, but if I were to use something like the Okto8 with their 13V output option would my signal degradation be minimized when running to an active speaker? Or does the combination of length/gauge override all other variables?

I realize in my example I would need a balanced to unbalanced conversion, that's just the first DAC I thought of with such a high output available and I'm really only trying to understand the transmission and degradation aspects of longer runs. I guess the Q could also apply to something like Topping L30, really anything that would increase gain enough to minimize audible noise.
 
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Lambda

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Yes more signal will give you more signal to noise. but at some point you need to add an attenuator at the end.
What kind of cable is this, do you have shielding and a extra ground wire ?

100ft. sounds like you differently want to use balanced cables

Or if the source is digital, send SPDIF over the wires.
 
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T

tifune

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Yes more signal will give you more signal to noise. but at some point you need to add an attenuator at the end.
What kind of cable is this, do you have shielding and a extra ground wire ?

100ft. sounds like you differently want to use balanced cables

Or if the source is digital, send SPDIF over the wires.

The cable is already in the wall, so I'm stuck. Its either 14 or 16AWG, and it has the coating required in US for in-wall installation which I believe is fire retardant but probably does nothing for noise.

Because all active speakers have volume knobs, I was hoping I could just those as attenuators if needed? I certainly wouldn't hook up a power amp to these.

I'd love to send SPDIF but all the guides I've seen suggest 10M is max length for a coax connection. Not sure how accurate that is
 

Lambda

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I certainly wouldn't hook up a power amp to these.
Why not... would be a way to get relatively high voltage levels.

What to do also kind of depends on the Active speakers to. do they have manis ground or are they double insulated.
If they don't have a mains ground they kind of relay on the ground form the RCA or XLR in.
If they have a ground connecting his long wire runs would probably create aground loop.

Audio Isolation transformers can solve this but they also created distortion
http://web.mit.edu/jhawk/tmp/p/EST016_Ground_Loops_handout.pdf
Page 14

I'd love to send SPDIF but all the guides I've seen suggest 10M is max length for a coax connection. Not sure how accurate that is
I have send SPDIF or AES/EBU trough some relay long and crappy wires.

AESSPDIFFigure2.jpg

110Ohm is probably not to far of from zip-cord speaker wire and you can convert from one to the other.
 

raindance

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That's unshielded speaker wire. The only line level signal that would work would be balanced.
 

mansr

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I'd love to send SPDIF but all the guides I've seen suggest 10M is max length for a coax connection. Not sure how accurate that is
That's not accurate at all.

110Ohm is probably not to far of from zip-cord speaker wire and you can convert from one to the other.
Speaker wire isn't suitable for digital signals.

The cable is already in the wall, so I'm stuck. Its either 14 or 16AWG
Is that speaker wire, aka zip cord? If so, analogue balanced signal with the highest voltage you can obtain is probably the best choice. What sort of inputs do your active speakers have?
 

sergeauckland

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That's not accurate at all.


Speaker wire isn't suitable for digital signals.


Is that speaker wire, aka zip cord? If so, analogue balanced signal with the highest voltage you can obtain is probably the best choice. What sort of inputs do your active speakers have?

It might be. AES-EBU balanced digital is nominally 110 ohms, which is not all that far from what a normal loudspeaker cable is, and anyway, it's not at all critical even for 100ft length, so worth a try. It'll either work fine, or not work at all, as it won't affect audio quality, just whether it works reliably or not. It doesn't need screening.

Balanced analogue is actually more difficult, as normal loudspeaker cable isn't a twisted pair, just laid side-by side, so isn't necessarily well balanced and doesn't reject hum as well as a twisted pair. Analogue balanced twisted pair at line level doesn't always need screening, although helps if it is and clearly, does no harm.

I've been surprised at just how rugged digital audio actually is, so well worth a try.

S.
 

Lambda

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Speaker wire isn't suitable for digital signals.
Its digital so if it works, it works. if not you will definitely hear it.
http://www.dl2lto.de/sc/HB_DRILLF.htm (German)
http://www.w1npp.org/events/2010/2010-f~1/antennas/WIRE/790303~1.PDF

Screenshot_2021-02-22_13-52-59.png

As i said speaker wire can be close to 110Ohm and when use with a transformer it can be used for 75Ohm transmission.
It's not ideal because its not twisted and not shielded but it can work. (and is has worked for me)
https://www.ranecommercial.com/legacy/note149.html
 
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Lambda

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Screenshot_2021-02-22_14-25-50.png


A quick idea to uses balanced signals over two wires and the common mode as ground reference
The (audio)Transformers here acts only as a choke.
Depending on the used amplifier the left halve is maybe not needed.
 

Trouble Maker

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Would this be the proper application for 70V audio system? Very long speaker level runs seems like where one would want to use that.
But then I assume your amp/speaker section goes massively down and anything there is probably not high fidelity, especially at a given cost.
 

mansr

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It might be. AES-EBU balanced digital is nominally 110 ohms, which is not all that far from what a normal loudspeaker cable is, and anyway, it's not at all critical even for 100ft length, so worth a try. It'll either work fine, or not work at all, as it won't affect audio quality, just whether it works reliably or not. It doesn't need screening.
I'm not talking about impedance matching. Regular speaker wire of the lengths discussed here will have considerable losses at the frequencies required for digital transmission (tens of MHz). It's also not twisted, which makes things even worse. A while ago, someone at work (unwittingly) tried to use a plain untwisted cable of about 5 m for RS485 (electrically compatible with AES3) at 38400 bps. It was extremely unreliable.
 

sergeauckland

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I'm not talking about impedance matching. Regular speaker wire of the lengths discussed here will have considerable losses at the frequencies required for digital transmission (tens of MHz). It's also not twisted, which makes things even worse. A while ago, someone at work (unwittingly) tried to use a plain untwisted cable of about 5 m for RS485 (electrically compatible with AES3) at 38400 bps. It was extremely unreliable.
Yes, could be certainly, but equally, might work fine. Depends on the details of the cable itself. There's no specific reason why loudspeaker cable won't work, and it's free to try. If it works, then great, if it doesn't, then too bad.

I've sent S-PDIF through my body with wet hands perfectly reliably, (albeit I had to increase the voltage somewhat as my losses are considerable) but was surprised how well it worked. I wonder if you ever saw Canford Audio's demo at an AES exhibition some years ago where they sent AES-EBU though two bits of wet string. They were wet because they went through a fish tank, with fish swimming about. I would expect the losses to be very high, and the impedance very variable, as it would depend on where the fish were.

S.
 

Lambda

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here will have considerable losses at the frequencies required for digital transmission (tens of MHz)
Screenshot_2021-02-22_15-17-04.png

ASE3 can be 7Vpp SPDIF needs min.0.2Vpp (might even worke with less) so some loss can be accepted

they also sell this impedance converter for video
Screenshot_2021-02-22_15-32-26.png
 

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mansr

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ASE3 can be 7Vpp SPDIF needs min.0.2Vpp (might even worke with less) so some loss can be accepted
7 Vpp is the maximum allowed, and many transmitters have much lower voltage. S/PDIF transmitters are 0.5 Vpp.

Also, "zip cord" isn't a well-defined thing. The figures and graphs you're quoting are presumably valid for one specific product. Another one can have wildly different properties. A random speaker cable might work fine. More likely, it will work mostly fine, except when the fridge turn on, a car passes in the street, etc.

If plain zip cord was all anyone ever needed, coax and twisted pair wouldn't have been invented.
 

Lambda

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Another one can have wildly different properties. A random speaker cable might work fine. More likely, it will work mostly fine, except when the fridge turn on, a car passes in the street, etc.
Yes. It might work and since adapters to test it go for <10$
(Assuming OP already has source and an SPDIF receiver) i would give it a try.
If not spdif to analog box from ebay is like 3-10$

Of cause noting is guaranteed but its not impossible.

photo5305506920053977639.jpg


Using Only the finest* proper 75Ohm HF** cables i made this contraption.
Worked Flawless

*cheapest
**Not
 
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