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Howdy,
The only thing that makes a balanced line balanced is that the impedance of both signals is equal. It matters not if the Minus conductor has an inverted signal on it, it can be a ground. The balanced driving circuit has equal output impedance to ground on both the + and - signals. And in theory the balanced receiving circuit has equal input impedance to ground on both the + and - signals. This allows the input to reject common mode(noise) signals that are present on both wires because of any interference picked up on the cable run. This also allows the chassis of balanced equipment to be at earth ground potential, not signal ground ( although the two are tied together a one point in the equipment usually at the power supply).
In unbalanced equipment signal and chassis ground are the same point. So the low side of the signal carrying conductor, the shield for instance in an RCA patch cable, has zero impedance to ground and the high side, the center conductor, does not. It is unbalanced. Since the shield is carrying the signal return current and current between the chassis it is absolutely imperative that the shield be of the lowest resistance possible
Much more info can be found at the Jensen Transformer website.(NO affiliation) Especially see their app notes.

babadono
 

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Ain't that the truth :bigsmile:
What was said is the wisdom... I have literally been in more bad situations of my own making, just because it seemed like a good idea and money was burning a proverbial hole in my pocket. Ahh, that 20/20 hindsight. It seems fairly true that good equipment set up correctly, will whip a good amount of poorly setup exceptional quality equipment as well. And, as most have hopefully learned, expensive does not always equate to good or exceptional.
 

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Hello, new member here!

This is an excellent and very informative post. I was searching the web on this topic. I read a few other pages before this and stopped here becasue this explains everything I need to know without the technical confusion.

In addition to Tony, thanks also to other contributors for additional clarifications.

The AVR that I am looking at only has unbalanced RCA connections for pre-outs and I plan to add an amp in due course. Based on what I understand from this post, it would work pefectly well if I pick an amp that takes unbalanced input and I connect them with good RCA cables (they will be in the same shelf less than 2 ft from each other). Correct?

I also have a question about the cables. I read on many web-based buyer guides and online forums that expensive cables are a rip-off. The general recommendation is to go with any decent competetively priced online sellers of cables. Do 'good RCA cables' in this case also fall into the same category or are they an exception?

Thanks again.
Satyaa
 

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Reply:

................The AVR that I am looking at only has unbalanced RCA connections for pre-outs and I plan to add an amp in due course. Based on what I understand from this post, it would work pefectly well if I pick an amp that takes unbalanced input and I connect them with good RCA cables (they will be in the same shelf less than 2 ft from each other). Correct?

Absolutely. The only way you might run into problems is if the AVR and the external amp were plugged into different 110VAC circuits and that is unlikely.

I also have a question about the cables. I read on many web-based buyer guides and online forums that expensive cables are a rip-off. The general recommendation is to go with any decent competetively priced online sellers of cables. Do 'good RCA cables' in this case also fall into the same category or are they an exception?

Again you're on the right track. Many expensive cables don't offer any improvements in sound quality and that applies to "RCA cables" as well. Just be sure to buy cables that have decent connectors and durable construction. Monoprice has a great offering of audio cables that would meet your needs.
 

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Very informative, Tony! Thanks for taking the time to write this.

I have a quick question. I'm looking at this HDR HDMI switch for a future setup, https://bzbexpress.com/AT-HDR-H2H-88MA-4K-HDR-HDMI-Matrix-Switcher-by-Atlona.html and it says that I can extract the audio from HDMI and i'll get an unbalanced audio out. Does this mean I need to purchase an amp that can convert the unbalanced audio to a balanced audio if I plan to setup a 5.1 surround sound system?
 

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This is excellent information on the audio signal. This article provides in-depth and valuable information about the audio's technical aspects. Thanks!
 

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Its been discussed many times in different posts and it seems there is some confusion on the subject.

This post will help make this much clearer and hopefully with the input of others clear up the does and don'ts of proper connection to pro audio gear.
I do not want to make this sound confusing so I will spell this out in plain English without all the mumbo-jumbo.

Home consumer audio gear uses unbalanced analog audio connections that is designed for short distances and low cost. These connections are usually "rca" and have a shield and a single positive for the signal.
In the graph below you will see the signal (a sine wave in this case) and the shield connected to ground which means it has no signal on it.


A line level audio signal can be looked at as a low voltage signal and unbalanced audio signals are usually between 200mv and 1volt depending on weather it is a fixed or adjustable level.
Given this "lower" voltage signal, long distant runs are susceptible to interference and thus is only good for short runs of usually less than 20ft (50ft can be done if the cable is of better quality).

The problem with using home audio gear with professional audio gear is that the pro gear uses balanced input and output signals. Amps in particular either use a 1/4" Tip Ring Sleeve (TRS) connector
or an XLR connector

The audio signal used in these connectors is at a higher voltage ussually 1.5v and as seen in the graph below has twice the signal as an unbalanced signal.


There are two alternating signals -1.5v & +1.5v and the shield. The advantage of this connection is that when used for long distances the noise (interference) is not only canceled out by the alternating voltages but because its a higher signal voltage it can travel much longer distances without interference (as far as 1000ft) without a booster. The primary factor that allows longer connections with balanced lines has more to do with impedance than voltage. A balanced line has a low impedance (200 to 600 Ohms) while an unbalanced line typically has a 10k impedance or so.

Now here is the problem, when we try to use pro audio gear with balanced inputs connecting to the home audio equipment with unbalanced outputs you usually get incompatibility problems. These problems consisting of noise (usually 60Hz hum) or the signal coming into the pro gear being to low causing the noise floor to be raised when you boost the signal too much making the background hiss or hum to be amplified to the point that it becomes unusable sometimes referred to as signal to noise ratio.
On some amps or other pro gear you may have the ability to "short" the two connectors on the 1/4" TRS to make it a TS unbalanced input. The misconception of this option is that the voltage signal is also boosted but this is not normally the case and is still lower than what a balanced signal should have meaning that the amp at MAX on the level controls will not output the full amount of power it can. If your running this configuration and your amp levels are at MAX to achieve the levels you want I suspect that you have this problem as pro amps should not need to be run more than 75% of its max level control.

The fix to this issue is to use a line balancing transformer like the Samson S-Convert costing around $50


This properly takes the unbalanced signal and converts it to a balanced signal and raises the voltage. Adapters can be bought or made to go from XLR to 1/4" TRS as well as seen on the S-Convert there is only XLR outputs.

There are also several companies that make consumer grade high quality external amps that have proper unbalanced inputs so looking at that rout if your planning on getting an external amp can be a good option. The big plus to using some of the pro gear is that the price seems to be much lower per watts and can be found for under $300 new for two channel amps offering well over 200watts X2 like the Berhinger EP lineup.


Please feel free to comment in this thread and add more info.
The actual cancellation of noise is because the balanced cable carries two identical signals. One is created to be the inverse of the other. If noise enters the cable along the cable length, the noise is picked up on both signals. When the redceiving signals are again subjected to reinversion of one and summed, the noise is nullified.
 
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