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Do balanced (XLR) inputs offer much better sound? - Page 2

post #16 of 23
5/1/03 at 8:41pm
Thread Starter 
I finally decided to buy the amp with standard unbalanced inputs... it was a bit cheaper, and I guess it'll do just fine.
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post #17 of 23
5/2/03 at 7:37pm
Orpheus. What I meant by lower noise floor is that balanced cables reject noice. This is important with long runs. If you are familiar with CJ preamps you would know that they recommend single ended connections. They also seem to be VERY sensitive in terms of cable length and RF interferences. This of course is a design issue.

I think you will notice a difference when you have a fully balanced system throughout the chain especially if you have long runs.

The thing is that this argument really isn't too important. What's important is the gear itself. Depending on the gear and subjectivity, the use of balanced cables can have its rewards.

That said nobody is recommend anyone choosing a piece of gear because they have balanced connections. Just try it out. Balanced cables might give you something that is worth the extra $ while it might be worse. Still I think we can all agree that cable quality is much more important than whether it is balanced or not.
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post #18 of 23
5/2/03 at 8:47pm
Quote:
Orpheus. What I meant by lower noise floor is that balanced cables reject noice.
yes, i know what you mean. afterall, that's EXACTLY what balanced cables were made for!... but anyway... my point is that in a consumer system, balanced cables don't have much value.
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post #19 of 23
5/2/03 at 9:20pm
Quote:
my point is that in a consumer system, balanced cables don't have much value.
I think this is an important point. The definition of "consumer system" is also of great importance.

If your system isn't revealing enough it would be stupid to spend the money on balanced cables. But if you have a $100,000K system is it still a consumer system? The key is whether you'll hear the difference. It's only worth it if you hear a difference. Your system can be $100,000K and you might not hear a difference while your system might be only $10K and you hear a dramatic difference in noice floor. But in my opinion I think cable and component manufacturer's recommendations generally have something behind it.
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post #20 of 23
5/2/03 at 9:33pm
my definition of a "consumer system" is less than 10 components. has nothing to do with value to me. just the complexity.

there are cheap and expensive pro audio components, just like cheap and expensive audiophile components. the main difference is just the complexity of the system.

and like i said before, it doesn't matter how expensive or revealing your system is... if you got only a couple components, balanced cables don't matter at all. and actually hurt the performance. doesn't matter you got a $30,000 turntable, $30,000 preamp, $30,000 amp, $100,000 speakers.................. if you only got these 4 components, balanced cables still do NOTHING for you.

that's what i meant.
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post #21 of 23
5/3/03 at 6:27am
Well I'll never go so far as to say nothing because there are many many happy balanced cable users out there and I know in some instances balanced is required because RCA picked up too much noice.
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post #22 of 23
5/4/03 at 6:27am
Can someone put this into perspective for me...say in terms of a Max vs. a Blockhead?
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post #23 of 23
5/4/03 at 3:55pm
Here are excerpts from two white papers; one by Nelson Pass (a) and one from the Atma-Sphere website (b) re: the pros and cons of balanced/differential designs.

(a) Nelson Pass

Quote:
One of the figures of merit for balanced circuits is called the Common Mode Rejection Ratio (CMRR). As previously mentioned, one of the benefits of balanced circuitry is that it amplifies input differences while ignoring or rejecting common signal (noise). The CMRR of this circuit is slightly greater than 80 dB, as illustrated in Figure 13, which shows the performance from 20 Hz to 20 KHz. This is a factor of about 10,000 to 1, so that a 1 volt common input comes out as about .0001 volt when measured differentially at the output.. This figure was achieved with unmatched gain devices, but careful matching does not significantly improve the performance.
This figure was achieved differentially at the output. If you are using only one polarity of the output signal, you will find the rejection is only about a factor of 10 (-20 dB). Obviously this isn’t nearly as good, but in point of fact it still represents a factor of 10 better than an unbalanced circuit, and usually this is plenty. I have read assertions that 60 dB CMRR figures are the minimum acceptable, but no good reason to why this figure is essential. In my book, any reduction of noise picked up is a plus.
In actual practice with real systems, I have noticed that there is usually about a 20 dB difference in background noise between balanced and unbalanced systems, and a circuit with 20 dB rejection will preserve this difference fairly well. As an alternative to having to use the balanced output only, you can replace the resistors R3, R4 and R5, R6 with 40 mA active constant current sources. This will restore the 80 dB CMRR figure for unbalanced output.

This is from Atma-Speher's website (b):

Quote:
Differential Amplifiers

Figure 2, Differential Amplifier


Differential amplifiers are the basic building block of our voltage
amplifiers. Differential amplifiers have a number of advantages over
conventional single-ended amplifiers. Differential amplifiers are a type
of balanced amplifier, although certainly not the only type. A
differential amplifier consists of two single stages of gain, connected
together by their cathodes (or other emitting devices). This means that
there two inputs to a differential amplifier and two outputs. Any signal
at the input of one side of the amplifier will result in two outputs,
equal but opposite of each other. The main advantages are:

1. Greater power supply immunity. Differential amplifiers present a
constant load to the power supply, resulting in less noise in the
power supply. Differential amplifiers also resist input (noise)
from the power supply to a much greater degree.

2. Lower noise. Differential amplifiers have roughly 6 dB lower noise
then the same circuit executed in a single-ended manner. This can
be very important in moving-coil preamp sections.

3. Lower distortion. Differential amplifiers tend to cancel
distortions that single-ended amplifiers cannot.

4. Drift is reduced by the tight coupling of the two halves of the
amplifier. Performance over time is improved.

5. Noise rejection. Common-mode rejection ratio is the measurement of
a differential amplifier's ability to not amplify noise that is
common to both inputs. It is typically at least 55 dB, and can
approach 140 dB in some critically-tuned designs.

There are also some disadvantages:

1. Increased cost. Differential amplification takes more parts to
execute. For a given number of stages of gain, differential
amplifiers have about 50% more parts.

2. Greater complexity. Although the number of stages of amplification
remains the same for single-ended and differential amplifiers,
differential amplifiers have more requirements to execute, for
example, a negative-voltage power supply.

On the bench, in the textbook and in real life, differential
amplification provides greater performance, particularly from DC to 100
KHz, the audio region. Reliability in practical terms equals or exceeds
that of conventional single-ended circuits, if designed properly.
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