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PRYML
20-07-2010, 18:48
Can anyone enlighten me on the pros and cons of Balanced connections between source and pre/amp? :)

It's a feature I sometimes see in the audio magazines etc; however, the reviewers don't really elaborate on why they're pleased to see the option available on the equipment... :scratch:

Malek

DSJR
20-07-2010, 21:22
If you're using VERY long lengths of interconnect (tens of metres), then a balanced line done right minimises hum, noise and losses in the cable as I remember.

The "thing" about single ended screened cable, as most of us use domestically, is impedance matching between source and receiving item. Since the valve days, these things have become more important IMO and can be the main cause of the "sound" of different cables, as the latter's characteristics get caught up with one item trying to "match" with another.

Apologies for the very clumsy attempt at an answer, but in a domestic system and if the source has a low output impedance and the ability to drive several metres of cable, then balanced connections "at home" shouldn't really be necessary and takes an op-amp or two out of the signal path. However, and I'm expecting DSDL Neil to chip in here, balanced at home can work better. It just depends on the equipment used..



Quick examples - I have a preamp at home with se phono outputs only, yet its 5 Ohm output impedance and Class A buffer stage will happily drive tens of meters of interconnect to remote amps (in active monitors for example). My Quad 33 recommends a maximum length of cable between itself and the power amp (around 50 feet I think without checking), yet my beloved Croft prefers a very few metres tops to maintain treble.

The Grand Wazoo
20-07-2010, 22:46
As Dave says above low noise is what they are supposed to be for. A side effect (good, bad or irrelevant, depending on your own particular application) is that true balanced configuration will be louder for a given volume setting by 3dB and you should be aware of, and compensate for this, if comparing balanced and single ended systems side by side.

Spectral Morn
20-07-2010, 22:55
Hi

A lot of what Dave says is right.... though I feel that even if the cabling is only a meter long it is still worth doing.

The main thing I have found is that the benefit for hooking up via XLR cables is only to be found if the components are true dual differential in design i.e true balanced. This means that the internal layout of the item be it a CD player pre-amplifier or power-amplifier has duplicate circuits for the right and left channels so if you look inside you will see two identical boards.

This link to wikipedia reads as being okay (anyone think its not) and tells you about balanced designs but it is written from a pro audio view point...http://en.wikipedia.org/wiki/Balanced_audio This link tells you more about the cabling and plugs used http://en.wikipedia.org/wiki/XLR_connector.

This is an example of a true balanced design. Note the left and right sides being identical and there being two boards for the left and right audio outputs. Balanced Audio Technology an American company specialise in true balanced designs.

http://www.balanced.com/products/line/Vk-52SE/images/VK-52SETop.jpg

If you hook a balanced design up as it is meant to be used, it will have a much lower noise floor with fine signal details being more obvious, the sound stage will be a bit bigger, deeper and wider and bass is usually better too. If you only use RCA connection you wont be hearing it fully. Of course these are generalisations and some balanced kit sound pretty good hooked up either way but in my experience it is worth the extra gains to hook it up right.

There is as Chris says usually a difference in volume level but even after compensating for this, the quality of sound via XLR connection is still in my experience better and this has nothing to do with volume.


Regards D S D L

Mike
20-07-2010, 23:59
true balanced configuration will be louder for a given volume setting by 3dB

Hmmmmm..... :hmm:

I'd say that the signal level will be ~6dB higher (twice the voltage), but 3dB "louder"?... I'm not so sure, I think that would be dependent on the system TBH. ;)

Mike
21-07-2010, 00:02
the benefit for hooking up via XLR cables is only to be found if the components are true dual differential in design

Agreed... but there's alway the added 'benefit' of getting rid of those silly RCA connectors too! ;)

PRYML
22-07-2010, 07:49
Thank you AOS mentors for your input :respect:

At least, I've now a general idea and can begin my own personal research in the matter. I also now know why they're more expensive to implement as well, as you need "paired" sets of components to support the application...

Because I was wondering why, if it was so good, was it not more widely available etc :)

Regards,

Malek

hifi_dave
22-07-2010, 09:12
As I understand it, true balanced operation requires separate amplifier circuits for the negative half of the signal and another for the positive half. These circuits must be very carefully matched or else gross distortion will be generated. These two amplifier circuits are used for each of the two stereo channels. ie a positive and a negative amp for each of the channels.

Naturally, this is a very expensive and complicated thing to achieve and there are very few companies prepared or able to manufacture such products. The most obvious adopter of this technology for many years has been Mark Levinson.

The majority of companies claiming they have a balanced output and/or input are using either a circuit (chip) or small transformer to allow the use of the XLR sockets and balanced (microphone) type cables. This give lower noise but does not provide 'better sound' as does the true balanced.

Reid Malenfant
14-09-2010, 19:23
Hmm, balanced connections are definately superior to unbalanced via phonos for a few reasons ;)

The connectors are locking, though admittedly this can be gotten round by using locking phonos which clamp onto the connector.

The most important bit though is what Neil the Dalek brought up.

With balanced connections there is an automatic rejection of any interference that the cable may have to deal with (it's not 100% rejection but consider an unbalanced cable has zero if crap can get through the screen!). In a standard unbalanced connection any junk will affect what you listen to simply because the only way of rejecting interference is down to the cable screening which ultimately isn't 100%.

With any balanced connection the interference will be on both inner conductors (& in the same phase) & because one internal wire is + & the other - the interference is naturally cancelled once it's fed to the following piece of equipment as any common mode junk is eliminated to a great extent.

It may not seem like a lot but reducing the crap that does get into the leads makes quite a bit of difference. Given a similar expenditure on cables & connectors i feel damn sure you'd prefer the balanced over unbalanced connection, even if it is short as Neil mentioned ;)

Steve Eddy
16-09-2010, 02:13
As I understand it, true balanced operation requires separate amplifier circuits for the negative half of the signal and another for the positive half. These circuits must be very carefully matched or else gross distortion will be generated. These two amplifier circuits are used for each of the two stereo channels. ie a positive and a negative amp for each of the channels.

That's a common misconception that's been perpetuated by those who don't have any idea of what balanced interfaces are and how they work.

The whole raison d'etre of balanced interfaces is the rejection of common-mode noise, i.e. noise that appears equally on each line such as what happens when a cable picks up noise from outside sources.

The term "balanced" refers to a balance of each line's impedance with respect to ground. This balancing of impedances is critical for the rejection of common-mode noise. Any imbalance will result in reduced noise rejection.

However what's required for common-mode noise rejection is a differential input. A differential input only amplifies the difference it sees between its two input terminals. Therefore, in the case of common-mode noise that's of equal amplitude and equal polarity on each line, the output will be 1 - 1 = 0.

The signal is differential so the input will see a positive voltage at one input terminal and a negative voltage at the other input terminal, so the output will be (+1) - (-1) = +2.

Creating a balanced input using two separate circuits for each line, while the impedances may be balanced with respect to ground, it is NOT a differential input.

Instead of rejecting common-mode noise, such a circuit will actually amplify it as if it were a signal and pass that amplified noise on to the next component.

Now, some companies will implement a balanced circuit by maintaining a differential topology from input to output, but this is not the same as having two separate circuits. Differential circuits are cross coupled to each other.


The majority of companies claiming they have a balanced output and/or input are using either a circuit (chip) or small transformer to allow the use of the XLR sockets and balanced (microphone) type cables. This give lower noise but does not provide 'better sound' as does the true balanced.

They do indeed provide "true balanced." Those who are claiming that completely separate circuits are "true balanced" simply don't know what they're talking about and simply lend credence to those who say that high end audio is a technological backwater.

se

Steve Eddy
16-09-2010, 02:19
Hmm, balanced connections are definately superior to unbalanced via phonos for a few reasons ;)

The connectors are locking, though admittedly this can be gotten round by using locking phonos which clamp onto the connector.

Never understood the desirability of locking connectors in a home audio environment. In all my life I've never had a non-locking connector come undone on its own.

se