Balanced V/S Single Ended



I am trying to clear some myths around balanced mode of operation. As always I must add my 2c to the already heated debate.

Balanced sounds right (the word) . It sounds good. It feels good.  Balanced diet. Balanced person. Balanced opinion. By definition we assume positive meaning behind it.

That's exactly why many manufacturers sell products with balanced inputs and outputs.
A pair of XLR's at the back - usually elevates the price twofold compared to " mere SE". XLR's are Oh So Pro, wowie zowie. They are cool to have.

Some remarks on the subject:

1. The balanced way of signal transmission - external to the hifi product - is by means of twisted pair of wires. (plus reference ground wire on the side) We must distinguish between the balanced way of transmission and mode of operation (internal to the product),
The cabling standard is called Canon or XLR and allows relatively tiny signals of 2 V pp to be sent by cables for hundreds of meters. For example - from concert venue to the TV transmission bus. Or simply from the stadium stage to the console few hundreds feet behind.
In balanced cable the distortions from the cable and that picked from the air by the cable, as well as microphony of the cable itself -  are all cancelling out. It is so called common mode cancellation.
SE cables (concentric, chinch, RCA) allow transmission for 1, maximum 2 meters.

2. The balanced way of operation of hifi product means that the circuitry is doubled, one amplification path per channel per phase.

Balanced product has two phases: one is the actual musical signal, the other is the mirror opposite phase copy of the original. They are treated in identical way, all the way to the loudspeaker.

3. In stereo preamps, phono stages, Lampizators and amplifiers - balanced means simply FOUR PATHS - that's double the component count, double power consumption, double probability of failure, double space occupied, double heat, double power supply demand, double potentiometers, double wiring inside, double switches.  Apart from the power switch and the case - all is doubled. So little is achieved by so much.

A different story is at the beginning and at the end of the stereo system chain.
The source can be a LP cartridge. Its principle of operation allows for direct generation of symmetrical signal and sending it via twisted pair, ungrounded arm wire, and then amplification by balanced phono stage. It makes perfect sense. It reduces the RFI/EMI  induced distortions in the cable and in the cartridge.

In CD players the scenario is also very interesting. Obviously, on the CD disc the data stream is monophonic. The digital stream in the demodulator chip - is also monophonic (I mean single). The DAC is the first place where stereo appears.
Now this is critical point - DACS can be monophonic, stereo, or balanced. Or monophonic DACs can be used in quads and they became balanced.

The modus operandi of the DAC chip is such, that it creates musical signal from digits. In the process the DAC is imperfect, these imperfections can be called Errors of conversion.

Let's mark the Error like E
Let's mark musical signal like M

The mathematical equation for single ended DAC is

Output=M+E

In the balanced operation  we have Mp = positive phase of music, Mn = negative mirror copy,  Error is the same for both phases.

Output/Bal = difference between two signals = Mp+E - (Mn +E) = Mp-Mn but Mn = -Mp  so Output /Bal = 2M
The error cancels out.

All this is true if the dac is a TRUE balanced type. Sometimes it is hard to say, because DAC chip may have pins with all four signals, but internally the PROCESS is single ended, just the output stage of chip may have opamp-based phase doubler.  Rarely the chip is really internally fully balanced.
So if we want a really digitally fully balanced player, we will be safer to use the product with separate DACs - four mono or two stereo. They are fed by digital stream which easily can be mirrored by simple logical gate - flipper of absolute phase.

The "error cancelling equation" which I wrote above is also true for distortions which add to the analog signal inside balanced preamps and amps. The radio frequency interference (RFI), electromagnetic induced interference (EMI), transistor and tube non linearity, power supply distortions - all that is cancelled out by summation of the signal at the end of the journey.
Theoretically - we have a perfect error free machine. But remember - doubled circuitry adds double complexity.

At the end of the chain - in speakers, scenario is very easy. Negative and positive terminals of speaker are not grounded, they are both equal and work driven by opposite balanced signals from the amp. The two phases "meet"  inside the voice coil of the driver and musical information components add up (double) while error components cancel out.

When do we really want balanced operation ?

Well, the answer is not easy.
If the cable must be long, lets imagine a CD source in one corner of the room, near the listener, and  amps close to speakers - then we need circa 10 m of interconnect. We should use balanced interconnect.
If we need to plug the interconnect in HOT mode without blowing the amp and speakers - XLR is the only option. RCA has design error which causes the hot co connect before ground and this causes huge impulse if plugged in play mode.

For normal mode of hi fi use - we have the products stacked in the rack, the cables are short, and we don't plug cables in play mode. So the need of balanced is questionable.

Some of the best products in existence, like Audio Note, Kondo, Air Tight, Verdier, Jadis, etc. - are mostly single ended.

Knowing the balanced construction - we can assume that for equally well made products - the Balanced must cost double. The mode of operation makes sense, it promises good quality, but is it better than SE if SE could cost twice as much per phase ?
That is the key. A 2000 Eu Balanced amp has the construction for 500 Eu per phase. Does the balancing improve it as much to beat the 2000 Eu single ended amp which phase costs 1000 Eu ?

If you ask me - SE is the way to go. I mean - good SE.

A word of warning - having XLR sockets does NOT AUTOMATICALLY MEAN that the product is balanced. Many SE amps have balanced inputs which immediately get summed inside for SE and amplified as SE and then split again by opamp to XLR. So check before you buy.

AES/EBU balanced connection  for digital


Some transports and DACs have the SP/dif  signal available in balanced form  - the AES/EBU XLR. Is it good?

Well, ther sp/dif signal is generated in respective chip as single ended. To make it AES/EBU we need to add unnecessary ballancing transformer and to make "artificial balancing". This is sound degradation. But, at least, this signal can be sent on long distance, much longer than th maximum 1,2 m allowed by SP/DIF.
So if we work in the studio - AES/EBU is not optional.

The receiver part of the DAC has receiver chip with AES/EBY as a ready option (Rxn, Rxp inputs). So the AES/EBU does not require second unballancing transformer, it is indifferent to standard.
Concerning the cable - EX/EBU is a much better option, with better RFI immunity, better common mode rejection, less influence of cable quality, better plugs, better shielding, everything.
All things being equal, If I had my way I would use AES/EBU rather than sp/dif but making damn sure, that my balancing transformer in the transport is top notch , good to 30 MHz. Thatrs a worthwhile upgrade.