The right twist for interference-free signals
Balanced transmission for headphones
(A lot of theory ahead – if you aren’t interested in how balanced transmission works, you can jump directly to the ‘TL;DR’ summary at the end of the next paragraph. But if you are, prepare for a concentrated, although still simplified, dose of technical theory:)
Protected from interference due to 180° phase shift
When we talk about electrical signal transmission regarding audio technology, we usually mean a voltage that changes according to the signal to transmit the information via cable. This can be done with unbalanced lines (for example RCA) or balanced lines (for example XLR). Phone jacks can be unbalanced or balanced. Just a quick side note: In the following, when talking about ‘balanced transmission’, we are actually referring to ‘differential signalling using balanced lines’. Technically, there is a difference between ‘transmission using balanced lines’ and ‘differential signalling’, but the term ‘balanced transmission’ is commonly used to describe both.
Unbalanced transmission uses one signal wire that carries the voltage. The ground wire acts as a reference point. Balanced transmission uses two signal wires that both carry the voltage – but the signal on one of them is phase-shifted by 180°, so it is exactly inverted. Sidenote: The wire carrying the original signal is called ‘Hot’, the one carrying the inverted signal is called ‘Cold’. The receiving device determines the voltage difference between both wires – so effectively, there is a subtraction of the voltages. But why all that hassle?
The magic of balanced transmission becomes apparent when external interferences rear their ugly heads. They lurk everywhere around us in the form of electric and magnetic fields, just waiting to spoil our enjoyment of music. These interferences directly affect the signal of unbalanced transmissions, the only protection is the shielding of the cable. But when using balanced transmission, the interferences affect both the Hot and the Cold wire in the same way – and are cancelled out in the voltage subtraction. This becomes clear when looking at it mathematically:
One wire carries the signal S, the other one the inverted signal -S. When we have an interference I, it looks like this:
Wire 1 (Hot): S+I
Wire 2 (Cold): -S+I
When the subtraction happens, this results in:
(N+S) – (-N+S) = N+S+N-S = 2N
That means that the interference disappears completely, leaving us with just twice the signal. This chart illustrates it:
Image 1: Balanced signal transmission using two wires with the original signal ‘Hot’ above and the inverted signal ‘Cold’ below.
Image 2: An external interference affects both wires identically.
Image 3: When subtracting the signals, the interference works in opposite directions and is eliminated.
TL;DR (Summary): Unlike unbalanced transmission, balanced transmission ensures that the signal is unaffected by external interferences.
That’s all fine and dandy – but what does that mean for my headphones?
Immunity against interference is a big advantage in and of itself and the reason why audio professionals prefer balanced signal transmission. Especially in a studio with numerous electrical devices and countless cables running over long distances, interference poses quite the challenge. Balanced transmission is a great way to ensure clean signals in such an environment. This will also benefit you in your enjoyment of music, although in that case, the potential for external interference is very low, especially when using headphones – at least if you aren’t living in a transformer station.
The ‘wow’ factor when using balanced headphones has a different reason: channel separation and its nemesis, crosstalk. Headphones need two signals, one for the left channel and one for the right channel. Unbalanced transmission runs the signal wires for both next to each other, sharing the ground as reference. This results in crosstalk: The left signal affects the right one and the other way around. This doesn’t happen with balanced transmission, resulting in perfect channel separation. You will hear the difference!
The result of this improved channel separation is a more spatial and detailed sound. The acoustic reproduction is clearer and each sound source can be located more accurately. All in all, the transmission is cleaner and the stereo image is more precise. You feel just as if you were on stage with the musicians! But beauty lies in the eye (or ear) of the beholder – some listeners may not actually like the high channel separation and prefer a more ‘compact’ stereo image. They would rather stand in front of the stage than on it, so to speak.
We here at ULTRASONE believe that everyone should experience music their own way, howsoever they enjoy it the most. That is why we give our customers the choice: the flagship models of our handmade ULTRASONE Edition series, for example the open-back premium headphones Edition 15 and the closed-back variant Edition 15 Veritas, are ‘balanced ready’. They can easily be customized for balanced use and come with LEMO connectors as well as four-wire cables. Decide for yourself how you would like to enjoy your favourite music!
Hear the difference – at Gut Raucherberg!
We are glad to help you when making your individual decision for or against balanced headphones. If you like, you can visit us at our manufactury at Gut Raucherberg near Lake Starnberg. Enjoy our Experience Center, try different ULTRASONE headphones and talk directly to our headphone experts. We are looking forward to your visit!