#INTERFACE WITH BALANCED SIGNAL PATH PLUS#
#INTERFACE WITH BALANCED SIGNAL PATH PROFESSIONAL#

It offers a sturdy connection, and because it locks in place it is difficult to disconnect accidentally, which makes it perfect for connecting devices that use phantom power.Most textbook explanations claim that a balanced interface requires two symmetrical signals of opposite polarity, passed over a pair of screened, twisted wires.

#INTERFACE WITH BALANCED SIGNAL PATH PROFESSIONAL#

The familiar XLR, used extensively in professional audio. That's why you can remove the screen connection of a balanced interface to prevent a ground loop, without losing the signal. Most people also know that whereas the screen/ground is essential in an unbalanced connection because it provides the signal return path, it plays no part in the signal path for a balanced interface, and is purely a screen to reduce interference.

#INTERFACE WITH BALANCED SIGNAL PATH PLUS#

The next key concept is that of the balanced interface, which is probably the most misunderstood concept in the entire world of audio! Most people know that a balanced interface involves three wires: hot and cold signal wires, plus a screen connection and an unbalanced interface has just two: signal and screen/ground.

For example, +22dB is fairly typical, and semi-pro devices will have even lower margins because of their lower nominal line level. Well designed professional equipment will run out of headroom and start to clip at about +28dBu, which means a whopping signal level of about 20V rms - although I've seen some really impressive equipment that can cope with more than +36dBu! Less well designed audio devices usually have lower headroom margins. Which explains why, if you connect a semi-pro device to a professional one, the average signal level is about 12dB quieter than expected and, going the other way, a professional signal peaks roughly 12dB higher than a semi-pro device expects!ДЄnother important signal level to be aware of is the maximum 'headroom'. The important practical point of this is that a -10dBV signal is almost exactly 12dB lower than the +4dBu professional line level. The 'V' denotes a reference of one volt instead of 0.775V, and that means that the semi-pro line level of -10dBV equates to 0.316V. Semi-professional and domestic equipment is generally designed to use a lower standard line-level, which is described as '-10.' However, there is a trap here: a different level reference is used - this is -10dBV. You will often see and hear references to professional equipment as having '+4' interfaces.

However, most professional audio equipment actually employs a slightly higher nominal line-level of +4dBu, or 1.223V rms.

In broadcasting circles, the nominal 'line level' is called the standard 'alignment level,' and is defined as 0dBu, or a signal of 0.775V rms. The 'u' means 'unterminated' and refers to the absence of 600О© terminations that used to be mandatory back when dinosaurs ruled the audio industry! The standard reference in professional audio is 0.775V rms, and we use the term dBu to denote it. The decibel is simply a logarithmic ratio of two signal amplitudes: one is the signal we are interested in, and the other is a stated reference value. Hopefully, the use of the decibel is already familiar to most readers. The 'rms' stands for 'root mean square,' a shorthand way of conveying the slightly involved method of describing an 'average signal voltage,' which is necessary because we are talking about varying AC signals here, rather than a steady-state DC voltage. Of course, there is no such thing: the actual level can vary wildly from microvolts (if you put a ribbon microphone at the back of a hall while someone plays quietly on a piano), to whole volts (from a capacitor mic inside a kick drum)! In general, though, most people would consider something like -50dBu to be a typical starting point for a nominal microphone level, and that equates to about 2.5mV rms. Starting at the lowest, we have 'microphone level' - the typical level you could expect to come from a typical microphone placed in a typical position in front of a typical instrument. There are, fundamentally, five distinct nominal signal levels to be aware of. The first thing to deal with is the topic of analogue signal levels. This article is therefore intended to serve as a definitive guide to the basics. Analogue interfacing formats are stable and mature, but nevertheless it's surprising how often I am asked questions about connecting. With so much focus on computer workstations these days, wiring up analogue gear is becoming a bit of a lost art, but don't fear: all you need to know is here.Дespite the prevalence of digital audio in today's home studios, we still rely on analogue connections at some points in our signal chains.

Interface with balanced signal path