Live Sound Recording: cables, AD/DA, Clocking, Desks and DAW Setup

Analog, Digital and Hybrid desks

When Sound Live Recording comes, depending on the venue, it’s pretty common dealing with several models of desk, unless you provide your in-house one.

The nature of the desk could meet the FOH expectations in terms of sound and user experience, but it can also affect the signal routing for recording purposes.

If analog desks use exclusively traditional analog cables, a hybrid desk gives you the option to use both analog and digital connections, whereas digital desk are focus only on digital cables.

Analog cables solutions

An analog/hybrid desk can be connected using several types of analog cables:

– Dual RCA connectors to 3.5 mm stereo jack into mic/line of my laptop

– Dual RCA connectors to Dual RCA to plug into the sound card

– Y cable with two mono 6.5mm from Left and Right mixer outputs to a mini jack 3.5mm stereo into the sound card

– Y cable with two mono 6.5mm from Left and Right mixer outputs to a mini jack 6.5mm stereo into the sound card.

– Y cable with a 6.5mm headphones stereo output to two mono 6.5mm inputs into a sound card or any other recording device.

– 2x mono jacks 6.5mm from Left and Right mixer outputs to Left and Right sound card inputs.

– 2x XLR cables from Left and Right mixer outputs to Left and Right sound card XLR inputs.

– 2x XLR cables from Left and Right mixer outputs to Stereo 3.5mm or 6.5mm jack.

– A 6.5mm jack stereo cable from monitors/phones output to 3.5 / 6.5mm stereo input of a sound card, laptop or any other recording device

Digital cables 

– In alternative, it’s possible using USB, Firewire, HDMI (supports 7.1 surround systems), SPDIF cables (with 5.1 surround system support) such as Coaxial (RCA looks like) or Opticals (Toslink) or Ethernet.

FireWire vs. USB

FireWire connections handle more data than USB cables. A 2.0 USB has a data transfer rate of 480 Mbps, whereas an 800 FireWire can handle 800 Mbps.

SPDIF

You might use SPDIF if the audio source doesn’t have an HDMI connector or if you want only to connect audio, not video.

There are two types of consumer SPDIF connectors: coaxial (RCA) and optical (Toslink). The two devices you would want to connect must use the same connector type. You can’t connect an equipment with a coaxial SPDIF output to an audio receiver which has only an optical SPDIF input. Both connectors ends should be the same.

Coaxial

Coaxial cables are a single shielded copper wire which uses electricity to transmit audio.

PRO: they support DTS (Digital Theatre System) 5.1 or Dolby Surround. They are robust with no orientation needed. They provide familiar RCA jacks on each end and a greater bandwidth available supporting 24-bit/192kHz.

CONS: susceptible to radio frequency or electromagnetic interferences, if hum or noise floor is present they can transfer it between components. Signal loss over long distances.

Optical

Optical: they transfer audio signals via light that is beamed through a glass or plastic fiber optic medium. When the signal travels from the source through the cable it’s converted from an electrical to an optical signal. Once the signal reaches the other end, the optical signal becomes electrical again. There’s only one orientation for plugging it in.

PRO: they support DTS (Digital Theatre System) 5.1 or Dolby Surround. They are not susceptible to RFI or EMI, neither to signal loss over distance.

CONS: more fragile than Coaxial, connection less tight or secure than RCA type connectors, support up not more than 96kHz sample rate.

The difference of quality between Coaxial and Optical is pretty subtle and noticeable more in high-end systems. 

HDMI

HDMI: cables that can transmit audio and video with a higher quality.

PRO: uncompressed audio,  7.1 surround systems support, 3D and 4K handling

CONS: more expensive, distance limitations.

Audio over Ethernet: the Dante Technology

Dante combines software, hardware and network protocols together with the goal of delivering uncompressed, multi-channel, low-latency digital audio over a Layer 3 IP packets, basically a standard Ethernet network.

There are many advantages of using digital audio over analog distribution. Transmitting audio over long analog cables can degrade the signal quality because of electromagnetic interferences, high-frequency attenuation or voltage drops. Further, Digital multiplexing changed the requirements of digital cables and the native gigabit support provides both lower latency and automatic configuration.

Less noise and more dynamic range with Audient

Star Lane Studio, the studio of Song Like a Pro, provides an ID44 by Audient a modern audio interface which uses the Dual Converter Technology developed by Audient..

What does it mean?

Audient measured three main aspects, which all largely affect the performance and the sound of an audio interface.

Total Harmonic Distortion (+ Noise)

The amount of additional harmonic overtones introduced by the conversion process, which means noise.

Dynamic Range

The difference between the highest and lowest signal level expressed in decibels. A larger dynamic range will generate a more natural sound during the  playback.

Frequency Response

The level of attenuation or boost of a signal level within its frequency range.  

The majority of manufacturers use the same converter for both the ADC (Analog to Digital Conversion) and DAC’s (Digital to Analog Conversion) or a single combined ADC/DAC option

As Audient is focused on quality rather than quantity, the company decided that rather than using the same manufacturer they would use two different converters, one for the ADC and one for the DAC, that’s why they called it Dual Converter Technology. An approach which allowed to get both inputs and outputs at very high specifications.

Clocking

During ADC and DAC, the signal needs to be clocked precisely to fight unpleasant distorted sounds.

When using multiple devices, these need to be synced in order to read and play back audio at the same rate. The process of syncing two devices is called ‘Clocking’.

In order to achieve Clocking, you have to choose the “Master” device. The best choice is generally the one connected to the computer, such as an audio card.

When opening Logic Pro or Pro Tools, the audio interface will try to match the sample rate of the project and the other slave devices will do the same.

A dedicated master clock unit, which will affect all the other devices of the chain, would be the cleanest solution.

How to send the clock signal?

You can send the clock information via a dedicated BNC cable or embedding it into a digital audio signal via ADAT, S/PDIF or AES/EBU.

How to record audio from a desk?

Once you have connected the desk to your computer (a digital desk often provides a built-in audio interface with a USB output), you are ready to open your favourite DAW and create a new blank project.

DAW Setup

First thing first, check the audio software preferences making sure you are using the right audio interface for your recording session.
Create as many tracks as the number of separate audio sources you have been asked to record. If you have to record a live gig involving drums, bass, guitar and a vocalist, you are probably going to match the number of audio sources (microphones and D.I.) from the stage, which means at least 4 tracks for drums, leading to a total of 7 tracks in your DAW.

The next step is assigning for each track a specific input from the audio interface. Let’s say the audio card in use provides 16 Inputs, you can choose Input 1 for the first track, Input 2 for the second one and so on.

Check Levels

It’s a time for a quick sound check now. 

Whether you work as Front Of House or alongside him/her, try to check the all individual sources levels from your DAW during the sound check. However, you should always keep an eye on that even during the Live performance. It might happen that signals are fine on the desk, but they  gets hotter or too weak in DAW domain. In that case, if that happens during the Live performance, wait the end of a song or scene (in order to preserve the consistency of the show) and adjust the interested track at the right moment.

Arm and go

Remember to arm all tracks before starting the recording process. It may seem trivial, but I heard that some people forgot to arm all channels and lost a great opportunity to be professional.

Save, save and save!

Last, but not least, save your project regularly. We suggest to use your hard drive during the recording phase and moving the project folder to an external hard drive only later. Why? There might be issues with your USB connection or the hard drive itself. So it’s good practice stay safe and run the recording phase using your main computer volume.