Focusrite Rednet AM2 by TMetzinger
The AM2 is part of the Focusrite RedNet audio networking product line, a full range of analog and digital interfaces (including AES, MADI, ADAT, S/PDIF) designed to integrate studio-grade audio into Dante networks. The product line is particularly popular in educational and large production facilities. The AM2 is a small unit, approximately (HWD) 2.3”x5.5”x4.6”. The sloped top panel has separate volume knobs for the headphone and line outputs, as well as status lights and a mute button for the line outputs. The rear panel includes a power input for the included power supply,a pair of Ethernet Ethercon jacks, and a pair of male XLR outputs. The bottom has rubber feet and a 3/8” stand mount. The front has a standard 1/4” stereo headphone output. The unit ships with a manual and registration card with information on where to download additional resources.
Why Dante, anyway?
I’m using Dante as the interface between my computers and audio devices as a replacement for USB/Firewire type connections. Fundamentally, Dante offers several advantages:
1. Ethernet transport makes things “standard”. Follow the rules for Ethernet in terms of distance, cable types, etc., and your audio can be transported alongside your e-mail, cat videos, and social network updates. Most home networks will handle all the traffic without issue, but you can also set up dedicated switches for your Dante network if you like. If you are connecting to a corporate network, be sure to talk to the LAN engineers about configuring the switches to use advanced features for traffic prioritization and multicast support.Usage and Testing:
2. Dramatic reduction in cabling requirements. A single gigabit Ethernet connection can transport hundreds of channels of audio, and all “patching” is done with a software application. Each Dante device has a set number of transmit and receive points that can be linked to ship your audio wherever it needs to go. At the small scale, I use it to connect my rack-mount mixer near the musicians to my monitoring/recording area down the hall with a single cable instead of a multicore snake. In a large scale, imagine a recording or broadcast complex. Instead of hundreds of expensive tie lines and patch panels, all that’s needed is an Ethernet infrastructure that would be installed for computer and voice support anyway. Dante also supports redundant networking on higher end devices, so that you can have two separate Ethernet infrastructures in critical situations and the traffic will flow even if you lose a cable, or a switch, or a Dante port.
3. Dramatic increase in flexibility. Bits are bits, and packets are packets, whether it’s audio or some other content. Dante takes advantage of technologies invented when Ethernet networks converged and began carrying many different types of traffic, including traffic where real-time performance was important, such as telephony, Voice-Over-IP (VOIP), and medical telemetry. These technologies allow network administrators to reserve bandwidth for packets that have tags showing them to be high-priority. On a properly configured network, your cat videos will never interfere with your Dante audio, though the reverse may occur. Dante also allows multiple receivers to be patched to a single transmitter, with NO decrease in signal quality (it’s all bits now, and bits are EASY to copy). This means you can have a Dante transmitter like a mixer or stage box, and easily feed ALL the channels to whoever needs them – a monitor mixer, a broadcast truck, a recorder (or two, or three…), even your sound reinforcement amplifiers.
I started by just connecting the AM2 to my network switch, a Cisco SG200 that offers Power over Ethernet (PoE). The AM2 took about fifteen seconds to power up, sync to my network (indicated by green lights for power and network) and appear on my Dante controller application as a two-channel receiver, where I quickly patched it (“subscribed” in Dante terminology) to a pair of transmitters on my laptop. With iTunes shipping signal out to the unit I saw the signal light flicker and confirmed sound by plugging in a pair of headphones, though the volume was lower than expected. The Cisco switch reported delivering 4900 mW to the unit.
I then downloaded installed the RedNet control software from the Focusrite web site. This software allows remote control of the products and access to specific configurations. When the software started, it found all the Dante devices on the network and let me move the AM2 to a slot on the right side, where it gave a visual representation of status, showing power, network, mute, and signal level. Importantly, the little wrench icon gives access to setup parameters, and it’s here that we find the single weirdness with the unit as shipped. By default, the unit is set for the line outputs to be set to +24 dBu at 0 dBFS though that can be selected to +18 dBu. The headphone output, in contrast, is set with a default gain reduction of 12 dB, which explains why the volume seemed low during my first run-through with the unit. So be sure to check this if you use the device with monitoring headphones that require high levels! Once you make the change, it’s retained through future reboots.
Measured voltage at -20 dBFS was 1.16 Vrms on both line output channels. I sent a -20 dBFS sweep and 1K tones through the unit and observed a flat frequency response from 20Hz-20KHz, and harmonics down over 100dB, verifying the claimed performance of very low distortion.
The dual Ethernet ports on the back of the unit allow daisy-chaining other Ethernet devices, although the unit will not supply power to downstream units. The unit does get warm, but not hot, to the touch, once it is powered on.
I recently did a series of location recordings where my recording/monitoring space was over 150 feet from the stage. I placed my mixer/interface (with 8 mics) near the stage, and then ran Ethernet to the recording space. Because I was travelling light, I hadn’t brought my Dante-enabled monitoring rack. Using the AM2 let me drive a small pair of powered monitors and headphones, and I just daisy-chained in the laptop I use for recording and remote control.
In another situation, I used it to drive a remote pair of speakers in an “overflow” room when the main venue was full.
The unit does exactly what it claims to do. At $400 US from most resellers, it’s comparable to other Dante 2-channel headphone/line output devices, and has the advantage of operating at 96 KHz sampling rates where competitors top out at 48 KHz. I give it a "4" on bang for buck only because I wish it were a little less expensive.