Ferrofish A16 Ultra MkII

16-channel A-D/D-A Converter

Published in SOS October 2012
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Reviews : Mixer

The A16 Ultra MkII can add 16 channels of line-level I/O to any audio interface that features MADI or dual-ADAT ports — all in the space of a 1U box and for a bargain price!

Hugh Robjohns

Ferrofish A16 Ultra MkII

Ferrofish are a relatively new company, founded last year by Juergen Kindermann, who was formerly a hardware engineer with Creamware and, after buying that company's intellectual property when they folded, became the Managing Director of Sonic Core. The idea behind Ferrofish is to allow Kindermann to revisit and develop some of the technology employed in the old Creamware products, the first examples being the B4000+ organ emulation module, and the A16 Ultra MkII, reviewed here. The B4000+ employs an Analog Devices Sharc DSP, which might help to explain the Ferrofish company name! The A16 MkII is a MADI and ADAT A-D/D-A converter and is, naturally enough, a development of Creamware's A16 Ultra. It's not a simple repackaging, though: as well as adding MADI functionality, they've improved the performance, thanks to the latest generation of AKM AK4620B converter chips and redesigned clock circuitry.

Overview

Most of the rear panel is taken up with the 32 balanced TRS jack sockets, which provide the analogue line I/O and have been offset so the A16 Ultra MkII can accommodate the larger professional quality jack plugs that some 1U multi-channel devices struggle with.Most of the rear panel is taken up with the 32 balanced TRS jack sockets, which provide the analogue line I/O and have been offset so the A16 Ultra MkII can accommodate the larger professional quality jack plugs that some 1U multi-channel devices struggle with.

In essence, the A16 MkII is a 16-in, 16-out A-D and D-A converter featuring both ADAT- and MADI-format digital interfaces, and versatile internal audio routing facilities — although, like most standard converters, there's no latency-free monitoring facility and no direct USB or Firewire computer interfacing. The steel rackmount case extends only about 170mm behind the rack ears, but makes this a surprisingly heavy box, at almost 3.2kg. The power supply is an external 12V DC in-line lump that has a flying output lead terminated in a coaxial connector for the back of the A16 MkII (with a loop and tie-wrap on the rackmount box to retain the cable, if required). The line lump connects to the mains supply via a C7 (figure-of-eight) moulded plug, and can accept any supply in the range 100-240V AC.

On the rear panel, most of the space is taken up by two offset rows of 16 TRS sockets for the balanced analogue ins and outs, which can be adjusted individually between +4dBu and -10dBu (yes, dBu, not dBV) reference levels. MIDI In, Out and Thru are provided for remote-control purposes, with the digital interfaces occupying a very small area at the left-hand side. The MADI interface is optical, with a dual TX/RX socket neatly protected by a rubber dust cap. Word clock in and out appears on BNC connectors alongside. The ADAT interface is doubled up (ADAT A/ADAT B) in and out to accommodate up to 16 channels.

The A16 Ultra MkII's digital I/O includes dual ADAT ports, a MADI connector and BNC word clock connectivity, not to mention MIDI ports to allow for remote control.The A16 Ultra MkII's digital I/O includes dual ADAT ports, a MADI connector and BNC word clock connectivity, not to mention MIDI ports to allow for remote control.The front panel is deceptively simple, hosting two colour TFT screens and four push-buttons. Normally, the left-hand TFT shows bar-graph meters for the 16 analogue inputs while the right-hand screen does the same for the 16 analogue outputs. The rightmost push-button powers the unit, while the others are marked Sample Rate (<), Synchronisation (>), and Menu (•). These access and navigate the various configuration menus in a fairly intuitive and logical way.

Under the input bar-graphs are labels for the current sample rate (32-192 kHz), while the output side display carries labels for the current clock source (master, MADI, ADAT and BNC word clock). The S/MUX protocol can be used to overcome the inherent limitations of the ADAT and MADI formats when working with double or quad sample rates, halving or quartering, respectively, the number of interface audio channels. MADI can work with double sample rates with or without S/MUX encoding, but requires S/MUX for quad rates, while ADAT requires S/MUX for both double and quad rates.

Signal Routing

Originally, MADI transmitted 56 channels, but had the ability to cope with varispeed sample rates of ±10 percent. However, the A16 MkII supports MADI-X, which is capable of carrying 64 channels at standard sample rates. The question, then, is: how are the A16 MkII's 16 A-D and D-A converters configured in relation to the MADI channels? Usefully, they can be assigned in blocks of 16 channels, either manually, or via pre-defined routing configurations, which are accessed by holding the Menu button down for a few seconds.

The 16 A-D and D-A converters can be assigned independently to MADI channels 1-16, 17-32, 33-48 or 49-64. All other MADI channels are passed uninterrupted, so four A16 MkII units can be used together, with the MADI signal daisy-chained between them, to encode a complete 64-channel MADI stream, if required.

Regardless of the selected MADI routing, the 16 A-D outputs are also dispatched simultaneously via the two ADAT ports. A fifth preset routing option passes the ADAT inputs to the D-A converters, and sends the A-D outputs via the ADAT outputs as well as the first 16 MADI channels.

Menus

Opening the rack case reveals a neat circuit layout, which is dominated by the numerous analogue jack connectors.Opening the rack case reveals a neat circuit layout, which is dominated by the numerous analogue jack connectors.

Pressing the Menu button briefly accesses a screen that lists seven menu options, starting with Status. This indicates which inputs (analogue, digital and clock) are receiving signals, which are clock-locked, and what the current clock source and sample rate are.

The Levels menu displays a set of output faders which can be adjusted in 0.5dB increments, individually, in pairs, in eights, or all 16 at once, between +4 and -10dBu. The Gain menu works in a similar way for the input levels, scaled from -4 to +10dBu. In practice, a 0dBu analogue input provides -20dBFS at any of the digital outputs when the input gain is set to the default -4dB reference setting. With the maximum +10dB input gain, an analogue input of 0dBu provides a digital output of -7dBFS. To put it another way, the minimum input for 0dBFS is +7dBu (+4.8dBV), and the maximum is +20dBu, depending on the input-gain setting.

The Routing menu allows the MADI and ADAT inputs to be assigned to the 16 D-A converters, and the outputs of the A-D converters to be assigned to the MADI and ADAT outputs. An S/MUX menu allows selection of 48kHz or 96kHz sample rates, while the System menu provides the unit's serial number, firmware version and feature code. The last menu option is Exit, but that can be achieved from any window by simply holding the Menu button down for a few seconds. Navigating the menus and parameters is via left and right scrolling using the Sample rate and Synchronisation buttons, in a very intuitive and familiar way.

Impressions

Ferrofish A16 Ultra MkII

The Ferrofish user manual suffers from some amusing and occasionally confusing German-English translation errors, but it provides useful explanations of the few aspects of the device that aren't entirely intuitive. That said, I found that the A16 MkII was extremely easy to use and configure: it does exactly what it claims to do. The audio quality is very good, with commendably low crosstalk and noise floors, and while, in sheer technical terms, there are measurably better converters around, none of those come anywhere close to the price of the A16 MkII.

The MADI interface format has been around for a very long time, and has been a common feature in larger live-sound installations, but it has only recently started to become more widely used in professional and project studios. Where it's necessary to move a large number of channels around, the MADI format has a lot going for it, and the Ferrofish A16 Ultra MkII offers a very cost-effective entry point, with a good level of performance, and the convenience of ADAT conversion thrown in.

Anyone needing to convert a large number of audio channels — for example, when hooking up lots of outboard or an analogue console to a computer recording system — should certainly consider the Ferrofish A16 Ultra MkII carefully, as it offers remarkable flexibility, and comes in a compact box at a pretty astonishing price.  .

Alternatives

There are no alternative MADI interfaces at anything like the cost of the A16 MkII. The RME ADI-8 QSM is an eight channel A-D/D-A and MADI interface, but costs well over twice as much as the 16-channel A16 MkII. Similarly, the Lynx Aurora 16 A-D/D-A and AES interface costs over twice as much. When it comes to ADAT-only products, there's comparable-quality competition from the likes of Focusrite, but although their Octopre MkII Dynamic also offers mic preamps and compressors, it provides only eight channels, and the company don't offer anything with this much line I/O in a single 1U rack case. At the more cost-conscious end of the market, Behringer's remarkably affordable ADA8000 offers eight channels of I/O (also with mic inputs), though the quality is reflected in the price.

Audio Precision Measurements

Ferrofish don't provide any technical specifications for the A16 Ultra MkII, so I obtained my own using an Audio Precision test set. Measuring the A-D side of the unit, I achieved a very good THD+N figure of 0.005 percent (-85dB). There was a slight emphasis towards odd harmonics with the input signal close to 0dBFS. However, as the input level was reduced, the trend was more towards a slight second-harmonic dominance.

The AES17 dynamic-range measurement (with the recommended CCIR-2K weighting filter) was 105.4dB, while the A-weighted signal-to noise measurement was 109dB. These figures represent a real-world converter performance equating to about 18 bits, and, while entirely adequate for most purposes, it does fall slightly behind the standards achieved by other multi-channel converters I've tested, which typically manage AES17 figures of 107-109dB. To put that in context, the best two-channel converters are achieving exceptional AES17 measurements of 118-120dB.

The frequency response is ruler flat, as you'd expect, falling by 0.5dB at 8Hz and reaching -3dB at about 3Hz. Crosstalk between adjacent channels with a +20dBu input signal at 10kHz measured an excellent -112dB.

Moving to D-A conversion, the THD+N figure was slightly better, at 0.001 percent (-98dB), while the AES17 measurement also improved, to 109.5dB (A-weighted signal-to-noise ratio of 113dB). The frequency response was identical to the A-D conversion.

Inside the A16 MkII, the construction is to a very high quality, with a large circuit board carrying SMD components across the base of the unit, and daughterboards to connect the upper rows of I/O sockets. The audio conversion is performed by eight AKM AK4620B chips, which provide combined A-D and D-A conversion within a single device. The supporting op-amps are Texas LM833 dual high-speed devices. System control is provided by a Toshiba TMPM330 32-bit ARM micro-controller, along with a Xylinx Spartan FPGA (field programmable gate array). The signal-routing latency is three samples, but the product latency is dominated by the converter filters — as always — and is typically between 0.6 and 0.9ms per conversion, depending on sample rate.

Remote Control

An unusual feature of the A16 MkII is the ability to control everything remotely via MIDI, either from a dedicated Windows PC program (no Mac equivalents yet, I'm afraid, but I'm told that they are being worked on...) or via MIDI embedded within a MADI stream. It's also possible to install a new start-up logo (220x176-pixel JPG or BMP image files), which will be displayed on the TFT screens during the boot-up process, and to name the A16 MkII so that it can be easily identified when remotely controlled.

Ferrofish A16 Ultra MkII £756$1390
pros
Simultaneous MADI and ADAT outputs.
The only 1U ADAT interface with 16 channels of I/O.
A remarkably cost-effective MADI interface.
Flexible MADI routing options.
Four A16 MkIIs can be daisy-chained to fill all 64 MADI channels.
Easy configuration and control via colour TFT screens.
Remote controllable via MIDI
PC configuration and control software available.
cons
Line-lump power supply.
Technical performance slightly inferior to the multi-channel competition.
summary
This is one of the most compact and cost effective ways of adding a large amount of analogue line-level I/O to an audio interface that features ADAT or MADI ports. The audio quality is very good, and while technically superior converters are available, they will cost at least double the price.
information
£756.15 including VAT.
Ferrofish + 49 (0) 228 6420713
$1390.
Ferrofish + 49 (0) 228 6420713

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