Prism Sound Dream ADA-128

Building on Prism's high‑end converter range, the ADA‑128 caters for those working with high channel counts and multiple signal types.

For over 35 years, Prism Sound have been well known for offering some of the highest‑quality analogue‑to‑digital converters. One of their best‑known and longest‑serving products is the modular ADA‑8 (the current version is the ADA‑8XR), a configurable A‑D/D‑A converter system providing either eight channels in/out, or 16 channels in a single direction. It also serves as a system master clock, can handle different sample rates on different signal paths, and can be fitted with a variety of digital interface modules to suit different installations. Racks of ADA‑8XRs are a common sight in recording studios, mastering rooms and post‑production theatres throughout the world's high‑end facilities — I think it fair to say that this is a genuine 'industry standard'.

Popular though the ADA‑8XR remains, the advent of technologies with high channel counts, for example Dolby Atmos and Dante interfacing, have increased industry demand for converter systems with many more channels in a single, integrated package. Prism Sound have responded to this with the new Dream ADA‑128, reviewed here. Building on the concepts established in the ADA‑8XR, the new Dream's model numbering highlights its most significant feature: the ability to handle up to 128 analogue audio channels in and out simultaneously — thus accommodating the maximum channel count of the Dolby Atmos specification — and more (up to 384x384, depending on the cards) with digital audio. And all of this is contained within an elegant 2U rackmount box, and controlled either using a front‑panel touchscreen or remotely, through a standard browser over a network connection.

Overview

The Dream ADA‑128 is an all‑new design, but clearly builds on the company's considerable experience in advanced converter and digital routing technology. The very modest‑looking 2U chassis belies the enormous power within, as the unit can be configured and customised in myriad ways simply by installing different modules in its 20 rear‑panel slots. These modules come in two formats, called I/O and Host, and the ADA‑128 can accommodate up to 16 I/Os and four Hosts.

At the time of writing, there are currently three different options for the I/O modules, all designed to deliver or accept analogue or digital signals to/from external peripheral devices: an eight‑channel line‑level A‑D converter, an eight‑channel line‑level D‑A converter, and an 8x8 AES3 interface. But scheduled for imminent release is another eight‑channel A‑D module with both mic and line input capability. Every I/O module contains its own onboard DSP, which takes care of things like clocking, signal routing, programmable bi‑quad filters (eg. for 80Hz HPFs), M‑S processing and Verifile generation/checking. But Prism have hinted that there's additional processing capacity, which may be employed in future firmware updates to extend the system's overall functionality.

Host slots are intended to pipe multi‑channel signals from multiple I/O modules in and out of a DAW or other audio recording/playback system. Currently, there are two Host module options (both catering for 64 channels in and out) to interface with ProTools HDX or Dante. A 64x64‑channel MADI module is also expected soon, and alternative host formats will be developed as customer needs evolve, such as USB, Thunderbolt, Ravenna, AES67, and so on.

Central to the Dream ADA‑128's functionality is a system called ADRA (Advanced Digital Routing Architecture). This is controlled from a dedicated master routing DSP module installed in every ADA‑128, and this creates and manages all of the internal signal paths between the I/O and Host modules according to the user's requirements. Additionally, this routing system also supports direct routing between different I/O modules and for Host‑to‑Host bridging, if required. All routing setups are saved and loaded as 'configurations', with a number of typical configurations pre‑installed to assist in the initial setup. Obviously, personalised configurations can be created and stored by the user, too.

I don't know of any other single digital audio processor or router with such a versatile four‑clock capability.

One of the most impressive aspects of the Dream ADA‑128 is called QClock, and this provides four totally separate word‑clock 'domains', each capable of running independently at different sample rates from either internal or external clock sources (traditionally, converters, routers and everything connected to them had to be synchronised under the control of a single master clock, to ensure everything ran at the same sample rate and delivered samples at precisely the right time). Each I/O and Host module within the ADA‑128 can be assigned to and controlled by any one of these four clock domains, as required, affording exceptional flexibility and allowing a single ADA‑128 to route and process signals from, for example, four separate project studios or production systems, each running independently on their own local clock masters. Alternatively, subsets of digital equipment within, say, a complex transfer suite, can be interconnected in myriad ways while running under separate clocking regimes. Prism's ADA‑8XR could divide the signal paths to work with two separate clock systems, but I don't know of any other single digital audio processor or router with such a versatile four‑clock capability.

Another innovative feature of the Dream ADA‑128 — one that received little fanfare when introduced by Prism Sound a few years ago in their second‑generation DAW interfaces — is Verifile metadata [see box, later]. In essence, this ingenious technology modulates inaudibly the dither applied in each A‑D converter module, adding unique metadata to every audio sample. This metadata can subsequently be detected and analysed, either in a recorded audio file or in a real‑time digital audio stream, to confirm the absolute integrity of the recorded or transmitted signal, logging any data glitches that may have occurred during its passage from the A‑D. This feature is highly valued in professional archiving and mastering applications, but knowing that the stored file is uncorrupted also provides considerable peace of mind when recording in unrepeatable situations.

In practical terms, Verifile encoding is fully automatic and completely transparent to the user. All that's necessary to check a file is to open it using the Verifile Checker app, which generates a log file listing any audio data corruptions. To check an audio stream, all of the Dream ADA‑128's digital outputs can analyse the metadata in real time, indicating any detected errors on the unit's front panel or within the remote‑control app's metering display....