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Prism Sound Titan

USB Audio Interface
Published September 2014
By Hugh Robjohns

Prism Sound's latest interface looks set to dwarf even their legendary Orpheus...

Ask any gathering of recording engineers to list the best converters and interfaces, and it's a dead‑cert that Prism Sound's Orpheus will appear amongst the front runners, and rightly so. I reviewed the Orpheus back in September 2008 and it set a very high benchmark at that time. The pro audio world has moved on in the intervening six years, but there have been few contenders to challenge the quality or capability of the Orpheus... until now. Perhaps it's not surprising, but the new challenger is from exactly the same stock, albeit a younger, attention‑seeking sibling that does just a little bit better in almost everything!

Apart from a fancy new gloss‑white paint job, the Titan looks exactly the same as the Orpheus to the casual observer. It's still a 1U rackmounting unit with detachable rack‑ears, sporting a large rotary encoder and two headphone volume controls on the front panel, along with the distinctive 'rainbow' meters and a handful of status indicator lights. However, there are several significant changes hidden inside and on the rear panel, all of which came about as a result of customer feedback. It's also worth noting that most of these enhancements and improvements were introduced first in the little Lyra 2 USB interface (reviewed in November 2012).

Overview

Like the original Orpheus, the Titan features eight analogue input channels (four with mic preamps) and up to 10 digital inputs, plus eight analogue, 10 digital and dual-stereo headphone outputs. So that makes 18 simultaneous inputs to the host computer with 20 outputs, and a well‑specified remote‑controlled digital mixer within the Titan allows latency‑free monitoring at any output pair derived from any combination of inputs.

The first two mic preamps also have front‑panel instrument input sockets and the option to switch in digital RIAA filters to handle the stereo output from a turntable pickup, if desired. The four mic inputs have switchable phantom power, of course, while every analogue input has a selectable 80Hz high‑pass filter and polarity reverse. The line inputs can be switched individually between +4dBu and ‑10dBV nominal operating levels, too, as can all of the analogue line outputs. The two front‑panel headphone outputs have independent amplifiers and volume controls, but they always share the same signal source.

The rear-panel connectivity for the audio I/O listed above is exactly the same as the Orpheus, with combi‑XLRs for the first four channels, followed by four TRS sockets for the line‑only inputs and eight TRS sockets for the line outputs. The analogue inputs and output are all electronically balanced, with a 'bootstrapping' topology for the outputs which ensures the correct level is maintained when feeding unbalanced destinations. Prism Sound's 'Overkiller' protective limiter, first seen on the company's ADA8XR, is also available on all analogue inputs to catch fast transients if the input gains have been set with insufficient headroom! When activated, the 'overkiller' function applies a little gentle limiting as signals approach 2dB below clipping, handling peak transients in an attractive tape‑like way.

The 10 digital I/O channels comprise two RCA‑phono sockets compatible with S/PDIF and AES3 signals (up to 192kHz) in and out, plus TOSLink optical sockets which can be configured for S/PDIF or ADAT in and out, with automatic SMUX/2 coding for four channels of ADAT at double sample rates. A pair of XLR-to-RCA‑phono adapter cables is even included in the box to connect AES3 equipment, and the software control panel allows S/PDIF or AES output formats to be selected, configuring the operating voltage and Channel Status format appropriately.

Connectivity Changes

The IEC mains inlet accepts supplies between 90 and 250 V AC, but it is the panel section between the mains inlet and analogue outputs which reveals the Titan's main differences from the Orpheus. A pair of BNC sockets is still present for wordclock in and out, but the MIDI in/out sockets and Firewire ports have gone. In their place are a USB 2 B socket, a 10Mbps Ethernet port, and a blank panel hiding Prism's brand-new MDIO expansion slot system. The Ethernet port is 'reserved for future use', which probably means AVB capability, as is also promised for the Lyra 2. The MDIO slot (miniature digital I/O) is intended to accommodate a variety of digital interface and expansion options, with the first two planned and announced modules comprising an eight‑channel AES3 interface and a Pro Tools HDX direct connection port. However, neither is available at the time of writing, although I'm told the HDX card exists physically and work is nearing completion on the firmware and software. Apparently a Thunderbolt interface is under consideration too...

There's not a lot of space wasted on the Titan's rear panel, and they've even managed to find room for an IEC power supply.With the increasing rarity of Firewire since Apple decided to ditch it in favour of Thunderbolt, Prism's switch to the universally supported USB 2 format makes a great deal of sense, not least because it offers genuinely long‑term support and stability thanks to the inherently backwards‑compatible nature of USB 3. Technology‑wise, the new USB 2 interface relies upon the ARM processor core that was first introduced (and is now well proven) in the compact two‑channel Lyra interfaces.

Internal Upgrades

Besides these physical connection changes, some of the internal circuitry has been updated too, starting with the superb mic preamps. Customer feedback revealed that they were a little on the sensitive side and easy to overload with hot mics in front of loud sources. As a result the circuitry was modified for the Lyra to include a ‑20dB pad (configured from the software control panel), and this same feature has been carried over into the Titan. With the pad switched out the input sensitivity to achieve 0dBFS ranges from ‑56 to ‑1 dBu (in 1dB increments), but with the pad engaged signals up to +19dBu can be accommodated.

Plugging into the centre TRS part of the first four channels' combi‑XLRs automatically switches the channel to line input mode, but the instrument inputs auto‑switch only when they detect an audio signal (not an inserted plug). This means you can leave a cable connected to the front-panel socket if desired without disabling the rear-panel mic input, provided the instrument source is muted! The instrument sensitivity is adjustable from ‑38 to +17 dBu for a 0dBFS output.

Other small but important improvements include a 4.5dB power hike for the two headphone amplifiers, and the main volume encoder knob's push switch now mutes/unmutes whatever outputs it is assigned to control. The built‑in DSP monitor mixer has been enhanced to allow the ADAT channels to contribute to any of the monitoring outputs. All of the original mixer features have been retained, each output channel being equipped with a fader (stereo‑linking is available between adjacent channel pairs), pan/balance, mute and solo buttons, as well as a 'rainbow' meter. The S/PDIF (and AES3) digital outputs can be word‑length reduced using triangular dither or four different Prism SNS noise‑shaping algorithms, and a sample‑rate converter can be switched into the S/PDIF (and AES3) input or output if required. This enables a 44.1kHz output to be produced when the system is running at 96kHz, for example. Although operating in the digital domain, the monitoring latency between analogue inputs and outputs is impressively low at just under 0.5ms for base sample rates, and significantly lower at double and quad rates.

USB Matters

The USB 2 interface is fully Class 2 compliant, meaning it is supported natively in Mac OS X (10.4.11 and later Intel machines), iOS, Linux and Android platforms. As Microsoft are still stuck in the 20th Century an ASIO driver is provided for Windows Vista, 7 and 8, with 32‑ and 64‑bit variants. Multiple Titans can be used together in Mac systems via the aggregate arrangement, but sadly that option is not yet available for Windows users. However, the Prism Sound boffins are working on an updated ASIO driver that will provide multiple box support. Apparently they thought they'd cracked it in January this year and put out a press release to that effect, but their excitement turned out to be a little premature! (See /news?NewsID=16918.)

The current Windows ASIO driver version (v1.05) provides an improved round-trip latency of about 6ms for PCs that are fast enough, and Prism have tested this extensively, recording continuously for 24‑hours with zero bit errors. I found a buffer size of 176 samples worked reliably on my system at 44.1kHz sample rates.

The Titan software showing the output mixer setup for line out 7/8.The Titan software control panel is incorporated with the ASIO driver install for Windows platforms, but is installed separately for Macs. The control panel configures the Titan ASIO interface and sets up all input-conditioning and mixer functions, as well as assigning which output levels are controlled by the physical encoder on the Titan front panel. However, once configured, the Titan will operate in a stand‑alone mode because it retains its settings when powered down. When re‑powered everything works exactly as before — analogue and digital sources will appear at the analogue and digital outputs — but you can't adjust any levels (other than the headphone levels), change the input-conditioning parameters, or adjust the clocking parameters, for example.

Technical Performance

Prism's converters are calibrated through the firmware — there are no trimmers on the circuit boards to become unreliable or drift — and a great deal of attention was given to eradicating power supply and grounding hums. The results are impressive: with maximum gain dialled into the mic amp (and the input terminated with 200 Ohms) mains-hum components were all below ‑90dBFS. At minimum gain (and for line inputs) they fell to below ‑145dBFS, which is a very impressive result indeed!

Using an Audio Precision test system I obtained AES17 dynamic range figures for the A‑D and D‑A sections and was a little surprised to find the A‑D scored 118dBA, while the D‑A was 116dBA. These correlate with Prism's published specifications and are both perfectly respectable figures, but they are not as good as some products I've measured recently. For example, the A‑D score matches the converters in my Crookwood mastering console, is a tad better than Focusrite's Rednet, UAD's Apollo and Audient's ASP880, but it's not as good as the Apogee Symphony (120dBA), Lynx Hilo (121.3dBA), or the current record holder, Lavry's AD11 at 123dBA. Similarly, the D‑A converter's AES17 performance matches the Antelope Orion 32 and Benchmark DAC 1, but it is well below the likes of the Grace Design M905 (119.7dBA), Lynx Hilo (120.5dBA) and Benchmark DAC2 HGC (125dBA), let alone the current record holder, Apogee's Symphony at 129dBA.

Now I'm the first to admit that the AES17 dynamic-range measurement indicates only one small aspect of a converter's performance, and it's the whole that defines the full performance envelope, so don't let those figures alone influence your impression too much. In other areas the Titan's technical performance was easily amongst the best I've ever measured. For example, crosstalk between adjacent channels was an outstanding ‑112dB at 10kHz, and THD+N measured just 0.0005 percent for the D‑A and even better at 0.0003 percent for the A‑D. The other aspect to bear in mind is that the limiting factor for interface performance is the clocking, and that's something in which Prism Sound is unsurpassed.

Impressions

Installing the latest ASIO driver and control panel was painless, but it appeared initially to be buggy: the control panel flickered and kept taking priority in Windows. On checking the Titan's firmware I discovered it was a very early version and not compatible with the latest control-panel software, but a quick firmware flash cured the problem completely, delivering rock-solid performance thereafter. The control-panel app is very straightforward with everything, being logical enough to find and use, and there is a button to access the online manual if you need help. The input and output windows expand and contract sensibly as the ADAT ports are enabled or disabled, too.

As I said in my Orpheus review, from the first moment audio passed through the box its class and quality really shone through, and I stand by that statement for the Titan too. Stereo imaging has depth and clarity, the microphone preamps are very clean and quiet with a larger‑than‑life character at the bottom end, and the Titan sounds totally transparent but not bland. I'd be delighted to use it within a mastering environment, let alone in tracking and mixing situations. The Orpheus set the class standard, but the new Titan has raised the bar even higher from a usability and convenience perspective. Do I really have to send this one back?  

Alternatives

If you need more than four mic inputs, or want MIDI access, Prism Sound offers the Atlas, which is basically a Titan that's eaten all the pies! This 2U box incorporates eight mic preamps and the additional rear-panel space has allowed the reinstatement of the MIDI in/out sockets, but in all other respects it is identical to the Titan.

Published September 2014

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