UK-based Prism Sound Ltd. was established as an R&D consultancy in 1987 by former AMS-Neve engineers Graham Boswell and Ian Dennis. In the mid-nineties, the two engineers started channeling their R&D strength into the development and marketing of the Prism Sound line of high-end, high-resolution digital audio converters which now includes the AD-2 and DA-2 converters and the venerable ADA-8XR modular hi-res PCM/DSD converter system.
In the last decade, Prism expanded its reach to include digital audio test equipment and some innovative audio logging/transcribing tools, as well as a line of well-received, high-end analog products designed by producer/engineer Leif Mases. Mases is best known for his work with top recording artists including Abba, Led Zeppelin, ELO, Jeff Beck, Scorpions and Black Sabbath, as well as his co-ownership of Marcus Studios in London. This Prism-Maselec partnership has produced the MEA-2 two-channel precision equalizer, the MLA-2 two-channel compressor and the precision MMA-4 preamp.
Studio, post production
Four-channel precision microphone preamp; 21-poistion stepped gain knobs; phantom power, phase reverse and mute switches per channel; silver-plated XLR I/O connectors; five-LED PPM metering per channel
Prism Sound USA
Prism recently reworked the exterior elements of the four-channel MMA-4 mic preamp so it would match the company’s ADA-8XR converter system, with which the preamp is often paired. The external redesign required alterations to the circuit board layout in order to accommodate changed control positions. This gave Mases the opportunity to dive in and tweak some circuit path elements, eeking out even better performance in a number of areas and shifting the available gain range upwards by 9 dB. The result is the newly dubbed MMA-4XR ($4,275).
The single rack-space MMA-4XR features a new sculpted metal front panel. Like the original, the front panel is divided into four identical preamp sections, with the power switch and power status LED at the far left. Each of the four preamp sections are comprised of a gain knob (rotary switch, actually), three mini toggle switches and a vertical LED PPM meter.
The large rotary gain control switch in each preamp section has 21 discrete positions, measured out in 3 dB steps. Whereas the original MMA-4 featured a gain range of 0 to 60 dB, the updated XR version has a minimum gain of 9 dB and a max gain of 69 dB. The three horizontally oriented toggle switches engage 48V phantom power, signal phase reverse and output cut (mute) functions. The channel meters indicate output levels from -20 dBu to +18 dBu across four green LEDs and a single red LED indicates overload.
The rear panel of the MMA-4XR is outfitted with gold-plated XLR I/O connectors for each preamp channel. A “ground lift” mini toggle switch disconnects the audio ground from the chassis ground. A binding post/banana jack allows the unit to be connected directly to an external grounding point. A standard IEC cable provides power to the unit.
The Prism MMA-4XR has many things going for it to justify paying its relatively high price per channel. One is the excellent Prism and Maselec pedigree: both companies are known for their adherence to strict sound and build-quality standards. Another is its excellent control-room ergonomics: the MMA-4XR boasts over-large gain switch knobs with dB markings per position for repeatability and bright LED meters that can be scanned quickly from across the room. I was disapointed, however, to see that the tricolor, 10-LED PPM bar-graph meters on the original MMA-4 had been replaced with a five-LED meter.
Of course the best justification to shell out hard-earned ducats for a high-end microphone preamp is its performance, and here, as with its predecessor, the MMA-4XR is worth the investment. The accuracy and transparency of the MMA-4XR is on par with the finest precision preamps I have had the pleasure of using. As opposed to preamps loaded with their own color or character (which certainly have their time and place), the MMA-4XR gives the microphones connected to it room to breathe and be heard for what they really are.
The several sessions on which I used the MMA-4XR included a Jazz quintet, string section overdubs and a variety of vocal and acoustic guitar recordings. Though the Prism preamp proved to be excellent in all uses, it really shined on critical solo instruments and vocals when used with high-end microphones – a match made in audio heaven. I should note that, in one instance, the worth of the four microphones (ELAM-251, Neumann U 67 and Neumann U 89 stereo) plus the preamp was over $14K. When combined with excellent musicians, it was like I said: audio heaven.
Shifting the gain range up 9 dB over the MMA-4 proved to be a smart move, especially when the preamp was used with low-output ribbons and/or low-output acoustic instruments (and a very low-output, breathy female vocalist). Designer Leif Mases made a number of other internal tweaks – including moving to a discrete matched-pair transistor input stage – that, says Mases, resulted in improved output headroom, a greater signal-to-noise ratio, and lower distortion specs. According to Mases, some tweaks are still being finalized, so full performance specifications for the MMA-4XR were not available to me. These stated improvements, however, are in areas in which the original MMA-4 was already a superb performer, so I have no reason to doubt his word. (The MMA-4 specs can be found on the Prism website).
With the exception of live ensembles and solo performances, most of the recordings I do are built up, adding acoustic guitar, solo instruments and vocals, etc. in separate layers. This, I suspect, is true for the majority of recordings these days.
In these cases, the best place to put limited dollars is in a few top-notch mics and a few high-end preamps that allow the mics to perform at their best. The ultra-transparent, high-performance Prism MMA-4XR should be a top contender, as it is an excellent choice for layered production studio recordings and critical solo and ensemble live recordings alike.