Regular readers will know that our Technical Editor isn't prone to excessive use of hyperbole — so when he calls a product "awesome", "stunning" and "sublime", it's probably time to sit up and take notice...
The American manufacturers Grace Design have established a reputation for very nice-sounding professional audio products, and the latest addition to the Grace family is the model reviewed here: the M201 two‑channel mic preamp. This employs exactly the same preamp design as that in Grace's renowned 801 model, but has some interesting bells and whistles, including an optional A‑D converter. It's worth noting that the original model 201 preamp was in production for 12 years, but it has been superseded by this all‑new M201 model. There are many differences between the two, including size: the new model is twice as large as its forebear. It also features a completely revised circuit design with a fully balanced signal path throughout, high-current output drivers, and a ribbon‑microphone mode, amongst other highlights.
Grace Design's philosophy has always been to build products that do the job right, rather than build them to meet a target budget, so Grace products could never be called cheap — but I think they can still be described as cost‑effective. For a start, they offer a five‑year warranty, which says something about the faith they have in the reliability of their products, but also the build quality, the component selection and the generally over‑engineered approach that makes Grace products virtually bomb‑proof. I know of Grace units in daily use after more than 10 years that still look, work and sound like new: these things are built to last, and that makes the initial investment worthwhile, in my book.
Whereas most two‑channel mic preamps are housed in half‑rack‑width cases, or a 1U rackmount chassis at most, the Grace M201 is a very substantial 2U rackmount unit. It needs the larger cabinet, too — there isn't a lot of wasted space in the box, and you'll need to have spent time with the exercise weights to move this beast about, since it weighs an astonishing 7.5kg (16.5lbs). I've owned cars made of thinner steel, and I've seen smaller torroidal transformers in serious power amplifiers. There are a lot of compact multi-channel mixers on the market, with less complicated circuit boards in them, too! All the rotary controls are high-quality switches — gold‑plated Elnas for the gain controls — the push buttons are all illuminated, and all signal and mode switching is via sealed gold‑contact relays. This is one seriously over‑engineered piece of kit with a build quality that is — and I hate using this word but can think of none more appropriate — awesome. Truly awesome.
The M201 is available in two versions: with or without a high-performance, 24-bit, 192kHz A‑D module. However, this is not offered as a user‑installed option, not least because it requires a replacement face plate; but it can be ordered pre‑installed from the factory, or retrofitted to standard M201s by the dealer.
The rear panel of the M201 is laid out clearly and simply, although it does offer some surprises. Mains power is connected via the usual IEC socket with integrated voltage selector, fuse holder and RFI filter. Each preamp channel is provided with a female XLR for the normal mic input and two male XLRs (wired in parallel) for the line-level outputs. These duplicated outputs make it easy to record the output on two machines at the same time, or send one output to a recorder and the other to a monitoring system. A further pair of male XLRs provides the line outputs of a built‑in sum-and-difference matrix, of which more in a moment.
Another optional fitment provides a pair of four‑pin female XLRs, mounted above the main channel I/Os. These connectors provide a second set of microphone inputs equipped with 130V powering, specifically for DPA's high-voltage capacitor microphones (4003, 4012 and 4016). These specialist mics boast an extraordinary maximum SPL capability — typically 10dB more than a standard mic — which is useful if you plan to record a Space Shuttle taking off from the launch‑pad, but of limited use in musical applications...
If the optional A‑D module is fitted, a further eight connectors are added to the list. Two more female XLRs accept external line inputs to the converter, while two male XLRs provide duplicated or dual‑wire AES3 outputs. There is also an RCA/phono socket and optical TOSlink connector for S/PDIF interfaces, and a pair of BNC connectors for word clock in and out. The word clock input will also work with Digidesign's LoopSync system, and all the digital outputs are active simultaneously.
The front-panel controls are laid out very spaciously, and clearly labelled. The two identically equipped mic-channel control sections dominate the left-hand side, while the sum-and-difference matrix section fills the middle. In the standard M201, the remaining front panel is blank apart from a large illuminated power switch, but the review model was fitted with the optional A‑D module, which fills this space with a meter and function display panel, accompanied by six additional push buttons to configure the converter.
The largest control knobs are the channel gain switches, and these span a range of 18 to 64dB in 24 precise 2dB steps. The adjacent rotary controls are input mode/select switches. The topmost option is the standard mic input mode (confusingly labelled '48V'), while the next position is for ribbon mics, followed by the DI input mode and finally the 130V DPA mic input (if that option is installed). The DI input socket is located below this source switch and is, unusually, balanced (although it will accept unbalanced sources quite happily). The input impedance is a very healthy 1MΩ for unbalanced sources (and 2MΩ for balanced ones), while the gain range is automatically padded down 20dB from normal, to span ‑2dB to +44dB.
The ribbon-mic mode disables phantom power, bypasses the input DC blocking capacitors, adds 10dB of gain (to bring the range up to 28‑74dB) and increases the input impedance to around 20Ω — which is widely recognised as the optimal impedance for this kind of mic. Of course, this mode can also be used to advantage with other low-output dynamic mics, as well as valve microphones powered from dedicated PSUs.
The standard mic input mode presents an input impedance of 8kΩ, which is significantly higher than the usual 1.5 to 2.4kΩ range of most mic inputs. However, there is growing acceptance that higher input impedances sound better, and a lot of high-end preamps (particularly Rupert Neve‑influenced ones) follow this practice. Despite the '48V' label on the input switch, phantom power is not turned on by default in this mode; you still have to select it manually via an illuminated push button below the gain control. Interestingly, the red LED in this switch is powered by the phantom voltage itself, which means that if the input is fed from a mic splitter that passes phantom power, the LED will illuminate even if the local phantom power hasn't been activated! This phantom switch also activates the 130V supply to the DPA inputs (if installed). The measured phantom voltage was spot-on 48V and didn't drop at all when the second channel was heavily loaded, indicating a very solid power supply.
Alongside the phantom‑power button on each channel, two other buttons provide a polarity reverse and a 20dB pad. The pad switch doesn't operate in the DI mode but will affect the normal, ribbon and high-voltage inputs. The polarity reversal affects all inputs. There is no traditional level meter on the standard unit, but a bi‑colour LED to the right of the gain switch turns green for output signals above ‑14dBu and red for signals above +16dBu (12dB below clipping). If the A‑D module is installed, a large bar-graph meter displays signal levels very clearly.
The built in sum-and-difference matrix takes the outputs from the two mic preamp channels just before their output drivers, and passes them through sum‑and‑difference amplifiers to provide matrixed outputs. This facility converts M/S inputs to left‑right stereo, or vice versa. So if you connect two microphones to the preamp configured as a Mid/Side array (Mid to channel 1, Side to channel 2), then this matrix will decode their signals to normal left and right stereo signals and output them from the dedicated output sockets (the main preamp channel outputs will still carry the individual microphone signals of course — Mid and Side). A 12‑way switch on the front panel allows the stereo width of the Matrix output to be adjusted from full mono (100 percent mid) to ultra‑wide stereo (30 percent mid and 70 percent side), with an equal Mid:Side ratio at the 12 o'clock position. It is worth remembering that if a traditional (coincident) stereo mic configuration is used, the Matrix outputs will provide encoded Mid and Side signals, which may be useful in some applications.
The A-D converter module presents a large, 20-segment, horizontal, stereo bar-graph meter, with a 60dB range, various back‑lit status displays, and six push buttons (three above and three below the display) to configure the operating mode. The input to the A‑D section is determined using the bottom left button, which cycles around three options: main preamp outputs, M/S Matrix outputs, and rear-panel line-inputs. The last option allows the A‑D converter to be used with external line-level signals, which is a useful facility — particularly because it makes it very easy to insert some external processing between the preamp and converter, such as an equaliser or compressor.
The top left button selects any of the six standard sample rates (from 44.1 up to 192kHz), plus Off. The last setting puts the A‑D module in a low‑power standby mode that stops the sample clock oscillator. The next button along is used to select the clock source — which may be internal, external word clock, or external LoopSync mode. In the case of this last option, the word clock output socket is connected directly to the clock input socket, whereas in the other modes the clock output carries the internally generated or reclocked external clock signal. External synchronisation benefits from Grace Design's proprietary dual‑stage jitter-reduction system, called 's‑Lock', and its logo is displayed when this system is active, along with the current sample-rate and clock-source settings.
The top right‑hand button configures the digital output mode (professional or consumer formats), and also offers the dual‑wire interface mode for high‑rate AES3 interfaces. The meter's peak-hold mode is determined by the bottom right-hand button, while the one next to that selects one of two configurable A‑D calibrations. The two factory options equate 0dBFS with either +22 or +18dBFS, but full instructions are provided for setting alternative alignments of +20 or +24dBu.
The Grace preamp signal path is fully balanced throughout, and there are no transformers or electrolytic capacitors in this signal path other than for DC blocking of phantom power — and even they are bypassed in the ribbon-mic mode. The fully balanced signal path provides more headroom than do single‑sided designs (clipping occurs at +28dBu, in fact), and a high‑current output stage is claimed to be able to drive extremely long cable runs (up to 1500 feet) and low-impedance capacitive loads without any signal loss. The gain stages are based on 'transimpedance' amplifiers (current amplifiers) which Grace suggest provide better dynamic performance than the more traditional voltage amplifiers employed in most preamp designs, and extensive use is made of integrated circuits, on the basis that the technology now provides far better component matching, device matching and temperature tracking than is possible with discrete circuitry.
A lot of attention has been paid to the selection of the types of passive components used — resistors and capacitors, relays and switches — and it is very clear that this attention to detail is what endows the M201 with its sonic character, or rather the absence of character. This is an extremely clean and neutral-sounding preamp, which never seems congested or strained, even at high gain settings.
The 24-bit, 192kHz-capable A‑D converter module is based on the Cirrus CS5381 — a fifth-order, multi-bit, delta‑sigma converter — and is claimed to have ultra-low latency (about 0.3ms at a 44.1kHz sample rate). This is a differential input device that integrates well with the M201's fully balanced architecture, and very careful design ensures that the analogue and digital power supplies and grounds are kept separate. Grace Design apparently selected this particular A‑D converter chip because it has a more gentle anti‑alias filter than most of the alternatives, and this was found to provide more musical‑sounding results. Distortion and noise artifacts are still below ‑110dBFS, which is more than adequate.
The crystal‑based internal clock has a very low intrinsic jitter, and external clocks are processed through a two‑stage process. The first PLL can lock to a wide sample-rate range (about ±8 percent) and rejects jitter above about 500Hz, with increasing attenuation of 12dB/octave as the jitter frequency rises. However, if the sample rate is within ±200ppm of nominal, the second stage s‑Lock PLL is able to reject incoming jitter from 0.1Hz, with more than 60dB of attenuation at 1kHz. The result is a very stable and accurate A‑D conversion, even if clocked from an external reference.
The Grace M201 is, in every way, a stunning microphone preamp. The build quality is uber‑impressive, the feature set is comprehensive, the options are well thought out, the A‑D stage sounds sublime, and the preamp itself is about as good as it gets. I've not found many microphone amplifiers that compare well with my own GML 8304 preamps, but the Grace does, easily. It is one of the cleanest sounding preamps I've ever had the pleasure of using and it does the job asked of it without any fuss at all — even at extreme gain settings. It sounds very open and airy at the top end while also being extremely well extended and full at the bottom end, and that doesn't change with gain at all. It sounds big and spacious when working with stereo pairs, with completely stable and solid imaging.
I tested it with a pair of AEA R92 ribbon mics, both in X/Y and M/S configurations, and found that it performed every bit as well as the TRP preamp that I normally use with these ribbons. There was plenty of gain in hand and masses of headroom. In one draughty recording venue, the lack of a high‑pass filter on the preamp channels concerned me at first, but there was so much headroom and so little distortion that the subsonic rumbles captured by the ribbons were handled with ease, and could be removed with precision later in the DAW. Many preamps would have suffered from intermodulation or even overload problems in similar circumstances. The built‑in matrix facility is handy, and although the width control only provides 12 settings, I found that these proved more than sufficient in practice.
The DI input performed as well as everything else, and was much liked by my guitarists — although it is exceptionally clean, and some 'in the box' processing to add character was a definite necessity. And, not surprisingly, the A‑D converter stage impressed all who heard it, too — both with the internal preamp as a source and when fed from an external line signal. The meter is easy to read and well scaled, and the output formatting caters for all scenarios. I couldn't test the high-voltage mic inputs because I don't have any suitable mics, but the fact that the option is available is yet another feather in Grace Design's cap.
While the M201 is far from a budget mic preamp — especially if fitted with the A‑D option — the sense of quality when using it, as well as the sublime sound it creates, certainly reflects the investment. If I needed a bullet‑proof two-channel preamp that had to be capable of handling any two‑channel situation and providing the highest quality results, I would choose this without any hesitation — and over several more expensive alternatives too. It really is that impressive.
In this part of the two‑channel mic preamp market there's quite a lot of choice, and all are good in their own ways. Amongst the valve‑based offerings is the Summit Audio TPA200B, the Universal Audio 2‑610, the Aphex 1100 MkII and, at a push, the Tube‑Tech MP1A. Solid‑state options include the API A2D, the Avalon AD2022, the Focusrite Red 8, GML's 8302, the Neve 1073DPD and the Great River MP‑2NV. To vary the options, you could also consider the Manley TNT, which has one valve channel and one solid state. These products all have their own sound characters and slightly different feature sets, and choice comes down to sonic preferences and requirements.