Many mic preamps are marketed on the strength of the sound they claim to impart to your recordings, but the Event EMP1 is designed to sit as unobtrusively in your signal path as possible, amplifying quietly to itself. Hugh Robjohns investigates...
Mic preamps frequently constitute the weakest links in the signal path in recording mixers (especially budget and mid‑price models), the reason for this being that the average mixer has to contain so many of them. Consequently, it is common practice in the recording industry to use a very high‑quality stand‑alone mic preamp for the most critical jobs. Indeed, this is can be a very cost‑effective way to significantly improve the performance of an otherwise so‑so mixer.
Mention stand‑alone mic preamps and most people would probably think in terms of exotic units like classic Neve modules, or state‑of‑the‑art machines from Focusrite, GML, and Amek. At the more affordable end of the market are the preamps from manufacturers like Digitech, Drawmer, Joemeek and ART. Excellent though many of these units are, they are often beyond the budget of many home studios, and this is where Event Electronics' new EMP1, priced at a remarkably modest £265, comes in.
The Box
The EMP1 is housed in a distinctively arched, brushed metal case. There is no provision for rackmounting and although the sides feature what appear to be heat‑sink fins, these are merely a design feature. The lid is secured with anti‑tamper fastenings (making it hard to peek inside) and the unit measures roughly 160 x 155 x 30mm (wdh), rising to 42mm high in the middle.
The front and rear panels are formed from the folded ends of the base and carry all the controls and connectors. The rear panel has an (inverted) IEC mains socket and associated On/Off rocker switch, and although the power supply is fused, this is not accessible externally. There are also three Switchcraft audio connectors: an XLR microphone input, and two line‑level outputs; one on an XLR and the other on a quarter‑inch TRS jack socket. All connectors are electronically balanced, but the output jack socket will also accept a tip‑sleeve jack for use in an unbalanced system.
The front panel carries a mere four controls and five LEDs. Push buttons provide for phantom power, a high‑pass filter, and polarity inversion (each with a green status LED), and a rotary knob adjusts gain in a continuous sweep from +20 to +60dB. The two remaining LEDs indicate when the unit is powered (green) and the presence of signal and overloads. This last LED shows green for signals above ‑2.5dBu and red when they exceed the clipping point at +23dBu.
Technology
The circuitry employed in the EMP1 is entirely solid‑state and has been designed to maximise audio quality whilst keeping costs in check. The unit has a frequency response which remains flat to within 0.1dB between 20Hz and 20kHz and is only 3dB down at 122kHz (this falls to 90kHz with phantom power switched on, presumably because of the need for DC blocking capacitors on the input). Apparently, the response of the amplifier stages, excluding the input and output filtering, extends to around 1MHz which allows a very fast slew rate of around 15V/µS to help preserve delicate transient information. However, the input and output filtering has apparently been designed to reduce the likelihood of RF and electro‑magnetic interference.
Another interesting design feature is that a DC servo is employed to eliminate any DC offset at the output instead of series blocking capacitors (which are often cited as introducing distortion in lesser designs). The output stage uses a discrete high‑current topology capable of driving long cables and further discrete circuitry is used in the power supply regulation stages.
The high‑pass filter is unusually gentle at only 6dB/octave and starts rolling off at an extraordinarily low 24Hz (‑3dB point). In my experience, if a microphone is creating problematic rumbles the high‑pass filter needs to be rather more vigorous than this design, although it will be of some use where modest levels of sub‑bass noise exist.
In Use
The Event unit looks very rugged and reliable and weighs enough to confirm that impression when handled. Connecting the EMP1 is a simple process and setting up the preamp is just as easy, involving little more than selecting phantom power and advancing the gain control until sufficient output level is achieved.
The circuitry appears to have a very wide dynamic range and as long as the 'signal' LED is illuminated when the input signal is present, the signal‑to‑noise of the system seemed very good. For some reason best known to Event, they have chosen to quote the Equivalent Input Noise in terms of dBV rather than dBu, (and without reference to the source impedance). When converted, the impressive‑sounding ‑129dBV comes out as a slightly less impressive ‑126.8dBu and so it would be fair to say that the EMP1 is not the ultimate in low‑noise mic preamps, although it is undoubtedly significantly better than most budget mixer mic stages.
If the microphone input signal is excessively loud, or the gain is advanced too far, the amplifier will inevitably clip and although plainly audible (and accompanied by the front‑panel LED glowing red), it was not as unpleasant an experience as would be expected from many comparable units. I don't think anyone would want to overdrive the EMP1 in the way you might with a valve preamp, but its clipping characteristics were relatively benign for a solid‑state device. Although there is no separate input attenuator, the EMP1 proved quite capable of handling very loud sources such as drums and close‑miked brass without difficulty, provided the gain control was adjusted sensibly.
The only major disappointment for me was that when the polarity inversion was selected or deselected, an enormous tweeter‑destroying splat was created. You might expect that kind of thing when switching phantom power on or off, but not the phase reverse!
The Audition
Event's new mic preamp is certainly no slouch ? overall, its performance was very good ? and although not quite in the same league as the really big names in this field, it is not far off. For the price, it is a very impressive unit and certainly worthy of a personal audition.
On careful listening tests, the EMP1 seemed able to preserve the detail and clarity of microphones costing many times more than the EMP1 itself. For example, it coped admirably with the intricate and complex harmonics of 12‑string guitar (a pretty severe test for mic preamps) and this is undoubtedly due in part to the wide bandwidth circuitry employed. The EMP1 has ample headroom and although the noise performance is perhaps not quite as startling as the marketing hype suggests, it is perfectly respectable for the vast majority of applications.
Overall then, this is a decent mic preamp which offers an impressive quality/price balance and which would be a worthwhile upgrade for anyone who is squandering the quality of a decent mic by using run‑of‑the‑mill mixer mic amps.
(Not) Down To Earth
The EMP1's metal case is connected to the earth pin of the mains socket ? as it should be of course ? but so too are the earth pins of the microphone input and both outputs. Unfortunately, there is no provision to 'lift' the earths of the output connectors and so earth loops and hum are a distinct possibility. Although I did not experience such problems while I was using the EMP1, I remain concerned because should earth loops become a problem I fear some users might resort to disconnecting the earth pin in the mains plug ? with potentially lethal results. A simple earth lift facility on the output sockets would surely have been a sensible and practical addition with significant safety benefits.
Pros
- Superb quality/price balance.
- Easy to use.
- Ample headroom and relatively benign clipping characteristics.
- Low noise and extended frequency response.
Cons
- No earth lift facility on outputs.
- Polarity reversal switch creates loud splats.
- High‑pass filter rather gentle.
- No provision for rackmounting.
Summary
This is a no‑fills mic preamp which redefines the quality/price balance. The EMP1's carefully designed transformerless circuitry retains virtually all the detail and clarity captured by high‑quality mics.