AMS Neve 1081 Classic

Mic Preamp & Equaliser

Published in SOS March 2004
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Reviews : Preamp

Photos: Mike Cameron

Analogue electronics really came of age in the '70s, and while the cost of modern electronic equipment has fallen dramatically, the performance and sonic quality are rarely much better, and are often inferior — at least in the opinion of this reviewer. No surprise then, that many state-of-the-art designs from that era are still very much sought after, and not just for nostalgia. One highly revered design dating back 30 years or so is the Neve 1081 module. Designed in 1972, it was originally conceived as a combined mic/line preamp and equaliser section for the Neve modular consoles of the time, such as the 8048.

Today, the 1081 Classic is available either as a stand-alone module for installation in a console or other custom system, or in one of two rackmount configurations. The module itself requires a single-sided 24V DC power supply, plus a separate 48V supply for phantom power. In the rackmount versions these supplies are provided by integral universal power units. The review model was the 3U version, containing two 1081 Classic modules mounted horizontally together with a power supply section. The alternative 7U rack unit contains eight 1081 modules arranged in their original vertical configuration with a larger universal mains power supply.

With big switches, heavy transformers and strong metalwork, the 3U unit is big and heavy enough, measuring 400mm from front to back and weighing 17kg. So at 46kg, the 7U box is officially a 'two-person lift' and should be considered for fixed installations or wheeled flightcases only!

Transformer-balanced Line and Mic inputs are provided on the rear panel via XLRs, with a third XLR carrying the transformer-balanced output. The second module's I/O connections are arranged below those of the first module. To the left is an IEC mains inlet with retainer clip, and a pair of terminals with a copper bar to link the chassis earth and the power supply's 0V terminal. The handbook (supplied as an Acrobat file on CD-ROM, and complete with scans of all the original circuit diagrams, board layouts and module wiring!) explicitly states that if these two terminals are disconnected, instability may result. To the right of the XLRs is a 25-pin D-Sub connector which carries unbalanced main and solo outputs from each module (both at a nominal -10dBu), plus two switch contacts from each channel — more of which later.

The construction method for this type of module in the early 1970s was to employ a motherboard carrying the bulky passive components and sockets for various plug-in daughter boards. The latter contain the discrete transistor amplifier circuits, and a lot of hand wiring links the circuitry to the front panel controls and rear panel connector. The whole thing is encased in a metal 'cassette' which originally plugged into the console chassis, but now sits in the rackmount case, secured by two front-panel thumbscrews. The modern 1081 Classic is still constructed in exactly the same way as the originals, with no less than eleven separate cards and sub-assemblies detailed in the parts list, together with a further six elements for the rack housing itself.

According to the wiring schedules, the 1081 Classic employs a PL10338C for the input amp stage as part of the PL301081C channel amplifier, with a PL10340C output circuit card. The equaliser section is built around a pair of PL10338C high-gain circuits for the equaliser's shelves and mid-sections, with a PL10306C voltage follower for the filter section. One important difference from the original design is a number of components included in the input wiring to help the 1081 meet current EMC regulations for the rejection of external electromagnetic interference. However, jumpers can be fitted to bypass these components (three-terminal capacitors and common-mode inductors), for the purists out there.

Internally, the microphone input can be configured for either 300(omega) or 1200(omega) input impedance, and the gain is switched in 5dB steps from a massive +80dB to +10dB. The line input presents a 10k(omega) bridging impedance, and the gain range spans +20dB to -15dB, also in 5dB steps. Both inputs are transformer balanced and floating (ie. earth-free). The rear panel of each module cassette carries a toggle switch to select the desired microphone input impedance, and a screwdriver trimmer calibrates the output gain. The output can provide up to +26dB into loads greater than 600(omega), and it is transformer balanced and floating. There is also an unbalanced output available on the Auxiliary connector, roughly 10dB below the level of the balanced output.

The overall distortion figure is better than 0.07 percent even at a +20dBm output level (for all signals between 50Hz and 15kHz), and the frequency response extends from 20Hz to 20kHz within ±0.5dB limits. The overall bandwidth is actually specified as spanning 7Hz to 35kHz at the -3dB points. To complete the specifications, the equivalent input noise on the microphone input is -125dBu — one figure than can be usefully bettered by more modern designs — and the output noise is better than -80dBu at all line input levels.

The control layout is identical to the original module, naturally, but while this makes perfect sense in its original vertical orientation, the order of the controls and their revised panel markings is inherently a little odd in the horizontal version. Starting from the left (top), the first control is a chunky rotary gain switch which has 24 positions. The maximum gain setting (the fully clockwise position) provides +80dB for the microphone input, and rotating the switch anticlockwise logically decreases the gain to +10dB in 5dB steps. Turning the switch to the next click stop automatically selects the line input instead of the mic input, with the gain ranging from +15dB down to -25dB. This is a fantastically intuitive and elegant way of working, and the enormous gain range for both mic and line inputs means there is nothing that this preamp can't accommodate with ease — other than DI guitar inputs, of course! Just setting up the input gain instantly brought flashbacks of my days using the last generations of Neve broadcast consoles... Ah, happy memories!

The dual-concentric controls on each of the EQ bands comprise an switched rotary outer ring for frequency selection (top) and a continuously variable inner knob (bottom) which can adjust gain over a ±18dB range. The dual-concentric controls on each of the EQ bands comprise an switched rotary outer ring for frequency selection (top) and a continuously variable inner knob (bottom) which can adjust gain over a ±18dB range. The dual-concentric controls on each of the EQ bands comprise an switched rotary outer ring for frequency selection (top) and a continuously variable inner knob (bottom) which can adjust gain over a ±18dB range. The dual-concentric controls on each of the EQ bands comprise an switched rotary outer ring for frequency selection (top) and a continuously variable inner knob (bottom) which can adjust gain over a ±18dB range. The dual-concentric controls on each of the EQ bands comprise an switched rotary outer ring for frequency selection (top) and a continuously variable inner knob (bottom) which can adjust gain over a ±18dB range.

The equaliser is divided into two sections on the front panel — a four-band equaliser and separate high and low filters. This is where the horizontal configuration and revised panel markings become a little confusing to the unwary, since the first control adjusts the high-frequency shelf section, followed by the high mid-band, low mid-band and finally the low shelf. It's a sensible order in the vertical module configuration, but reversed from the norm when used horizontally, as in this 3U rackmount version.

The two shelf sections can be configured individually with buttons to operate with a bell response instead, and the Q (bandwidth) of the two mid-sections can also be switched individually to a high-Q setting (ie. narrow bandwidth). Each of the four equaliser sections is operated with dual-concentric controls, which is both space efficient and user friendly. The outer ring is a rotary switch to determine the frequency setting, and every section includes an off (bypass) position, while the inner knob provides up to 18dB of cut or boost.

The high and low shelf controls each offer five frequency settings: 3.3, 4.7, 6.8, 10, and 15kHz for the high section; and 33, 56, 100, 180 and 330Hz for the low section. The frequency settings are arranged so that rotating the switch from the off position gradually reduces the high turnover and gradually increases the low turnover, respectively — it's a small point, but one which makes the operation very logical and practical. The two mid-range controls are configured in the same way, but with ten frequency positions. The values are: 220, 270, 330, 390, 470, 560, 680, 820, 1000 and 1200Hz for the low mid-band; and 1.5, 1.8, 2.2, 2.7, 3.3, 4.7, 5.6, 6.8 and 8.2kHz for the high mid-band.

The filters section comprises a pair of concentric rotary switches, with the high-pass filter controlled by the outer ring, and the low-pass controller by the inner knob. The two components of the control are arranged to operate in opposite directions about the central Off position. The high-pass filter is equipped with 27, 47, 82, 150, and 270Hz turnover frequencies, while the low-pass includes 18, 12, 8.2, 5.6, and 3.9kHz settings. Both filter sections have 18dB/octave slopes. Again, the operation is wonderfully intuitive and logical.

Finally, there are four square buttons, only three of which are labelled. The first is marked PH for Phase (polarity reversal) and it is engineered to reverse the connections of the output transformer. The next two buttons provide an overall equaliser bypass facility (marked EQ), and activate the Solo mode, which outputs the unbalanced solo (post-fader) monitoring signal via the auxiliary connector on the rear panel.

As well as activating the Solo output signal, a spare pair of switching contacts on the Solo button can also be accessed from the auxiliary connector (to activate a remote monitoring switch-over, for example), along with the contacts associated with the unmarked fourth button. If memory serves, the fourth button was originally used to switch line-up tone through the channel when the module was incorporated in a console.

The two rackmount units incorporate an additional panel to the right of the 1081 modules which provides a variable output level control and a phantom power switch for each channel. There is also a large mains on/off button and a pair of LEDs to indicate the presence of both the 24V and phantom supply voltages. The output level control is positioned in the signal path between the equaliser section and the output driver, just where the channel fader would be if the modules were installed in a console. The standard calibration provides unity gain with the control fully open, and at the mid position it is 10dB down — so it can be used much like a conventional fader if you want to ride the level while tracking.

One of the advantages of the modular construction is that individual channels can be easily removed for servicing without removing the whole power supply unit from your rack. In the case of the 7U model, this would mean that you could repair faulty channels while all the others remained in use. One of the advantages of the modular construction is that individual channels can be easily removed for servicing without removing the whole power supply unit from your rack. In the case of the 7U model, this would mean that you could repair faulty channels while all the others remained in use. One of the advantages of the modular construction is that individual channels can be easily removed for servicing without removing the whole power supply unit from your rack. In the case of the 7U model, this would mean that you could repair faulty channels while all the others remained in use.

They certainly don't build them like this any more! The quality of the rotary switches and the general construction of the 1081 Classic are obviously superior to most modern audio equipment — even a lot of the expensive stuff! Everything about this preamp feels right, and it really is a joy to use. I have to say that the translation to the horizontal configuration, while obviously the most practical solution for a two channel unit, is not ideal. The illogical sequence of controls and the cluttered panel legends tend to detract from an otherwise superb product, and the eight-channel model with the modules arranged in their original vertical configuration is far more successful. Having said that, once you have become familiar with the sideways configuration, it is perfectly manageable.

The Neve preamp is not the most transparent in the world. The input and output transformers seal that fate, but it is still extremely clean and neutral, and eminently musical. In fact, I would have to say the sound quality is simply sublime! Everything sounds slightly larger than life, and richer somehow. The bass is full and natural while the mid-range is clear and the highs are extended and clean. Transients are treated gently, possibly with the slightest amount of crushing to tame them a little, but they remain an integral element of the sounds. Some lesser preamps seem to overemphasise fast transients, which I always find rather distracting.

I tried the 1081 Classic on various small projects, such as recording an amateur string quartet, an organ recital, and several 'SCWAGs' (some chap with a guitar!) using a variety of microphones including AKG C414s, Microtech Gefell M930s, Neumann KM184s and TLM103s, Sennheiser MKH40s, Blue Baby Bottles and even the Brauner Valvet. Everything I tried just worked wonderfully well, with plenty of gain when distant miking and extremely adaptive EQ when required. The high and low filters are fantastic for taming out-of-band noises when close miking, and the flexibility and precision of the switched mid-range controls makes the whole process of equalisation a pure joy.

I compared the preamp to my own reference GML unit (which lacks equalisation facilities) and found the two designs to be similar in terms of the fullness of sound — the rich natural bottom end that is so characteristic of a really good preamp. The GML was slightly quieter and arguably cleaner in the upper mid-range and top end, but I found myself preferring the Neve over it on some occasions, and the GML over the Neve on others — which I took as a good sign!

I had forgotten just how responsive and user-friendly this Neve 1081 module design is, and it really does reveal the surprising lack of progress made over the last thirty years in terms of ergonomics and functionality, as well as in sonic excellence. The reason for the continuing interest in the classic 'Neve sound' is apparent from the moment you plug a mic in and turn up the gain. It's not the quietest preamp around, nor the fastest, nor the most transparent — but its particular blend of properties and characteristics sounds so right for pretty much everything that technical improvements seem unnecessary. Above all else, this is a musical tool which enables the user to extract and control the sound they want easily, quickly, and repeatedly with all of the most subtle tonalities preserved and enhanced in the way only Neve and his various disciples have been able to achieve in recent decades.

Expensive it may be in real terms — but when you see the craftsmanship in the construction and the bulky and expensive components, controls and hardware; and you listen to the full, rich, detailed and musical sound — it seems worth every penny. If money were no object, I'd recommend the eight-channel version for two reasons. Firstly because the panel makes more sense when mounted vertically, and secondly because two channels will never be enough! Definitely one for the fantasy studio equipment list.