Multichannel Mic Preamps

Jun 1, 2003 12:00 PM, BY RANDY ALBERTS

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Once considered an anomaly, multichannel mic preamps are becoming more commonplace. Why? The reasons are many, but certainly among them are a resurgence in live tracking, an increased demand for surround production, and the convenience of compact, remote location recording packages. Multichannel preamps often present an ideal solution in the console-less studio environment, where DAW mixing is done onscreen and the “console” doesn't have preamps at all! But perhaps the biggest reason for the popularity of outboard preamps stems from users looking for a different (or improved) performance over the stock preamps in their consoles.

We decided to look at the current crop of top-of-the-line multichannel preamps, priced from under $1,000 up to $28,000. Some offer amenities such as remote-control capability, allowing the preamps to be situated near the mics, while affording the ease of fingertip gain control from the control room or recording truck; some include digital outputs (either as standard or optional offerings); and others have the good old analog outs we're accustomed to using.

This article focuses solely on units with four or more channels, although it should be noted that most manufacturers of single- and dual-channel preamps — such as Apogee Digital, Avalon Design, Martech, Speck Electronics and Summit — can package their preamps into multichannel rack solutions. We've limited the scope of this guide to stand-alone products, so preamp/front ends designed to be used exclusively with computer-based systems — such as the ESI MAXIO or MOTU 896 — are not covered here.

The latest addition to AMS Neve's (www.ams-neve.com) line of inline and outboard gear is the 1081R Remote Microphone Rack, a sharp stand-alone version of the company's 1081 channel amplifier first introduced in 1972. This rig can interface directly with the company's Encore Automation Computer and 88R mixer for full control from the board, and an optional PC remote-control software package is available for staying in touch with the 1081R rack. Transformer-balanced XLR mic input to balanced line output is provided via the unit's multiway Varicon rear-panel connector. Up to 12 1081R modules fit into the 4U “intelligent” rack housing, which provides front-panel controls over gain, phantom power, pad, phase reverse and a Bypass button that routes XLR inputs direct to the outputs.

Put eight preamps, remote MIDI control, wordclock, and analog and digital outputs into two rackspaces and you've got something akin to the Aphex (www.aphex.com) Model 1788 Remote-Controlled Mic Preamp ($4,995 with control software; $5,990 with optical digital outs; and optional remote-control unit, $1,495). Employing an audio DAC approach to lower-stepped gain resolution when the optional controller is being used, the Model 1788 can also be controlled by any device sending MIDI. Up to 16 units and 128 channels can be controlled by one control line using the RS-422 output to daisy-chain devices. The company's limiter circuit on the front end can limit mic output levels by as much as -20 dB, and the 1788's digital outputs appear on two DB25 connectors (AES/EBU and TDIF) and optical Toslink for ADAT connectivity.

API (www.apiaudio.com) has long been known for its preamp and EQ modules, such as the $795 512C mic preamp/DI input card, which can be mounted in consoles, an outboard 500V 10-module rack or the popular 4-slot 500B4 “Lunchbox.” API also offers the more compact 212L preamp card ($695), which has 4- and 12-module rack housings available. The latest multichannel preamp from the company is the 3124+, a 4-channel unit that packs the same preamp used in all API consoles into a single-rackspace chassis. The 3124+ retails at $2,795 and is also available as the 3124MB+ ($3,695), which is similar but adds a 4×2 stereo mixer with aux send and stereo aux return.

ATI (Audio Toys Inc., www.audiotoys.com) reissued its 8MX2 Mic Preamp/Mixer ($2,995), which combines eight ATI high-voltage mic preamps with limiters and an 8×2 line mixer into a single rackspace. Stereo bus mixing with full monitoring capabilities and individual level, pan, limiter and phantom power controls per channel are possible. The 8MX2's cue system allows input, attenuable pre/post limiting or line-return monitoring. A multipin input to the mixer's eight line returns and a multipin output are perfect for monitoring, mixing or recording DAW and MDM tracks. A front-panel headphone jack, rear-panel monitor/cue output and fully balanced outputs are also standard equipment on each born-again 8MX2.

Unveiled at Musikmesse 2003, but not shipping until later this year, is the Behringer (www.behringer.com) UltraGain Pro-8 Digital ADA8000, a single-rackspace chassis with eight channels of AD/DA conversion, eight mic preamps, eight XLR analog outs and ADAT Lightpipe I/Os. The unit offers 24-bit 44.1/48kHz operation and includes BNC wordclock sync and both XLR mic and ¼-inch line inputs.

Besides “conventional” rackmount multichannel mic preamps — such as its MPS-400/420 models — Benchmark Media Systems (www.benchmarkmedia.com) offers a huge range of modular systems based on a variety of plug-in analog and digital modules, such as digital converters, mic preamps, distribution amps, mixers and routers. The System 1000 is a rack frame with 10 or 12 input modules, and accessory daughterboards add other functions to the modules, such as remote gain or mono/stereo mode control. The single-channel, $400 MDA-101PA is a high-performance mic preamp (with specs like 160kHz bandwidth and -130dBu EIN) that can drive up to 10 line-level outputs. It's also available as the $415 MDA-101PA-ra preamp module with remotely controlled attenuation. A MDA-102PA dual-mic preamp module with similar specs but only five line outputs/channel is $495, and a remote attenuation version of that module is $520. Benchmark also offers the MicroFrame Series, which packs up to 16 of its $230 MP-2 preamp modules into a single-rackspace frame.

CLM Dynamics (dist. in the U.S. by Wave Distributions, www.wavedistribution.com) offers the DB8000s, a three-rackspace unit with eight independent preamps and ADAT Lightpipe digital outputs. Additionally, three analog outputs from each channel enable the DB8000s to act as an active mic splitter when multiple feeds are required for broadcast, recording or live sound. Each channel also has hi-Z inputs, allowing direct injection of instruments or other line-level signals. Onboard mid/side decoding is supported, using pairs of channels. Each preamp also has a (switchable) SoftStop protection circuit with variable threshold to prevent overloads, and these are linkable in pairs to prevent image shifting in stereo or surround sound recordings.

For a song and $7,500, consider the Crane Song (www.cranesong.com) Spider, an 8-channel preamp that provides stereo analog and 8-channel and stereo digital outputs. Low-noise, high-quality discrete Class-A preamp and digital converter modules are used, the latter including a DSP process for tape emulation. Spider's preamps are similar in design to the company's 2-channel Flamingo mic preamp, providing pan control for the stereo output bus, phase and phantom power switches, a low-cut filter, and 16-segment signal meter LEDs from 6 to 66dB gain in 6dB steps. Analog dither control between 15 and 24 bits; sample-rate selection up to 96 kHz; and AES, ADAT optical or TDIF outputs are available in the Spider's digital output section, as well.

Curtis Technology's (www.curtis-technology.com) $3,495 Opre8 has eight channels, each with 10-segment LED VU meters and backlit buttons for -20dB pad, phantom power and phase reverse. The power supply is a torroidal design with distributed dual-voltage regulation to minimize crosstalk. Each channel features a separate digital circuit controlling relays within the main analog path, and each channel on the Opre8 has transformer-balanced inputs and electronically balanced outs.

Designed as an optional offering for Digidesign's (www.digidesign.com) 96/192kHz Pro Tools|HD environment — but also usable stand-alone with an external MIDI controller — the $2,495 PRE features eight discrete, matched-transistor, hybrid preamp circuits. PRE accepts nearly any input signal — mic, line and direct DI level inputs — on all eight channels. Its comprehensive remote-controllable operation from the Pro Tools software interface or Digidesign control surfaces allows PRE to be placed anywhere in the studio with full parameter accessibility.

Earthworks' (www.earthworksaudio.com) 1024 ZDT preamp ($3,500) is a low-noise unit touting a total overall distortion less than 0.0001% at its balanced, stepped differential outputs. The 1024's high-input impedance of 100k-ohms makes it ideal for use with ribbon mics. Features include clip LED indicators, a standby switch that maintains 48V phantom while muting a channel and a frequency response of 1 to 200k Hz (±0.5 dB).

The 8-channel Focusrite (www.focusrite.com) Class-A ISA 428 Pre Pack is potent yet tidy. ISA 428 Pre Pack supports four channels of 192kHz performance when its optional A/D conversion card is installed. An ideal multichannel front end for any professional DAW, the Pre Pack sports four classic Rupert Neve-designed transformer preamps with switchable impedance and direct instrument inputs. Retail is $1,995. The company also offers the $1,169 OctoPre, a single-rackspace, 8-channel preamp in its Platinum line.

The 8304 4-channel preamp ($2,900) from George Massenburg Labs (www.gmlinc.com) is a transformerless unit with all-discrete, bipolar, transistor circuit topology for increased transparency and lower noise. The single-rackspace unit is hand-built in limited production runs and requires the GML 8355 external power supply. The 8304's outputs are direct-coupled; 15 dB to 70 dB of gain is front panel-selectable in 5dB steps, and no FETs, ICs or electrolytic capacitors are used in the unit's signal path.

Grace Design's (www.gracedesign.com) Model 801 ($4,795) is a solid-state, 8-channel mic preamp that uses a Class-AB design. The front panel includes illuminated phantom, phase and -20dB pad switches and rotary 24-position gain switches with an 18- to 64dB gain range in 2dB steps. Also available is the Model 801R ($4,995), an 8-channel preamp featuring the company's proprietary LNLD (Low Noise Low Distortion) digital gain-control cell that can be digitally controlled by an optional $995 RCU (remote-control unit). Up to eight model 801Rs (64 channels) can be controlled from up to 1,000 feet away.

The MP-4 Standard ($2,899) from Great River Electronics (www.greatriverelectronics.com) is a 4-channel preamp employing a transformer-coupled, Class-A discrete design. Each channel features a -15dB pad, polarity control and +48VDC phantom switches, and a 24-position gain switch. All connections are gold-plated XLRs. Versions of the MP-4 Standard with output transformers (MP-4M; $3,499) and unbalanced pigtails are also available.

First introduced in 1987, the M-1 mic preamps from The John Hardy Company (www.imjohn.com/JohnHardy) are available in a variety of models, including 4-channel rackmount versions. The M-1 and the M-2 (which is similar to the M-1, but offers a 16-position gain switch with 1% metal-film resistors for accurate, repeatable settings) are available with one to four channels, and they feature Jensen JT-16-B input transformers, 990 discrete op amps and no capacitors from the signal path. A 4-channel M-2 with the optional VU meter and Jensen JT-11-BMQ output transformers is $3,085.

Joemeek's (www.joemeek.com) recently announced JM828 8×2 Channel microphone preamp ($999.99) is the first Joemeek unit produced under the new ownership of the PMI Audio Group. Features include an external power supply, a stereo L/R output control (in addition to separate ¼-inch line outs for each channel), a headphone jack with volume control, L/R LED meters and a solo LED for monitoring. Each unit also features an in/out expansion port to cascade up to 32 inputs to the L/R master.

Marquette Audio Labs (www.marquetteaudiolabs.com) custom builds its multichannel preamp packages, including the Telefunken V672 4-Channel ($2,600 to $3,000) and Langevin AM16 4- and 6-Channel ($3,000 to $4,000) offerings. The Telefunken V672 uses custom vintage Telefunken '60s Class-A discrete mic preamps, housed in a three-rackspace chassis with custom-engraved faceplates for pad, phase, gain and 48VDC switches; Cinemag DI transformers are optional. The Langevin AM16 “6-Pack” is a custom 6-channel version of the same package with an internal power supply. (External PSU is optional.) MAL's Telefunken V672 modules are discrete, solid-state versions of the V72. Both packages include input pad, variable gain control, phase reverse, and phantom on/off controls and XLR I/O per channel.

The HV-3D from Millennia Music (www.mil-media.com) retails at $2,995 for four channels or $3,995 for eight channels, and is built on the same design as the company's TEC Award-nominated HV-3 solid-state preamp circuitry. The HV-3D features high-resolution gain switching (36 steps at 1.5 dB per step), a passive summing option and optional powering for 130V DPA (or B&K) mics. The two-rackspace HV-3D provides an entirely balanced audio path, requires no input pads and it can reportedly drive 1,000-foot cables without detectable signal degradation.

The $2,880 OctaSonic Plus from Oram Audio (www.oram.co.uk) is an 8-channel unit that uses the same circuitry as the popular BEQ Series 24 console. It also incorporates a group delay feature that delays LF content with respect to HF content. Oram preamps handle a hot +22dBu input and boast an 18- to 73kHz bandwidth. When used together with an Oram OctaMix or OctaFade, the OctaSonic also provides a stereo output 8-channel mixer for live sound, broadcast and theater applications.

The two-rackspace PreSonus (www.presonus.com) M80 ($2,299.95) is an 8-channel mic/instrument preamp with balanced input transformers, an ultralow-impedance mix bus for assigning and panning any channel to the main stereo output connectors, and a high-gain headphone output for main bus. The M80 also allows adjustment of a signal's even harmonics for tape and tube-saturation emulation.

RME (dist. by X-Vision Audio, www.xvisionaudio.com) offers both QuadMic and OctaMic preamps, both featuring the option of battery-powered operation. More than just a dual QuadMic, RME's top-of-the-line OctaMic is an 8-channel unit with a discrete Class-A design and provides specs such as 129dB EIN and a 5 to 200k Hz (-0.5dB) bandwidth. Each channel has switches for 48VDC phantom, low-cut filter and phase reverse. Outputs are balanced TRS (switchable to -10 dBV, +4 dBu or +21 dBu) and a 25-pin D-sub connector for a direct, one-cable connection to RME's 8-channel A/D converters. It's due out this month.

The ($472/single-channel) SE-Pre 1 from Sage Electronics (www.sageelectronics.com) is a discrete Class-A transistor preamp series offered in single, dual, 4- and 8-channel configurations. The oak or Brazilian purple heartwood front panels have a classic, vintage big-knob audio look. Hand-built, wired and assembled by producer Phillip Victor Bova and family, the SE-Pre 1 has gold-plated XLR I/Os, 48VDC phantom power and high-voltage external power supply.

SPL (Sound Performance Labs, www.spl-usa.com) has two 5-channel offerings that are ideal for surround audio production. The SPL Atmos 5.1 Surround Miking System ($27,990, including mic array) sports the company's new triple-gain-stage mic preamps and unique motorized master gain controls, the latter allowing users to adjust all five channels with a single control knob. Atmos features Lundahl input transformers, pads, phase reverse, phantom power, low-cut filters, and switchable insert and tape send/returns per channel. Although the Atmos 5.1 accepts any mic input, the Brauner ASM 5 Adjustable Surround Microphone array included with the Atmos 5.1 package is a perfect companion. If you don't need the mics and frills, SPL's Area 5.1 Surround Microphone Preamp ($4,599) also has five matched gain-stage preamps with motorized master/slave gain controls.

Whether in the company's second-generation, DC-coupled SuperAnalog console or as a stand-alone preamp, Solid State Logic's (www.solid-state-logic.com) XL SuperPre is configurable, with each unit supporting up to 24 preamps via modular cards providing four inputs each. Total Recall is integrated with the XL SuperPre, and stepless remote gain control is provided via servo-driven motorized potentiometers. Each channel provides -20dB pad, +48V phantom power and impedance switching for handling line and mic inputs. Housed in a stage box design with minimal depth dimensions, the XL SuperPre can also be remote-controlled with the company's optional SuperPre Remote.

The four preamps in Sytek's (www.sytek-audio-systems.com) A-SYS MPX-4A use a Class-A, Auto-Bias Bridge configuration, hybrid-input stage preamplifier for low -134dB EIN (50-ohm) performance, and a stated 10 to 85k Hz (±0.25dB) response. The $1,678 unit also includes a useful Mute function in addition to the usual 48VDC phantom and phase switching. The company also offers the A-SYS MPX-4D, with similar performance, but in a $2,860 digitally controllable package. Under MS-DOS software or Windows 3.1 (or higher), up to 256 MPX-4Ds are supported in a single user package, as a true AES15 standard PA422 interface or simple RS232C. Future developments will support Mac and MIDI interfacing, which will be free to registered users.

TL Audio's (dist. by HHB, www.hhb.co.uk) Ivory2 5001 4-channel tube preamp ($749) provides four quality discrete tube mic preamps in a two-rackspace chassis. Separate input and output level controls, -30dB pad, 90Hz low-cut filter, phase reverse and phantom power are standard. Drive- and signal-level LEDs and DI inputs are offered, and there's an optional 4-channel 24-bit digital output upgrade. Each channel of the Ivory2 5001 uses one-half of an ECC83/12AX7A Sovtek dual-triode valve run from a 150VDC supply, and the unit's valve stage is positioned just after the initial discrete mic preamp stage.

The Precision 8 ($2,850) from True Audio Systems (www.true-systems.com) elegantly fits eight solid-state mic preamps into a single-rackspace unit, and then some. Two FET direct inputs are available, and the Precision 8's built-in M-S (Mid-Side) decoding allows for creative spatial image and stereo control without readjusting mics or settings. Five-segment level indicators with peak-hold feature and selectable peak reference allow rapid optimization of program levels between the Precision 8 and other devices. Also included are continuous gain controls, dual DB25/TRS outputs and a totally balanced dual-servo design that is DC-coupled at the output.

Vintech Audio (www.vintech-audio.com) is now shipping its 473 ($3,195; external power supply, $150), a 4-channel, Class-A discrete unit that features four Neve 1073-style mic preamps with EQ on every channel. EQ frequency choices are 3.2 kHz and 12 kHz for the highs and 60Hz and 220Hz low-shelving, and customers can special-order units at other EQ frequency settings. Each channel also offers an input-sensitivity adjustment allowing up to 70 dB of gain, an input impedance switch, a mic-line switch, an instrument input, and switches for phantom power, phase reverse and EQ on/off.

Housed in a two-rackspace chassis, the AD824 from Yamaha (www.yamaha.com/proaudio) is an 8-channel, remote-controllable mic/line amplifier. The rear panel has eight analog XLR inputs, eight TRS balanced insert-in and -out jacks (the latter also doubles as direct recording outputs), BNC wordclock I/O and a Mini-YGDAI output slot, which accepts optional cards for 44.1/48kHz, 16/20/24-bit multichannel digital outputs in ADAT Lightpipe, AES/EBU or Tascam TDIF formats. Remote-gain trim control of one or more AD824s is possible from a Yamaha DME32, PC or other device connected to the unit's COM PC/RS-422 ports.


Randy Alberts is a San Francisco Bay Area-based technical writer, musician and composer.






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