Sweet and Warm

Few pieces of gear get serious audio hounds salivating like a nice, juicy tube microphone preamp. Whether it's a dusty relic recently rescued from an

Few pieces of gear get serious audio hounds salivating like a nice, juicy tube microphone preamp. Whether it's a dusty relic recently rescued from an ancient studio, or the latest state-of-the-art innovation, when the tubes light up, the listeners do too.

Our survey of manufacturers confirmed that there's no shortage of tube preamps available, many offering additional processing, such as high-impedance DI inputs, EQ, compression and de-essing. These units may be used as alternatives to console preamps or as the front end of digital recording systems, and several sport AES/EBU or S/PDIF outs for connecting directly to the digital domain.

Many companies offer more than one model of tube mic pre (including multichannel versions of the mono or stereo units), but for the purposes of this article, we limited the scope to one product per manufacturer, so the two dozen on our list are basically the cream of the current crop.


Unveiled at Winter NAMM 2002, the MP-2 is a two-rackspace chassis housing two tube mic preamps. The unit uses a zero feedback design with transformer-balanced I/O, using Jensen transformers on the inputs and custom-wound transformers on the outs. The straightforward front panel includes independent controls for polarity, phantom power and level, as well as two large, backlit, true VU meters. Also standard is 10k/600-ohm output impedance switching. Retail: $1,499.


Best known for its handcrafted studio compressors and DI boxes, Anthony DeMaria Labs will release its first microphone preamp later this year. The stereo MTS-2 will use three tubes per channel — two 6922s and a 12AT7a — and features stepped gain, a level pot, and mic/line and phase- reversal switches. Its ¼-inch instrument and XLR (with 48V phantom power) inputs and outputs will be transformer-balanced, and early indications are that it will have a frequency response of 20 to 50k Hz, 0.15% THD and +4dBm output. Retail: TBA.

APHEX 1100

The midnight-blue, dual-channel Aphex 1100 features an all-discrete, Class-A PNP first stage, Reflected Plate Amplifier (RPA) tube circuitry in the second and analog output stages, and 24-bit/96kHz AES/EBU digital outputs. Aphex's proprietary MicLim protection circuit prevents clipping prior to preamplification, and internally optimized A/D converters eliminate overloading of the digital outputs. Both channels have 12 stages of preamp gain in 4dB steps (21 to 65 dB), 11 steps of low-frequency cut (30 to 195 Hz), a Mute function (>60 dB), a 20dB pad and a three-turn output matching pot. The 1100 syncs to an internal crystal clock (44.1, 48 or 96kHz sample rates), or to word- or AES/EBU clock. There are balanced XLR and ¼-inch analog outputs, and AES/EBU digital outs. Retail: $2,495.


The single-rackspace DI/O Preamp System (DPS) from Applied Research & Technology delivers twin discrete preamps coupled with ART's Variable Valve Voicing (V3) 12AX7a gain stage, which includes the ART OPL Output Protection Limiter. The unit accepts mic and instrument sources — there are programmable presets for voice, guitar, bass and acoustic instruments — and insert loops on each channel allow additional patching flexibility. Monitoring is via two analog meters. Analog and digital outputs are provided, with separate gain controls for each for simultaneous use. Digital outputs include S/PDIF, Toslink and ADAT. The A/D converter is adjustable from 44.1 to 96 kHz, and syncs to ADAT or external wordclock (32 to 100 kHz). Retail: $319.


This high-voltage, discrete, Class-A device consists of a preamp, a passive optical compressor/limiter (with stereo link), and a 4-band EQ with passive high/low bands and overlapping dual-mid bands with variable frequencies and adjustable Q. The equalizer can be switched pre/post-compressor, or inserted into the sidechain for de-essing and other spectral processing. The preamp section has transformer-balanced mic, unbalanced instrument (¼-inch) and XLR line inputs. There's also a passive variable highpass filter (-6 dB per octave, 30 to 140 Hz) and a High Gain switch that boosts the overall gain of the preamp. A large VU meter monitors output level and compressor gain reduction. Retail: $2,295.


The dual-channel Tube Ultragain T1953 features twin 12AX7 tubes and Behringer's proprietary Ultra-Tube circuitry, allowing users to vary the amount of tube “warmth” added to the signal. There are discrete line and mic (with 48V phantom power) input stages, and independent line drivers for converting 10dBV signals to +4 dBu. Tunable and switchable 12dB highpass filters, phase-reverse switches and true RMS level meters are also provided, and a “soft mute” feature eliminates nasty noises when the unit is being powered up or down. XLR and ¼-inch TRS servo-balanced inputs/outputs are standard. Retail: $399.


The RP533 combines a tube mic pre, an optical compressor/limiter and spectral enhancer in a two-rackspace unit. There are transformer-balanced mic (XLR, with 48V phantom power) and unbalanced ¼-inch inputs, and electronically balanced (XLR) and unbalanced (¼-inch) outputs. Unbalanced ¼-inch compressor sidechain I/O is also included. The compressor uses new dynamic gain-reduction circuitry and has controls for ratio, attack, release and output level. There's also a large VU meter (switchable between input level, output level or compressor gain reduction) and switches for polarity reverse and 30dB pad. Frequency response is 20 to 40k Hz. Retail: $700.


The bright-red VT-2 dual-channel tube preamp is wired point-to-point and assembled on a rugged aluminum chassis. The active circuits in each channel utilize four Class-A triode amplifier sections (in two tubes), and 1% resistors and polypropylene caps are used throughout. Monitoring is via amplifier-isolated “true” VU meters, and switchable phase reversal and -20dB pads and 48V phantom power are available on both channels. Gold XLR I/O connectors lead to/from custom-designed Jensen transformers, and all audio switching is through gold-contact relays. Line-level processing can be accomplished using an optional LP-1 Line Pad accessory. Retail: $3,500.

DBX 576

The two-rackspace 576 Vacuum Tube Preamp/Compressor is a combo mic/instrument preamp, compressor/limiter and EQ unit. The preamp uses 12AU7 tubes and features a Drive control, a 20dB pad, a highpass filter and a phase-invert switch. The 3-band EQ has sweepable mids and adjustable Q. The compressor offers OverEasy, Auto and Contour functions, as well as a sidechain and PeakPlus limiting. Analog VU meters monitor tube drive, insert level, gain reduction or output level. There are electronically balanced (XLR) mic and line inputs, an unbalanced (¼-inch) line input, balanced (XLR) and unbalanced (¼-inch) outputs, and (¼-inch TRS) insert I/O on the preamp. The optional Type IV Conversion System adds AES/EBU and coaxial S/PDIF digital outputs at 16/20/24-bit resolution. Retail: $1,299.95.


The HXM-1 Mic Preamp is a single-rackspace, dual-channel hybrid unit combining a 12AX7-driven tube input stage and solid-state output stage in a cobalt-blue aluminum and steel casing. High-quality components such as film capacitors and metal film resistors are used throughout, and a fully regulated internal power supply delivers 225 volts to the tubes and -18 volts to the solid-state components, resulting in expanded headroom. Jensen transformer-balanced mic and ¼-inch instrument inputs, and both XLR and ¼-inch TRS active-balanced outputs are provided. Retail: $1,399.


The Drawmer 1969 Mercenary Edition results from a transatlantic collaboration between Drawmer and Mercenary Audio. Roughly based on the Drawmer 1960, the 1969 is a hybrid tube/solid-state design featuring dual mic/line preamps and soft-knee compressors. The mic pre's produce up to 66 dB of gain in 6dB steps, and feature 48V phantom power, filters and phase reverse. The instrument (DI) pre's include 2-band EQ, phase reverse and brightness boost, and can create guitar overdrive effects. The J-FET cell-based compressor has adjustable attack/release and threshold controls. True stereo linkage (with a “Big” position), inserts and sidechain access are provided. Illuminated VU meters indicate output level or gain reduction. Retail: $2,995.


The EAR 824M Microphone Amplifier is a stereo device that functions as a microphone preamp and as a level booster/line driver. Gain is switchable over a range of 16 to 60 dB in 4dB steps (though 2dB steps can be ordered as an option). The 824M provides 48V phantom power, but other options such as 130V power for B&K mics and the EAR matching transformer for ribbon mics are also available. EAR proprietary hand-wound input and output transformers are utilized, and output is balanced using wide-band 650Ω transformers capable of driving long lengths of cable. Onboard M/S decoding is also available as an option. Retail: $5,345.


The sporty-looking black and silver VIPRE (Variable Impedance Microphone Preamplifier) is a single-channel, balanced, Class-A device that incorporates eight Groove Tubes into a fully differential signal path, resulting in extremely wide bandwidth (7 Hz to 100+ kHz). Its variable impedance mic input loads mics at 300, 600, 1,200 or 2,400 ohms using a custom transformer, and there are transformerless balanced bridged line and instrument inputs. A Variable Rise Time control provides a choice of five amplification types — from Smooth-and-Classic (slow) to Bright-and-Modern (fast) — and custom-built ceramic deck attenuators regulate 75 dB of gain in 5 and 1dB stepped increments. A large VU meter can be switched between five viewing ranges. Retail: $3,000.


The two-rackspace VC2 Tube Channel is a combination mono mic preamp, photo-optical tube compressor and enhancer/exciter, with a tube gain makeup amp. A highpass filter (25 Hz, 12 dB per octave) and phase-reverse switch are also included. There's a transformer-balanced, floating mic input (XLR, with switchable 48V phantom power) with two amplification stages and a switchable 20dB pad; a floating, balanced line input (XLR); an unbalanced mix input (¼-inch); and an unbalanced insert (¼-inch TRS) switchable from the front panel. Balanced high- and low-level XLR and ¼-inch TRS outputs are provided. Retail: $1,999.99.


The two-rackspace Manley Mic/EQ 500 Combo's mic pre section sports fully differential topology (using two 5751, and single 6414 and 7044 dual triodes), offers up to 46 dB of gain with a frequency response of 5 to 60 kHz, and has 48V phantom powering and phase-reverse capabilities. Its EQ 500 passive EQ circuitry is coupled to a second differential line-amp, with a choice of Peak or Shelf modes for each band, and includes an insert point. Separate input and output gain controls allow the unit to produce overdriven tube effects, which can be monitored on an illuminated VU meter. All I/O is balanced transformer-coupled. Special mastering versions with calibrated and detented controls are available by custom order. Retail: $2,900.


The single-channel STT-1 incorporates Millennia's HV-3 discrete hybrid solid-state mic pre, M-2b Class-A tube mic pre, NSEQ 4-band Class-A parametric EQ, TCL opto-compressor/limiter, an opto-de-esser and a Class-A tube instrument DI in a single unit. The EQ, compressor and de-esser can be switched between tube-based or solid-state-based amplifiers, and combined with a preamp in any configuration, with a choice of transformer-coupled or transformerless audio paths. Balanced monolithic direct, unbalanced XLR (from a Class-A discrete J-FET amp) and XLR balanced monolithic outputs are available. A backlit analog meter indicates output level or gain reduction. Retail: $2,895.


Housed in a two-rackspace chassis, the VMP-2 is a stereo unit with two tube mic preamps and two tube EQs. Each channel also includes a ¼-inch, high-impedance instrument input and switches for -20dB pad, 48VDC phantom power, EQ bypass, and -12dB/octave highpass filter at 40 or 80 Hz. XLR transformer-balanced inputs and outputs and ¼-inch unbalanced outputs are standard. The 2-band EQ is a shelving-type (±10 dB at 100 Hz and ±10 dB at 10 kHz). Frequency response is stated as 10 to 40k Hz (+0 dB, -3 dB). Retail is $949.99.


The MDP-1 is a 2-channel pure Class-A mic/DI preamp with a transformerless output stage. The MDP-1 can be ordered with either Jensen 13K7A or custom-wound transformers, and the DI signal path is completely transformerless, with a selection of three input load impedances for piezo-electric acoustic instrument pickups, magnetic pickups and line-level sources. The MDP-1 also includes a phase-reverse switch, a 20dB input pad, a low-cut filter with 10 frequencies, and large, illuminated VU meters. Retail: $2,495.


The bright-blue, half-rackspace DigiTUBE Mic Pre/EQ is a combination tube preamp and EQ with a 24-bit digital output. The preamp has a dual servo input that accepts mic, instrument and line signals, with 70 dB of gain and 22 dB of headroom. The 3-band sweepable EQ has overlapping bands and a Bypass switch. Analog output is via XLR connector, and there's a ¼-inch TRS insert. Digital output (at 44.1 and 48kHz sample rates) is via a coaxial S/PDIF connector. Retail: $299.95.


The dual-channel Requisite Y7s Mk III is handcrafted using point-to-point wiring and uses four 12AY7, two 12AX7 and two 6414 tubes. There are four input types: transformer-balanced mic (XLR) with 48V phantom power, transformer-balanced line (XLR), transformer-balanced ribbon mic (XLR) and unbalanced line (¼-inch) — selectable with five-position rotary switches. Outputs are transformer-balanced (XLR). Gain, feedback and output level controls are also included. The Y7s Mk III produces more than 75 dB of gain with a 10 to 100kHz frequency response. Retail: $3,500.


The Channel One is a channel strip device containing a tube mic pre, a de-esser, a compressor/limiter with noise gate, an EQ and a headphone monitor. The preamp stage provides three input options: mic (XLR) with 48V phantom power, phase reverse and subsonic filter; low-impedance line (XLR); and high-impedance instrument (¼-inch). The compressor/limiter section is based on SPL's Double-VCA-Drive circuitry; the de-esser includes a proprietary Auto-Threshold mode; and the EQ features low, mid-hi and air-band filters, along with a field-effect distortion stage. XLR outputs and insert points are included, and a 24/96 AD/DA converter is available as an option. Retail: about $1,700.


The robustly constructed MPC-100A is a single-channel tube preamplifier and tube compressor/limiter combined in a two-rackspace unit. It uses two 12AX7a tubes, two 990 discrete operational amplifiers, 15 integrated circuits, three transistors and two compression cells; it accepts electronically balanced line and mic, and unbalanced high-impedance input signals. Output is at +4 dBu via balanced XLR and unbalanced ¼-inch connectors. The compressor/limiter section has very fast attack times, making it ideal for optimizing signal prior to entering the digital domain. Frequency response is 5 to 65k Hz. Retail: $1,950.


The dual-channel PA-1 is a hybrid preamp that employs transformer-coupled inputs feeding an EF86 pentode amplifier stage, followed by two ECC83 triode stages, with a solid-state output amp. Both channels feature highpass and lowpass filters, 48V phantom power, drive and peak LEDs, input and output level controls, and backlit VU meters — with phase reverse on channel B. Input gain is switchable between 20 and 50 dB in 10dB steps, and a Nominal Gain switch on the rear panel adjusts the level of both outputs. Both balanced XLR and unbalanced ¼-inch I/O are provided. Retail: $1,599.


The Tube-Tech MP1A is a combination dual mic pre/DI amplifier with independent preamps for mics or instruments. The balanced mic inputs provide 48V phantom power and a switchable 20dB pad. Gain is adjustable from 20 to 70 dB in 5dB steps. The DI inputs are unbalanced with a gain range of 10 to 60 dB. The amplifiers are all tube-based, the heaters are fed DC voltage and the transformers are enclosed in mu-metal cans — all greatly reducing hum. Input and output transformers come with a static-screen between primary and secondary wirings to eliminate ground loops. Mic inputs and outputs are balanced and fully floating. Retail: $2,395.


The Universal Audio 2-610 is a 2-channel tube microphone preamplifier based on the amplifier section of the Universal Audio 610 modular console. It uses one 12AX7 and one 6072 tube in each channel, and produces up to 61 dB of gain, with a frequency response of 20 to 20k Hz. A 2-band shelving EQ section offers up to 9dB boost/cut at 4.5/7/10 kHz (high) and 70/100/200 Hz (low). There are balanced mic and line (XLR, with 48V phantom power on the mic inputs) and unbalanced high-impedance line/instrument (¼-inch) inputs. Output is via a balanced (XLR) connector. Retail: $2,295.

Barry Cleveland is a Bay Area-based recording artist, engineer and producer (, and author of Creative Music Production: Joe Meek's Bold Techniques (, a book about the visionary British producer's contributions to the art of recording.

A Designs818/
Anthony DeMaria Labs845/
Bellari/Rolls Corporation801/ D.W.
Groove Tubes818/
Joemeek (dist. by PMI Audio)877/
Manley Labs/Langevin909/
Pendulum Audio908/
Requisite Audio Engineering818/
SPL (dist. by Group One)631/
Summit Audio831/
TL Audio (dist. by HHB)310/
Tube-Tech/TC Electronic805/
Universal Audio831/
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