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GT Electronics Vipre Preamplifier

One of the big buzz items at the AES show in September 2000 was the GT Electronics (a division of Alesis) Vipre. The buzz carried to the Alesis booth at this winter's NAMM show and now that units are finally shipping, the Vipre is likely to remain on the tip of people's tongues.

One of the big buzz items at the AES show in September 2000 was the GT Electronics (a division of Alesis) Vipre. The buzz carried to the Alesis booth at this winter’s NAMM show and now that units are finally shipping, the Vipre is likely to remain on the tip of people’s tongues. The Vipre is a single-channel, vacuum tube-based, variable impedance microphone preamp.
Product PointsApplications: Studio recording

Key Features: Single channel all-tube variable impedance mic preamplifier; balanced 1/4-inch instrument input; XLR and unbalanced 1/4-inch outputs; variable rise time

Price: $2,199

Contact: GT Electronics/Alesis Corp.; 800-525-3747 310-255-3400; Web Site


+ Quiet

+ Great sound

+ Versatile


– Expensive

The Score: Variable impedance and rise times make the GT Vipre all-tube mic pre one of my favorite new studio tools.

The GT Electronics Vipre ($2,199) is the world’s first all-tube variable impedance mic preamp. It uses a fully differential Class A vacuum tube design. Transistors, integrated circuits and electrolytic capacitors do not tarnish the signal path – its sonic character is created by eight tubes (6DJ8 x 4, 6AQ5 x 2, 12AT7 x 1 and GT6205 x 1). The 3U box looks amazing, reminiscent of some powerful audio device that Austin Powers’ Dr. Evil might use to take over the world. The inside of the box is equally impressive.

The Vipre’s rear panel is logically laid out and clearly labeled. A female XLR connector provides microphone signal input (+8 dBu max) and a 1/4-inch TRS jack provides balanced line input (+28 dBu max). The balanced input allows the box to add that cherished tube warmth to a line level signal. Output is provided through both a male XLR connector and a 1/4-inch TRS jack. An unbalanced, -10 dBV output is provided through a 1/4-inch jack. A standard IEC connector accepts 120V. There is a voltage selection card located to the left of the fuse receptacle, which can be configured by the user for the appropriate voltage (100V, 120V, 220V and 240V).

The front panel’s classic design is complemented by a large round VU meter (nearly three inches in diameter) and two steel mesh-covered vents. The Input knob selects input as Instrument (-20 dB), Instrument, Balanced Bridge (transformerless) or Balanced XFMR. If either of the instrument inputs is selected, input is provided via the front panel’s 1/4-inch jack.

The Impedance knob selects the impedance when using the microphone input. The impedance can be selected as 300, 600, 1,200 or 2,400 ohms. There are two huge gain knobs reminiscent of those found on a piece of old RCA radio equipment. The first adjusts gain in 5 dB increments from 20 to 70 dB and the second, in 1 dB increments over a +/-5 dB range.

The VU Meter Range knob sets the meter range at 0 VU Expand, 0 VU, +10 VU, +20 VU or +30 VU. The Rise Time knob sets the rise time at Slow, MS (medium slow), MED, MF (medium fast) or Fast. The rise time describes how fast the circuit responds to a transient. It is similar to the slew rate of an amplifier. Changing the rise time completely changes the sound of the preamp. One rise time does not necessarily sound better than another; it simply sounds different. I found that I preferred the Fast setting about 70 percent of the time. The remaining 30 percent was fairly evenly split up between the other four settings.

Six sturdy toggle switches allow different features to be accessed. The Polarity switch reverses the polarity of the signals. The Hi-Pass switch inserts a high-pass filter in the circuit. The +48 V phantom switch activates phantom power; a green LED notifies the user if this has been selected.

The Mute switch activates the mute function; a yellow LED notifies the user if selected. The Standby switch puts the circuit in standby mode; indicated by a red LED. Finally, the power switch turns the preamp on and off. A blue LED signifies the unit is powered up. There are two Signal LEDs: green when the signal reaches -3 dB and red when clipping occurs.

In use

I recorded male lead vocals with a Royer SF-1 microphone through the Vipre with first-rate results. I also had excellent results using the Vipre with my Sony C-800G microphone while recording both male and female vocals. With the SF-1, I always preferred the sound of the preamp set to the Fast rise time.

The SF-1 worked so well with the Vipre that I used the pair – along with my GML EQ and my Pendulum 6386 Limiter – to record acoustic guitars and percussion. Both instances yielded wonderful results. The Vipre’s quiet 75 dB of gain eliminates the typical low-gain problems commonly associated with ribbon microphones. This is the highest gain available from any production preamp on the market today. The preamp’s high gain pairs nicely with its extremely low noise. THD distortion at 1 kHz is less than 0.025 percent at 45 dB gain.

The Vipre did an extraordinary job recording electric guitars as well. I experimented with both a Shure SM57 and a Royer R-121, and in both instances I had great results. Although I usually prefer the sound of the transformer, the option of transformerless recording is always nice.

The instrument inputs work well. My Gibson EB2C bass gave its best sonic performance ever when plugged directly into the Vipre’s instrument input with the rise time set to Slow.


Until I had the opportunity to spend a couple of weeks with the Avalon 2022 microphone preamplifier, I was unaware of the difference variable impedance could make in a microphone preamplifier. Now, I am a believer. And now that I have had the occasion to have variable impedance in an all-tube audio path with the ability to adjust the circuits rise time, I am in hog heaven. The GT Electronics Vipre is as good as it gets.