Inside the Vipre

Aspen Pittman and the rest of the GT Electronics crew have designed and built the Vipre to be a "wish list" preamp. In other words, GT incorporated into the Vipre everything it could think of to make a better tube preamp.
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Aspen Pittman and the rest of the GT Electronics crew have designed and built the Vipre to be a "wish list" preamp. In other words, GT incorporated into the Vipre everything it could think of to make a better tube preamp. Let's take a look at the circuitry inside:

* The Vipre uses an all-tube signal path (no semiconductors or electrolytic caps). A total of eight hand-selected, high performance tubes are used in the design, all of which function only as gain stages. There are four 6922 tubes in the first gain stages. The output stage is Class A balanced and push-pull using 6005/6AQ5 JAN spec tubes.

* All tubes are mounted onto the PCB using high-grade ceramic/rubber sockets. The sockets keep tube heat from affecting the PC board and reduce transmission of vibration from PC board to the tube. The nine socket pins are hand wired onto the PC boards, totaling 18 hand-soldered connections for each of the eight tubes. All Vipre tubes are U.S. made from late production models originally manufactured for military applications by Phillips and GE.

* No potentiometers are used in the audio path. Instead, GT created custom multideck ceramic rotary switches to which 1 percent tolerance resistors and high precision capacitors are soldered. The use of switches instead of pots allows precise and repeatable gain settings and ensures balanced gain integrity, providing improved noise and distortion specs. This "high-road" solution is not without cost: a precision potentiometer can be had for around two dollars and are easily soldered to a PCB with just three contacts; a ceramic rotary deck switch, like those in the Vipre, costs $80 to $100, and require about 100 hand-soldered connections and about an hour to assemble, according to GT.

* Fully-balanced input circuit options: balanced transformer mic in, balanced bridged mic in (bypasses transformer and goes directly to first grid of tube), balanced transformer line in, balanced bridged (-20 dB line input bypasses transformer and goes directly to first grid of tube), and front panel unbalanced instrument input (connects to first tube stage and converts to a balanced signal).

* Selectable input impedance at 300, 600, 1,200 and 2,400 ohms. This section features a true multitap humbucking nickel core transformer. This balanced input transformer, custom manufactured by Cinemag, is sealed in a dual-wall Mu metal shell to reject interference.

* The dual secondary output transformer, weighing in at a massive 2.3 pounds, delivers +4 dbM at the XLR output and -10 dBV on the 1/4-inch TRS output simultaneously.

* Selectable rise times (and in combination with the selectable impedance) allow adjustment of tonal character and definition without using active EQ circuits that can add noise and harmonic distortion. The variable impedance and rise times provide a combination of 25 different settings, all of which can greatly affect the dynamics and tone of the microphone without using EQ or compression.

* Low-capacitance balanced cable is used throughout the audio path for wider audio bandwidth (the Vipre frequency specs out from about 7 Hz to well over 100 kHz).

* High-capacity power supply capacitors, larger than the caps used in 100 Watt Marshall amps, retain more than 60 Joules, providing plenty of dynamic headroom, especially in the bass frequency response range.

* The Vipre VU metering system features special switching circuitry using still another specially designed multideck ceramic rotary switch, allowing for precise audio metering in a multiple of ranges up to +30 dBM.

* Perhaps the most interesting construction feature of the Vipre is its spring-mounted circuit board. This system uses eight four-inch springs to isolate the PCB from the chassis, preventing vibration transmission to the high gain circuitry.