AUDIO-GD MASTER 1 Vacuum - Tube preamplifier 6H2N-EB / 6U4N-EB

AUDIO-GD Master 1 Vacuum with power delay - Tube preamplifier 6H2N-EB / 6U4N-EB

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Audio-GD Master 1 Vacuum

Tube Preamplifier


Master 1 Vacuum is a 100% tube preamplifier   the power stage and the preamplifier / buffer stage are constructed exclusively with tubes, resistors and capacitors. In other words, it is a pure tube design developed specifically to offer the best of this technology. The Master 1 Vacuum and will delight audiophiles who enjoy the sound signature characteristic of the tubes without sacrificing the transparency and tonal accuracy, dynamics of high-fidelity equipments.

Thisversion of the Master 1 Vacuum is equipped with output delay relay stage. This option eliminates the need to manually operate the ignition sequence and prevents poc at power-on.

100% tube Preamplifier


Following Audio-GD tradition, great care is given to channel separation. The unit consists of two individual circuits, each dedicated to its own channel. With the right choice of carefully paired tubes (which is the case here) this configuration offers wide and clear sound stage without altering the transparency of the signal.

Capacitors SOLEN film are used for power supply and signal filtering. This type of component is particularly suitable in a tube preamp design.

To provide the tube sound in all its depth, Audio GD chose not to use components that color the signal in such a way to decrease the tube feeling The circuit thus contains only low power film capacitors (no high capacity electrolytic capacitor), no shock self, no power regulation : almost only the tubes are in charge of dealing with the signal and power.

The power stage itself is constructed from tubes exclusively, which definitively eliminates any possibility of degrading the tube architecture harmonics with transistors-based power supply noise.

Designed as a modern high-fidelity tube preamplifier, the Master 1 Vacuum has a very elaborate low-gain input to operate without compromise with nowaday's sources (which already have a high level output).

The circuit operates with 6 6H2N-EB tubes and 6U4N 4-EB tubes. This tube model was developed for Russian aviation. It offers a level of precision and excellent durability over time.


Optimized volume control for all-tube preamplifier

The volume control works thanks to two relay switches (one per channel). This prevents signal degradation due to the presence of a potentiometer between stages.

Designed to optimize performance and reduce as much distortion as possible,  Master 1 Vacuum volume control works on an unusual design. A first attenuation (still controlled by relay) takes place directly on the preamplifier input. This ensures that the signal will remain at optimal levels in accordance with the specifications of the tubes. A second attenuation located this time at the output of the gain stage, maintains the signal level in an optimal range for the power amplifier. In order to have enough headroom, two tubes connected in parallel  justafter the buffer stage are used to stabilize the signal when high output level is required.

Because this volume  stage is very sensitive,  volume control circuits are isolated in a copper casing to avoid captation of interference.

A consequence of this type of installation is to have variable a signal / noise relative to volume. This does not mean that performance is erratic, but on the contrary, the Master 1 Vacuum is optimized to provide the best signal / noise as possible for a tube preamplifier with output levels that match the standards of modern Hi-Fi.

Another consequence of this architecture is to increase accuracy in low volume signal. The double attenuation makes it possible to greatly increase the level of the input signal (prior to noise captation) to then reduce to a conventional level, which leads to dividing the noise by the same order of magnitude.


This particular design allows a first preamplification upstream of the main noise sources, which significantly improves the signal to noise ratio and results in impressive performance for a tube preamplifier. It also respects the particular signature of this technology as a whole. The Master 1 Vacuum offers a THD + N of less than 0.05% with disconcerting linearity on the audio spectrum.

Metal Remote Control

Master 1 Vacuum comes with its metal, brushed-aluminum finish remote. It displays 2 buttons for source select and 3 buttons for volume control (increase / decrease / mute). This useful and well-designed tool relects Audio-GD chic sobriety.

Télécommande métal

Wide connectivity and source selection


At ease in any analog section, the Master 1 Vacuum has 5 RCA stereo inputs. The remote control (included) allows a remote source selection.

The device has two RCA outputs and an XLR output. Caution, this is unbalanced XLR output : Audio GD decided that a symmetrical design would involve too much of a compromise (it would mean to sacrifice either THD or some of the tube signature).


Tubes6H2N-EB x 6
6U4N-EB x 4
S / NR> 88dB (2V In / Out 2Vrms / no load)
Output Impedance<300Ω
Input sensitivity1 VRMS Out: 280mV
Power supply220-240AC 50 / 60hz
Power consumption31W
Dimensions430 x 430 x 93mm
Package Contents
1xAudio-GD Master 1 Vacuum
1xPower cable
1xMetal remote
Data sheet
Channel2 channels (Stereo)
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