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Audio-GD - MASTER 1 Vacuum Valve - Tube preamplifier (RCA, XLR)

€ 1.799
€ 1.487 excl VAT
Power cable (Default C13 EURO)
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  • Description
  • Specifications

Audio-GD - MASTER 1 Vacuum Valve - Tube preamplifier (RCA, XLR)

Master 1 Vacuum Valve preamplifier's design is not one of a kind!
It is the purest vacuum valve design possible, even the power supply has been built around tubes. Only DALE resistors, SOLEN capacitors and vacuum valves are used.

Due to its unique design the SN ratio has been boost up to 98dB on normal listening volume. 
So, its sound may have some different than some vacuum valve units you have ever listened with.

Sound is transparent, detailed and dynamic while the musical tube sound is preserved.


The preamplifier is designed around vacuum valves, resistors and SOLEN film capacitors. That’s it! No concessions or compromises. Only the best is good enough. The preamplifier can be ordered as single ended unit or as balanced preamplifier. 

NO built-in power regulators; NO built-in choking coil or electrolytic capacitors.  

This special design has more special features. The S / N ratio is designed to reach 98dB at normal listening level. Therefore, the sound experience will differ from all other vacuum valves you have been listening to most likely. When listening you might expect the typical “tube”; thick, slow and warm sound.  When listening to this preamplifier you will experience a transparent detailed and dynamic sound with the typical tube musicality.

Except for the vacuum valves which only have 3 months warranty, the preamplifier itself has our standard 2 year and 10-year repair warranty policy. We recommend to renew the vacuum valves after 5000 hours, (Every day 3 hours, it is around 5 years). After replacement around 150 hours burn in is advised.


  • HE1 Single Ended model Tube amplifier consist of 8 vacuum valves
  • HE1 Balanced model Tube amplifier consist of 10 vacuum valves
  • Listening volume S/N Ratio up to 98 dB
  • Vacuum rectifier has implemented. Zero silicon elements in signal and tube power circuits
  • Equipped with SOLEN film caps
  • Vacuum valves powered with AC voltage
  • Remote Control inclulded


While we designed this preamplifier unit, we have chosen the most optimal area of the components used.Active components have A nonlinear character, they are not perfect in the hole spectrum but have its sweet spot. Realizing most power amps input sensitivity is around 1V and preamplifier output level will work best when its output is at 10V output. This tube preamplifier has its sweet spot around 2V output level, its maximum is over 15V though.

The frequency band has been adjusted to obtain the best sound and long term listening. The preamplifier consists of two identical PCB’s, one for left and one for right. Not built in mirror like our solid-state equipment because vacuum valves do not allow such design without impact on the sound.

The power caps and signal coupling caps are all premium grade SOLEN film capacitors. The vacuum valves chosen are selected based on best combination of different types and models We have over 15 years’ experience designing and building vacuum vale amplifiers. We do not advise users to change or replace components even if they have good DIY skills to preserve best match on musical and precise performance.
The total gain is 11dB which will allow the user to control the volume smooth and gradually.


  • 1. XLR balanced
  • 2. RCA single ended
  • 3. XLR balanced
  • 4. RCA single ended
  • 5. XLR balanced


  • Balanced (XLR)
  • Semi-Balanced (XLR)
  • Single ended (RCA / Cinch)


Vacuum valves are nonlinear components. This means when the input signal increases the distortion will increase and variation in low and high signal level will again increase distortion.To reduce distortion on the tube preamplifier a dual volume control ports was implemented. The first port placed at the preamp input reduces the input level, this will avoid high input level to increase distortion. The second port is placed on the gain tube output, to select and apply the sweet spot of the vacuum valve.To obtain stronger output ability two vacuum valves are put in parallel and function buffers after the second volume control port.


Volume control consist of relay-controlled attenuators. Fully-independent, fully-balanced stereo volume controls. The volume controls feature consist of high-precision 0.05% tolerance film resistors and golden contact relays. Buffered inputs and outputs.There 4 channels volume boards are built in the unit to achieve ultimate balanced volume control. They are controlled by a digital signal controlling the high quality relays switching the precision resistors in analog area.

Audio-GD lineair volume characteristic Volume steps in comparison to standard volume control
volumecontrol1 volumecontrol2

Quality of volume control is very important in balanced applications . It have to effectuate the four channels to work as synchronous as possible to keep the balanced signal in perfect shape. In traditional volume controls the balanced output will introduce distortion which will negatively influence sound quality and performance and might even get worse than a single ended setup and waste the advantages of balanced designed solution.

Current mode volume control system

Traditionally volume controls are either potentiometers ore digital volume controls. Both are degradation of sound quality, specially where everything counts like this vacuum valve preamplifier. 
Master 1 Vacuum uses a current mode volume control: The signal only goes through a resistor then feed to the next stage. Without going through a volume control port. This design was published already in 2005 by Mr. Kingwa the founder of Audio-GD.

Master 1 Vacuum has 95DdB volume control range, below volume step 0-15 the volume increases just a few dB Above volume setting 15, the increase is 0.75dB with every step, resulting in a smooth and precise volume control adjustment.
To avoid any noise can be picked-up, the volume control board has been shielded by a thick copper enclosure.

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Weight: 16 kg
Width: 430 mm
Length: 430 mm
Height: 93 mm
Magna Hifi - Webshop: Audio-GDAudio-GD


>88DB (2V input,2VRMS output , Unweighted )
0.775 V RMS @ RCA 1.55V RMS @ XLR 2mA RMS @ ACSS
Linear @ 70 steps Exponent @ 99 steps
XLR 10V RMS (balanced, max)
W430 X L430 X H93(MM, Fully aluminium )
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