all tube preamp + D.I. box for bass guitar

100% Valve

The classic vacuum tube design stays true to your signal and lifts it up to a new level 

Adaptable EQ

Linear frequency response at 12 o clock and boost + buck for high and low frequencies – it is your choise  

Legendary transformer sound

Top-Notch JENSEN®  signal transformer for a clean and symetric signal feed for your audio interface or the FoH 

Bass Cut

Eliminate mud and rumble from your sound by switching in the effective low cut

Practical outputs

Its choice of signal outputs make the Transformator an all-purpose weapon for all occasions. XLR, 1/4″ jack, balanced + non balanced ; its all here

Fits into your gig-bag

This small high-end full tube signal amplifier will fit into any gig-bag or on even a small pedal board

Transformator ? What for ?

The transformer ensures that your signal is always available in studio quality, whether you are recording at home, in the rehearsal room, on the club stage or on tour. 

With the possibilities available to us today you can change, bend and improve the sound of your instrument in all possible ways.

However, the result greatly depends on the quality of the signal at the beginning of the signal chain.

This is where the transformer lays the solid foundation for your sound building.

Adrian Kehlbacher

Adrian Kehlbacher is a professional musician and gave the impulse for the development of the Transformator

The Mission

Your instrument keeps its own, unique sound.

The Transformer highlights and supports your playing technique.

No compromise on signal quality and integrity.

Quick access to frequencies and harmonics.

Intuitive operation which won’t distract you from playing.

Classic full-tube circuit. We are convinced of the superiority of tube technology in this application.

The transformer is small and light, so you can easily transport it to any place in the world.

Transformator Input

Rigid full-metal  Switchcraft 1/4″ socket to connect your instrument cable to.

Transformator EQ + BassCut

Treble and Bass EQ can be set linear at  12 o clock. The Bass Cut switch is above the Bass knob.

Transformator JENSEN Übertrager

The JENSEN transformer provides a balanced (symmetric) and potential-free (isolated) signal and brings the „larger than live“ sound into the Transformer


The transformer is designed to start your signal chain. This means that you plug the instrument into the input of the unit with your 1/4″ instrument cable.

From there it goes directly to the control grid of the first tube. This tube drives a passive EQ, inspired by the legendary Treble + Bass EQs of early tube bass amps.

The EQ can be set to remain linear, so it won’t bend your signal. You can boost and cut highs and basses depending on the location, instrument, amp and speaker you are using.

To avoid rumble, impact noise and boomy sounds in the band context, a bass cut switch is at your disposal. The cut frequency has been carefully chosen to cut rumble – not sound.

Your signal continues to the second tube, which drives a JENSEN transformer.

This transformer has two main tasks:

1. It converts the unbalanced signal of the bass guitar (Hot+Ground) into a balanced signal. The signal becomes more powerful and is absolutely immune to interference. With an XLR cable, the signal can be routed over long distances to the FoH console or the studio audio interface without any signal loss or hum.

2. The transformer adds a certain magic to the sound. This may sound strange, but it’s true. This sound is often described as „larger than live“. Overall, the sound becomes richer and more transparent. Experts know this sound from the old Neumann tube microphones, for example, which almost always used output transformers for their signal.

In addition to the XLR output, two further outputs are available, which can all be used simultaneously.

An unbalanced 1/4″ jack line output can supply your stage amp with a signal. The volume potentiometer on the Transformer gives you control over the level of that signal.

This potentiometer only changes the level of this output. The XLR output remains unaffected. So you can adjust your stage sound without changing the level to the FoH (front of house mixing console).

A further 1/4″ jack output is available for even more flexibility. This picks up the signal after the transformer and can, for example, control another bass amplifier or send the larger-than-life sound to a power amplifier on stage.

To avoid phase cancellation between e.g. two amps, a phase switch is provided which turns the signal of this output by 180°.

Transformator symetrischer XLR Ausgang

Complete output section for every situation in a musician’s life.

  • lXLR out balanced + isolated + ground lift switch
  • 1/4″ Jack unbalanced and isolated + phase switch
  • Line Out 1/4″ full-metal jack unbalanced and volume controlled for the stage amplifier



Get your ultimate All-Tube-Sound-Tool for your sound now !

799,00 Euro*

including German VAT for customers within the EU

*689 Euro fur muscians outside of the EU and Switzerland

Transformator scheme

The transformer is as useful for the live playing and recording bassist as his guitar strap.

In every situation, in the studio, during home recording and of course on stage.

Transformator Größe Kaffeetasse

Despite its uncompromising 100% tube signal treatment and all the useful features, the transformer should be as small and light as possible.

With two 12AU7 tubes with mains transformer and JENSEN signal transformer, this was really no easy task. Despite the physical proximity of all components to each other, we succeeded in making the transformer pedalboard friendly, small and light. 

Transformator Größe Pedale
Transformator Netzanschluß

The rear of the transformer shows the two 12AU7 tube shielding cups, the mains socket with mains switch and fuses, and the unbalanced, potential-free 6.3mm jack output with phase switch according to the JENSEN transmitter.

Get your ultimate All-Tube-Sound-Tool for your sound now !

799,00 Euro*

including German VAT for customers within the EU

*689 Euro fur muscians outside of the EU and Switzerland

Here, I present the TRANSFORMER in the video in full detail (German). 

The video starts from the actual description, after the intro.

Transformator – Specification

Hardware :


  • with  x height x depth : 195x90x120mm
  • weight 1,2kg
  • color coated aluminum housing
  • two ECC82/12AU7 tubes
  • full-metal alumnium knobs anodized
  • full-metal potentiometer shafts
  • 1/4″ Input + Line Out Switchcraft full-metal
  • XLR connector + Transformator OUT Neutrik
  • transformer JENSEN made in USA Mu-metal shielded
  • DALE extrem low noise resistors + WIMA foil capacitors
  • very low signal output impedance  ; on the XLR and Line Out for very long cable runs to a mixer, audio interface or stage amplifier without any loss of sound quality
Arne Rudiger Bassist

Arne Rudiger – Diploma musician for  bass guitar / upright bass / Diploma music educationalist helped and supported the early stages of testing the Transformer design and concept in real live

Electrical data :

  • volume boost Line Out +10dBV
  • 0dB to +4dB unbalanced Line OUT
  • output impedance Line Out 300Ohm
  • linear frequency response 10Hz-19.000Hz -1dBV/0dBV
  • Bass Cut -6B@65Hz
  • two band center frequency @300Hz boost +15dBV and 400Hz cut -11dBV
  • treble knob center frequency 600Hz cut and 200Hz boost /  3dB/octave
  • bass knob center frequency 200Hz cut and 280Hz boost / -3dB/octave cut ; +4dB/octave boost
  • signal noise ratio >86dB
  • nominal signal level +4dBu balanced / unbalanced behind XLR-transformer
  • output impedance XLR OUT 200Ohm @ 1okOhm (input impedance of following equipment) 
  • supply 230V AC / 50Hz / 9 watts

All product photos on this page are made by Mr. Alex Henke, thank you  !