The Vahlbruch 6-PHI-4 is a hand-made analog phaser pedal built in Germany by Vahlbruch. It is the builder's take on the classic analog JFET phasing circuit, using hand-selected and matched new-old-stock 2N5952 transistors, and it offers a choice of 4-stage or 6-stage phasing selected by a toggle switch1.
Vahlbruch says the hand-selection and tight matching of the transistors gives the pedal an especially deep and homogenous modulation, very low background noise, and a transparent, organic tone. In 6-stage mode the maker describes the sound as expanding into Univibe and Leslie territory, while 4-stage mode covers what Delicious Audio called "your favorite vintage 4-stage script logo phasing"12.
What it does: analog JFET phasing in four or six stages
A phaser splits the guitar signal and shifts the phase of one path through a series of filter stages, then recombines the two paths so cancellations sweep up and down the frequency range. The 6-PHI-4 does this with JFET transistors, the approach used by the classic vintage phasers, and Vahlbruch calls it "the latest version of my interpretation of the famous analog JFET phasing which we all love"1.
The circuit uses new-old-stock 2N5952 transistors, hand-selected and supplied as a matched set of 4 or 6. A toggle switch selects whether the pedal runs as a 4-stage or a 6-stage phaser1.
What that means in practice:
- 4-stage mode: the configuration of the vintage script-logo phasers, the subtler and more familiar phase sound2.
- 6-stage mode: more depth and swirl, which Vahlbruch says reaches into Univibe and Leslie territory1.
Delicious Audio described the range as running "from your favorite vintage 4-stage script logo phasing to 6-stage phase swirl with even more depth," and noted the pedal is very transparent with super low background noise2.
Controls and switching
The control set is minimal. Unlike most vintage pedals, Vahlbruch says the 6-PHI-4 has plenty of control ability, but the single knob is12:
A continuously pulsating LED on the pedal indicates the speed of the modulation, so you can see the rate at a glance while adjusting it1.
MagTraB switching
Vahlbruch puts a lot of emphasis on its proprietary switching technology, MagTraB, which Delicious Audio described as "allegedly indestructible" and completely silent2. The way it works:
- Pressing the switch moves a magnet past a sensor, with no mechanical audio contact to wear out.
- The sensor passes the information to a micro-controller.
- The micro-controller drives a gold-plated relay, which does the actual audio signal switching1.
The result is relay-based true bypass: when the pedal is off, the audio path is not loaded by the switching circuit, and the switch itself has no mechanical audio contacts to degrade over time1.
Power and connections
The 6-PHI-4 requires an external regulated 9V power supply, which is not included, and there is no battery option. Its polarity is positive at the ring and negative at the tip, the reverse of the center-negative standard on most modern pedals, so it should not be plugged into a daisy chain or shared supply without checking polarity12.
The pedal draws 40mA, presents a 1M Ohm input impedance to the guitar, and drives the amp or next pedal at 100 Ohms output impedance1.
The builder and how to get one
The 6-PHI-4 is built by Vahlbruch, whose maker describes it as "the latest version of my interpretation of the famous analog JFET phasing which we all love"1. It is priced at $258 in the USA and 229 € in the European Union including VAT1.
The list price is $258 in the USA, or 229 € in the European Union including VAT1.
Videos
Pete Thorn
Mike Hermans
Alberto Barrero
Questions
What is the difference between 4-stage and 6-stage mode on the 6-PHI-4?
A toggle switch selects between a matched set of 4 or 6 phasing stages. Four stages give the classic vintage script-logo phaser sound, while six stages add more depth and swirl, which Vahlbruch says moves into Univibe and Leslie territory. The transistors are hand-selected and matched for either configuration.
Does the Vahlbruch 6-PHI-4 take a battery?
No. The pedal requires an external regulated 9V power supply, which is not included with the pedal. There is no battery option, so it needs a wall supply or an isolated pedalboard power source to run.
What is MagTraB switching?
MagTraB is Vahlbruch's proprietary magnetic switching technology. Pressing the switch passes a magnet past a sensor, and a micro-controller sends the information to a gold-plated relay that does the actual audio switching. Vahlbruch describes it as completely silent in operation.
What power polarity does the 6-PHI-4 use?
The 6-PHI-4 runs on an external regulated 9V power supply with positive at the ring and negative at the tip of the plug. That is the opposite of the center-negative standard used by most modern pedals, so check the polarity before plugging it into a shared supply.
Where is the Vahlbruch 6-PHI-4 made?
The 6-PHI-4 is handmade in Germany by Vahlbruch. It is ordered directly from the builder by email, with payment by bank transfer or PayPal and delivery to your stated address.
Sources (2)
- Vahlbruch, Analog Phaser Pedal, MagTraB switching, made in Germany, vahlbruch-fx.com, 2026
- Vahlbruch FX 6-PHI-4 Phaser, Delicious Audio, 2022-04-17
