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Radial Engineering Phazer Active Class-A Analogue Phase Controller   

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The Radial Phazer is a +4dB line level phase alignment tool that lets you bring two sound sources into phase alignment to guarantee that the fundamen...Click To Read More About This Product

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An essential tool for phase-coherent, multi-mic recording.

The Radial Phazer is a +4dB line level phase alignment tool that lets you bring two sound sources into phase alignment to guarantee that the fundamental frequencies play in sync. On electric guitar, for example, you can use the Radial Phaser to combine the direct feed from an amp with the signal of a room mic to create incredibly fat, rich tones. On a kick drum you can combine the attack from a close mic'd bass drum batter head with the boom picked up by an ambient shell mic. Combining top and bottom snare mic signals nets you a big in-your-face sound. For acoustic instruments, combining a spot mic with a room mic captures textures like you've never heard before.

Unlike Class-AB devices that suffer from zero-cross distortion, the Radial Phazer is designed from the ground up for optimum sound quality and features 100% discreet Class-A circuitry. This results in smooth and natural sounding phase curves that are particularly important in the lower frequency spectrum. 0 to 180 degree phase adjustment is performed with a single knob, making it easy to zone in on the sweet spot. For the more adventurous, a 180-degree polarity reverse switch accesses the 181 to 360 degree range and lets you create weird to absurd 'Phazed' tonal textures. This is augmented with a variable low-pass filter that lets you focus the effect in the lower frequency spectrum where phasing is most audible.

Built Radial-tough for the road, the Phazer is equipped with an innovative bookend design that creates a protective zone around the knobs and switches. Construction is 14-gauge steel with a welded internal I-beam frame that protects the sensitive electronics in even the harshest touring environments. A bottom no-slip pad provides electrical insulation to eliminate electrical bonding, and mechanical isolation to reduce mishap.

The Radial Phazer is a creative tool for the studio designed to expand your tonal palette. Live, it delivers great sound fast and may well turn into your best audio soul mate.


Messing around with 'time travel' is not new¦ In the dark ages of the 1970s, MXR, with their groundbreaking Phase 90 and Phase 100, ignited interest in phasing by way of modulating the phase effect for electric guitar. This inspired Radial's chief engineer Denis Rozon to start messing with phase circuits in the early 1980s. Fast-forward 20 years, MXR is re-launched by Dunlop and these 'vintage' remakes are once again available to the masses. Radial has taken a different route, targeting not guitar pedals, but audio signal paths.

What few realize is that beyond the sweeping phase effect, minute phase adjustments can lead to actually creating more natural sounds. It has to do with physics or more precisely, the physical location of the desired sound source and the various devices used to capture the sound.

Sound travels at roughly 1100 feet per second (340 meters per second) while electricity is estimated to travel at 650,000 feet per second (200,000 meters per second) or roughly 600 times faster. This means that if you were to combine the direct feed from a guitar amplifier with a microphone, by the time the amplifier pushes the speaker outwards and the sound travels through air before it enters the mic, it will be minutely delayed with respect to the direct (hard wired) signal.

This 'phase mismatch' is even more pronounced when two microphones are used on the same instrument. Imagine, for instance, an acoustic guitar with one microphone positioned directly adjacent to the sound hole and a second mic elevated and 10 feet (3 meters) away from the instrument in an effort to capture a sense of natural space and ambiance. Some sound engineers often spend hours moving microphones around the room in an effort to find the sweet spot or the position where phase anomalies will be less pronounced.

These phase anomalies create an effect known as comb filtering. This occurs when a sound is combined with a delayed version of itself in a given acoustic space. When the fundamentals and harmonics mix together the frequencies will either combine to amplify each other when in phase or cancel each other out when out of phase, depending on where you place the two microphones relative to each other. Visually, the resulting frequency response curve looks somewhat like a comb, hence the name comb-filter. This usually produces a hollow or unnatural tone.

Reality check #1: Comb filtering is an integral part of all sounds. Our ears and brain use phase along with frequency and loudness to localize sound. In fact it is impossible to be in perfect phase at all frequencies as each of the infinite number of frequencies has a different wavelength. In other words, if you perfectly time-align 500Hz (wavelength is 2.2 feet long or about 1.5 meter), then 510 Hz will be out of phase because the wavelength is slightly longer.

Reality check #2: Since you cannot ever be in perfect phase, don't stress over it. Use your ears and listen. This is exactly what those finicky engineers do when trying to get a great sound. They listen to the combined sound of the two mics using their ears. It is no different when combining two sounds electronically by adjusting the phase. This is in fact what the Phazer is all about. It is a device that lets you precisely adjust the phase relationship between two sources by delaying one of the sources. Phase adjusting is most often applied to the nearest source so that the fundamental frequencies line up and sound best.

A common application is electric guitar. In live touring, the goal during sound check is to get the sound up fast so that the band and crew can go have dinner before the show starts. Taking a direct feed from an amp, using a device like the Radial JDX amplifier DI for example, provides a consistent sound because inconsistencies such as room acoustics or mic placement are eliminated. But since the time when Keith Richards started playing guitar, the venerable Shure SM57 has always enjoyed front row positioning an inch or two away from the speaker. This familiar look and sound is important on many levels. For the guitarist, it provides a safety net whereby he knows his amp sound will be projected through the PA system. For the FOH engineer, the familiar ground makes for a good starting point in capturing the sound for the evening's event... but potential problems abound. If the microphone moves ever so slightly, either to the side or further from the speaker, the sound will be completely different. So, as a means to circumvent this problem, a direct feed using a device like the Radial JDX is an excellent solution and has become a standard practice for the smart engineer.

This solves one problem, but unfortunately creates another. The direct feed from the microphone traveling at two thirds the speed of light will arrive at the mixing console slightly ahead of the slower mic signal. The Phazer solves this problem by allowing the engineer to slow down the direct feed so that both signals sound good together. Within seconds, you can combine two sounds and get better, more consistent results.

Designed for positioning at the mixing board, the Phazer is usually inserted into the signal path using the insert ports on a console. This allows the Phazer to be used on all types of sources: microphones, direct feeds, transducers and so on.

It is important to emphasize that the Phazer is a tool designed to spur on the creative process. In this day and age of virtually unlimited tracks, try using the Phazer in creative ways that can produce some fun and unexpected results. If you do not like the effect, mute the track - the point is to have fun, and experiment. Who knows what results you can achieve!

Feature set

Front panel

1. PHASE ON switch - bypass switch used to compare signal with or without the Phazer

2. INVERT switch - moves phase effect from 0 to 180 degree range to 181 to 360 degree range

3. SHIFT control - this knob adjusts the phase delay

4. FILTER ON switch - Bypass switch used to engage the high pass filter

5. RANGE - switches the cutoff frequency range of the filter

6. CUT-OFF control - this knob lets you adjust the cut-off frequency point

7. GROUND switch - used to lift ground to reduce hum & buzz

8. POWER switch - on-off switch

9. Book end design creates protective barrier around knobs and switches

10. Full bottom no-slip pad keeps the Phazer in place

Rear panel

11. DC power jack - for the 15VDC that comes with your Phazer

12. 1/4"" jacks - balanced +4dB and unbalanced -10dB insert points

13. XLR male & female jacks for +4dB balanced hookup


14. 100% discreet Class-A electronics for best audio
15. Tough I-beam construction with 14 gauge welded steel

16. Full two-sided ground plane to reduce RF susceptibility

17. Double-sided mil spec PCB for durability
18. Heavy duty, high-cycle switches with steel casing

19. Glass filled nylon connectors for trouble-free connectivity

The Radial Phazer is intuitive and very easy to use. It is most often connected using insert jacks on a channel of the mixing console, but may also be used in-line from a mic preamplifier or any other line level source. The Radial Phazer is in fact made up of two completely independent circuits: the phase adjustment controls on the left and the low-pass filter controls on the right. These can be used independently or together depending on your desired results.

The phase alignment section features three controls: an on-off switch that lets you audition and compare the phasing effect when engaged or when out of circuit, an invert switch that extends the phase range from 0 degree to 180 degree to 181 degree to 360 degree and the shift control that is used to control the amount of phase shift that is applied to the signal.

Due to the greater energy and longer wavelengths found in bass frequencies, you will hear most of the Phazer's effects during the first half of the knob's rotation. In fact, phase changes in upper frequencies are often inaudible. Because of this, Radial thought that adding a high-cut filter (low pass) would help eliminate some of the phase anomalies and better focus the phase effect where it matters most -- in the bass.

The low pass filter also features three controls. Because the filter is completely independent, it can be bypassed using the FILTER on/off switch that allows you to compare the filter effect with the original tone. A cutoff range has been provided that lets you select between 38kHz down to 3kHz range or from the 3.8kHz down to 300Hz range. A smooth 6dB per octave (?) filter is applied which is then controlled via the cut-off knob.

Using the Phazer

The Radial Phazer is a phase adjustment tool designed to allow the user to quickly time-align two sources to create fat rich tones or to open the audio landscape to all kinds of new and exciting sounds. The concept is simple. When you have two microphones in a room, the microphone nearest to the sound source will capture the sound. A few milliseconds later, the second microphone will capture the same sound. When both microphones are on, the minute delay will cause phase cancellation. By inserting the Phazer on the nearest microphone, you can phase-align or delay the sound of the first source so that it will be in sync with the second.


Before making any connections, make sure all levels are off so that you do not harm your sound system. Line level connections are either done via the insert point of the console by connecting a 1/4" TRS insert cable or by taking a direct feed from a line level device such as a mic preamplifier and connecting the Phazer in-line using the +4dB XLR connectors. Power comes from the 15VDC supply that is provided. Once you are powered up, try turning up the levels. If you encounter noise, try lifting the ground switch. This can often eliminate ground loops, which are the most common cause of system buzz and hum.

Start by setting up both microphones in the room and make sure the PHASE and FILTER are bypassed. Listen to make sure both microphones are working. Mute the near microphone. Now position the distant microphone where it sounds best. Turn on the near microphone and listen.

The phase adjustment tool:

The Phazer features two basic control sections: a variable phase shift that spans from 0 degree 180 degree and a low-pass (high-cut) filter. Both feature an on-off switch* that lets you monitor the effect when introduced into the signal path. Usually, one would start by adjusting phase of the nearest source (i.e. close mic versus room mic) by turning the knob until the two sources 'sound' right. *Note: A polarity reverse switch is used to toggle the phase from the 0 degree 180 degree to 181 degree 360 degree range. This is performed at the XLR output. Engage the Phazer with the PHASE control set to 8 o'clock (completely counter-clockwise).

As microphones and/or direct boxes can often be phase reversed, start by depressing the polarity reverse (360 degree) switch to see what range sounds most natural. Now, slowly turn the phase control clockwise and listen. Most of the audible effect will occur between 8 and 11 o'clock due to the energy in the low frequency band. As you move beyond this point, the potentiometer will mostly affect higher frequencies that will not be as audible. For fun, try reversing the polarity by hitting the SHIFT switch. This will again toggle the phasing effect from 0 180 degree to 181 - 360 degree.

The low pass filter

Once you have found the 'sweet spot' try engaging the low-pass filter to hear its effect. This filter is designed to roll off high frequencies so that you can focus the Phazer's effect on the fundamentals or bass frequencies. When the knob is fully clockwise, the filter is essentially out. As you rotate counter-clockwise, the filter cut-off point will begin to take effect. The filter is a completely independent low pass filter that can be used alone or with the Phazer.

There are two ranges to choose from. These let you focus on either high frequencies where the effect will be subtle, or down into the mid range where the effect will be extreme. When you first get your Phazer, you should take the time to listen to the low pass filter effect without engaging the phase adjustment circuit so that you get familiar with how it works. Start with the filter range set to the 3kHz to 38kHz range. Set the filter knob to 5 o'clock and slowly turn the knob counter-clockwise. Now listen to the effect using the lower 300Hz to 3.8kHz - again starting at 5 o'clock and rotating the control slowly.

Combining the two effects

Only through experimentation will you begin to fully understand the possibilities. So have fun and listen. Keep in mind that it is impossible for all frequencies to line up or be in phase as each frequency has a different wavelength and the physical distance and/or propagation time will vary. Ultimately, when using the Phazer you must use your ears to find what sounds best to you.

Best of all, the Phazer can be used on all types of musical sources. You do not have to limit yourself to what sounds best¦ For instance, a fun effect is to combine a direct feed from a guitar amp direct box like the Radial JDX, with a mic'd feed from the amplifier and purposely set these out of phase. This can result in tones reminiscent of Tom Schulz's 1970s band Boston that are absolutely stunning!

The Phazer is a fun creative tool for studio and a must have to speed up live sound checks.


Can I connect a mic directly to the Phazer?

No. You must first connect the mic to a preamplifier and then to the Phazer, as it is designed to accept +4dB or -10dB line level signals. A microphone does not have sufficient output to drive the Phazer's circuit.

Can I use the Phazer on stage on a bass amp to improve the mix in my monitors?

Yes. Bass players often complain of hot spots on stage where the sound can be very boomy or where the bass will completely disappear. This is caused by the interaction of the bass amplifier with the PA system. Inserting the Phazer into either the PA system or the line-level insert on the bass amplifier can minimize this effect.

How does the Phazer compare to the Little Labs device?

Little Labs make some really cool devices that are very well designed. They employ Class-AB circuits and chips and manage to make them sound just fine. The Radial Phazer is a pure Class-A device that employs discreet components (more old-school if you wish). Radial found that the Phazer has been characterized as having a beefier bottom end. Both are very good and will complement each other in any studio.

Why not build the Phazer into a direct box?

Radial originally did this, only to find out that nine out of ten times, the person who really needs to control the phase is at the mix position. Trying to adjust the phase of a 100W Marshall while standing right next to it is absolutely futile. You need to hear both sources to make a value judgment.

Can I use the Phazer like an effects pedal and sweep the sound?

Sure! You can create phase shifter effects by rotating the knob back and forth to create fun effects. Half the fun in recording is creating new sounds. The Phazer should be viewed as a fun tool to do just that.

Can I create a similar phasing effect by sliding tracks on my digital recorder?

Yes, however because the phasing effect in the Phazer is 100% analogue, it sounds very different. Also, the proprietary phase curves employed were developed by Radial's engineering team to sound good - not be clinically correct.

  • Class-A phase alignment tool
  • Easy, single knob control gets there fast

Phazer Active Class-A Analogue Phase Controller

  • Input/output: +4dB balanced, -10dB unbalanced
    Connectors: XLR female input, XLR male output AES standard pin-1 ground, pin-2 hot
    1/4" TRS for balanced lines and TS for unbalanced connections
    Ground lift: lifts pin 1 on the XLR output
    Phase shift: Variable ” 0 degree to 180 degree
    Polarity: Electrical ” reverses pins 2 and 3 and extends phase shift from 181 degree to 360 degree
    Filter: Variable - Low pass from 38kHz to 300Hz ” two ranges
    Power: 15VDC- 400mA (various country specs)
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