Radial Headload review

A guitarist’s ‘Swiss army knife’ with switchable attenuation, EQ-able direct cab-sim outputs and more.

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The Headload is many things, but first and foremost it’s an attenuator. Many will already be familiar with the process of plugging powerful valve amps into an attenuator, then cranking up to optimise your tone at volume levels which are practical for smaller gigs, studio and home use.

However, Radial refers to the Headload as a `load box’ because it’s equipped with the Radial JDX direct box, which the company says ™captures both the signal from the head plus the reactive load from the speaker cabinet for a more natural feel∫.

The Headload can handle up to 120 watts RMS and transient peaks up to 180 watts. Our unit was 8 ohms only, but 4- and 16-ohm versions are available and the Headload has a second speaker output to drive an extension cabinet.

Onboard are cement-encrusted, epoxy-coated copper resistor coils coupled with a cooling fan. Interestingly, the signal level from the amp governs the speed of the fan. The attenuator has six switchable settings and the lowest is tied to a trim control, which can dial the power down from 20 per cent to one per cent.

There’s also an off position, which can be selected when you’re using the headphone output, or if you’re recording via the JDX direct outputs. Direct signals can be taken pre/post JDX equalisation. Both balanced outputs have ground lift switching and the post-EQ out has polarity switching. The pre- and post-EQ unbalanced outs share a level control, but there’s no ground lift and polarity is fixed. A speaker must be connected at all times – even when in `silent’ mode.


The onboard Radial Phazer is a phase adjustment tool, which allows you to time-align the JDX output with signals from the speaker or a microphone in front of the cabinet. The Loadbox can be used free-standing, but a rackmount kit is also available – it’s easy enough to fit the `ears’ and remove the handle. The power supply is external and connects to the Loadbox via a locking 4-pin XLR.


As with so many power soak devices, it’s sometimes hard to determine how and why the tone changes as attenuation is increased. It’s well established that our perceptions of high- and low-frequency content change along with volume, and the Headload’s resonance switches are on there to compensate.

Then there are speakers to consider. Where hi-fi and studio monitors are concerned, linearity is paramount, but guitar speakers are generally prized for the way they colour the tone, not to mention their compression and overload characteristics when pushed hard. So when an attenuator is used, the sound may change substantially, even if it does a good job of maintaining the integrity of the amplifier’s tone.

Reviewing the Headload at the same time as the Marshall Astoria Classic provided an opportunity to compare the Headload with the amp’s onboard power scaling, and thereby remove the speaker as a variable to a large extent.

The Headload setting that corresponded most closely with the Astoria’s five-watt power scaling was around 60 per cent and the sonic results were consistent. The Astoria Classic’s onboard power scaling retained the sound of the amp extremely well, but with the

Headrush there was a very slight loss of high frequencies and bass weight. The attenuator’s `lo’ resonance switch compensated pretty well, but some lower midrange definition was lost.

Activating the `hi’ resonance restored the Astoria Classic’s chime and clarity, and any remaining differences were so minor that they could be corrected with subtle shifts of the amp’s tone controls.

To test the Headload’s direct output, we swapped over to a Dr Z. combo. As impressive as the attenuator’s performance was, the Headload’s direct out is even better. You can use it in combination with the amplifier’s onboard speaker, or switch the attenuator to the `off’ position, in order to mute the amp.

As there’s no output level control for the balanced direct outputs, they’re best connected to a mic preamp. Direct devices can often sound sterile and fizzy, but the Headload is very natural.

There’s a lot of onboard tone shaping, too. Simple bass and treble adjustments are made using the low and high controls of the EQ section, but the voicing switch is where the magic happens. It appears to comprise six preset equalisation curves with various midrange voicings, to simulate a range of cabinet and speaker types. These options allow you to try to match the setting to your regular speaker, dial in something complimentary or even totally different.


It’s a more than viable alternative to mic’ing up a cabinet, and the sound quality is good enough for recording and live work. However, our test amp had an onboard spring reverb, which was less evident in the Headload’s output than through the amplifier speaker.

For best results, you may find that a touch of studio-grade compression will help to provide a more natural playing feel, and many recording channels have built-in compressors these day. At least you won’t also need equalisation, but should you prefer to add your own processing, you can use the Headload’s pre-equalisation direct output instead.

When you combine the direct out with a microphone signal, or even the sound straight off the speaker, there’s likely to be some degree of phase shift due to time delay. Activating the Headload’s `Phazer’ feature can compensate for this, as it employs a variable, all-analogue delay circuit to re-align the signals.

Technically, the two signals will be most closely aligned when the sound is at its fattest and most full-bodied, but some degree of phase shift can help to sculpt the sound by introducing comb filtering at various frequencies. There’s no set way of achieving this balance between the signals, except to use your ears – suffice to say, if it sounds great to you, then you’re good to go.

The Headload is a well-designed multi-purpose tool for gigging, recording and practising. It’s easy to use, sounds impressive and achieves great results without fuss or noise.

Key features
Radial Headload
• Price £1,099
• Description Resistive attenuator with integral direct box, balanced and unbalanced direct outputs, phase correction tool and headphone output. Made in Canada
• Controls Load resonance hi/lo switches, range trim, load switch, low/high EQ, speaker cab voicing switch, phaser shift & 360 degree switch, headphone level
• Dimensions 305 (w) x 88 (d) x 154mm (h)
Weight 3.75kg
• Contact Shure Distribution 01992 703058
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