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Fractal Audio AMP models: Herbie (Diezel Herbert)


* EDIT: Up-to-date information is available in Yek's Guide to the Fractal Audio Amplifier Models *

HERBIE: based on Diezel Herbert

The Herbert is younger than the VH4. It covers the same territory as the VH4 (rock to metal) but feels and sounds differently. It’s immensely powerful with its 180 watts! It uses KT66 or KT77 tubes and has a single input. It supports MIDI.


“Its main difference from the VH4 models are in voicing, circuit design, and general layout. Overall the Herbert has a more familiar, slightly looser feel than the VH4, without losing much of the Diezel signature definition and tightness. Simply put, the amp is a player's amp, forgiving and ready for whatever one's soul and mood desires.​

The amp has three channels: 1 Clean – 2 Crunch/Heavy – 3 Lead. The voicing of the channels is very different. Channel 1 (Clean) hasn’t been modeled so we’ll focus on channels 2 and 3 and their models.


Channel 2:

“Channel two is a dual purpose channel, it's two voicings can be selected with a toggle switch. The (-) mode of this channel has dynamics to range from a vintage type clean sound to a broad crunch. The (+) mode of this channel offers similar voice, but much more gain. Both modes provide ample pick sensitivity.”​

“Channel 2 offers the whole spectrum of crunch sounds (or even lead) you can think of. In the minus position and the gain around 35% you`ll get typical cranked Plexi sounds, setting the gain a bit higher to say 60% (keeping all other pots noon) - voilà: 800s territory. Now flip the switch to the + mode and get the typical Diezel trademark crunch (gain around 40%). Tight, punchy, fast attack. Adream for those who prefer the harder stuff. Rotate the gain to 60% and play leads.”​

“This channel’s main objective is to cover soft and heavy overdrive and distortion sounds. It features a voicing switch, with -/+ settings. With the (-) setting selected, blues and classic rock sounds can easily be realized. The (+) setting kicks everything up a few notches and offers crunch with a good bite, allowing you to dial in punchy heavy rhythm and searing solo tones.”​

Channel 3:

“Channel three offers a high gain structure, but again with very good pick sensitivity and easy control. The distortion structure is transparent, but yet percussive and brutal.”​

“With the gain around 30% you`ll get your metal rythm channel - use the mid cut to land in Recto territory. Without the mid cut engaged, gain @ 50% and the mids a bit cranked you`ll get a screaming or creamy lead - just depends on your style/axe/fingers. Crank the mids a bit above noon to add some bite.If you want to use it for both, rythm AND lead - find your ideal setting and simply engage the second master to get your personal volume boost.”​

“This channel is voiced for highly articulate single note lines or for very heavy and massive rhythm guitar. Due to its slight midrange accent and very high gain structure, it possesses good punch and will, with ease and authority, rule any stage or studio. The “less is often more” rule applies here also.”​

We’ve got models of the “+” and “-“ modes of channel 2, and channel 3.

The amp controls are: Gain, Volume, Treble, Mid, Bass, Deep (120 Hz), Presence (> 3 kHz) and the +/- Gain Boost switch on channel 2.

Here are sample settings.


“The tone controls work in an unusually wide range, so a little adjustment goes a long way. As with so many other things - less is often more. We suggest you start exploring the channels with all controls set to 12:00 o’clock, and the master volume just slightly cracked open.”​

The Herbert also features a Mid Cut switch on every channel. This hasn’t been modeled. You can replicate it if you want. Cliff:

"Use a Peak EQ filter at 400 Hz with a Q of 1.4. Decrease its Gain until the desired scoop is achieved. Play with the Q to set the width of the scoop."​

Combine the amp with V30 or G12-K100 speakers. Take your pick from the stock cabs.

Fractal Audio / ML Sound and OwnHammer have IR libraries of Diezel cabinets.​

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This is my current go to amp! I don't know how close it is to the real life thing but if it is....what an amp.

Curious about a couple of things:
1-doesn't the mid cut have an knob for the cut plus an intensity knob? How do we do that? Or is the suggested fix above cover it?
2-it seems like High Gainers these days fall into one of two categories Marshall-esque, or Mesa-esque. Which would you guys say this one falls more closely into?


Power User
2-it seems like High Gainers these days fall into one of two categories Marshall-esque, or Mesa-esque. Which would you guys say this one falls more closely into?
Definitely closer to Mesa style, but the bottom end in particular doesn't "feel" like a Mesa. Try playing some Metallica with the Herbert and you'll see what I mean - it sounds GREAT, but different from their tone, which is solid Mesa tone on the major albums.


So is it kind of like a make up for perceived volume loss when the mid cut is engaged?
Sorry, it's not LEVEL, it's GAIN in the Filter block. That determines how 'deep' the cut is.

LEVEL indeed compensates the loss of volume.


I've played one of these beasts and I absolutely loved it.

I could never get anything sounding REMOTELY half decent with this amp model in the AFX. Can somebody post a preset as a decent starting point?


Herbert is my favorite Diezel. The new Diezel Paul may change that though, can't wait until those hit the U.S.
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