Since Jackson Ampworks began in 2003, we have receiving many requests from bass players all over the world asking us to create a bass amp that delivers all of the flexibility, power and portability of our guitar amplifiers and debuting at Winter NAMM 2012, we are very pleased to offer the most feature rich, powerful and portable hand wired tube bass amplifier on the market.

The Behemoth is the marriage of two of the most iconic bass amps of all time; The B-15N and the SVT. These two amps are the most recorded and widely used bass amps in the history of music. From Motown to arena rock, these amps were there for all of it!

As great as they are, these amps have two major pitfalls. At 30W the B-15N is not powerful enough for larger live gigs and at 300W the SVT is too big and heavy for most gigs.

The Behemoth is a 2 Channel, 120W All Tube Bass Amp that delivers all of the classic B-15N and SVT tones in a small, powerful and portable package!

Channel 1 of the Behemoth is the Vintage Channel and is based on the 8-pin 6SL7 preamp tube. This preamp tube, known for it’s warmth and wide frequency response is where Channel 1 gets its Vintage 1960’s Motown and West Coast tones. The moment you plug in a Fender Precision or Jazz bass into Channel 1 you will immediately recognize where all the rich classic bass tones of the Beach Boys, Phil Spector and James Jamerson (Motown) came from! This channel with its Tone Shaping Switches allow a bassist to cover anything from early 1950’s Jazz and Rock to many of the classic bass tones of the 60’s and 70’s!

Channel 2 of the Behemoth is the more Modern Channel and is based on the 9-pin 12AX7 preamp tube. This channel, which is modeled after a simplified version of the SVT, is higher gain and punchier than Channel 1, and is better suited for Rock tones and musical styles that demand crisp tight bass tones. This channel with its Tone Shaping Switches allow a bassist to cover anything from Classic Rock to R&B and solo bass styles.

Looking at the front panel from left to right you will see two input jacks with the top jack reading “1/2” and the lower jacks reading “2”. Channels 1 and 2 are internally linked so that the use of the input labeled “1/2” sends the bass signal to both channels equally. In this arrangement, each channel is active along with its associated tone controls and switches and blending of the two channels is as simple as adjusting the Volume control for each channel. The true advantage of this type of arrangement lies in the ability to blend Channels 1 and 2 together while still allowing tonal shaping of each channel via their respective controls and switches. It should be noted that each channel runs in parallel with each other and are completely isolated from each other.

Plugging into the input labeled “2” breaks the internal connection between Channels 1 and 2 thereby allowing them to function independently. This feature allows the musician to use a completely different signal chain (floor based effects etc.) for each channel if desired, and is fully expanded by the use of an ABY box to select channels 1, 2 or both.

By including two channels and allowing independent tone shaping in each one, you can create tones never-before heard as you blend Channel 1 with Channel 2 making the Behemoth essentially a 3 Channel Amp! (Channel 1, Channel 2 and Blended Channels)

The front panel controls for each channel are: Gain, Volume, Treble and Bass along with 3 Tone Shaping Switches and finally a Master Volume that acts as a global volume control for the entire amplifier.

Gain – To make each channel more flexible, we have added a Gain control which acts as a gain reduction to reduce the sensitivity of the channel when using active basses or very high output pickups. Turned fully clockwise, the Gain control is out of the circuit and the channel is back to normal vintage operation. Turned counter clockwise, the Gain control will reduce the amount of signal being fed to the first gain stage of the preamp tube and has enough range to tame even the highest output pickups/preamps made.

Volume – The Volume control works to control the volume of its respective channel. Rotating this control to the max setting with the Master Volume turned down will help create some great “fuzz bass” tones.

Treble – The Treble control is used to fine tune the high-end response of the amp. Turning the control clockwise adds more treble.

Bass – The Bass control is used to fine tune the low-end response of the amp. Turning the control clockwise adds more bass.

Master Volume - The Master Volume on the Behemoth is located after Channels 1 and 2 and before the power amp section of the amp. By placing the Master Volume here, you are now able to blend Channel 1 and Channel 2 to get the tone you are looking for, and raise or lower the overall volume of the amplifier without changing the tone you just dialed in. Also the Master Volume will allow you to turn the Gain and Volume controls up as much as you want and dial down the overall volume. This especially effective for laying down “fuzz bass” parts etc.

One of the first questions most bass players ask when they first plug into the Behemoth is, “Where is the Mid control knob?” There is no Mid control knob on the panel, but you can control the Mid frequencies by rotating the Treble and Bass controls in tandem. If you have the Treble and Bass controls set at 12:00 and rotate them both clockwise, you will get a Mid decrease as the Highs and Lows are brought up. Conversely, if you have the Treble and Bass controls set at 12:00 and rotate them both counter-clockwise, you will get a Mid boost as the Highs and Lows are lowered. You might have to adjust the Volume control on the channel to compensate for the volume change as you move the Treble and Bass controls in tandem.

Each channel features Ultra-Hi, Mid Boost and Ultra-Lo switches to increase the flexibility of the channel and allows for use in other more modern musical styles.

Ultra-Hi – The Ultra-Hi switch will add increased high end beyond the range of the Treble control and works great for more modern styles or when playing more electric bass centric parts.

Mid Boost – The Mid Boost switch adds Mid range presence again for parts where the electric bass needs to stand out more in the mix.

Ultra-Lo – The Ultra-Lo switch shifts the entire frequency response of the channel down towards the low end and creates a very warm and full low end that you will feel more than hear. You may find that you need to adjust the Volume of the channel higher to compensate for the shift in frequency response.

The Behemoth is the only bass amp anywhere that offers switchable power output of either 30W Class A/B using (2) 6L6’s, 60W Class A/B using (4) 6L6’s or 120W Class A/B using (4) 6L6’s! This adjustable power feature allows the player to tailor the amps response to any given musical setting.

In high volume situations, select the 120W mode for maximum volume and clean headroom. When less volume or earlier breakup is desired, select the 60W or 30W mode and enjoy the early breakup and harmonic richness that only comes from low power cathode biased operation.

30W Class A/B – (2) 6L6 – When in 30W Class A/B mode, the Behemoth is cathode biased and features a proprietary circuit that exactly reproduces the natural compression and sustain of a tube rectifier but has the reliability of a solid state rectifier. These features along with the classic 6L6 tone give the 30W mode its own unique voice and a softer, more spongy attack.

60W Class A/B – (4) 6L6 – Like the 30W mode, the 60W Class A/B mode is cathode biased and uses the same simulated tube rectifier circuit to emulate the tonal effects of a tube rectifier. The tone of this mode is tighter and with more headroom than the 30W mode.

120W Class A/B – (4) 6L6 – In 120W Class A/B mode, the Behemoth switches to high voltage operation and is now fixed biased without the tube rectifier simulator. The combination of high voltage and fixed bias allows the Behemoth to have a very quick and aggressive attack with increased headroom and volume.

Each of the three power modes have been developed to add versatility and character to the tone while giving the player the ability to carry one small amp that will work in any musical setting.

Given it’s power and flexibility, the Behemoth is one of the most powerful and versatile bass amps ever made!

The Behemoth is one of the few amps available whose back panel is as feature rich as its front panel!
From left to right we have:

B+ Fuse – This fuse is used to protect the amp in the event of a short in the high voltage circuit. (located under the back panel)

IEC Module – In addition to serving as the power entry for the Behemoth, the IEC module also doubles as a voltage selector for the amplifier and is used to select between either 120 or 240V operation. With this features you can travel worldwide with the Behemoth and regardless of line voltages have consistently great tone without having to carry a step-up/step-down transformer! Lastly the IEC module also contains the 4.0 AMP Mains Fuse for the amp as well as a spare fuse.

Power Switch – This switch turns the amp on and off and when on powers the cooling fan and every circuit except for the high voltage DC circuit.

Standby Switch – This Standby Switch interrupts the high voltage DC inside the amp and effectively puts the amp in a resting state until the user selects the Play position.

Bias Trimmer and Test Points – To make changing tubes easier, we have included an external bias adjustment that is used to adjust the plate current of new tubes when they are installed. Simply attach a multimeter (set to read mV) to the red and black tip jacks and adjust the trimmer until the multimeter reads 40mV. Note: This is ONLY for use in the 120W mode!

Power Mode Switch – This three position rotary switch is used to select either the 30W Class A/B, 60W Class A/B or the 120W Class A/B power modes for the Behemoth. Note: The amplifier should be placed on Standby before changing power modes and given a 10 second rest period after changing power modes. Doing so will give the voltages inside the amplifier time to settle before playing.

Line Out Jack + Level Control - For recording or playing live, we have included a Line Out jack as well as a Line Out Level control on the back panel. Use this jack to sample a small portion of the signal going to the speaker cabinet and send it directly to the mixing board or front of house/monitor board. The Line Out level is tapped off the speaker jack so the tone going to the speaker cabinet is the same tone going to the board. Note: You must use a speaker cabinet or suitable load when using the Line Out! The Line Out feature does include a load!

Impedance Selector Switch – The Impedance Selector Switch allows the player to use the amp with any guitar speaker cabinet available as long as it is either a 4 or 8 ohm cabinet.

Parallel Speaker Jacks – Parallel speaker jacks allow the player to use more than one speaker cabinet at a time with the Behemoth. Because these jacks are wired in parallel, there is no difference in tone between them and either one or both can be used without effect.

FX Loop – To make the Behemoth even more flexible, we have incorporated a series FX loop between the preamp and power-amp (after the Master Volume). Adding an FX loop here allows the player to use his/her effects in the loop and not interfere with the critical relationship between the guitar and preamp.