Darkglass Microtubes B7K Ultra Bass Preamp Pedal

Written by

Jed Van Wyngaardt

The Darkglass Microtubes B7K Ultra steps up where the regular B7K leaves off giving you a preamp and overdrive in one pedal with even more control than ever before. The B7K was already known for having an incredible range of tones in one pedal but the B7K Ultra takes it a step further with extra switches, knobs and footswitches to help you dial in your sound.

Separate Distortion and Preamp

Before the B7K had a single footswitch that controlled both the overdrive and preamp sections of the pedal. Now these are controlled independently meaning even your clean tone can still have the same incredible B7K attack and shimmer and then you can dial in the overdrive when you need it.

So Many Controls

Just like the B7K you can do a lot with the B7K Ultra. Starting off on the top row of controls you have your Master volume for the preamp, Blend to mix the clean and overdriven signals, Level sets the volume of the overdriven signal  and finally Drive sets the amount of overdrive. Just with these controls you have enough to get everything from a subtle boost to your signal to all our overdriven Djent heaven.

Moving down a layer you hit the EQ section. Bass, Lo Mids, Hi Mids and Treble all act like you would expect but it still has a couple more tricks. For example the Grunt switch sets the amount of low end signal to saturate by applying a boost to a set range of frequencies before clipping. The Attack does the same thing but for the high end frequencies. Finally you can select the frequencies you want to control with a pair of switches that let you go between three options for both the hi mid and lo mid controls.

Here's what Darkglass say about the Microtubes B7K Ultra

The Microtubes B7K Ultra features all the versatility and sonic possibilities its predecessor is known for plus amazing features: (1) A dedicated Footswitch to engage the overdrive section independently. (2) A Master volume to control the overall unit level. (3) Three way toggle switches for each mid control, with a total of 6 different mid frequencies at your disposal the B7K Ultra allows you to create and tailor your tone to perfection: From crisp, punchy clean preamp to obliterating high gain distortion, and everything in between. The B7K is an universal tone crafting machine.


Whereas the Level Knob controls the output of the overdrive section the Master volume adjusts the overall volume of the unit. Ideal for fine tuning the output on clean mode. It also serves as a DI level control.

Mixes the clean input signal with the overdriven signal. The clean signal remains at unity gain while the volume of the overdriven signal is set by the Level knob, allowing for fine control of the blend ratio.

Sets the volume of the overdriven signal.

Sets the amount of saturation in the overdriven signal.

 Attack Switch
Sets the amount of treble content to saturate: The "Boost" setting emphasizes the treble content extra clarity and presence. The "Flat" position leaves this register untouched while the "Cut" position will reduce the amount of high frequencies being saturated.

 Grunt Switch
Sets the amount of low frequency content to saturate by selecting between three different bass boost levels before the clipping stage.

+-12dB @ 100Hz

Lo Mids
+-12dB switchable 250Hz, 500Hz and 1kHz

Hi Mids
+-12dB switchable 750Hz, 1.5KHz and 3kHz

+-12dB @ 5kHz

Direct Output
A balanced version of the ¼” output, useful for running into PA’s or studio mixing consoles.

10.7x12 cm (4.21x4.72 in)

The Microtubes B7K Ultra has a current draw of 30mA. Only use a regulated 9V DC adapter with a center-negative plug. Due to ecological reasons it does not accept batteries. Unregulated power supplies and/or higher voltages may result in suboptimal noise performance and even damage your unit, voiding the warranty


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