Darkglass Microtubes 900 Bass Head Amp

Written by

Jed Van Wyngaardt

The Microtubes 900 is the first amp from Darkglass and it delivers monstrous bass guitar tones! It can go from clean and sparkly to huge, dirty bass sounds. With up to 900w of class D power, you can be sure that you will fill any room/stadium.

Microtubes Circuit

Built into the amp is a microtubes circuit (from their Microtubes pedal, famed for their distortion tones) and you can choose whether or not you want to engage it with a small switch on the amp head or with the footswitch.

When not engaged, you will get a clean, open bass tone with plenty of headroom and power. The fun really starts when you turn it on though, because you can choose how much distorted signal you want to add to your clean signal with the Blend switch. So if you want a touch of dirt to fatten up your bass tone, or if you want all-out craziness you can control that with the Blend.

2 voices

The microtubes circuit has got 2 different voices that will suit different players. The VMT setting will give you more harmonic warmth and a more vintage tone while the B3K will take you into hard rock and metal territory. And while you're at it, you can choose if you want the amp to respond to a passive bass or active bass. This will affect how it distorts the signal coming in. (Passive basses have a lower signal output)

4-Band EQ

A lot of people don't realize that the mid-range is very important for a bass guitar because this will sculpt how the bass sounds in a band mix. On the Microtubes 900 you have got your standard Bass and Treble control, but you also have a Low-mid and High-Mid knob to really colour the mid-range with the ability to narrow down certain frequencies in that range.


  • 500 Hz
  • 1KHz
  • 250Hz


  • 1.5Khz
  • 3KHz
  • 750Hz

Here's what Darkglass say about the Microtubes 900

The Microtubes 900 is a 900W amplifier equipped with an all analog preamplifier and a Class D Power Module. The first thing you will notice from the Microtubes 900 is its unusual control layout:

On the right side you’ll find the clean section which is the foundation of your tone.
It features Gain and Master controls an active 4 band EQ. Along with Low and Treble controls you will find Low Mids and Hi Mids control, each knob with their own 3-way frequency switch.

On the left side you will find the Microtubes Engine which acts as an extra channel that can bring your clean tone to the next level by helping you cut through the mix while adding anything from subtle tube break up, harmonics and natural compression to obliterating distortion.

We equipped the power module with some unique control over the power output and minimum speaker loads:

The standard mode will deliver 900W RMS at 4/500W at 8. If you select the 2 Mode via the rear panel switch the amplifier will deliver 900W at 2/500W at 4 and 350W at 8.


Front Panel

  • Dimensions: 26.7x23x6.4 cm (10.5x9.05x2.52in)
  • Input: Connect your instrument via a standard ¼” mono cable.
  • Passive/Active: Switch from passive to active mode. Some active basses can have a hotter signal output which can make the amp distort early (feel free to use it on Passive move even with active basses if such additional distortion is desired).
  • Microtubes: Turns on or off the Microtubes Engine to add natural compression, organic harmonic enhancement, and saturation ranging from mild overdrive to high gain bass rage.
  • The Microtubes Engine operates before the clean section (you can therefore use the 4 Band Active EQ for additional tone shaping in addition to the Tone knob described below).
  • Drive: Controls the amount of distortion that the Microtubes Engine will deliver. It will change from a soft warm overdrive to a massive modern distorted tone.
  • Tone: Controls the high harmonic content of the Microtubes Engine via a variable low pass filter: crank it up for additional attack and definition or dim it down for a smoother sound. This is handy if running bright clean EQ settings or cabinets with tweeters.
  • Level: Controls the Microtubes Engine’s output volume.
  • Blend: Mixes between the Clean signal and the Distortion signal (Microtubes Engine).
  • B3K/VMT: Selects between two overdrive voicings: B3K mode will deliver an aggressive, percussive sound while the VMT will bring up the mids for a warmer, more neutral character.
  • Gain: Changes the volume of the signal the Active 4 Band EQ. You can set it low prior to ensuring the cleanest operation possible or set it higher for more aggressive growl.
  • Bass: +-12dB at 80Hz. Changes the low content of the signal.
  • Low Mids: +-12dB of the selected frequency via the LOW MIDS ƒ switch (described below). Changes the lower mid content of the signal.
  • Low Mids ƒ: Use this switch to change the frequency of the low mid band from 250Hz, 500Hz or 1kHZ.
  • Hi Mids:  +-12dB of the selected frequency via the HI MIDS ƒ switch (described below). Changes the higher mid content of the signal.
  • Hi Mids ƒ: Use this switch to change the frequency of the hi mid band from 750Hz, 1.5kHz and 3kHZ.
  • Treble: +-12dB at 5kHz. Changes the high content of the signal.
  • Master: Controls the overall volume of the amplifier.
  • Mute: Mutes the amplifier.

Rear Panel

  • Speaker Output: Connects the amplifier to your cabinet. This Speakon combo jack allows for either Speakon or ¼” speaker cable operation.
  • Min-Load: Press when using a 2 load. You can use this control to lower the output if your 4 cabinet is not able to handle more than 500W (you can also get 350W with an 8 cabinet in this configuration).
  • Preamp Out: This output connects the preamp to a different power amp.
  • Power Amp In: Use this input to connect a different preamp to the power amp. (master volume will be disabled)
  • Post-Pre: Selects what signal will be delivered by the DI output. Selecting PRE, sends a clean copy of your input bass signal. Selecting POST delivers a signal processed by the preamp of the amp (gain, distortion, eq, master, etc.)
  • Ground Lift: Lifts the ground of the DI XLR output.  If a ground noise in you DI signal is experienced, try changing the setting of this control.
  • Balanced Output: Connects the Microtubes 900™ preamplifier to balanced equipment (mic preamp, console, recorder, compressor, audio interface, etc.) via a standard XLR jack.
  • Footswitch: The Footswitch allows you to remotely engage and disengage the Microtubes Engine. Hold the footswitch to Mute the amplifier. The VMT/B3K push button will remain operational with the Intelligent Footswitch plugged in.
  • AC Socket: Connects the power cord to the amplifier.
  • AC Power ON/OFF: Turns the amplifier on or off.

Intelligent Footswitch

The Intelligent Footswitch is an intuitive yet versatile accessory for your Microtubes 900. One tap will engage and disengage the Microtubes Engine, while holding for 3 seconds will Mute the amplifier. It is connected to the head via a standard 1/4" cable and it's powered by a microcontroller that sends commands to the head using a proprietary communication protocol.

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