Darkglass – Microtubes B7K Ultra REVIEW

The first of many Darkglass pedal hits was the B3K Bass Overdrive. Then, the B7K that added 4-band EQ was brought to the table, and now the Microtubes B7K Ultra takes it one step further. Let’s plug it in and investigate… 

In short, the Ultra version of the famous B7K bass overdrive adds a second footswitch that allows you to punch the drive and preamp circuits in and out separately. It may sound like a small feature, but it is expanding the versatility by a mile. You also get even more control over the critical LOW-MID and HI-MID EQ bands, as you can now choose between 3 different target frequencies for each of the mid bands. But of course that’s only part of the story, so let’s take a more detailed look.



darkglass-b7k-ultra-bass-overdrive-control-knobsThe B7K Ultra is packed. You will find no less than 8 knobs, 4 3-way toggle switches, 2 foot switches and 2 LEDs on the surface of the pedal. On the rear panel you have the in and out jack connectors, as well as the power supply input. On the left side, there is an XLR connector to send a DI signal to the FOH and on the right side you get a little push knob to engage GROUND LIFT.The lower row of 4 knobs controls the EQ section. From left to right you get: BASS, LO MIDS, HI MIDS and TREBLE. For each of the mid bands, you will also find a toggle switch that allows you to choose between 3 different target frequencies. For the LO MIDS they are: 250 Hz, 500 Hz and 1 kHz. For the HI MIDS they are: 750 Hz, 1.5 kHz and 3 kHz.

The top row of knobs mostly deals with the overdrive circuit. On the far right, you’ll find the DRIVE knob that simply sets the amount of drive you want to use. The next sets the LEVEL and the BLEND allows you to create a mix of your dry signal (including the EQ you dialed in using the lower row of knobs) and the overdrive signal. Finally, you get a MASTER knob setting the overall output level, which is excellent for keep the pedal at unity gain when you punch it in.

On the drive section there is also 2 toggle switches that are familiar if you have ever used the B3K or B7K pedals. First, the ATTACK switch affects the high end of the drive signal and you can choose to set it either flat or to boost or cut. Similarly, the GRUNT switch have the same options, but deals with the low end of your overdrive tone.

The two foot switches are named BYPASS and DISTORTION. They work independently, but obviously you have to engage the pedal in the first place to kick in the distortion part. So, you can press only the BYPASS foot switch and use the pedal as a dedicated preamp / EQ pedal to shape your clean tone. Then you can kick in distortion on top of that as you see fit with the second foot switch. If you don’t want to use it as an always-on preamp, you can simply engage the DISTORTION switch and then bypass the pedal altogether. Then, when you step on BYPASS, you get both the EQ and distortion in at the same time.



white headphone with rhythm symbol

The sound clips are based on the same sound example and are divided into no less than 11 rounds:

  • Bass
  • Lo Mids (250 Hz)
  • Lo Mids (500 Hz)
  • Lo Mids (1 kHz)
  • Hi Mids (750 Hz)
  • Hi Mids (1.5 kHz)
  • Hi Mids (3 kHz)
  • Treble
  • Scoop
  • Attack/Grunt
  • Mixed Drive Examples


NOTE! Please use headphones or ‘real’ speakers. You simply can’t judge low-end material on laptop, tablet or phone speakers…!

NOTE! If you are on a mobile device, please turn it to landscape mode to see the knob settings of the pedal for each audio clip.





If there was a versatile pedal top list around, this would definitely be on it. As a preamp / EQ pedal alone, it is more versatile than most pedals in that category, and if you look at the drive section in an isolated context, it certainly shines there as well. Now, if you add the two parts together you obviously get an even more impressive result. I would actually claim that you would be hard pressed to identify a more versatile drive pedal anywhere. You may find a few dedicated EQ pedals that are as versatile, but they don’t have that delicious and crunchy drive.

The addition of the second foot switch also adds immensely to the versatility compared to its predecessor. And even though I prefer using the DI on my amp, it’s great to have an additional one right at hand (or at your feet) – just in case.

There is little more to be said in this department. The Microtubes B7K Ultra is extremely versatile. Period.



Qualitywise, the Ultra seems to be right up there along with the other Darkglass pedals. No further marks, everything seems to be solid and ready to take a beating on the road for ages. Of course, this pedal is brand new and I haven’t been able to long-term road test it, but based on previous experience with this pedal brand, I have no reason to doubt that there will be no issues with this one in the years to come.

Overall, the design is good. The footprint is similar to the B7K, Vintage Deluxe and Super Symmetry Compressor pedals. Only, the design is ‘landscape’ and it’s a little taller. The I/O design is perfect to my taste as I like the connectors to be separated as much as possible to prevent cable clutter.

if there is one thing to mention, it would be that due to the high count of controls, the toggle switches are not that accessible. If you want to quickly flick one of the switches on the fly, you better be precise. Especially the cut/flat/boost switches for the ATTACK and GRUNT control are hidden in between the dialing knobs. I guess that in most cases you would find the tone you want anyway, and the switches are probably meant as set-and-forget controls, but having said that, I often find different rooms and venues to need different effect and amp settings. I would not be surprised if I would actually want to flick some switches id-song at some point. Maybe I should set aside a bit of practice time for that exact exercise…



Today (2016), the B7K Ultra retails at $389. It’s an expensive pedal, but as I have mentioned a few times, great pedals are great pedals regardless of the price, whereas poor pedals will never represent good value for money in my book no matter how cheap they might be. In this case, even this price is justified and while I think it’s a lot of money for a pedal, i also find that it is really offering great value for money.



Basically, good remarks all around. Just one small issue regarding ‘hidden’ toggle switches. At the end of the day, I would not hesitate recommending this pedal to anyone on the lookout for a super versatile overdrive and/or preamp pedal. It excels in both departments. If all you need is drive and you already have a preamp / EQ you love, the B3K may be an alternative.



Sounds great

Extremely versatile

Good value for money

2 foot switches

Built-in DI w/ Ground Lift



Toggle switches crammed in between knobs










(As a DRIVE Pedal)


(As a PREAMP Pedal)


Find the Best Price




Leave a Reply

Your email address will not be published. Required fields are marked *