JP's Gear Review v2.0 - Ep. 5 - 3-for-one ZVEX special!


A few weeks ago, I was on the lookout for a dynamic overdrive/dirt pedal for my bass. After doing some research, I came up with a few potential candidates, but the only one in stock anywhere was ZVEX's Basstortion, and this purchase opened the door for two more to happen (and an incidental third purchase that isn't a ZVEX but was on sale; it's in the pile of gear to review).


What exactly is the Basstortion? It's not exactly a distortion, not exactly a boost, and not exactly an overdrive. It's a mix of all three. It is a very dynamic circuit that will react differently depending on your playing. The sound it creates is very reminiscent of the beloved Ampeg SVT "Blue Line" grind and it reacts in a very similar way, but it's not exactly a clone of that either. As it behaves similarly to the front end of a tube amp, it is preferable to place it last in the signal chain (or before your reverb and delay).

Basstortion pedal in its natural habitat.

The pedal has three knobs: one volume, one tone, and one drive. It also has a bright/dark switch which adds more tone control possibilities. The tone control is very responsive, and I find myself often setting the toggle to bright and setting the tone at around 75% because the bass is too heavy. The drive control, however, controls a lot differently than one would expect. Below 50%, it's a light and responsive overdrive that gives a good SVT grind feeling: the more you dig in the strings, the more dirt you get. Above 50%, it turns into a fat tube-like distortion. One particularity of the circuit is that it will crackle when the drive knob is turned. This is normal, and the enclosure is marked as such ("Crackle Okay" around the knob itself).

Interior view of the Basstortion, sans battery.

Transistor close-up.

It uses a set of three BS170 N-Channel MOSFET transistors to achieve its responsive grind.

This pedal shipped with a "Extra Heavy Duty" 9V battery, which would most likely last you a few years since the Basstortion only draws 2mA of power. It accepts a 9V, 2.1mm Boss-style center-negative power supply.

The settings I currently use are the ones pictured above:

  • Volume at 40%
  • Toggle switch set to Bright
  • Tone at 70-75%
  • Drive anywhere between 5% and 25%
Although it is a very capable and versatile overdrive/distortion, I use it as an always-on, set-and-forget pedal (unless when I need a clean, unadulterated signal). It is located at the very end of my signal chain, just before the reverb and delay, otherwise these get muddy. I really like this pedal as it gives another dimension to your tone without breaking the bank, at least compared to the cost of a vintage Ampeg SVT "Blue Line" amplifier...

All-Important Rating™

Ease of use: 9/10 (Dialing the drive can be tricky at times.)
Build quality: 10/10 (It's really well done and solid.)
Effect quality: 10/10 (It sounds very similar to vintage Ampeg amplifiers, but not quite. That slight difference is what makes it great.)

Fat Fuzz Factory

What do you get when you take a standard Fuzz Face circuit and replace almost every resistor with a potentiometer? You get the craziest fuzz pedal I've ever had the pleasure to play with: the Fuzz Factory. The Fat Fuzz Factory is an enhancement over this already crazy idea that adds a Subs selector switch for three different low-end modes, making it a great circuit for bass.

My unit being a special anniversary edition, it was wrapped nicely in a soft piece of fleece cloth, tied at the top using a pink hair tie with two dice on the end; really snazzy. "Normal" ZVEX pedals - at least the Vexter series ones - comes wrapped in a paper bag neatly cradled in the box along with the manual and the warranty registration card. The 25th Anniversary Edition has UV printed graphics instead of the more traditional silk-screen printed graphics.

The hair tie is a nice touch.

25th Anniversary Edition Vexter Fat Fuzz Factory

The Fuzz Factory is a scary pedal, and it has a steep learning curve. The controls are not intuitive (except for the volume knob), and they will affect each other. Many settings on that pedal will simply not work and make the thing squeal. Although the documentation is limited, it does a good job of explaining "sorta what the knobs control". Each knob controls operating levels and biases to basically let you create a customized fuzz circuit on-the-fly.

The pedal has 6 controls:

  1. Volume: that one is pretty obvious.
  2. Gate: it's not a noise gate per se. It controls the squelches after the end of sustain. Adjust to the right to eliminate squealing and buzzing, or turn to the left to open the gate.
  3. Comp(ress): harder attack on the left, softer to the right, to the point of pinching the tone when fully clockwise.
  4. Drive: increases distortion when used as "normal" fuzz, and adjusts the feedback pitch and thickness. This knob doesn't do anything when the Compress knob is fully clockwise.
  5. Stab(ility): it's actually a voltage sag knob. The manual recommends to keep it fully clockwise, or at least at 60%. Lower values will produce a soft and squishy fuzz. It's also used to control the feedback pitch. This is the knob that will cause the pedal to squeal and annoy your neighbours, significant other, and-or pets.
  6. Subs switch. (In)conveniently located between the Drive and Stab knobs. It is difficult to toggle unless you have a stiff pick handy, or really long and solid nails. Controls the low-end frequencies at which the pedal will oscillate between three different modes:
    1. Sub level 1: Original Fuzz Factory
    2. Sub level 2: Lower frequencies
    3. Sub level 3: Lowest frequencies
Like most pedals on the market, it accepts a 9V, 2.1mm Boss-style center-negative power supply. The power draw is twice that of the Basstortion at a whooping 4mA. A Extra Heavy Duty battery was included in it as well.

The circuit seems to be a basic Fuzz Face circuit, using 2 new old stock germanium transistors from the 1960's. My unit has 2 NJS (New Jersey Semiconductors) transistors, which at first glance look like either 2N1304 or 2N404 (the identification is hidden, but the digit "4" is visible on the first one). Further inspection using a dental mirror revealed both are 2N404 PNP transistors.

Interior view with battery installed.

Barely visible transistor identification.

Magic mirror on the wall dental tool...

It is a difficult pedal to control and master, and many settings just won't work. Since the knobs will affect each other, it's like a mad scientist experiment every time you change one setting. The possibilities are limited only by your imagination (and the potentiometers' range). It's not a pedal that I keep on my board all the time since it's difficult to dial in the tone you want/need, but when I need some crazy fuzz settings, it's the one I'll try first second (the Mastotron will be first because it's much easier to use).

All-Important Rating™

Ease of use: 3/10 (Many setting just don't work, and it's a lot of fiddling around before you reach something that's acceptable. The learning curve is steep.)
Build quality: 10/10 (It's really well done and solid. The UV printing looks great.)
Effect quality: 7/10 (It's versatile, I'll give it that, but even when you do get it to sound good most of the times there's still some lingering artifacts in the sound. It's the nature of the beast, though...)


The Mastotron needs no introduction. It's one of ZVEX most well-known fuzzes, along with the Wolly Mammoth. This pedals give you a wide range of fuzz sounds, and is perfectly suited for bass. It has a few unusual features that makes its charm (and versatility).

Nice blue finish, with a simple silk-screen printing

The enclosure is clean and simple, and the controls are straightforward to manipulate (unlike the Fuzz Factory). It has 5 knobs and one toggle switch:
  1. Volume: that one is obvious.
  2. Tone: shapes the treble without sacrificing the bass and subs.
  3. Pulse width: allows you to select between a standard square wave when fully counter-clockwise, and narrow pulses when fully clockwise.
  4. Fuzz: adjusts the level of fuzziness of the pedal.
  5. Relax/Push: this knob will introduce source impedance on the input signal. When fully clockwise, the signal is raw. When turned down, impedance is added to soften the input. This is useful for active pickups
  6. Subs switch: it suffers from the same issue as the subs switch of the Fat Fuzz Factory, but worse. It is located a few millimeters lower between the volume and tone knobs. Selects how much sub content the fuzz will generate. The difference between each mode is pretty intense:
    1. Sub level 1: no subs.
    2. Sub level 2: medium subs.
    3. Sub level 3: all the subs.
It accepts a 9V, 2.1mm Boss-style center-negative power supply. The power draw on the Mastotron is an unbelievable... 1mA. A Extra Heavy Duty battery was included in it like the previous two in this review, and I'm reasonably convinced that changing the battery in this pedal is not something that will need to be done anytime soon.

I believe the circuit is, like the Fuzz Factory, a simple Fuzz Face with some bells and whistles added. Unlike the previous two in this review, the Mastotron is using surface-mounted components.

Interior view, sans battery. Only the electrolytics capacitors are visible.

PCB and transistors close-up.

The versatility of this fuzz is ridiculous. In my opinion, it is more versatile than the Fuzz Factory, a lot more usable, and infinitely easier to use. Well, anything is easier to use than a Fuzz Factory... The Relax/Push knob is great for instruments with active pickups, where their output is much louder and can cause the fuzz to misbehave, but it also allows you to retain it and use that higher output to your advantage. The pulse width knob is great, and combined with a full-on fuzz you can dial some sweet velcro fuzz and gating fuzz sounds. The subs toggle adds a whole extra dimension. You can get a really thin sound with no subs at all, and a rich, thick fuzz with everything the transistors have to offer.

All-Important Rating™

Ease of use: 8/10 (Getting some sounds and tones can be tricky. Still fairly straightforward and simple compared to, say, a Fuzz Factory. The subs switch is even more difficult to toggle than the Fat Fuzz Factory one.)
Build quality: 9.5/10 (It's really well done and solid, however the paint is chipping in the screw recesses in the backplate.)
Effect quality: 10/10 (It sounds great, and the subs toggle switch makes a huge difference.)

Audio demos

I managed to make a quick audio demo of these 3 pedals, however a few things happened that made it more difficult than it should:
  • Audio recording quality was mediocre at best. I had to source a decent USB-C microphone instead of relying on the camera's microphone.
  • Source videos ended up corrupted, but some of the audio survived.
  • Pinnacle Studio decided to stop working. No way for me to do anything without it crashing left and right. I had to find an alternative, which lead to...
  • Steep learning curve on the alternative software I found. Its free tier is somewhat limited in export capabilities (720p max), but at least it works.
I was able to use most of the audio, and used still images I captured during the original recording. The point, anyway, is to listen to the pedals, not necessarily look at them...

Honorable mention


When I visited the music store a few weeks ago, I was originally intending to get the Fuzzolo. However, they had a Mastotron in stock so I tested both and found the Mastotron way more versatile.

The Fuzzolo is a micro-pedal that is a mix of the Wolly Mammoth and the Mastotron, with some extra changes.

There's only two knobs: a volume control and a pulse width control. No tone or fuzz control. It's basically a one-knob fuzz with a pulse width control. It is extremely simple and it also sounds very good.

In order to use it with a bass or with active pickups, you need to change a jumper by removing the backplate. From what I understand, this jumper is the equivalent to the Relax/Push knob on the Mastotron: fully opened in one position, and fully closed in the other. I like the idea, but it should have been a sliding switch instead of a jumper. It forces you to unscrew it every time you need to change it.

The main difference I noted is the output volume. The Fuzzolo has a boost stage after the fuzz circuit, which makes the output insanely loud. It's loud to the point where it's barely usable in most of the amps I tried it with unless I keep the volume as low as the potentiometer allows me to without completely killing the output.

It's a good little pedal, but it's quite limited, and I don't think the boost stage was a necessary addition to the circuit. It's not for me, but it has a nice bison drawing on it.

Logo borrowed from ZVEX web site.


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