Italy has a long-standing history of building supreme sports cars, not to mention their reputation for delicious cuisine. Now, thanks to companies like Mezzabarba, you can add premium guitar amps to the list of excellent exports. Piereangelo Mezzabarba founded his company in 2013 after years of perfecting his amp building skills, and he strives to deliver the best sounding amps that money can buy. Best is of course a relative term, but one thing is certain: the Mezzabarba Mzero Overdrive amplifier is one outstanding tone machine.

The Mzero Overdrive is Mezzabarba’s latest hand-wired, 100-watt model. Yes, there are many recently introduced, super-modded, 100W, EL34, boutique amps on the market. It’s a crowded playing field. Thus, the big question is: Did Mezzabarba bring something different to the table? We think they did, and after reading our review, maybe you’ll think so, too!

Category Value Rating
Features 20% 3 Stars
Usability 25% 3.5 Stars
Sound 25% 4 Stars
Documentation & Support 10% 3 Stars
Price 20% 2.5 Stars


3.6 stars or better: Outstanding, WIHO Award
3 stars or better: Worth considering
2 stars or better: Suited to specific needs
1 star or less: Not recommended


The Mzero Overdrive is a two-channel, two-master volume amp with a boost circuit. The front panel of the amp has a few interesting features not typically found in the hot rodded, Marshall-esque category. Next to the quarter-inch input jack are a Boost and a Bright toggle switch, which influence the tone of Channel One, the Drive channel. This channel is designed to go from clean to cruch, tone-wise. Channel Two is the Overdrive channel, designed for your high-gain, harmonically-rich tones.

Separate Drive and Overdrive controls for each channel follow after the Drive channel’s toggle switches, subsequently followed by a shared Bass, Middle, Treble EQ section. Following this are independent volume knobs for each channel, and finally shared Depth, Feedback, and Presence controls. The Feedback knob provides control over the negative feedback loop of the amp, inherent in all high gain amplifiers but rarely (if ever) adjustable.

The rear panel has a common IEC power input (in case you forget your cable, you can find one just about anywhere) and the Mains and HV fuses to the far left. Curiously, Mezzabarba uses a DIN-5 jack for the included two-button footswitch, but this is not a MIDI jack, so don’t attempt to use it as such. This is a convenient cable format, though, since standard MIDI cables are universally available. An effects loop Send and Return jack follow this to the right, though there are no controls for the level.

Mezzabarba Mzero Overdrive
Click amp to enlarge...

A Slave Out jack with a send level is provided for those of us who love to use IRs for re-amping. Just remember to keep the amp loaded down at all times. Finally, on the rear of the unit, we have a full complement of speaker output jacks for 4-, 8-, and 16-ohm speaker cabinets, clearly labeled to avoid confusion as to the proper way to connect your various cabinets.

We would be remiss to not describe the absolutely gorgeous aesthetic of this amp. Two huge, custom, bright red ONORI transformers stare out the black metal mesh design of the faceplate like the red brake caliper covers lurking behind a sports car’s wheels. Finished in sleek, black Tolex, the Mzero Overdrive looks every bit of its boutique pedigree. But was it easy to use?


The Mzero Overdrive  is very easy to use given its straightforward design. We paired the amp with a Mesa/Boogie Rectifier 4x12 cabinet (V30s) and were up and running in minutes. The included footswitch toggled between the clean and dirty channels on one button, and the second button engaged/disengaged the boost circuit on the clean channel, effectively providing access to three tones. Dialing in our favorite sounds was easy with the basic, shared EQ circuit.

The series effects loop was straightforward to use assuming you connect instrument-level signals to it, as there is no switch or level control for use with line-level sources. We would have loved to see a send/return level control, or at least a -20dB pad switch. We had no problems using our TC Electronic G-System (its levels are selectable) or pedals such as our Eventide H9 in the loop. Some players would surely prefer the option to hard-bypass the loop, but we didn’t find any issues of it messing with our tone when nothing was attached.

Another note on the effects loop. Tip: It is imperative you do not plug/unplug your effects into the loop while the amp is on (not in standby) or you will blow the power fuse! We found this out the hard way, but fortunately the high-voltage fuse is easily accessible on the rear panel of the amp.

Setting levels could not have been made any easier. Independent Gain and Volume controls are provided, so once your basic sound is dialed in and you’re happy with your levels, there’s not much more to it. The Boost feature on the Drive channel did more to influence saturation than volume. For volume boosts, you’ll need to either switch channels or make use of a volume/boost pedal.


Mezzabarba 412 cabinetBravissimo!!! Let’s face it. The Sound section is what it all comes down to. The amp is easy to use and has a feature set we like, but at the end of the day, that doesn’t matter much if the tone doesn’t inspire us. Fortunately, the Mezzabarba Mzero Overdrive does indeed inspire us. This just might be our new favorite sounding amp (not a crown usually worn for long, mind you… it’s a bloody tone battlefield in the studios).

We unboxed the Mzero Overdrive and as stated, connected it to an old, early-to-mid ‘90s Mesa Rectifier oversized 4x12 cabinet (V30 speakers). We had no effects in the loop for this sound test. We simply plugged in our Knaggs SSC and played. WOW, this amp was LOUD! Cutting the volume back to around the 2 mark (not 2:00), we continued on with our sound testing.

We were pleasantly surprised with the clean channel. We were able to take it from a pristine clean to a nice, smooth-yet-aggressive, overdrive on this channel. It was so pleasing to the ear, we played through this channel for a long time. Just as we can’t put a good guitar down, we can’t turn a great amplifier off, either. We loved the sound of the clean channel instantly. Given the manual indicates the clean channel is the same as the Mzero Standard (a one-channel amp), we can see how this channel is all you need for a great sounding amp. The tone cut through jamming to some of our pre-recorded backing tracks with a beautiful, finished sound. The Boost switch provided an excellent division between lead and rhythm tones (as well as feel and compression). Channel 2 is where things got even more interesting.

Where Channel 1 left us with edgy, hair band levels of gain, Channel 2 picked up and took us into modern metal territory. We palm muted a slow rhythm and the trails on the mutes continued on with earth-moving sound. This amp proved to be particularly strong in the lows, so we applied bass and depth knobs quite sparingly. We found a good balance in tone well before 12:00 on both EQ knobs.

Our next sound test was at our ‘80s tribute band gig in a 200-person capacity room. Hearing the Mzero Overdrive in the mix with a live band gave us a different perspective, and it’s always a little nerve wracking using a piece of still-unproven gear. We are happy to report our nerves were at ease after the first chord. The sound filled the room beautifully through a Friedman 4x12 cabinet (mix of Greenback and V30 speakers) and starting our set with a sustained chord, the depth of the sound, given the pronounced lows of the amp, was an experience we usually don’t experience with EL34-based amps. They get a beautiful sound, obviously, and we have many examples we love. But none of our other EL34 amps get this kind of girth while retaining the highs and air in the sound so well.

Video courtesy of Mezzabarba and Doug Rappoport.

We proved our assessment of the first channel by staying on it most of the night. With a little compression in front of the amp, we had no worries with our leads. The amp cut through beautifully. We really only used Channel 2 at the gig for cadenzas and whacky type, completely over-the-top, parts like the solo section from Duran Duran’s “Hungry Like The Wolf.” We faithfully covered songs from ‘80s pop through Van Halen, Bon Jovi, and AC/DC with no problems at all on just the first channel.

The effects loop, although simplistic as stated earlier, functioned as designed and we noticed zero loss of tone with our gear connected. We ran a TC Electronic G-System and an Eventide H9 through the loop, and the levels were perfect out of the box. Our sounds were as we are accustomed to: lush and three-dimensional.

Our final sound test was through our Mezzabarba 4x12 Mzero 69 cabinet. Loaded with four Greenbacks at 100W, we felt the amp sounded a little bit more focused than it was through the Friedman cab, without losing any of the width we had grown to love about this amp. We tested the Mezzabarba cab both in the studio and in a mid-sized club, and we felt the cab had a beautiful natural resonance to it. We were thrilled to have been sent the Greenbacks over V30s, and feel the sound of these speakers really suited this amp well.

Documentation and Product Support
Mezzabarba, as a boutique builder, handles customer support as a very high priority. Multiple emails (we bugged them more than usual) were answered within a day and fielded either by their distributor or by Piereangelo Mezzabarba himself!

The mZero Overdrive includes a well-written manual that covers all of the basics regarding amplifier use, speaker hookup considerations, and maintenance. There is some nice commentary from the builder as well, but we would have liked a bit more detail regarding the effects loop (since it’s series and fixed).

We love lifetime warranties, and Mezzabarba thoughtfully and confidently provides a limited lifetime warranty to the original purchaser. Tubes and transformers are covered for 90 days, with pots covered for two years. We think this a fair warranty.

Mezzabarba also offers customization of their amps! Whatever you can think of, they are open to making your amp your dream amp. “If it only had….” They’ll make it so.


The Mezzabarba Mzero Overdrive sells for $4,000. Ok, catch your breath. Yes, its pricey. It’s not the most expensive amp on the market, but it’s certainly beyond reach for the average player, and in the features-for-dollars competition, it’s a little bit on the lean side. But if you’re in the market for a boutique, 100W, EL34-based amp, you’re already prepared to spend a bit more for “ultimate tone,” and the Mzero Overdrive is an amp you’ll want on your short list. This just might become your desert island amp.

Contact Information
Mezzabarba Custom Amplification

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