Review: The Phil Jones Bass X4 Nanobass Combo Amplifier May Be Light, but It’s No Lightweight

It doesn’t weigh much, but the Phil Jones Bass X4 Nanobass combo amp is no lightweight. Its ability to produce warm, clean lows is impressive for an amp its size.

Discounting novelties and low-watt amps for electric guitar, the Phil Jones Bass X4 Nanobass 35-watt digital combo is physically the smallest amp I’ve tested since the Trace Elliot Acoustic Cube came out about 20 years back. 

Technology has come a long way since then. Not only is the Jones lighter, it uses advanced digital processing to produce better headroom and more accurate sound reproduction than I would have dreamed about from a small combo back in the day. Despite housing a four-inch speaker—more on this later—it has reported frequency response of 68Hz–15Kz.

While it has the word bass in its name, the Nanobass seems ideally tuned for acoustic guitar. I gave it a go with a range of instruments and pickup types, and even threw in some mandolin for good measure. But before we get into that, let’s take a look at the basics.

  • Phil Jones Bass X4 Nanobass combo amplifier controls
  • Phil Jones Bass X4 Nanobass combo amplifier front
  • Phil Jones Bass X4 Nanobass combo amplifier back
  • Phil Jones Bass X4 Nanobass combo amplifier in black, red, and white
  • Phil Jones Bass X4 Nanobass combo amplifier controls in red
  • Phil Jones Bass X4 Nanobass combo amplifier in black

A Tight Package

Measuring around 6x8x8 inches and weighing just over five pounds, the Nanobass can literally fit into a backpack. In keeping with its travel-friendly footprint, the amp’s internal power supply is designed to adjust automatically to international voltages from 100 to 240 without the need for external converters.


The Nanobass may be small, but it is a tight package—and its design plays a role in making its four-inch speaker outperform its modest size. Our test model had a white cabinet with a black top-mounted control plate, but black and red cabinets are also available. The cabinet is made from MDF, which the company says is stiffer than plywood, and covered in rugged Tolex. 

Save for the AC plug, all the connections and controls are top mounted. Inputs include a high-impedance 1/4-inch jack for guitar, a mini 1/8-inch aux jack, and Bluetooth 5.0 (aptX HD). It was easy to pair my iPhone with the amp without having to search for the instructions. There’s also a stereo mini-jack for headphones. I was a bit surprised not to find an XLR DI output, which is becoming more common on bass and acoustic amps.

Despite the amp’s tiny footprint, the controls are full-sized and have a sturdy tactile feel. In addition to the power switch, there are nicely spaced knobs for input level (with LED clip indicator light), aux/Bluetooth level and mode, individual controls for bass, mid, and treble, and master volume (which controls the instrument input’s level separate from the aux input). The panel layout made it easy to adjust the sound by feel without having to bend down and look at the controls.

In Action

Talk about serendipity: The Nanobass arrived in the middle of rehearsals for a performance of Eric Clapton’s Unplugged album, and my role was to cover parts played by both Clapton and Andy Fairweather Low. As a result, I played a Takamine nylon-string, a Taylor GTe, a Breedlove Pursuit Exotic (in open G for slide), a Taylor T5 12-string, and an Epiphone F-style mandolin. The show includes some songs with a full band, including keyboards, drums, electric bass, percussion, background vocals, and more, so rehearsals provided a pretty good test for the amp.

In terms of volume, the amp was able to cope with the band in a rehearsal setting. I wouldn’t say it was loud enough for a club gig without PA support, but it was ample for the rehearsal room, and more important, it was consistent and clean when I turned the volume knob up.


If you play a range of acoustic guitars with different pickup systems, you’ll know that switching instruments can often mean making big adjustments to the electronics. Not only do you have to contend with the different output levels or EQ curves from various types and brands of pickup/preamp combinations, you have to account for the tone of the instruments themselves. 

I tested the amp with the guitars plugged in directly and with an Eventide H9 Harmonizer providing some reverb, but did not use outboard compression or EQ. Most of the time, I left the tone controls relatively flat and used the instruments’ onboard tone controls to find a balance. At the rehearsals, I slightly boosted the highs and the bass to help the guitars sit in the mix. For the most part, this set-and-forget approach worked. But there were times when the amp’s EQ solved problems more effectively than a guitar’s onboard controls. 

With my Takamine, I used the Nano’s EQ to dial out finger squeaks and some of the percussive parts’ harsher qualities while keeping the clarity I needed for solos. The low strings sounded round and warm as well. With the Taylor, I did a lot of strumming and took one very bluesy solo. Chords sounded well-balanced. The Nano didn’t quite produce the air you’d get from amp/PA with a tweeter, but it didn’t sound dull or nasal like an electric guitar amp might. 

As for the Breedlove, I used the Nanobass to emphasize the midrange for slide playing. The low D in open-G tuning came through especially nicely, and the EQ also helped me reduce the papery treble that can sometimes plague my Epiphone mandolin when I plug it in. 

My Taylor 12-string is a hybrid that offers both acoustic-electric and electric tones. In this case, the lack of a tweeter was a plus. The acoustic settings were still well-balanced, while the electric tones weren’t as strident they would be through a tweeter-equipped amp or PA. 

While I normally ignore the aux inputs on an instrument amp, testing out the Bluetooth on the Nanobass actually revealed the little amp’s low end when I used it to listen to a few tracks on Spotify.

The Bottom Line

It doesn’t weigh much, but the Nanobass is no lightweight. Its ability to produce warm, clean lows really impressed me for an amp its size. Nicely made and intelligently designed, it’s a good option for rehearsal, and the aux input can work for solo gigs with backing tracks. The amp gets loud enough for coffeehouses, places of worship, and other small venues. For larger gigs with a band, I really wish it had a direct output because its front end would make a very nice preamp feeding a PA. But with a street price just under $360, the X4 Nanobass more than exceeds expectations.

acoustic guitar amplification essentials - everything you need to know about amplifying your acoustic guitar
Emile Menasché
Emile Menasché

Guitarist, composer, writer.

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