Blackstar Sonnet 60 review

As a live sound engineer I’ve encountered and used all sorts of amplification systems for acoustic instruments, from powered PA speakers to Roland keyboard amps to various dedicated ‘acoustic’ amplifiers. When I first started out in the early 2000s these usually resembled electric guitar amplifiers, but with fullrange drivers, perhaps a tweeter or two and a control panel that included a microphone input. Typical of these was the Marshall AS50D, which was good and loud but definitely on the heavy side at 16 kilos/35 pounds. As time has gone by, live sound equipment and instrument amplifiers have both become more compact and lighter in weight, and in May 2022 I decided to purchase a Blackstar Sonnet 60 to see what the state of the art was.

Coming from old-school acoustic amps, a couple of things that impressed me from the outset were the size (345mm wide x 310mm high x 250mm deep, or roughly a 1-foot cube) and the weight of 7.7 kilos/16.9 lbs. This was significantly less than the 10.5 kilos/23.1 lbs of the Boss Acoustic Singer pro, another amp I was considering. When you are carrying guitar, microphone stand, cables, power extension etc every kilo makes a difference, especially in Singapore, where load-ins often involve stairs and narrow doorways.

I also compared the Sonnet 60 to my Bose S1 Pro, which up to that point been my primary acoustic amplification system. Bose are known for a very processed approach to sound reinforcement, with their ToneMatch presets and also the degree of processing applied to their loudspeaker systems. The Blackstar by contrast is quite straightforward, relying more on cabinet voicing and traditional EQ controls to get a good sound – more on those later. It is also a thoroughly modern amplifier, having Bluetooth, USB and stereo 3.5mm connectivity in addition to the 1/4″ and XLR top panel inputs.

Having used this amp for about ten months now, here are some of my thoughts:

The sound: This amp has a LOT of low end, more than any equivalent acoustic amp I have ever used or heard. Blackstar do not give any frequency-response specifications, but the fact that the High Pass Filter has a range of 27 to 175Hz suggests that the amp goes down well into subwoofer territory. In use the amp’s bottom end is undeniable which makes it great for playing recorded music as well as the percussive playing style adopted by musicians such as Jon Gomm, who co-designed the Sonnet series. The cabinet uses a side-ported design, which I remember fondly from my days of owning an Acme Low B1 bass cabinet. The tradeoff is that the amp sounds, in my opinion, just slightly lacking in the high midrange, which has a noticeable but not unpleasant effect on music playback. On the other hand, drum machines and other percussive low frequency sources sound awesome through this combo – I will sometimes run the output of my drum machine into the minijack input in the back panel, enabling me to have drums, guitar and vocals all running through the same amp.

The channel EQ on the Sonnet 60 is very musical indeed. On paper, they are Low: +/-10dB @ 80Hz, Mid: +/-10dB @ 700Hz and High: +/-10dB @ 10kHz. Blackstar do not give any additional technical details, but we can assume a shelving low and high and a peaking mid. 700Hz is a good choice for the single midrange control in this context, allowing the user to reduce the quack of a typical under-saddle piezo pickup or give more body to the sound of other pickup types. Most notably, I have found that this particular EQ works very well with my Taylor GTe Urban Ash (pictured above) with the ES-2 pickup system. This pickup/preamp combination is somewhat notorious for being overly bright-sounding and to my ear is rather lacking in midrange, quite ironic considering that it is a piezo system! Boosting the midrange on the amp improves the plugged-in sound of this guitar considerably. Combined with a slight HF cut on the guitar this gives a very usable sound, to my ears anyway. On the Sonnet 60 the 2nd channel omits the MID control, which I do not consider a major loss. Also of note is the very positive center detent on the main EQ knobs, which makes it extremely easy to find the flat position by feel.

The shape circuit on the two channels is identical: +3dB @ 120Hz, -7dB @ 1kHz and +3dB @ 10kHz. At the risk of stating the obvious, it’s good that Blackstar chose different frequencies to those used by the channel EQ knobs! I think the trick here is to use this switch on just one of the channels, helping the inputs work together. For example, if you have both a microphone and a pickup on the same instrument, engaging the switch on the mic channel can help the midrange of the pickup to come through, or vice versa. I find that using it on a vocal mic tends to cause low-mid feedback and 1kHz is typically not a frequency you want to be cutting on your vocals! The fact that the 80Hz LOW EQ is well below 120Hz means that you can use both together to create a ‘bump’ at 120Hz whilst still attenuating the lower frequencies, much as you would combine a high pass filter and a peaking low band EQ on a mixing console. Good thinking Blackstar!

A must-mention are the global high pass filter and brilliance knobs, located just below the master knob. The former applies a 6dB (per octave? Blackstar don’t say) high pass/low cut filter to the entire amp, variable from 27Hz to 175Hz. This allows you to precisely tune the boom and thump to your particular needs, and I find myself running it around the 10 o’clock position most of the time. The latter is +/-12dB @ 16kHz, a frankly nearly ultrasonic frequency (many adults cannot hear a 16kHz test tone) that reminds me of the old AIR control found on some Mackie consoles. This allows you to darken or brighten the sound to taste – just bear in mind that this is a very VERY high frequency. Some reviewers have commented that these controls are too small and hard to adjust, but I suspect this was precisely the design intention – adjust them when you are setting up the amp and then leave them be until your inputs change. But yes they are small, round and prefer to be left alone.

Other points of interest that do not warrant their own paragraph:

• Only the two main channels go to the XLR line out, which Blackstar call the MIX D.I. OUTPUT, the Bluetooth, USB and 3.5mm line in do not. This allows for some creative setups: for example you can monitor a drum machine or click track through the amp without having it go to your sound engineer whilst sending him your guitar signal via the DI, something that could be useful both live and when recording. This output is also pre-master volume, which means that you can turn the amp’s internal speaker off and still use the XLR for recording or silent practice via an external headphone amplifier. As an added bonus, it is both post-EQ and post-effects: combine it with a separate DI box placed before the amplifier to get both a pre- and post-EQ send to your sound guy.
• The footswitch input is a quarter-inch tip-ring-sleeve connector that will accept any two-button latching footswitch. I use an old Marshall footswitch that I bought for my AS50D, some irony there. Left button mutes the two main channels (NOT the Bluetooth, USB and 3.5mm inputs – means you can mute the guitar/mic and still play break music) and the right button turns the reverb on and off. Again, very sensible, logical and real-world features here. Being able to mute the inputs without losing their relative knob positions is SO helpful in the real world.
• The side of the cabinet opposite the port is completely flat and square with the bottom of the amp, which means that the unit can be placed on its side (I would use some sort of no-slip pad) to give better access to the knobs in certain situations, say if the amp is placed on a bar top or a high table.
• The amp has an excellent handle and balances very well in hand.
• I love the fact that this amp has a steel speaker grille, unlike the flimsy grillecloth used on almost all of the competition.
• The amp feels solid and well made. It is not excessively heavy but has some heft to it which inspires confidence.
• Padded covers for this amp are available from Hot Covers in the UK, with or without the Blackstar logo. Tell Mr Hotchkiss that Bruno in Singapore sent ‘ya.

Other aspects of this amp which I feel work as advertised include the phase (actually polarity) switch, tilt-back stand, ‘dynamics control processing’ and reverb.

At time of writing I’m very happy with the Sonnet 60. I feel that it offers a real sonic alternative to both existing acoustic amps as well as fullrange PA speakers. It has a distinctively dark, smooth and mellow voice thanks to the extended bass response coupled with the use of a soft dome tweeter rather than a compression driver. It is therefore not the most high fidelity acoustic amp available, but sometimes that is a good thing. Add to that a very reasonable street price of US$300 at time of writing and this is definitely something worth considering.

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