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Sonic Farm Tantra

Valve Bass Preamp/Amplifier
Published October 2017
By Phil Ward

Sonic Farm Tantra

Sonic Farm’s latest creation is a processor and amplifier designed to cater for every possible bass guitar recording scenario.

Sonic Farm seem to achieve a rare combination of engaging idiosyncrasy and professional competence: they specialise in gear that goes a little off-piste while still doing the basics to a very high standard. Their Tantra bass preamp, which is my review subject here, is very much true to form, and is unlike any bass amp I’ve used before.

Concept & Control

The review model of the Tantra consists of a valve-based preamp and comprehensive EQ, followed by a Class-D power amp (500W into 8Ω or 1100W into 4Ω). This power-amp stage is optional, though, and Sonic Farm describe the Tantra as a preamp. Indeed, the most interesting aspect of the Tantra is that the preamp stage has been designed to offer enormous opportunities to sculpt the sound of an electric bass instrument, before you even start to think about the EQ; it’s hugely flexible and configurable in terms of its overdrive, distortion and compression behaviour.

Before I get on to describing the specifics of the Tantra, there was the small matter of a bass cab to test it with. Sonic Farm kindly supplied a Michael Arnopol Soundworks (MAS) Bodai-110 with the review unit. Michael was involved in the design of the Tantra, which is why his logo appears alongside Sonic Farm’s on the front panel. I felt that it would also be interesting to try the Tantra with a second cab which was a little more mainstream in terms of design, and Brighton’s Barefaced instrument cabinet and PA specialists generously loaned me one of their Big Baby II cabs. You can read more about both cabs in the ‘Cabinet Meeting’ box.

The first thing that struck me about the Tantra bass head was the sheer number of knobs and switches that adorn its front panel, and that their arrangement wasn’t immediately easy to understand. It didn’t help that I didn’t find the front-panel legends particularly easy to read and that, in a couple of cases, the printed switch legends didn’t intuitively tie in with the switch positions.

A clearer view of the Tantra’s controls.A clearer view of the Tantra’s controls.In rough left-to-right order, but with a few ups and downs thrown in, the amp offers a single high-impedance input, with gain-trim options that mean it should suit instrument output levels ranging from relatively quiet passive basses right up to the highest-output active instruments. Next is a variety of switches that configure the rear-panel DI output, in terms of the point in the internal signal flow at which the output is taken.

Next in line is a mute switch and 6dB attenuator. The mute is important, because some Tantra functional adjustments can result in healthy pops and clicks from the output, and the -6dB option is provided in order not to drive the effects send output too hard. Following the mute is the first of the Tantra’s switch options dedicated to sculpting tonal character. It’s fundamentally an LF shelving EQ, but part of its purpose is optionally to drive the preamp valve stages harder to change the tonal character of the overdriven sound. Speaking of the valve stages and overdrive, the heart of the Tantra preamp and its tonal versatility is a valve stage that can be configured in either pentode or triode mode. These alternative valve circuit topologies can be selected using yet another switch (and here’s where that mute switch is vital), and Sonic Farm say that the different overdrive and harmonic distortion profiles inherent to each results in distinctly different tonal characteristics.

A couple of knobs labelled H2 and H4 are also fundamental the to the Tantra’s distortion profile. H2 and H4 refer to second and fourth harmonics respectively, and winding the knobs around adds increasing levels of distortion to the preamp signal. Alongside the distortion knobs is a master volume control, below which is a clean gain control. These two knobs work in much the expected way, with the gain knob setting the clean preamp level and the master volume setting the output level to the power amp, but they are also fundamentally linked to the position of the single-knob compressor that’s just alongside, and the overdrive mix and gain controls that are a little further to the right. Perhaps more so than with any other instrument amp that I’ve come across, it’s vital to set the various gain, distortion and compression controls before turning up the master volume control to set your desired level. (A signal path schematic would have helped enormously in understanding the action of the amp controls — and Sonic Farm tell me they’ve now added a functional block diagram to the manual.)

Moving further to the right, the Tantra’s EQ comprises shelving bass and treble controls followed by three bands of variable-Q parametric control. The EQ section also incorporates switches providing a defeat option and three cutoff frequency options for a global high-pass filter. As with the input, distortion, overdrive and compression options, it’s hard to imagine a bassist needing further EQ possibilities.

And that’s just the front panel. Around the back, things are thankfully rather more simple in terms of facilities, but still pretty much every base (sorry) is covered. I can’t really imagine a gig situation in which anybody would need more in/out versatility. A nice touch, for example, is that there’s a mic-level DI output option to avoid the risk of overloading stage DI boxes and mic-level desk inputs. It’s a relief also that the power amp outputs are on Speakon sockets. It’s a complete mystery to me why anybody ever thought that jack plugs and sockets were a good idea for power-level connections, and it’s good to see the practice becoming a thing of the past on backline amps and cabs.

The rear-panel functionality is easy to understand thanks to good, clear labelling.The rear-panel functionality is easy to understand thanks to good, clear labelling.

Plugging In

There are three basses I regularly use at gigs: a 1983 Wal Custom fretless, an NS Design CR4 electric upright, and a home-built Fender-inspired four-string fretted passive bass, comprising an old Squier Tele bass neck and a custom-made Jaguar-style body.

The three basses used with the Tantra during the review tests.The three basses used with the Tantra during the review tests.I began with the Wal, initially with the Barefaced cab plugged in to the Tantra. Wal basses have a tonal identity all of their own that comes primarily from the pickup design and electronics. It’s a sound that emphasises mid-range and really helps the instrument cut through busy mixes on stage (it’s perhaps no surprise that Wal basses came to prominence in ’80s pop, when huge washes of analogue synth pad were the order of the day!). If an amp or cab doesn’t really suite a Wal, that mid-range emphasis can become overwhelming, leaving the bass sounding ‘nasal’ and cold. With the right amp and cab, though, the mid-range punch and rubbery warmth of a Wal, especially in fretless form, is addictive — and the combination of the Tantra and the Barefaced cab nailed it absolutely. The huge versatility of the Tantra’s overdrive, compression, EQ and distortion sculpting, for want of a better word, meant that the tonal possibilities were almost literally endless; and that was before I began to move away from my usual tonal settings on the bass.

As well as taking the Tantra and the cabs along to a band rehearsal, I’d organised a slot in a local studio, so that I could experiment with the Tantra and the cabs without wasting precious band time... and I began to run out of studio time before I’d even got halfway through all the sounds and subtle adjustments there were to discover!

Putting the Wal to one side, the results with my ‘Fender’ bass were equally inspiring — the Tantra really did seem to have every sound I could possibly want, and then some more that I didn’t know I wanted. The effect of the H2 and H4 knobs was particularly useful in giving what is a relatively warm-sounding passive bass some edge and character to its tone, without leaving it sounding thin.

Up to that point, I’d concentrated mostly on using just the Barefaced cab, but swapping to the Arnopol with the ‘Fender’ bass introduced a another palette of sounds. The Arnopol cab has more obvious character than the comparatively rounded and neutral Barefaced. It seems less extended in the low bass, although it’s still no slouch, and further up the spectrum, it has a distinct voice of its own. To my ears, it suited the combination of Tantra and either Wal or ‘Fender’ less well than the Barefaced cab — the extra character of the cab seemed just a step too far. But then I tried the Tantra/MAS combination with my NS electric upright bass (EUB) and was immediately back in addictive territory. No EUB, amp and cab can really hope accurately to reproduce the sound of an acoustic upright, and there’s always a possibility that the instrument ends up sounding like a big and slightly soft fretless bass. The best that can realistically be hoped for, I think, is something that conveys the character and idiosyncrasy of the instrument, rather than the genuine tone of the real thing. Together, the Tantra and Arnopol cab pulled off that trick with aplomb. There was character and idiosyncrasy beyond anything I’d heard the CR4 do before — especially, again, with the Tantra H2 and H4 controls in play, along with a dose of compression to emphasise the instrument’s transient thump. The result was a hugely seductive sound, full of warmth and power but also with a characterful and expressive mid-range honk that genuinely had something of a double bass about it.

A look inside the Tantra reveals a  neatly wired device that’s packed full of high-quality components. A look inside the Tantra reveals a neatly wired device that’s packed full of high-quality components. I had pretty much come to the end of my studio slot once I’d finished with the EUB, but I’d quite definitely learned enough about the Tantra to know that it is a really exceptional bass amp.

My only misgiving (which is significant for me, personally, but won’t be for everyone) is that the Tantra’s sheer complexity could prove daunting in a gig situation. I pictured myself turning around between songs to adjust the amp and bring my on-stage sound back to where I thought it was after the soundcheck. I glance at all those knobs and switches, in the semi-darkness, with the next song looming... and I don’t have a clue what to adjust! This complexity and the challenging learning curve mean that the Tantra won’t appeal to everyone. But to be fair to Sonic Farm, while a simplified and perhaps rationalised front panel could make the Tantra much more instantly gig-friendly, it would probably also make it rather more like all the other bass amps out there, and less like what we have here: a sophisticated device, whose combination of tonal versatility and idiosyncratic character along with great reserves of power are unlike pretty much anything else available.


The Tantra is the kind of product for which it’s almost impossible to write a conclusion. It offers so many possibilities that even though I used it in the house and in rehearsal studios for a good few weeks, I never really felt that I had discovered everything it had to offer, or fully understood all of its subtleties; it could do so many sounds. The other side of that coin is that on more than a couple of occasions I stood there, scratching my head, and wondered where the great sound I had half an hour ago had gone; I found it too easy to flick a switch or adjust a knob and be immediately confused. But if you’re brave enough or dedicated enough to learn this thing inside-out — and feel you can live with the Tantra’s complexity on stage — there’s much to love, and I really don’t think there’s anything else like it.

Cabinet Meeting

The MAS Bodai 110 cab.The MAS Bodai 110 cab.While the subject of this review is really the Tantra bass amp, it seems worth writing a little about the bass cabs I used with it.

As well as designing the bass cabinets that carry his name, Michael Arnopol ( is well known as a virtuoso upright bass player — listen to his work on albums by Patricia Barber, for example — so perhaps it’s no surprise that his cabinet should work so well with an electric upright bass.

The Bodai-110 cab is one of a slightly bewildering array of MAS products, each of which seems at first sight somewhat idiosyncratic. There’s a sort of home-spun look to the fit and finish of the Bodai cab, but in functional and performance terms I had few doubts about its abilities. It’s full of character, and if you like what the Bodai-110 does there are precious few alternatives.

The Barefaced Big Baby 2 cab.The Barefaced Big Baby 2 cab.Barefaced Bass (, like me, are based in Brighton, UK, and they’re the brainchild of Alex Claber. Alex, a bass player himself, was continually frustrated by heavy and often poorly performing bass cabs, so he turned his interest in speakers and his engineering degree into a business.

Barefaced have grown to become significant niche players in the bass cab and PA market, specialising in lightweight but immensely rigid cabinets fitted with custom-engineered neodymium magnet drivers. The Big Baby 2 model I was loaned is one of their most popular products, and comprises a single 12-inch driver combined with a horn-loaded compression driver in a 56cm x 45cm x 37cm ported enclosure. The whole system weighs only 13kg.

Tantric Recording

Sonic Farm manufacture a preamp-only version of the Tantra so, along with using the the review amp as intended in backline mode with a cab connected, I also spent some time using it as a recording instrument preamp — and, perhaps unsurprisingly, given that the preamp section of the amp does most of the work, it excelled in this role too.

Interestingly, though, it’s not just bass instruments that I could imagine using it with in the studio. Some of the warm and gently overdriven tones would work equally well with six-string guitars, and I suspect I’d end up trying it on pretty much all mono sources. I’ve even just wondered about using is as an insert on vocals — the Tantra may sound great on bass, but it is far too talented to be reserved for bass-amp duties alone!

Published October 2017