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Supro 1685RT Neptune Reverb Review

Supro teams with SIR to create a unique and potent backline workhorse.

Supro’s 2014 re-launch signaled a welcome return for a most revered amp brand. Players voiced their approval by snatching up both vintage-reissue, re-imagined, and entirely new models to take on tour and into the studio. The new 1685RT Neptune Reverb falls somewhere between the vintage and retro camps. It’s not a re-creation of any specific vintage Supro model (all of which were originally manufactured for the brand by Valco of Chicago). And it was designed—with input from backline rental company SIR—to deliver the same utility as standard-bearing backline amps like the Fender Twin Reverb and blackface Deluxe, and the Vox AC30.

Valco Decoder
Though Supro clearly put the Twin Reverb and AC30 in its sights designing the Neptune, it is easily differentiated from those classics by a lower, 25-watt power rating and the use of 6973 output tubes, which have a very distinctive voice and should help distinguish the Neptune from any rival, British or American. Those two factors should not be deterrents to the curious.

It takes very little effort to summon juicy, pleasing tones.

The 6973-driven tone is a big part of what made Supro so well loved in the first place, and 25 watts through two 75-watt, 12" speakers is plenty loud for most sound re-enforced stages these days.

But before you even consider what’s inside or on the control panel, there’s a good chance you’ll fall in love with the scrumptious look of this thing. Supro has sourced gorgeous re-creations of the blue-gray “rhino hide” vinyl covering and silver-and-black grille cloth of old, and up close and in person the Neptune Reverb is just short of stunning. Controls include a single volume with treble and bass pots in the tone stage.

There’s also a single control for adjusting the depth of the spring reverb signal, as well as speed and depth controls for the tremolo. Both effects are tube driven. The reverb uses a 17”, four-spring tank. Rectification is solid-state. The preamp, meanwhile is driven by four 12AX7s and one 12AT7 tube.

With the two British-voiced BD12 speakers, the combo weighs in at 54 pounds—not too heavy for a 2x12. Inside, components are laid out on two printed circuit boards. The tube sockets are also mounted to the PCBs. Replacing the tubes might be challenging for less experienced home amp mechanics, since it’s tricky to line up pins with sockets that are seated a good inch down inside the chassis walls. But it’s doable if you take care. It’s worth noting that while the 6973 output tubes look somewhat like fatter EL84s and use the same 9-pin sockets, they sound almost nothing like those British bottles. They’re more powerful and capable of handling higher voltages—which is why 25 watts from this cathode-biased design suffices. They also have a firm, punchy voice with appealingly thick and meaty midrange—all qualities that forged the good reputation of vintage Supros.


Characteristically meaty, punchy Supro tone with good dynamics and excellent reverb and tremolo. Appealing retro styling.

Reverb/tremolo footswitch must be purchased separately. Tubes might be tricky for some players to replace by themselves.


Ease of Use:




Supro 1685RT Neptune Reverb

Dazed and Abused
Even before I plugged in a Les Paul, a Telecaster, and a Heatley Parisienne equipped with vintage ’59 P-90s, I noted what a pleasure it was to explore such a simple amp. The 1685RT Neptune Reverb’s straightforward interface is extremely refreshing in this day of overdrive-channel this and voicing-switch that. And it takes very little effort to summon juicy, pleasing tones. You really can’t go wrong with the Neptune’s core sounds, which feature taut-yet-textured clean tones up to about 11 o’clock on the volume (depending on guitar and pickup), beefy edge-of-breakup from noon to about 2 o’clock, and thick vintage-voiced overdrive after that.

Players who feel they need more bells and whistles in an amp might not even get this far before bailing out. But they’ll miss out on the beautiful essence of unadulterated Supro tone. It’s easier to hear in the Neptune with the volume around noon. It’s thick, grindy—just a bit raw and gritty—yet still articulate and punchy. It’s very dynamic, too. And it’s a great voice for distinguishing yourself from more familiar classic-rock, blues, rock ’n’ roll, punk, or alt-rock tones.

You’d expect a backline amp to be agreeable with pedals, and the Neptune was very accommodating to varied sources of pedal drive. It sounded great with a Gurus Sexydrive MkII, an Xotic BB Preamp, and a Marshall-voiced JHS Angry Charlie distortion, and the ease with which the amp adapts to these voices enhances its versatility to no end. That said, I loved this amp with a guitar and nothing else.

The reverb sounds excellent and has a nice, useful taper before going completely splashy. I might have enjoyed a tad more speed from the tremolo now and then, but it has great range, and the output-bias-modulated circuit sounds great.

The Verdict
Did Supro build the ultimate backline amp in the form of the Neptune Reverb? Well, it isn’t as loud as a Fender Twin or Vox AC30. But most players will love the fact that it hits its sweet spots at much more tolerable volume levels. The 1685RT Neptune Reverb is a cool amp with an appealing simplicity and a great alternative voice. And while it’s assembled with PCBs, it is still very well put together. The Supro team has done an admirable job of keeping this American-made amp at a fair price. It has styling to die for coupled with infectious and dynamic tones that will help you stand out from the crowd—all of which counts for a lot these days.

Watch the Review Demo: