ISP Theta Combo(2)

This amp is a secret weapon right out of a Cold War espionage novel. Its stark and imposing frame is as terrifying as any hammer against capitalism the KGB could construct during the Khrushchev reign.
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It’s also armed with more firepower than a Russian MiG-17, and it wants to crush all bourgeois cretins who believe great tone only comes from tube amps. The official, unclassified name of this solid-state, 400-watt beastie is the Theta Combo ($1,800 retail/ $1,620 street), and it includes two channels (Clean and Distort), two preamp stages (one each for the distortion and clean channel; they cannot be stacked as a dual-preamp signal chain), sweepable midrange controls, an onboard Decimator noise-reduction system, digital reverb, an effects loops with a dedicated volume control, a Solo Level that delivers up to 6dB of boost, a foot controller, and, believe it or not, a 12" large-excursion neodymium woofer that is, for all intents and purposes, a subwoofer. Every element of the Theta collaborates to give guitarists an amp that can produce anything from crystalline clean sounds to searing metal distortion to bass fusillades that would frighten a rhino into charging for cover. Plug into this multi-purpose combo, and you’ll be so busy crafting cool sounds that you won’t care whether solid-state circuitry, tubes, or digital models are under the hood. There’s a lot to discover here.

But First a Bit About the Box…

While the Soviet references above are obviously whimsical, the Theta is not a modern-looking amp, nor is it retro in a hip way. It’s big, boxy, and heavy enough to elicit pained grunts from musicians whose frames are more Woody Allen than Arnold Schwarzenegger. Given the Theta’s 70-lb weight, its rubber handle is an uncomfortable lift-assist, and adding casters will require some customization, as the amp’s bottom panel is not pre-drilled for wheel assemblies. The amp’s back-panel access is through a recessed shelf that requires you to reach in about five inches to connect jacks. Plugging in 1/4" cables (as well as the XLR for the direct out) is a breeze, but the clearance is a bit tight for turning the locking screws on the 15-pin D-Sub connector for the foot con-troller cable.

On the plus side, you could fire a mortar shell at the Theta, and it wouldn’t even sniffle. Like Iron Man, this behemoth has a near-indestructible, armor-style shield—actually, 13-ply Baltic birch covered with the tough paint you often find on truck beds—that will likely parry away tour hardships, stage mishaps, and road disasters as if they were runt gnats. Choosing a Theta Combo as your amp of choice is kind of like buying a macaw as a pet—both companions will likely be around for a long, long time.

Now For Those Sounds…

So, unless you’re a battle-toughened gigger with chiseled strength from lugging half-stacks up fire escapes, the Theta Combo is going to be a teensy bit of a challenge to schlep to shows, studio sessions, and rehearsals. But here’s the big reward you get for your sweat: a fabulously versatile tone machine that not only produces a vast array of clean and distorted sounds, but also unique and weird timbres, as well as deep, rumbling lows that can rattle your bones (and flap your pants) like a movie theater THX system.

To get the best out of the Theta, you need to have the foot controller active to access both preamp stages, the solo boost, the effects loop on/off, and the reverb. (All other parameters can be tweaked from the front panel.) You’ll definitely need Preamp 1 online when playing through the Clean channel, as that channel doesn’t have the added front-panel Gain knob of the Distort channel, and the clean volume can be a tad anemic as a result. For example, I ran the Theta sans foot controller for a rehearsal (I was lazy), and when using the Clean channel for some jangly parts, I got my butt kicked by a 20-watt, 1x12 Ampeg J-20.

With the foot controller and preamps ready to rock, you get two sweepable midrange stages per channel that provide all the incisive tone-sculpting power of a big-studio recording console. Sweep offers a selectable center frequency between 300Hz (the chunky low-mid area) and 6kHz (the sting and kerrang area), and Mid provides 12dB of boost or cut for the selected frequency. Although the Sweep frequencies aren’t marked (as on a console channel strip), it’s easy enough to twist the knob, and then work the Mid boost/cut to hear how your sound changes. I was able to dial in some “awful-but-good,” White Stripes-style tones by boosting hollow-sounding mids, cutting all the low mids, and boosting Bass and Treble to taste. Of course, it was also a breeze crafting warm and fat—and more conventional—distorted tones by boosting some low mids and punchy mids in the 1kHz to 3kHz range. The sweepable mids make it possible to access a ton of colors—even before you start messing with the Bass, Treble, and Presence (Clean channel only) knobs. The other surprise is what having two Bass knobs (preamp and channel sections) and a dedicated woofer can do for your low end. There’s so much bass on tap that you could possibly knock the earth off its axis, so be careful. The EQ options and onboard woofer make the Theta a multi-instrumentalist’s dream rig, as it can accommodate players who switch between 6- and 7-string guitars, baritones, basses, and even keyboards during their stage shows.

Some gain and EQ settings can get pretty noisy, and the onboard Decimator noise-reduction circuit does a nice job at diminishing hum, buzz, and hiss. It’s a “turn- until-you-dig-it” control with no marked settings, but your ears won’t do you wrong. My only beef is that it can cause decays to stutter if used aggressively.

Roar and Rumble

The Theta Combo is loud enough to rock about any gig, and its tonal options are impressive at any volume. At $1,620 street, it’s keeping company with some other versatile tube and modeling amps, but only the Theta puts a woofer into the combo package. If you dig a rig that can produce everything from lo-fi spittle to the rumbles of a 7.5 earthquake, this big ol’ box may be your boy.

Decimator G-String

If you’re intrigued by the Theta’s onboard Decimator noise reduction, but already love your current amp rig, you can check out the Decimator G-String pedal ($224 retail). Unlike the Decimator control on the Theta, the G-String does list threshold ranges (+10dB, 0dB, and -10dB to -70dB), although you should still use your ears to dial in the best results. The G-String’s Time Vector Processing tracks your signal, and uses downward expansion to diminish the noise floor without producing artifacts when you go from clean to dirty sounds. It’s a neat trick, and it means you don’t have to worry about clicking the pedal on and off because you set the threshold too high for one patch as opposed to another. The G-String is definitely a cagey pedal that reduces audible hum, sizzle, and hiss without significantly coloring your tone. In most high-gain situations, it will knock down noise to silence, and only for uber-distorted sounds did a little audible hiss sneak through. Stuttering on decays is minimal, but it will happen if you set the threshold too high. This is a great pedal for those who detest noise, and want to bring “studio clean” sounds to the live stage.