Koch Powertone II

Koch amplifiers have been steadily gaining in popularity here and abroad, which isn’t surprising considering the quality, features, and performance of these Dutch-made tube amps.
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The newest model to roll out of Koch’s factory in Amersfoort, Netherlands, is the Powertone II, a three-channel amp designed to deliver tones ranging from super clean to insanely distorted. Besides using five tube stages in its Ultra-Gain channel to create additional distortion and compression, the preamp features a Bright Clean input that’s specifically intended for humbuckers. It incorporates a –6dB pad to improve headroom, as well as an active filter that provides a slight boost at 3kHz, primarily to compensate for guitar cable losses. Worth noting is that the Bright Clean circuitry only affects the Clean channel and is automatically bypassed when you switch to the Gain or Ultra-Gain channels.

A study of the front panel shows a Clean channel section with Volume, Bass, Mid, and Treble controls; a Gain channel section with Gain, Volume, Ultra-Gain, Volume, Presence, Bass, Mid, and Treble knobs; and a Master section with Rhythm Volume and Solo Volume controls. Accompanying the Power and Standby switches is a Speaker Damping switch with Low, High, and Ultra-Low settings.

On the rear panel resides a Channel Select switch, a multi-pin jack for the included 5-button footswitch (which has a screw-on connector), dual sets of jacks for the parallel and series effects loops, a Reverb/FX Mix knob, the speaker jacks (two 4ž, two 8ž, and one 16ž), and a q" Recording out. There’s no means of the adjusting the effect loop send or return levels, but both effects loops operate on a –10dBV signal level in order to be compatible with instrument- and line-level effects devices (i.e. stompboxes/floor processors or rack units). The birch-ply cabinet is covered neatly in black Tolex, and it houses a steel chassis that’s clad with thin aluminum panels on the front and back. Inside the chassis we find a clean, rugged PCB layout, ceramic tube sockets, and a special anti-vibration mounting plate for three of the 12AX7s to help prevent microphonic feedback.


Using a new Evidence Siren speaker cable, I connected the Powertone II to a Koch TS412SL slant-front 4x12 cabinet loaded with Koch VG12-90 speakers ($1,475 retail/street price N/A). After plugging in the included 5-button footswitch (which has three switches for channel selection, a Reverb/Effects Loop on/off switch, and a Rhythm/Solo switch) I grabbed a Gibson ’68 reissue Les Paul, a Fender Strat, and a PRS McCarty and got down to business.

The Powertone II’s Clean channel has a good deal of headroom, and with the Volume at 3, the Rhythm Volume on 10, and the tone knobs all parked at around 5, the tones were crisp and sparkling with a somewhat hi-fi sense of balance, clarity, and presence. Nudging the Volume closer to the halfway mark initiated some grind with the Les Paul and also required an immediate twist of the Rhythm Volume to tame the loudness. With the Volume control turned past the halfway point, the amp produced progressively grindier textures that worked nicely for bluesier tones and cleaned up well when I turned down my guitar. Perfect for this channel, the spring reverb sounds nice and dimensional and delivers great surf-style textures at higher settings.

Activating the Gain channel gives you an immediate appreciation for the Powertone II’s distortion capabilities. The grind comes on gently enough at low Gain settings and just keeps getting ballsier and more sustaining as you turn it up. Humbuckers and single-coils sounded equally cool through this channel, and the EQ is well voiced and flexible. With every guitar I used, it was easy to elicit just the right level of harmonically saturated grind for searing blues, hard rock, or classic metal.

If the Powertone II had just these two channels it would be a happening amp, but courtesy of its Ultra-Gain channel (which adds an extra tube stage for a grand total of five), the amp can attain breathtaking levels of overdrive. Acting like an extension of the Gain channel, Ultra-Gain shifts you seamlessly into stratospheric sustain without any heavy voicing changes. Yes, you’ll likely notice more compression and less dynamic headroom when using the Ultra-Gain channel, but here’s where the Solo Volume function comes in handy, as you can preset a footswitchable loudness boost that will enable you to stand out clearly in the mix.

The fact that the Gain and Ultra-Gain channels share a common set of tone controls might seem like a limiting factor, and in a sense it is, but being able to toggle between a heavy crunch tone on the Gain channel and a ridiculously overdriven sound in Ultra-Gain mode without having to do any tone-control tweaks is kind of refreshing. Anyone who has ever struggled with myriad switches and knobs trying to find their tone in the middle of a gig will likely appreciate the Powertone’s relatively Spartan tone-control options.

One cool feature that has nothing to do with EQ is the Speaker Damping switch, which basically lets you obtain the right dynamic feel for your style and the volume you typically play at. Damping refers to the degree of control that the power amp has over the cone motion of the speakers, and with the switch set to Ultra Low, the amp sounds looser and more in-your-face. Conversely, the High setting provides the tightest low-end response, which is cool for metal as well as other styles that demand a snappier, more aggressive attack.

Power Hungry

The Powertone II is a smartly configured amp that completely takes the angst out of getting great clean and overdriven tones. By not going out of its way to duplicate the voicings of other well-known amplifiers, Koch has forged a sound that—as with amps made by Bogner, Diezel, and Soldano—doesn’t necessarily make you think Marshall, Fender, or anything else for that matter. What the Powertone II accomplishes so easily is a broad spectrum of tones that sound great for blues, rock, or metal. And whether you’ve just started performing or are a seasoned vet looking for a loud and expressive amp that can complement whatever your bandmate is using, you’ll likely find the Powertone II an excellent choice.