Most modern hardware boxes that emulate miked speaker cabinets are now based on a convolution engine that can run impulse responses (IRs). Some also include a dummy load so that they can be used in place of a regular speaker cabinet, while others, like the TC Impulse, are designed to accept the output from a preamp, amp modeller or amplifier line‑output jack. The Impulse pedal can store up to 99 impulse responses and comes ready loaded with some excellent IRs from Celestion’s collection.
The same size as TC’s Hall Of Fame Mini, the Impulse has a footswitch that can be configured either as a bypass or as an A/B switch, in which case it toggles between two IRs. A 9V power source is required. A single Level knob offers a boost of up to +10dB and this is flanked by two buttons used to navigate up or down through the presets, which are displayed on a scrolling LED readout. Press both to access the global EQ page, for which the two buttons select a high‑ or low‑shelving EQ stage (100Hz and 10kHz, respectively), and the Volume knob adjusts the amount of cut or boost.
As shipped, there are 25 IRs already loaded on the pedal, but you can easily add your own. It’s drag‑and‑drop simple too, thanks to a USB connection that communicates with a Mac or Windows machine running the free TC IR organiser software. You can also drag any of the IRs to a new position in the list. User IRs can be WAV files up to 200ms long, in 12, 16 or 32‑bit (including 32‑bit float) resolutions and with sample rates of 44.1, 48 or 96 kHz. If longer than 200ms, the IRs are faded to length automatically. A USB cable is included with the pedal, and you don’t have to worry about messing things up, as there’s a handy factory reset option.
The first 12 included presets are speaker cabinet responses by Celestion, ranging from small single‑speaker affairs to 4x12s, and they include many familiar faces. The next eight presets combine speaker IRs with a specific amplifier’s tonal voicing, so you can get perfectly usable DI’d results by feeding the Impulse directly from a drive pedal. Finally, five of the presets are designed specifically to shape the tonality of a DI’d acoustic guitar that’s fitted with a piezo pickup. The sound quality generally is clean and quiet, and the cab IRs are every bit as good as we’ve come to expect from Celestion.
I quickly achieved some very workable recorded guitar sounds by feeding it the output from my OCD overdrive pedal.
If you already have an IR‑based plug‑in and need speaker emulation only for recording, then you might not consider the Impulse to be a studio essential. But I quickly achieved some very workable recorded guitar sounds by feeding it the output from my OCD overdrive pedal, before adding just a little ambience reverb in my DAW. In the live arena, the Impulse could turn a non‑emulated preamp out signal into a fully conditioned PA feed, and even if it’s not part of your primary rig having one in your bag could be a life‑saver if your amp packs up; you can feed it from your pedalboard and run directly into the PA or a spare powered floor wedge. All in all, then, this is a very impressive piece of kit that is as simple to use as it is diminutive.