How To Get A Katana To Sound Almost Like A Valve Amp

(Ingredients: a BOSS Katana, an EQ pedal or EQ effect in a digital effects board, guitar of your choice. Has been tested with humbuckers, not yet with single-coils.)

Valve amps have that sound. It pops and snaps, it's clean and clear and as crisp as fresh winter frost.

Which is no-one's description of the sound of a BOSS Katana.

Well, I'm here to tell you how to make a Katana sound like a valve amp. Nearly

Plug the guitar (or the end of your pedal chain or your DED) into the POWER AMP IN socket on the back of the Katana. This by-passes all the pre-amp and effects and sends the signal straight to the power-amp. The only controls that affect the sound are the power selector and the MASTER volume control. Put the power selector to 25W and the MASTER volume at 12:00. Alter to taste later - according to how much oomph your pickups provide.

Turn the guitar volume and tone pots to 7 or so. (On my 549 SE, the lower the volume pots are set, the less audible the effect of coil-splitting, tone-adjustment, and distortion effects from the HX Effects.)

Strike a note.

It should be whoa, that was sudden, or something similar. Tweak the volume on the amp to make it more neighbour-friendly (but not so much the sound hides away in the speakers. I find that happens before 10:00 on the dial.) And it should also be a soft around the edges of the notes.

On the 10-band EQ control, add at least 10dB to the 1kHz, 2kHz, 4KHz and 8kHz bands. (Unless you are a bat or a teenager, you will not hear the 16kHz stuff, but change that if you want). I find the 2kHz and 4kHz bands are better at +12.5dB, but your ears may vary.

Strike a note. Neck pick-up.

Sounds a whole lot more like a valve amp now.

Why?

The frequency response curve of a 12-inch Celestion Gold (available on the Celestion website), the kind of speaker used in valve amps, is

 (All their speakers have a broadly similar curve. Actually, so do all guitar speakers.) 

It comes on song around G on the low E-string, is reasonably consistent all the up to the 18th fret of the high E-string, and then has strong(er) area between 2kHz and 5kHz, after which the response drops off a cliff. 

Guitars produce a trail of harmonics, many less than 10 dB down from the base frequency. Reproducing the sound of a guitar properly means making sure those harmonics are amplified equally. Up to 5kHz, the Celestion Gold is giving good treatment to the first, second and third harmonics of all the notes on the guitar, and to at least the fourth harmonics of notes below middle-C (concert pitch - 2nd string 1st fret) - except for the harmonics between and 1kHz - 1.8kHz, where it's a bit soft.

The Katana speaker is not a Celestion. BOSS say it was designed to match the amplifier. My guess is that the Katana speaker remains flat up to 2kHz and then drops about 10dB - 15dB to 5kHz, when it too drops off a cliff, as all guitar speakers will. (Google can't find anything under various variations on "Katana speaker response curve", so BOSS will have to live with my speculations.)

To correct for that slump between 2kHz and 5kHz, we need to boost the frequencies in that range, which is what my suggestion does.

Give it a whirl.

Just not on the bridge pick-up. It's a pleasant sound on the neck, or in the middle position. But bridge down the low frets... twangy and nasal. But that's bridge pickups for you.