Inside the DigiTech RP150: guitar cabinets

The DigiTech RP150/RP155 family have been discontinued a long time ago and have been replaced by the RP360 and RP360XP, which have much better cabinet modelling.

Last updated: Nov. 14, 2016

The cabinet (or cabinet simulator) has a great effect on the overall tone. Unfortunately, only a few of the cabinets in the DigiTech RP150 are really usable - even with additional EQ. By measuring them (and measuring the equalizer section too) we are able to set more realistic guitar cabinets.

DigiTech RP150 printed circuit board

Here are some frequency plots of the cabinet simulator section of the DigiTech RP150. Note: this is not a complete list, there are 12 cabinets in the RP150, but these are the most usable ones.

The Twin 2x12 (Fender Twin Reverb) needs +3...+5dB mid boost at 1300 Hz. The answer is hidden in the frequency graph below.

DigiTech RP150 Twin 2x12 frequency response
Twin 2x12

To my ears the British 4x12 and Vintage 4x12 sound too "boxy". The midrange hump is smaller (and quite different) in the close miked response of a real 4x12 guitar cabinet.

frequency response of DigiTech RP150 Vintage 4x12 cabinet
Vintage 4x12

The DigiTech Alt 4x12 is much better than the Vintage 4x12 or British 4x12 models. It is much closer to an original miked 4x12 guitar cabinet with Celestion V30 guitar speakers than the Vintage 4x12. I like to boost the midrange at 500 Hz with 2-3 dB because the dip at 500 Hz is quite annoying.

DigiTech Alt 4x12 cabinet frequency response
DigiTech Alt 4x12

Another cabinet simulation that I've found useful is the DigiTech Metal 4x12. Very bright, nice for clean tones and if it sounds too "ear cutting" then just cut some treble at 2000Hz with the EQ (~ 4 dB). Another option is boosting the mid at 900 Hz with 3 dB and boosting the bass with 3-6 dB.

DigiTech Metal 4x12 cabinet frequency response
DigiTech Metal 4x12

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