Ashdown Rootmaster RM-220H Bass Amp Head

The RM-220 is a "fabrique en chine" solid state bass amp head that puts out a healthy 220W at 4ohms. Ashdown describes it as being compact, reliable, and "loaded with tone-shaping power and flexible features." Having used this head (paired with an Ashdown RM-MAG-115 cab) with Kuantan's River Blues Band onstage for over a year, I wholeheartedly agree. Now, let's take a closer look at some of the RM-220's features and specs.

Front Panel
Input Jack:  single low noise/high impedance, adequate headroom for active basses
Input Control:  sets the signal level through the preamp section in conjunction with the Input Level VU Meter  
Shape Button:  when activated, provides +8bd boost at 50hz and +10db boost at 10khz
EQ Button:  defeats/activates the Bass, 240Hz, Middle, 1K5Hz and Treble controls
Compression Button: defeats/activates compression
Compression Control:  adjusts the degree of compression
Drive Button:  defeats/activates the amp's "tube-emulated overdrive" feature
Drive Control:  adjusts the gain from "warm overdrive through to distorted filth"  
Sub Control:  footswitch activated, adds a sub-octave to the "notes being played"
Output Control:  controls the overall level of the amplifier
Line Mix Control:    adjusts the signal from a connected external sound source
Bass EQ Control:  +/- 15db @ 100hz
240Hz EQ Control:  +/- 15db @ 340hz
Middle EQ Control:  +/- 15db @ 660hz
1K5Hz EQ Control:  +/- 15db @ 1.6Khz
Treble EQ Control:  +/- 15db @ 7khz (shelving)

Back Panel Sockets
FS-2 Out:  optional footswitch for activating/deactivating drive and sub harmonics
FX Send/Return:  post-EQ serial effects loop
Line In:  input from CD/mp3 player/drum machine/external sound source
Speaker Out:  combined jack/Speakon socket (minimum 4ohm load)
DI Out:  XLR, post effects/EQ

References
RM-220 Legacy Head - Ashdown Engineering
Ashdown Engineering User Manual

YouTube Videos
Premier Guitar
GAK Vision
TVjamsession

Pics