London Power’s MINI-MARSHMALLOW Dumble-style tube guitar preamp builds on the tone legacy of Alexander “Howard” Dumble’s famous topology, providing classic, warm, clean tones and an over-driven amp tone. Tubes create the entire sound, while solid-state circuitry provides a low-noise effects loop, dual outputs, DI and buffered Link for connection to other preamps.MINI-MARSHMALLOW Tube Guitar Preamp
• uses two of 12AX7 or any of 12AT7, 12AU7, 12AY7, 12AX7, ECC-81/-82/-83, or equivalent
• low-gain channel has 2 voicing switches
• high-gain channel has 2 voicing switches
• front-panel effects loop controls
• low-noise effects loop and output circuitry
• dual impedance-matched ground-compensated TRS 1/4″ outputs
• impedance-matched ground-compensated XLR for D.I. output
• front panel switches for channel and loop selection
• remote control via TRS jacks or DIN6
• regulated voltages
• 1U 3.4kg, 17″W x 1.7″H x 6.5″ D (plus tubes)
• 120V, 240V range switch
• rack-mountable with optional kit
MINI-MARSHMALLOW Dumble-style tube guitar preamp covers the range of pristine clean, warm clean, mild over-drive, to heavy over-drive that is smooth for jazz, blues or hard rock. Classic clean sounds and mild to heavy saturation are produced with low noise and excellent note articulation and sustain. The player can set the voicing and gain structure using the voicing switches and Drive and Level controls for each channel, and then easily switch between a Low-Gain sound and a High-Gain sound using the front-panel switch or remote control.
A shared EQ provides easy tone shaping, but each channel has its own “Rock/Jazz” switch and “mid-shift” switch. Set each channel as you wish and use Loud to make everything louder or quieter without altering the channel balance. Updated controls eliminate the need to set up the clean sound first, then set the over-drive sound: MINI-MARSHMALLOW gives new freedom to the player.
Download the MINI-MARSHMALLOW Operator Manual (118 kB PDF)
MINI-MARSHMALLOW has a full-feature effects loop that can handle line-level devices or pedals, as well as series or mixing modes. Front-panel Send and Return level controls combine with a rear-panel 20dB switch to accommodate any signal level, and any signal-handling capability of the external device. The loop is ground compensated and impedance matched to eliminate ground loops.MINI-MARSHMALLOW rear
MINI-MARSHMALLOW has two instrument input jacks, with the front panel jack over-riding the rear-panel jack. There is a buffered Link output to fan out the guitar signal to other preamps, tuner, etc. The buffered signal can be used to drive the tube stages if one wishes, by activation of the BF switch on the rear panel.
Dual main outputs allow many system connections, for use with multiple amplifiers or for split recording and monitoring. Each output has its own level control. The LP low-pass filter for the main outputs can be enabled for direct connection to a mixer or PA, or left ‘off’ to drive multiple guitar amps for a zoned stage. There is also a D.I. (direct injection) output that tracks the raw output after the effects loop. The main outputs use TRS 1/4″ jacks where the D.I. has an XLR. All outputs are impedance matched and ground compensated to eliminate ground loops between equipment.
All of MINI-MARSHMALLOW’s sounds and features can be accessed via front-panel switches. Standard 1-button and 2-button push-on/off foot switches can also be used for remote switching, connected by way of the TRS 1/4″ rear panel FSW jack. More sophisticated control is tied in via the DIN6 connector, matching London Power’s FS4-2W foot control (sold separately). FS4-2W provides direct-random access to either channel with or without the effects, so four system voices A,B,Ax,Bx; and it has 2-way communication: you can hit a switch on FS4-2W OR on MINI-MARSHMALLOW’s faceplate, and the LEDs on both will change along with the system status selected. Of course, one can use the DIN6 to link to other types of controller.
MINI-MARSHMALLOW incorporates all of London Power’s standard design and construction features:
• toroidal power transformers
• fusing for all transformer windings
• Galactic Grounding
• active hum filtering
• long-life capacitors
• low noise metal-film resistors
• metal-oxide and wire-wound power resistors
• zero wiring
• zero standby power when switched ‘off’
MINI-MARSHMALLOW can be rack mounted using the optional 1U6-BRKT, sold as pairs.