Valve Bass Amplification

BTA 400 400-watt Valve Bass Amp head

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BTA 400

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Handmade in our UK Custom Shop, the BTA-400 is a true contemporary bass masterpiece, for tonal connoisseurs who crave the traditional punch of valve amplification with the added flexibility of a modern preamp.

Combining the unmistakable tonal sophistication of our industry-standard ABM preamp with the sonic might of a fully-loaded 6x KT88 400W valve power amp, BTA400 is a stadium-ready powerhouse, currently rocking the world with players like Nate Mendel of the Foo Fighters.

All the ABM features are there – EQ In/Out footswitching, variable Tube/Solid-State input stages, on-board compressor, Sub-Harmonic Generator, balanced DI Output with Pre/Post EQ switching, FX loop, Tuner output and more....

Variable Valve Drive – from zero to rock hero

Whatever tonal character you're seeking, the valve drive control can take you there. Engage it and set on zero for a pristine solid state preamp tone, or wind it up to increase the level of true valve overdrive that gets blended into the signal, taking you from a hint of hair to a fat overdrive.

The Drive level be preset and kicked in and out via footswitch, providing access to a huge range of clean, warm and overdriven tones.

The best EQ in the business

Imagine the simplicity of a traditional 3-band EQ but with the flexibility of a graphic equaliser...that's what the acclaimed ABM preamp delivers, and that's why it's as popular with bass-purists as it is with modern tone-shifters.

Designed to be as simple to use as a 3-band EQ but offer outstanding tonal shaping options, the ABM EQ features familiar Bass, Middle and Treble rotary controls and two pairs of additional sliders.  

With the sliders set in the center position the three knobs function just like a classic 3-band EQ. But if you require more flexibility, the additional sliders allow you to fine tune the EQ in the regions the standard controls can't reach, providing a huge range of variation and allowing you to tailor the perfect sound for any gig.

The EQ can be switched in via footswitch taking you from a flat fretless sound to your favourite EQ setting instantly.

One knob compressor

Kick it in and this simple to use, great sounding compressor delivers a powerful, even sound, guaranteed to help your bass fill out any mix.

Sub-Harmonic Generator

Once heard – never forgotten. The ABM Sub-Harmonic generator adds an octave below the notes being played bringing fullness to any bass part. The Sub level is independently controllable, letting you dial in anything from a subtle hint of deep bass to a full-on subterranean funk.

Flexible Footswitching

Paired with our FS-4 footswitch (not included)  the ABM comes alive for onstage use, enabling on-the-fly tonal gearshifts. With footswitchable Valve Drive, Compression, EQ and Sub Harmonic Generator, ABM puts dozens of sound combinations at your feet, without so much as an effect pedal in sight.

Professional Connections

Not that you'd expect any less from any amp loaded with the ABM preamp section, BTA400 is loaded with connectivity. A Sub-Bass output to feed the desk or an additional amp, a tuner output, transparent FX loop and a Line Input for the connection of an external sampler or sound source. Output muting cuts the signal from the DI output but leaves the tuner output 'live', allowing the player to tune up in silence.

Classic Series cabs


Classic Series cabs have been developed to be the perfect partners to our range of valve heads, offering powerful performance and striking future-retro looks in 4x10”, 4x12”, 1x15”, 6x10” and 8x10” configurations.

Handmade in the UK from the finest Birch Ply Ashdown's Classic Series bass cabinets feature custom drivers, dual Speakon/jack connectors, horn control switch (4x10” only), heavy duty vinyl covering and vintage red grilles.

BTA 400 Specifications

Power Output 400 Watt
Power Handling 350 Watt Continuous
Power Requirement 115-230 Volts
Speaker Outputs 2 Ohm/ 4 Ohm/ 8 Ohm
Frequency Response -3dB @ 17Hz und 30kHz
High Instrument Input Impedance 3.9m Ohm, input range 150mV -
Low Instrument Input Impedance 10k Ohm, input range 300mV -
Line Input Impedance 22k Ohm, input level 0dBu nominal
Sub Output Impedance 1k Ohm, level 0dBu Nominal
DI Output 600 Ohm balanced, level 0dBu nominal
Tuner Output Impedanz 22k Ohm, level 0dBu nominal
Impedance Minimum impedance 2 Ohms
EQ Bass +/-15dB @ 45Hz Middle +/-15dB @ 660Hz Treble +/-15dB @ 7kHz shelving Slider 1 +/-15dB @ 180Hz Slider 2 +/-15dB @ 340Hz Slid
Effects Send Impedance 22k Ohm, level 0dBu nominal
Effects Return Impedanz 22k Ohm, input level 0dBu Nominal
Pre-Amp Tubes 1 X ECC 83 2 X ECC82 1 X ECC 99
Output Tubes 6 X KT88 ( JJ REC.D)
H x W x D (mm) 362 x 610 x 300
Weight (kg) 35