LBDI & RBDI TUBE INSTRUMENT DI BOX AN RE-AMPER
Key Features of the LBDI & RBDI at a Glance
Custom Designed CNC Machined Aluminum Knobs
The RBDI and LBDI Instrument Preamplifier and Direct Box feature custom solid aluminum CNC machined knobs designed by Mystery Magicians and crafted from premium 7068T6 aluminum
Each knob is precision machined for exceptional accuracy and consistency, then bead blasted to achieve a refined, brilliant matte finish. A clear anodized coating is applied to create a durable, wear resistant protective layer that maintains its appearance over years of use.
The indicator markings are created using a black glass enameling process rather than paint or ink. These markings are kiln baked and glazed directly into the surface, ensuring permanent, high contrast visibility that will not fade, chip, or wear off.
The result is a control interface that feels substantial, looks refined, and reflects the same level of precision and durability found throughout the RBDI and LBDI internals.
Highest Quality Components Used
The LBDI and RBDI use the finest components throughout the entire signal and power supply path. This includes Vishay low noise metal film resistors and a carefully selected range of high quality capacitors from WIMA, Panasonic, TRW, and Sangamo silver mica. All electrolytic capacitors used in both units are Rubycon to ensure long term reliability and stable performance.
All signal switching from the front panel is handled by Omron gold contact signal relays, keeping the audio path short and confined to the critical signal region. This approach minimizes signal degradation and preserves signal clarity
All potentiometers used in the LBDI and RBDI are Japanese made Tokyo Cosmos TOCOS military grade sealed potentiometers. These potentiometers are renowned for their high stability, low noise, and exceptional durability. They feature a long service life, machined stainless steel body, bushing, and shaft, along with IP67 waterproof sealing.
TOCOS potentiometers are known for producing smooth, low noise signal output, making them ideal for high fidelity audio applications.
Custom Designed & Wound Output Transformers
The LBDI and RBDI feature our own hand wound output transformers built entirely in house. These transformers are designed to deliver fully balanced operation with excellent isolation, effectively eliminating ground loops, buzz, hum, and unwanted external interference.
Each transformer is hermetically sealed and potted in a Mu metal enclosure to provide robust shielding from electromagnetic and RF interference. This construction protects the signal from contamination caused by nearby power supplies, lighting systems, and other sources of noise commonly found in professional audio setups.
We use only the finest raw materials in our transformers, including M6 grain oriented silicon steel for the core material. This high quality core steel offers low hysteresis, high permeability, and excellent magnetic linearity, allowing the transformer to handle wide dynamic range while preserving low frequency depth and high frequency detail.
Our dual chamber interleaved winding construction results in extremely low leakage inductance and tightly controlled coupling between windings. This design minimizes phase shift and distortion while maintaining extended bandwidth and accurate transient response.
NOS Joint Army Navy (JAN) 5814A Tubes
LBDI & RBDI are fitted with new old stock Philips ECG 5814A Joint Army Navy vacuum tubes. The 5814A is a dual triode tube known for its reliability, consistency, and refined sonic character. It was originally manufactured to meet demanding industrial and military standards, resulting in stable electrical performance, low noise, and excellent long term consistency in audio applications.
As a special quality tube, the 5814A is designed to resist shock, vibration, and microphonics, making it exceptionally well suited for professional audio equipment. It is capable of operating reliably under extreme electrical conditions while maintaining predictable and repeatable performance. Each tube was manufactured and inspected in accordance with applicable MIL E 1 specifications to ensure dependable operation and durability over time.
The 5814A is electrically equivalent to the 12AU7 and may be used interchangeably in compatible circuits, while offering enhanced mechanical robustness and quality control.
Exceptionally Versatile and Musical Equalizer
The LBDI and RBDI feature a three band equalizer designed to be highly versatile across a wide range of source material. The selected center and corner frequencies, along with the overall Q shape of the equalizer, are intentionally musical rather than surgical, allowing for broad tonal shaping that enhances sources without sounding harsh or corrective.
The bass band provides a wide cut and boost range of +15dBu to -15 dBu. The mid band offers +6dBu to -6dBu, while the treble band provides +10dBu to -10dBu, giving ample control for both subtle adjustments and more pronounced tonal shaping.
The bass and treble controls use shelving equalization, with the bass corner frequency set at 180Hz and the treble corner frequency at 3.5kHz. The mid band is centered at 600Hz, a carefully chosen frequency that allows effective shaping of body, and overall balance.
The equalizer circuit is fully vacuum tube based and exhibits a smooth, natural response. It is designed to deliver gentle character, making it well suited for both tracking and reamping applications.
Treble Boost Bright Switch
The Bright switch is a position dependent preset tied directly to the Input Gain control knob.
At lower gain settings, where human hearing naturally loses high frequency perception, the Bright circuit boosts high frequencies and gently rolls off the low end to maintain clarity and presence. As input gain is increased, the Bright effect progressively tapers off, preventing harshness and keeping the tone balanced at higher levels.
Using the Bright switch with the EQ lets you simultaneously boost and cut certain frequencies, somewhat enabling the Pultec (boost while cut) trick and a wide range of tonal options.
Beyond just adding sparkle, the Bright switch can shape your instrument’s character dynamically. It enhances articulation on single note passages, makes chords shimmer without becoming brittle, and adds definition in dense sound waves. It interacts with your playing and gain settings to deliver expressive tone. Instruments with naturally darker or rounder voicings benefit most, as the Bright circuit brings forward harmonics that might otherwise be buried, giving your sound a present edge.
Other features include:
Phase switch for phase reversal
Ground lift switch to eliminate ground loops
Front Thru connection for tuners, amps, or parallel processing
-20 dB balanced output pad to safely manage interface levels while pushing the tube stages hard
Premium construction specs:
Hand wound output transformers built in house
Phillips ECG 12AU7 NOS tubes
WIMA, Panasonic, and TRW audio grade capacitors
Metal film resistors
Japanese TOCOS sealed potentiometers for smooth, long lasting control
Omron audio grade relays for all signal switching
Custom designed and CNC machined anodized aluminum knobs
Dual tone hammertone powder coated steel chassis
Key features:
Input Impedance:
HI Z input impedance: 1MΩ
Reamp XLR input impedance: 100KΩ balanced (Pin 2 hot, Pin 3 cold)
Gain:
High Gain setting maximum gain: 53dBu (Input and Output knobs at maximum)
Low Gain setting maximum gain: 32dBu (Input and Output knobs at maximum)
Reamp input maximum gain: 10dBu (Output knob at maximum)
Output:
Line Output impedance: 150Ω balanced (Pin 2 hot, Pin 3 cold)
Recommended load impedance: 10KΩ or higher
Minimum recommended load impedance: 150Ω
Frequency Response:
Frequency response: 5Hz to 50kHz ±0.5dBu
Noise Performance:
Signal to noise ratio, Reamp input:
–101.71dB below 12.19dBV reference at 1% THD+Noise
Signal to noise ratio, Hi Z input:
–83.5dB below 11.15dBV reference at 1% THD+Noise
Distortion:
Maximum output level at 1% THD+Noise: +22dBu (Input and Output knobs at optimum position)
THD plus Noise at +4 dBu: 0.02 percent, second harmonic dominant
Power Requirements:
AC input voltage: 86VAC to 260VAC
Mains frequency: 50 to 60Hz
specifications:
Documentation:
Operation & Maintenance
LBDI & RBDI Signal Flow Chart
Compact, Elegant, Portable!
Versatile, Elegant, 1 Rack Unit Size!