Locomotive Weight Tank WT-72

The WT-72 is a tribute to the iconic V72 modules originally created for the German Radio Network. With its design inspired by these vintage modules, the WT-72 captures the essence of their sound while offering enhanced features. While the original modules provided 34 dB of gain, the WT-72 takes it a step further with an additional 22 dB of gain, achieved through careful circuit adjustments that preserve the beloved tone and character.

To deliver the performance and character reminiscent of its vintage inspiration, the WT-72 incorporates custom input and output transformers, as well as an output plate choke. These components play a crucial role in shaping the overall sound and ensuring a faithful representation of the original design.

Remaining true to the all-tube tradition, the WT-72 maintains an authentic vintage design by employing both AC and DC voltage feedback. This approach not only provides the proper gain but also ensures the necessary stability for optimal performance.

One standout feature of the WT-72 is its quiet gain switching mechanism. Traditional DC feedback switching can introduce large pops, posing a risk to monitors and hearing. To address this, the WT-72 features a special muting system that briefly mutes the output during each step of gain switching. This eliminates loud transients and allows the tubes to stabilize before the output is unmuted, offering a smoother and more user-friendly experience.

The WT-72 incorporates a hybrid switching system that combines an 11-position rotary switch with mechanical and photo relays. This design allows for flexible control over the amount of gain, offering versatility to suit various recording scenarios.

The gain knob settings on the WT-72 are divided into two sections. The off to 36 dB range is achieved by attenuating the signal to the first EF86 tube, while the remaining 20 dB of gain (36-56 dB) are switched by modifying AC and DC feedback. This approach minimizes noise at lower gain levels, providing a cleaner signal. For example, at 36 dB of gain, you can expect 20 dB less noise compared to 56 dB of gain. The WT-72 strikes a balance between gain flexibility and optimal noise performance by leveraging attenuation before the tube gain stages.

The transformers play a vital role in shaping the WT-72's sound. With transformer-balanced input and output, the unit preserves the character and qualities of the original design.
In terms of circuitry, the audio signal passes through two EF86 tubes, providing a total of 56 dB of gain. The signal path remains purely tube-based, with no solid-state components in the chain, ensuring a true vintage tube sound.

To accommodate line-level signals, the XLR IN switch features a "Line" option. When selected, a 36 dB pad is applied before the input transformer, allowing for seamless integration of line-level sources.

In summary, the WT-72 pays homage to the iconic V72 modules while introducing enhancements and features for modern recording needs. With its attention to detail, quiet gain switching, all-tube design, and thoughtful gain control, the WT-72 offers flexibility, vintage character, and improved performance for capturing and shaping audio signals.

Features

Mic / Line (XLR) and High Impedance DI Input 
DI defeats XLR input when plugged in
Two EF86 equivalent tubes
56 dB of gain
11 Position Gain Rotary Switch
Polarity reverse switch
36 dB pad switch (Line Select) 
48 volt phantom power switch 
XLR input and output connections
American input and output transformers and plate choke 
White LED indicators for phantom, power on, and output signal present (-12 dBu minimum for illumination)
Hand-built in USA 
115v/230v AC mains option on rear
Internal power supply
2-year warranty parts and labor

Technical Specs

Microphone Mode input load impedance: Approx. 4k Ω
Line Mode input load impedance: 9550 Ω
Output impedance: < 100Ω
1/4" DI impedance: 500kΩ
56 dB of gain
Frequency response: 20Hz-20kHz 
Maximum output level: +24dBu 
THD+N: <1%
S/N ratio: >70dB
Dimensions: 19"w x 3.5"h x 10"d (2u rackspace)
Shipping Weight: 15 lbs.
Power Consumption (120/240VAC): 25 watts