Hazelrigg Industries


Vacuum Tube Direct Input
Built-In Ground Lift
Convenient form factor for travel cases and gig bags
Assembled in the USA

The Hazelrigg Industries VDI Vacuum Tube DI is designed to provide recording professionals with a sonically superior method for recording electric and electronic musical instruments by direct injection (DI). The VDI is not mass-produced. Each one is hand-made and meticulously tested before shipment to the customer.

Vacuum Tube DI

Any instrument designed to operate into a “guitar amp” will work perfectly with the VDI. Typical instruments include: electric bass, electric guitar, electric piano, acoustic instruments with a pickup (piano, acoustic guitar, electric violin, etc.), synthesizers, and samplers. The VDI is a single-channel device that provides the optimum load impedance for these instruments. It is capable of quality reproduction of a wide range of instrument levels. The unit does not have the limitations of passive transformer-type DIs, and has greater headroom and warmth when compared to similar solidstate devices. It is designed to operate in the professional recording or performing environment. The output level is “hot” mic level (-30 dBm nominal). The output is transformer-balanced, using a custom transformer built for us by Jensen Transformers, Inc., and is designed to match 150 ohm professional mic inputs. Top-quality parts are used throughout. The case is machined from solid quarter-inch thick aluminum plate for ruggedness and durability. Both the filament and plate power supplies are fully regulated.

In this video, Derek Jones demonstrates the versatility of the VDI on a variety of basses and playing styles. “Not only does it sound wonderful – it feels great. It feels like you’re plugging into an old amp or old piece of gear that you’ve had forever.”

Since 2004, Derek has been the upright and electric bassist for Cirque du Soleil’s production of KA at the MGM Grand in Las Vegas.

On The Road

Bringing tube mojo to your performances has never been easier. Our vacuum tube Hazelrigg Industries VDI is #gigbagready!


The VDI has one channel. The musical instrument output connects to the VDI INPUT (2) via a standard ¼-inch single-conductor (monaural) phone jack. The input is unbalanced. Since the input cables carry very low-level audio, it is important that well-shielded cables are used. There should be no additional connectors, patch jacks, switches, etc. between the instrument and the VDI inputs. It is important to keep the input lines as short as possible. If desired, the musical instrument may be simultaneously connected to the input to an external instrument (guitar) amplifier. The THRU jack (1) is a ¼-inch single-conductor (monaural) phone jack wired directly in parallel with the INPUT jack. The OUTPUT connectors (4) are XLR-3 male wired according to AES standard: pin 1 is ground (shield), pin 2 is “high” or “+,” and pin 3 is “low” or “-.” The out- put is transformer-balanced. The output level is a nominal -30 dBm. This is somewhat higher in level than a typical microphone.


  • Vacuum Tube Direct Input
  • Amplifier and Power Supply Designed by D.W. Fearn
  • 200 mV nominal unbalanced input

  • All-Tube Signal Path
  • Custom-made Jensen transformer
  • 1 megohm minimum input load impedance
  • Transformer-balanced out

  • -10 dB gain

  • Frequency Response
    • +/- 0.2 dB 10 cps to 20 kc
    • -3 dB @ 0.5 cps and 95 kc
  • Unbalanced 1/4″ input
  • Balanced XLR output
  • <0.3% 20 cps to 20 kc THD + Noise

  • Front Panel Microphone/Instrument Input (Redundant Microphone Input on Rear Panel)
  • -30 dBm nominal “hot mic” output level

  • 6.25”W x 2.25”H x 9.5”D dimensions

  • Solid quarter-inch thick aluminum plate for ruggedness and durability
  • Limited 7-Year Warranty (90 days for vacuum tubes)

  • Handcrafted in the USA


“The VDI all-tube DI is reassuringly built and very robust sounding.”Wes “Wesonator” Maebe, Producer/Engineer (Sting, Chaka Khan, UB40 (ft. Ali Campbell & Astro), Specimen, Suzi Quattro, New Model Army, Carly Simon)




“The Hazelrigg Industries VDI has been my go to DI since I first played my bass through it. It goes with me to every session and it’s ALWAYS welcome. The tone just makes everything cozy, comfortable and relaxed. I LOVE IT!”.” – Derek Jones, Bass, Cirque Du Soleil: Ka





Purchase through select dealerships.