Russ Long, a Nashville-based producer/engineer, owns The Carport recording studio. He is a regular contributor to Pro Audio Review.
Groove Tubes has entered the tube direct box market with the DITTO (Direct Input, Tube Transformer Output) Box. Although the DITTO has a list price of only $399, Groove Tubes proclaims it the highest quality tube DI box available anywhere and they may be right.
Features
The ruggedly built DITTO is encased in a heavy duty, well-ventilated steel chassis with large rubber feet. At unity gain, the box has a frequency response of 6 Hz to 200 kHz (± 3 dB). To achieve the highest quality sound, the DITTO uses a custom nickel core output transformer and Neutrik connectors throughout.
Two unbalanced 1/4-inch jacks wired in parallel provide the box's high-impedance instrument input and an un-buffered loop output. The box's high impedance input level of one mega-ohm make it a perfect match for virtually any synthesizer, electric or acoustic guitar, bass or drum machine.
A male XLR connector (pin-2 hot) provides the DITTO Box's all-tube, transformer-coupled low impedance audio output. The output level is 18.5 dBm terminated at 600 ohms. The box has +30 dB of available gain and a dynamic range of 118 dB.
The DITTO is also equipped with a ground lift switch which isolates the signal ground from earth ground when activated. The switch does not unbalance the XLR transmission line or induce any noise or hum. A neon-blue power-status LED illuminates when the box is on.
The gain control pot allows the adjustment of the output gain. When the gain is set to 0 dB (unity gain), the signal's output level is identical to the input level although it is a balanced signal. Rotating the gain knob clockwise adds up to +30 dB of all tube preamp gain. This is enough gain to record direct to most tape or computer based recording devices.
On the panel opposite the audio input/output panel is a power switch, fuse holder, and IEC connector for the detachable AC cord. The box's input voltage is internally selectable between 100, 120, and 230 volts, 50-60 cycles.
The DITTO's tube character is derived from two triode tubes in the audio path. In the gain control circuit, a 12AX7 buffers the input signal and provides the gain. The box's gain control determines the amount of negative feedback returning to this input stage that varies the amount of gain output by the 12AX7. Then a 12AU7 tube drives the unit's custom-wound output transformer. The DITTO's high output makes it the only tube DI that I've encountered that doesn't require the use of a microphone preamp to attain adequate record levels. The DITTO's powerful tube driver makes cable runs of 500 feet or more are possible without any loss of signal strength or character.
In Use
I had exceptional results using the DITTO Box to record electric bass guitar on several tunes. The sound was round and tight, with exceptional bass frequency definition. The box worked equally well recording a Nord Lead synth bass patch. While tracking a Nichole Nordaman concert for a live album, I had nice results combining the signal of the DITTO on the pickup of an upright bass with that of a Neumann KM 84.
I found that while recording electric guitar through a Line 6 POD, the DITTO works particularly well between the POD's output and the input of my ProTools rig, adding a nice tube texture before entering the digital world.
I fortunately had a pair of DITTO boxes for my review so I was able to put them to use on a variety of stereo sources, the first being a handful of synthesizer tracks. The DITTO is perfectly suited for both analog and digital synths. The box has a smooth top end that did a wonderful job rounding the edge off the high frequencies of an unusually harsh synth patch. In this situation, I found the DITTO's audio quality to be reminiscent of analog tape saturation.
While recording an electric guitar with the musician in the control room and his amp about 50 feet away in an isolated room, I found the DITTO to work very well as a unity gain DI box. The DITTO was able to drive the signal this distance without any loss of audio performance or dynamic range.
Summary
The DITTO Box provides exceptional audio quality and accurate unity gain with the added clarity, dimension and dynamic response of tubes. Whether you are on a budget or not, the DITTO Box is a phenomenal tube direct box.
Contact Groove Tubes at 818-361-4500, www.groovetubes.com.
Review Setup
Apple 400MHz PowerMac G4; Pro Tools Mix Plus v5.1.3; iZ RADAR 24 hard disk recorder with a Nyquest 96 kHz card; Lucid Gen-X-96 clock; Line 6 POD; Mogami cabling; PMC TB1, Yamaha NS-10M monitors; Hafler amplification.
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