Radial Bassbone OD

The Radial Bassbone OD is a bass preamp and overdrive unit from Radial Engineering, announced at NAMM in January 2014 and shipping from May that year at an estimated retail price of $500 USD¹². It is a two-channel preamp: each channel has level control, a semi-parametric equalizer and a low frequency resonance filter, and you toggle between them with a footswitch, like playing through a two-channel amp¹. On top of the preamp it adds a built-in overdrive circuit, an effects loop for external pedals, and a full set of outputs for stage and front-of-house use.

Radial describes the design goal behind the overdrive in terms bass players will recognize:

In other words, the dry bass signal stays in the mix alongside the distortion, so the low end does not disappear when the drive is engaged. In Radial's NAMM demo, bassist Ric Fierabracci noted that slap playing keeps its crispness and that the drive can be dialed down to what he called an "SVT-like grunt"³.

The overdrive and effects loop

The overdrive section has its own Tone control and a Mix knob that sets the dry-wet balance between the original bass tone and the distortion⁶³. Radial's approach of mixing the dry signal back in is what keeps the instrument's fundamental intact at higher drive settings².

The effects loop is a set of send and receive 1/4" connections for external effects⁶. A Footswitch Assign switch sets what the OD footswitch activates: the overdrive, the effects loop, or both⁶². In the NAMM demo, Fierabracci described a further option: a separate switch can hold the loop on all the time, leaving the footswitch for drive only³. Radial notes that professional studio effects can be used in the loop, recommending unbalanced connections and levels kept below the distortion point⁷.

The XLR output can be routed pre or post, before or after the effects loop and overdrive, to suit the engineer's preference, using the Pre-Post switch⁶¹.

Channels, controls and switching

Channel-A carries Drag Control load correction, which Radial positions as a way to optimize tone and feel with a vintage passive instrument such as a Fender bass¹. Channel-B takes a different slant, with a PZB booster that increases the sensitivity and load to 10 meg ohms for piezo transducers as commonly used on upright bass¹. Because each channel has its own EQ, you can set them differently, for example bringing out 500 Hz on channel B for harmonics³.

Input-B uses a 1/4" switching jack: the bass connected to input-A can feed channel-B when input-B is not in use, so one bass gets both channels⁶. The two inputs can also be used simultaneously, for example an upright bass with a magnetic pickup and a piezo pickup, or two separate basses³.

A note on Drag Control: it has no audible effect with an active bass, because the bass's internal preamp already buffers the signal. Radial states it only works when coupled directly to the magnetic pickup⁷.

Power: 15V, 400 mA

The Bassbone OD runs on a 15V DC power supply⁶. Radial explains the choice: "By using a 15V, 400 mA power supply, we can increase the headroom and reduce distortion for a more natural bass tone"⁷. The unit requires 400 milliamps of current⁷.

The Bassbone OD is a unity gain device: it only boosts the signal when the power booster is activated, and Radial describes its EQ as passive-interactive, like an old Fender amp, hiding output power in the EQ⁷. Measured specifications from Radial include a frequency response of 20Hz to 18kHz, total harmonic distortion of 0.05% at -15dBu, dynamic range of 85dB, and a maximum input of +7 dBu⁵.

Outputs: amp, DI, tuner and headphones

The rear of the unit carries four outputs:

• Amp out: a 1/4" bass amp output used to feed the artist's personal stage amplifier⁶
• Balanced out: a built-in active Radial DI to feed the PA or recording system, with a 180° polarity reverse and ground lift⁶⁵
• Tuner out: a separately buffered, dedicated tuner output that is always on⁶
• Phones output: a 3.5mm TRS mono headphone output with level control⁶

The active DI output is unique to the Bassbone OD, but very similar to the buffering circuit used in the Radial J48⁷. The tuner out works with the mute footswitch for quiet on-stage tuning¹. It can also feed a second amp, but Radial cautions that it is always on and not isolated, so hum and buzz from ground loops may occur⁷.

The unit does not generate 48V phantom power for a condenser microphone; an external supply such as the Radial SB48 is needed. It is equipped with blocking capacitors that protect it from DC current if phantom power is present on a connected line⁷.

A BLEND switch on the unit lets you mix an external music source, such as an iPod, with the bass for practice. The Bassbone OD is mono, so a stereo mix is lost⁷.

Where it came from

Radial announced the Bassbone OD with shipping planned for Spring 2014 and an estimated retail price of $500 USD¹. By the time of Radial's shipping announcement, the Bassbone OD was available to buy². The OD footswitch may be assigned to the loop, overdrive or both, and Radial's approach to the overdrive was to maximize the frequency response, retain the dynamics and let the player mix in the dry original signal with the distortion²¹.

Radial's demo video, presented at the Radial booth, walks through the channels, Drag Control, the overdrive's tone and mix controls, and the pre/post balanced output⁶³:

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