AMP Lab – Radial Tonebone Bassbone V2

The Radial Tonebone series of pedals represents a diverse line of almost thirty different pedals. Within the series, you will find Tonebone models directed to distortion pedals, effects pedals, switcher pedals, and preamp/buffer pedals. Fortunately, Radial has kept the bass player in mind, with numerous pedals directed specifically to, or useful by, modern bass players. One such pedal, the Bassbone V2, happened across the Amp Lab, so let’s take a look and see what the Bassbone V2 can do.

Overview

Before getting into details, it is worth taking a quick tour to get an idea of the overall features of the Bassbone V2. There are two input channels, Channel 1 and Channel 2, which can be selected via a heavy duty footswitch. Each channel has its own, unique level control and equalization options. The Bassbone V2 also includes a parallel effects loop that can be assigned to Channel 1, Channel 2, or both, via a selector switch. A second heavy duty footswitch selectively engages and bypasses the effects loop. Also, the Bassbone V2 includes a variable-gain boost circuit. A third heavy duty footswitch selectively engages and bypasses the boost circuit. A switch allows the third footswitch to be repurposed from a boost footswitch to a mute footswitch. Other features include a ¼” amplifier output, a balanced DI output, DI ground lift, DI phase shift, and tuner output.

The Bassbone V2 is packaged in an extremely durable enclosure that is well laid out, with clean markings that are easy to see and distinguish. Yellow and white colors clearly indicate the controls associated with each channel. Referring to Fig. 1, peeling back the hood, we are greeted with a clean and exceptionally manufactured circuit board layout. There is literally no wasted space inside. Kudos here for excellent engineering.

Input

Starting off at the input section, it is immediately apparent that the Bassbone V2 offers a flexible set of options. The input section is comprised of two ¼” input jacks, two “set and forget” switches, and one heavy duty footswitch. The input jacks, identified as Channel 1 and Channel 2, are mounted on the right side of the pedal and serve as instrument inputs. The footswitch, labeled “Select,” normally switches between Channel 1 and Channel 2.

The two “set and forget” switches are recessed switches, also located on the right side of the pedal, and provide really cool configuration options. To access these switches, you need a small screwdriver or other pointed object. A first set and forget switch, labeled as the PZB switch, is a piezo option that both increases the input impedance to 10 meg-ohms and increases the gain by 10 dB (as measured on our bench). A second set and forget switch is labeled as a Blend switch. When the Blend switch is disengaged, the Select footswitch is active to select and change between Channel 1 and Channel 2. When the Blend switch is engaged, the footswitch is automatically disengaged, and Channel 1 and Channel 2 are blended together.

When a single instrument is plugged into Channel 1 and the Blend switch is disengaged, the Select footswitch is used to selectively route the instrument signal to either the Channel 1 equalization circuitry, or the Channel 2 equalization circuitry. With an input from our test generator plugged into Channel 1 (with Channel 1 enabled by the Select switch, and no input plugged into Channel 2), we measured an input impedance of 145 kOhm with the PZB switch disengaged. The input impedance measurement jumped to 432 kOhm with the PZB switch engaged. Plugging a second input into Channel 2, we measured an input impedance on Channel 1 of 460 kOhm regardless of whether the PBZ switch was engaged or disengaged.

Switching to Channel 2, with the PZB switch disengaged, we measured an input impedance of 213 kOhm both with, and without, an input plugged into the Channel 1 input jack. Depressing the PZB switch, the input impedance increased beyond our measurement tools. Radial identifies the input impedance as 10 meg-ohms, and this seems about right.

In use, a simple configuration is to plug a bass guitar into the input of Channel 1. In this configuration, the Bassbone V2 functions as a preamp switcher, which allows the user to toggle between two different preamp and equalization settings by toggling the Select footswitch. Connecting a first bass to the Channel 1 input and a second bass to the Channel 2 input allows the user to toggle between basses and corresponding preamps using the Select footswitch. Toggling on the PZB switch may prove useful for piezo instruments, including upright bass. If your bass has two outputs, e.g., an acoustic bass with piezo and mic, engaging the blend switch allows you to mix the sound of both pickups.

Input Range

Referring to Fig. 2 (black trace), in Channel 1, we measured a frequency response of +/- 4.4 dB 20Hz – 20kHz, 200 mVrms swept sin, and a frequency response of +/- 0.7 dB in our “optimal passband” of 80Hz – 8kHz, 200 mVrms swept sin. As noted in Fig. 2, the output of Channel 1 is flat, with substantially all of the deviation as a result of a fixed high-pass filter, which appears to have a corner frequency around 50Hz.

FIG. 1 Gutshot

FIG. 2 Channel 1 vs channel 2 optimally flat

Switching over to Channel 2 (blue trace), the frequency response is not as flat as the frequency response of thanking the lower frequency extension of Channel 2, we measured a frequency response of +/- 3.1 dB 20Hz – 20kHz, 200 mVrms swept sin, with a frequency response of +/- 0.6 dB from 80Hz – 8kHz, 200 mVrms swept sin in our optimal passband.

Each channel includes a level control. Since the Bassbone V2 can function as a mixer, the Level control will not pass a signal at the minimum setting. This is another cool way to get a “mute” function out of the pedal. Dial the level control of one of the channels to “off,” and with the Select switch, you can toggle between an effective mute and “bass on.” You might want to do this if you also want to use the Boost function.On Channel 1, with the level control at about 9 o’clock, we could dial up an input signal of over 2 Vrms before any sign of distortion, so this channel is quite usable with any active or passive bass. The distortion characteristics reveal that the negative edge clips before the positive edge, providing an asymmetrical distortion. Channel 2 appears to have a bit more gain (thus a bit less headroom) compared to Channel 1. Channel 1. However,

EQ Options

Channel 1 has a simple three-position toggle switch for selecting between preset EQ curves. Referring to Fig. 3, the Normal setting (black trace) is the flattest setting. The Tone-A setting (blue trace) shows a mid scoop at about 700Hz, with a bass peak around 100Hz, and a treble peak around 4kHz. This setting also appears to have a low-pass filter, cutting off the treble frequencies. The Tone-B setting (red trace) shows a relatively tighter mid scoop, compared to the Tone-A curve. Also, the mid cut is shifted down to about 350Hz. The bass frequencies are slightly attenuated, yet extended, compared to the Tone-A curve.

However, the key difference is the treble side of the frequency response. There is a significant treble bump that appears to be centered around 8kHz.

FIG. 3 Channel 1 EQ-1 switch settings

Channel 2 has more user control options, compared to Channel 1. For instance, Channel 2 offers a three-position high-pass filter switch, as well as Bass, Mid, and High controls. Referring to Fig. 4, the high-pass filter settings are illustrated. The flat setting (black trace) shows that even in the “flat” setting, there is a high-pass filter in place, with the signal being about -3 dB down at about 35Hz. Moving the switch to the middle position (blue trace), we note just under a 3 dB boost in gain with a significantly steeper high-pass filtering function. Also, the signal is -3 dB down at about 50Hz. Switching to the last setting (red trace), the -3 dB down point has shifted up to around 90Hz.

The Bass sweep of Channel 2 is shown in Fig. 5 as having a set frequency around 80Hz and a gain of around +/- 12 dB. The Mid sweep of Channel 2 is shown in Fig. 6, having a center frequency just under 500Hz and a gain of about +/- 10 dB. The treble (High) sweep of Channel 2 is shown in Fig. 7, having a set frequency around 5.5kHz and a gain of about +/- 18 dB.

FIG. 4 Channel 2 HPF-2 settings

FIG. 5 Channel 2 bass sweep

FIG. 6 Channel 2 mid sweep

FIG. 7 Channel 2 high sweep

Boost

Referring to Fig. 8, the Boost feature has an effective implementation. With the Boost control at its minimum setting, there is no effective boost. As illustrated, turning up the Boost control yields a smooth change in gain up to about 12 dB of boost with the control fully on (maximum clockwise rotation).

FIG. 8 Boost sweep

Effects Loop

The effects loop is exceptionally well implemented. There are two main controls, including a dry/wet Loop control, and a three-position switch that allows the effects loop to apply to Channel 1 only, Channel 2 only, or both channels. Even if you do not use effects, the effects loop can be used to great effect. Let’s say that you want to repurpose the Boost switch to function as a mute for silent tuning. As noted above, this can be accomplished my setting a Boost/Mute “set-and-forget” switch on the left side of the pedal. However, you may also need a small gain adjustment at times. Loop a small instrument patch cable from the send to the return and adjust to taste.

Referring to Fig. 9, we see the Channel 1 normal (Norm) setting with loop disengaged (black trace). Kicking on the loop with simply a patch cable connecting the send to the return, the Loop control set to dry results in about 2 dB attenuation (blue trace). This is about the equivalent of using the Boost feature with the Boost control set to about 9 o’clock, but in attenuation, not gain. We get back to just over unity by setting the Loop control to the center position (green trace), and yield about 8 dB of attenuation with the Loop control set to fully wet (red trace). The wet position, in this case, is equivalent to the Boost control in its 3:00 setting, but in attenuation, not gain.

FIG. 9 Effects loop settings

Another cool thing you can do is insert a shorting cable (a plug with the tip shorted to the sleeve) into the return jack. Referring to Fig. 10, you now have a variable attenuation control that adjusts from unity (black trace, loop off) to about 2 dB of attenuation with the Loop set to 9 o’clock (blue trace), just about 5 dB of attenuation with the Loop control at noon (green trace), about 19 dB of attenuation with the Loop control at about the 3 o’clock position, and full mute at the fully wet position. The cool thing here is that you can use the Loop switch to cause the attenuation or mute on Channel 1 only, Channel 2 only, or both Channel 1 and Channel 2. How you use this circuit is really only limited by your imagination.

FIG. 10 Effects loop settings

Output v DI output

Referring to Fig. 11, we see the DI output is about 6 dB hotter that the main output. Moreover, there appears to be some low-pass filtering that affects the high end, with about 3 dB of roll off by about 20kHz. The DI is a true Radial quality DI. However, there is one note of caution. The DI is post everything. Thus, the EQ settings, Boost setting, mute setting, etc., will all be directed through the DI output, as well as the main output. This is great where you really want to control your tone, not only to your amp/in-ears, but also to the FOH.

FIG.11 Output vs DI output

Distortion Characteristics

The Bassbone V2 is what I would call “squeaky clean.” Referring to Fig. 12, we set the level control to noon, and swept an input signal at 1kHz from about 50 mVrms to over 3 Vrms. We see that up to just over 700 mVrms in this test, the THD+N measurement was below 0.01 THD+N. We also see a steep, yet well-behaved, increase in THD+N as the signal goes into clipping, starting with a knee just over 1Vrms.

FIG.12 THD+N level control at noon

Conclusion

The Radial Tonebone V2 heralds itself as a Bass Command Center. I’d say that this pedal lives up to such a billing. The processing circuitry is super clean, with a studio-quality noise floor and distortion characteristics. The intuitive interface should make this device easy to use, but its sophistication is deceptively deep, if you are willing to spend some time with it.