Radial Tonebone AC-Driver

The  Radial Engineering Tonebone AC Driver Acoustic Instrument Preamp and Direct Box is a preamp and direct box for acoustic instruments. I purchased this preamp to help get better tone from my upright with my amplifiers. The reason I needed it was that I started using a Realist Lifeline pickup on my upright. I found that the signal from the Realist was not as strong as the K&K Bass Max on my other bass. In addition, with the Realist, I had an impedance mismatch when using my Phil Jones Briefcase bass amp. This caused a weak sound and a low hum. Neither of which is not desirable.

The solution to these issues, other than buying a new amplifier, is a preamp. The preamp boosts the signal and corrects the impedance. For instance, the Radial has a 10M ohm input impedance, perfect for piezo pickups, and a more amplifier friendly 4.4k ohm output impedance.

My first use of the Radial was as a direct box. I ran my signal from my bass through the AC-Driver then straight to the board. The sound guy was glad to see the Radial. He praised the company for their reputation for building rugged and reliable products. His first comment, once I plugged everything in, was, “Wow, that’s a quiet preamp.” This preamp is very quiet. The sound is clean without altering the signal. Exactly what I look for in a preamp.

The controls on the AC-Driver are very simple. There is no EQ. That can be seen as a pro or a con. I do not mind not having an EQ since I use the EQ on my amp. Some people like the ability to control their signal going to the board. For those, the AC-Driver is not going to give you that flexibility. The other controls on the AC-Driver include mute, level, notch filter, phase and low cut.

I found the notch filter very helpful. The idea with the notch filter is to slightly cut a frequency prone to feedback without impacting your overall tone. It worked amazingly well for me. The mute switch was very handy too. At one gig, there was no room on stage to store my bass in between sets. No problem with the mute switch. I mute the preamp and took my bass off stage without having to worry about changing my volume setting.

There are a couple things you should know before you purchase the AC-Driver. First, it is powered by an external power supply. That is your only option. Some of the competitor's preamps can also be powered by a 9-volt battery or phantom power in addition to the external power supply. I would prefer that flexibility. Also, an external power supply is not included. Luckily, I had an extra one to use. If you do not have one available, consider that into your cost.

The second item is that the gain on this preamp is not as high as other preamps. I was a little disappointed with the output level of the preamp. The AC-Driver did not boost the signal as much as I hoped for to get good sound out of my Phil Jones Briefcase amp. It was not an issue with my SWR amp that does has more gain than the Phil Jones. If you need more output from your preamp, Radial recommends using there PZ-Pre which has a +10dB boost when used with a piezo pickup.

Overall, I have been very impressed with the Radial Tonebone AC-Driver. It is one of those "everything you need, nothing you don't" products.