Russia's Soma Laboratory has built a new instrument called Dvina that's inspired by the sounds of classical Hindu music. Vibrations from the strings are picked up by a powerful magnet buried inside the wooden neck, the signal boosted and modulated and then output through an amplifier. And the result is hauntingly beautiful.
The Dvina is a two string wooden instrument that's rested against the shoulder and features a cross piece that can be adjusted for different playing positions. It can be bowed or picked/strummed, and breaks down into component parts for between play transport.
There's no chambered body to naturally amplify the acoustic sound so the Dvina needs to be paired with an instrument amplifier. But there's no conventional coil/magnet or piezo pickup system as such, vibrations are registered directly using a neodymium magnet hidden in the neck, the output signal gets boosted by a step-up transformer before being sent through effects pedals and onto an amp.
There is a built-in pre-amp though, which rocks tap delay and a soft distortion, help to give the instrument its own special sound. That neck of 88 cm (34.6 in) long with a scale length of 52 cm (20.4 in), there are no frets though markings on the neck should help with finger placement.
"Two sticks, two strings, no frets, it's as simple as possible, everything unnecessary has been removed," said Soma's Vlad Kreimer. ""It's only you and your spirit, mastery and imagination. This is a very simple but powerful instrument, with a strong connection to your body."
Soma Laboratory is currently at the prototype stage of development, and is seeking feedback from musicians before going into production. You can see and hear the Dvina tuned to C# and G# in the video below.
Source: Soma Laboratory
I'm guessing the internal amplifier is a simple impedance-converting op-amp (current gain but no voltage gain), at least for the first stage, likely AC-coupled through a capacitor to prevent amplifying any DC in the signal. It may also use a low-pass filter to prevent picking up AM radio stations and maybe a notch filter to prevent 50/60Hz hum. Further amplification takes place outside the instrument.
However he did it, it's ingenious and sounds great.
"Besides the wooden part itself, an integral part of DVINA is a special built step-up transformer that gains a weak signal from the strings enough for further processing. After the transformer, the signal is ready to be put to stompboxes or a cabinet. Also, there is a specially built HQ pre-amp with one tap delay and a soft distortion in the delay’s feedback. I used the pre-amp in the demo."
"I can expect the net price for the main part (DVINA + the step-up transformer) in span 200-500 Euros. The net price for the pre-amp/delay/distortion unit is around 300 Euros."
Mr. Kreimer, a radio engineer, also makes and sells analog synthesizers he designed himself for his own musical performances, so no doubt his approach using a step-up transformer for the DVINA works well, very likely better than my guess of how it could be done using op-amps.
Wouldn't you have more inductance using bass strings and way more magnets? Also.. The placement would need to be between the bridge and very highest fret... And since the strings move... The fretted string would increase it's power.. Interesting idea. I'm thinking of building a test bed for myself.. But not some stupid stick.. Also hum should be cancelled out anyhow if you wire in pairs which would be why he's using 2 strings guys... Lastly.. Why not just build a guitar with an acoustic body..