Groovetube
Groovetube is a synthesiser that produces sound using a plasma tube. Input signals are used to cause fluctuations in plasma current, which at different conditions may pass relatively unaltered or be combined with plasma noise. The plasma sound produced in the tube can have various effects on the input signal. For low-level signals it is mostly additive, a bit like 'noise in the pipes'. With enough drive, the plasma stability is directly affected and the output becomes an interaction between them, which can be expressively controlled with a magnet.
The synth can be controlled with external signals or with its own onboard control system. We have just built up a pre-production machine, testing out the transition from rats' nest of wire to circuit board. After correcting the errors this is now working well, and when changes have been made to the design we shall be able to order the first batch of pcbs. Demos showing this machine working, and also tests of a first custom-made plasma tube shall be posted soon!
Demos
Our most recent demo videos show the working prototype in an almost-finished state.
Operating alone:
And with other instruments:
This prototype has had many controls added and removed along the way, a different control layout has now been designed for the first production machines.
The fluorescent tubes used by this machine are due to be phased out soon, so we've secured adequate supplies for the short term. We intend to develop our own tubes for specific sound output - an exciting prospect that will take a little more time. First experiments are now being constructed, watch this space for any news.
Working Spec
A system voltage of around 350 VDC is used to drive a cold cathode discharge inside the tube, and run an RF generator for separate plasma excitation. RF energy is transferred to the plasma with two coils. Power to tube and excitation circuits is regulated by preamp valves, and valves are also used for the main audio circuit.
The synth is controlled by CV/gate and modulation signals, that can be generated internally for stand-alone operation, or used from an external source. Externally-generated audio can also be introduced. Onboard control uses a simple 8-step sequencer to run preset CV sequences and gate patterns, and generates a timing signal for synchronising with other equipment. Two digitally-controlled LFOs are used to create signals for modulating plasma voltage and excitation, allowing good control over frequency and phase, which significantly affect the plasma sound. Control signals are optically coupled into the telmatron systems, with a slide control for varying plasma stability.
Availability
In 2024 we intend to produce a batch of 100 instruments.
These will accept both 6W T5 fluorescent tubes and custom tubes once we start to produce them. We have a sufficient stock of fluorescents to supply a selection of 3 types with each machine.
PRICING
We are just starting production, and pricing is still to be confirmed. The cost will certainly be below £2K, and is currently looking to be closer to £1.5K... we will update this as soon as we can.
ORDERING
To reserve a machine please email telmatronics@gmail.com with 'order' in the subject field, we will then contact you with further details and to arrange payment of a £250 deposit required to secure a machine.
These will be allocated on a first-come, first-served basis.
In 2023 we made Groovetube available for pre-order in complete and kit form as part of a Kickstarter campaign, and we are currently focussed on production of this first batch of instruments. Once these have been delivered, we will move to the next orders, which we expect to deliver later in 2024.
Kits will be available for those wishing to build up their own machines, and we shall make individual components available/post schematics and construction notes when time allows - this will take some time, please be patient.