Thrax Dionysos preamplifier

Dionysos is a remote controlled single triode transformer coupled line level amplifier - the center of operations for your audio system.

FEATURES
Accepts both balanced and unbalanced input signals on RCA and XLR connectors
Switches ground plane with input selection preventing ground loops
Programmable ground arrangement for large systems
Dual balanced and unbalanced output for bi-amp
Home Theatre bypass feature for integration in Home Cinema systems
Shunt regulated constant current PSU for lowest noise and best dynamic behaviour
Choke input rectifier for lowest switching noise
Programmable absolute phase per input and accessible via remote control
Stepped volume control for perfect repeatability of level setting
Inductive volume control for best sound quality
Custom vacuum encapsulated signal relays for ultimate sound and reliability
Modular construction
Microprocessor controlled
Interlocking solid aluminium chassis
The control amplifier is still the centrepiece of each high-end audio system. It is responsible for source selection, signal conditioning and volume control.
It has to match the output of your source to the input of your power amp. Its output stage must be able to drive any power amplifier through any length of cable with optimal quality via balanced and unbalanced lines.
The input of our pre-amplifier provides optimal loading for the source component to develop its full potential, allowing it to extract the maximum amount of information while keeping all noise picked up on the way out of the signal chain.
During our research and evaluation of the various approaches we settled for a transformer. It provides complete isolation from the rest of the system, rejects common mode signals much better than any active solution, stops EMI/RFI and ensures a truly balanced differential input, while having very low DC resistance. The volume control of a pre-amplifier has to adjust the level of the input signal to the value required by the power amp without burying in noise the low level information and transferring enough power to properly drive the amplification stage without affecting its operation.
Potentiometers and resistor ladders, as sophisticated as they might be, have a fundamental flaw. They operate by unnecessarily dumping the signal across a resistor. It is like driving a car with fixed engine power (signal) and adjusting the speed with the brakes (resistor)!
Our solution is fundamentally different and as simple as it gets. We use a transformer with various winding ratios and we switch between them. In the above example it will operate as a gearbox, transferring all the power of the engine at all speeds. In other words CONTROL.
Our gain stage is realized by the use of a single low noise tube loaded with a step down transformer, making the output of the control amplifier low impedance, DC free, truly balanced, isolated from noise sources and decoupled from other components in the system, providing an absolute optimum driving signal for the following power amplifier’s input stage.
To further reduce the vanishingly low noise floor of the unit below a certain volume setting the active circuit is disabled and the attenuator is connected directly to the output providing low impedance noise free signal.
The power supply of Dionysos uses a choke input rectifier arrangement. This eliminates switching noise and any other disturbance that comes before the choke.
All this is governed by a microprocessor switching to the appropriate combination of relays and monitoring the status and incoming command.

The chassis is milled in house from solid plates of different thickness aluminum that are interlocked together to form a ring like structure.
We have the power supply mounted on the left sidewall of this structure and the signal transformers on the right side, crossed by two semi-flexible bars on which the motherboard and its heat sink are attached via vibration isolating Gel bushings.
The top and bottom plates link all sides of the ring with the flexible bars and the feet made from carbon doped plastic on flexible screws.
There are no screws visible anywhere on the chassis. And the chassis feels like a solid block.