The Orpheus phono pre amp with LCR RIAA equalizer is designed to amplify the delicate signal of your phono cartridge without loosing any of it and to apply the RIAA equalization. To achieve this our design accommodates for both MC and MM type cartridges trough the use of a built in Lundahl cobalt amorphous step-up transformer for the MC types. It is switchable for low and high impedance providing for appropriate load and gain to the wide variety of cartridges. 

The input stage is a super low noise D3A German

tube used as a triode. It provides the necessary

gain and output impedance to feed the custom

passive LCR RIAA correction. 


The equalization is done with high precision

custom made Sowter coils wound with Cardas

wire and Jupiter BeeWax impregnated paper

capacitors. As the equalization is passive the

next stage is another super low noise tube

(a Russian triode similar to WE417) loaded

by a Hashimoto transformer to bring the signal

up to the necessary level and provide complete

isolation of this sensitive circuit from the following components.

The equalization is realized through the use of constant impedance filters. This means that the input stage feeding it sees a constant load. This making its behaviour predictable at any signal level. The filter is out of any gain loops and sits between the two gain stages protected from any unpredictable influences. To make it properly, very precise high quality inductors are needed. The signal is in series with them so high wire quality and magnetic material with lowest hysteresis are used. This solution was made popular years ago by a Japanese transformer manufacturer called Tango. Due to the difficulty in manufacturing consistently and the high cost associated, penetration of the idea was very limited to just a few manufacturers. Yet this was enough to start a worldwide movement worshiping it. We decided to go a step further, making it from discrete components allowing us to tune it in context of the whole system. 


The power supply of Orpheus uses a very well known but extremely rarely used arrangement. We use a C core transformer with a gap in the core to prevent any saturation of the core from distorted mains or a DC component in the mains. As the power transformer is in the same case we chose a design that has two identical sets of windings (essentially two transformers) on the same core. This way all the nasty magnetic and electrostatic leaks are cancelled and it does not influence any of the other components in the chassis. To reduce power supply noise further instead of the normal arrangement of bridge rectifier and electrolytic capacitor bank we use a choke input full wave tube rectifier arrangement. This practically eliminates switching noise and anything that comes before the choke stays there. The other beauty of this topology is that the choke keeps the voltage on the capacitor bank quite constant. In our case, this allows for a considerably small capacitor bank opening the possibility to use vibration resistant military paper in oil capacitors for the job that would last a lifetime. 


The ergonomics. It does not matter how advanced a technology is, if it is not useful. We have tried to anticipate all the possible needs of our clients. Orpheus has 2 inputs on RCA and one on XLR connectors. All inputs are balanced differential unless the grounding option is engaged on the RCA inputs. As we switch the ground plane when switching inputs there are no hum loops and induced ground noises, allowing for large setups with multiple sources powered from different mains outlets in the house. It applies for the outputs as well. We have provisioned for balanced and unbalanced outputs. Switches on the back, which program the unit, set the gain and type of each input. We have included an absolute phase switch with memory for each input.

Thrax Orpheus Phono Pre Amplifier

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The Thrax Dionysos Line level Pre Amplifier is a single ended single triode stage transformer coupled remote controlled line level amplifier. The line level amplifier (or control amplifier as some call it) is still the centerpiece 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. It’s 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 a pre amplifier has to provide 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 the most obviously "perfect" one - a transformer. 

​Advantages: Inductive loads are very well received by almost all output topologies. It provides complete isolation from the rest of the system. It stops EMI/RFI and ensures truly balanced differential input. To be fair, transformers have disadvantages - expensive, and few know how to make them properly.

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 and transferring enough power to properly
drive the amplification stage without affecting it's
operation. 

​Potentiometer and resistor ladders, as sophisticated
as they might be, have a fundamental flaw. They
operate by dumping the unnecessary 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. 

​The output has to provide an absolute optimum driving signal for the following power amplifier's input stage. This would include: low impedance, DC free, truly balanced, isolated from noise sources and the other components in the system. The solution yet again is a transformer. As a bonus it is the perfect load for vacuum tubes. 

​The power supply of Dionysos uses a very well-known but very rarely used arrangement. We use a C core transformer with a gap in the core to prevent any saturation of the core from distorted mains or a DC component in the mains. As the power transformer is in the same case we chose a design that has two identical sets of windings (essentially two transformers) on the same core. This way all the nasty magnetic and electrostatic leaks cancel each other out, and it does not influence any of the other components in the chassis.

​To reduce power supply noise further instead of the normal arrangement of bridge rectifier and electrolytic capacitor bank we use a choke input full wave tube rectifier arrangement. This practically eliminates switching noise and, anything that comes before the choke stays there. The other beauty of this topology is that the choke keeps the voltage on the capacitor bank pretty constant. In our case, this allows for a considerably small capacitor bank, opening the possibility to use vibration resistant military paper in oil capacitors for the job that would last a lifetime. 

​The chassis to house all of the above had
to be a masterpiece itself. Milled from solid
plates of different thickness, 6061T651
grade aircraft certified aluminium 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. Two
semi-flexible bars on which the motherboard
and its heat sink are attached, which then
support this ring. 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. 

​The ergonomics. It does not matter how advanced a technology is, if it is not useful. We have tried to anticipate all the possible needs of our clients. The Dionysos has 4 inputs on RCA connectors and 2 inputs on XLR connectors. All inputs are balanced differential unless the grounding option is engaged on the RCA inputs. As we switch the ground plane when switching inputs there are no hum loops and induced ground noises, allowing for large setups with multiple sources powered from different mains outlets in the house. It applies for the outputs as well. For those that use bi-amping we have accommodated 2 sets of outputs active simultaneously. It might be considered legacy but we have implemented a buffered tape output that could be disengaged when not in use. We also have a level set function programmable on any input allowing the pre-amplifier to be in the loop of home cinema processors when the music and cinema systems share amps and front speakers. Controls are as simple as possible and self-explanatory, but we have also added an absolute phase switch with memory for each input. All functions are available on the supplied remote. 

Thrax Dionysos Line Level Pre Amplifier