The experience RCM gained in building the Sensor Prelude IC allowed them to launch the THERIAA MkII project and explore new and unique strategies to test the limits of what is technically possible. All elements of the design were thoroughly evaluated and tested before being deemed fit to be used in THERIAA. The resulting sound quality is testament to the painstaking work that went into the design.
The components used in THERIAA MkII are sourced from only the “best of the best” companies including Elna, Sanyo, Nichicon, Wima, TDK Epcos, Vishay, Burr-Brown, Analogue Devices and many others. All components are measured by hand, graded and then selected so that matched pairs are always used in the circuits. This ensures that the left and right channels are in perfect symmetry.
Any amplifier can only be as good as the power supply that feeds it.
THERIAA MkII uses a completely separate power supply housed in a strong aluminium case and connected to the main unit by a high quality shielded cable with Amphenol connectors. The power supply is a low distortion symmetrical design. The mains transformers are therefore isolated both mechanically and electrically from the sensitive amplification circuits resulting in an extremely low noise floor. The power supply is dual mono and houses the rectifiers and first stage of filtration for the voltage. The second and third stages of filtration are found in the main part of the preamplifier.
The main part of the THERIAA MkII is housed in a custom made cabinet made by one of the best suppliers of such enclosures, Fischer Elektronic, in Germany. The enclosure is made from thick anodized aluminium profiles with special damping plates inserted to control resonances. A 10mm thick partition separates the left and right PCB’s to achieve maximum isolation. The construction is simple, elegant and very rigid.
The signal amplification circuits of THERIAA MkII are fully balanced and will benefit from receiving a balanced input from the phono cartridge. The unit will work very well with a single ended input from the cartridge but if connected in balanced mode the noise floor will be lower resulting in superior dynamic range. The output from the THERIAA MkII is 2 volts and we have found that the optimum sound quality from a phono preamplifier is achieved if the level lies in the region of 1-2 volts. This imposes stringent requirements on all components in the circuit. They all need to be extremely low noise and precisely matched.
Adjustment of the input impedance, level of gain and input mode (balanced or unbalanced) is regulated by high quality Omron dipswitches easily accessible on the rear if the unit. The signal amplification is achieved with high quality IC’s that are hand measured and matched. Resistors are low noise and capacitors are polypropylene. RIAA equalization is achieved in a two-step passive circuit with a deviation of less than 0.2dB from 20Hz to 20kHz.
The expression “the whole is greater than the sum of the parts” applies to THERIAA MkII very well. Whilst every individual part is selected and manufactured with meticulous care, the overall result exceeds expectations. If you want a neutral, transparent and easy to use phono preamplifier that performs at the highest level, then THERIAA MkII is it!
The MkII is an improved version of the base Theria. The PCB boards have been changed, the RCA sockets have been replaced with the perfect Furutech FT-903R replacements.