The THERIAA phono preamplifier is the result of many years’ research and development in the domain of sound reproduction from the analogue turntable. The experience gained in building the Sensor Prelude IC allowed RCM to launch the THERIAA 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 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 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 with 251,200µF filtering. 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 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 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 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 dip switches 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 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 is it!
Type: Dual monoblock phonostage
Gain: 76 dB
RIAA Linearity: +/- 0.1 dB (20 Hz - 20 kHz)
Input Mode: Balanced via XLR or unbalanced via RCA
Nominal output level: 2 Vrms
Maximum Output Level: 9 Vrms
THD: < 0.1%
Input capacitance: 100 pF
Input sensitivity: 0.2 to 5 mV, adjustable in 8 steps
Input impedance: 20 Ohms - 47 kOhms, adjustable in 7 steps
Power Supply Enclosure: 4 mm aluminum profile with 5 mm front and rear panels, painted black.
Preamp Enclosure: 10 mm and 5 mm brushed, black anodized aluminum
Front: 10 mm brushed aluminum, anodized black or natural aluminum color
Feet: stainless steel, mounted flexibly.
∙ Error, indicating DC current on input,
∙ Overload, indicating input overload,
∙ Wait, on during system testing,
∙ Power, indicating power-on, separately for the left and right channels.
Power supply unit : W203 x D280 x H110 mm
main unit : W440 x D285 x H116 mm
Weight: amplifier unit - 9 kg, power supply - 4.5 kg
Shipping weight : 17,5 kg