R1.1 represents the top model of Opera Audio's current range of per-amplifiers. It is a 20dB gain line stage pre-amplifier using improved SRPP circuit with no global negative feedback. The equipment top uses cherry wood while equipment feet are brass cones for improved shock absorption. Front plate is of machined aluminum.
The internal components used are among the finest available in the world today. The potentiometer uses the single stereo ELMA 24 position series attenuator with 46 Holco 1% precision resistors. Apart from having excellent sonic characteristic, it guarantees the sound stage precision at any volume level. The capacitors used for signal coupling is both the exotic US MultiCap RTX and the Rel-Cap. Resistors used is a combination of Holco and Chinese made precision aerospace low temperature drift version. All connections are point to point wiring using Kimber high purity copper hook up wire. The circuit board acts as a support frame for the tubes and other components and actual point to point wirings are done beneath the circuit board.
The two tubes used in the main circuit is the fabulous sounding 12AU7 NOS made in the 50/60s. Due to limited supply they are very hard to find in the market and price-wise expensive but absolutely one of the very best. In order that users can try out different types of 12AU7, the R1.1 is designed to use components that has very little colored sound of their own. In this way, during tube rolling the R1.1 can clearly show off the sound of the tube itself. A lot of satisfaction will then be achieved by trying out other exotic tubes like the Telefunken and Mullard.
Good quality pre-amplifier calls for a good quality power supply. The power transformer and choke is shielded from the circuit board. A special silicon steel EI type power transformer and choke with good high frequency response is used together with large Solen MKP metallized polypropylene filtering capacitor. Its filtering characteristic is very uniform across the frequency range and adds to the purity of the sound.
To reduce the microphone effect, two Pearl tube coolers are used. Not only they are effective in reducing microphone effect, they are also a very good heat sink which can greatly extend tube life. Other convenient features are added like the -10dB muting switch, which can reduce the usage of the expensive potentiometer and as a result extends its life. |
Tube Line Stage
