Raysonic SP-120 Modification 
A customer wanted to know whether modifications could be performed on the Raysonic SP120 to improve its performance. After carefully analyzing the circuit design in detail, we determined that improvements could be performed on the circuitry. These changes would allow this outstanding amplifier to reach an unprecedented level of performance unattainable by the stock design. The modification was a time consuming process, and it entailed: Changing the filament voltage of all input and power tubes Changing the biasing circuit of the power tubes Adding AC balance on the 6SN7 phase inverter Adding decoupling resistor on the KT88 power supply Replacing and redirecting PCB traces with 18 gauge wires Replacing capacitors in the signal path coupling stages Replacing resistors in various stages of the entire circuit Applying heat shrink or Teflon coating to all exposed leads 72 hours continuous burn in Bypassing the remote control, and changing the volume control
We performed a standard bench test on the modified unit, and it showed significant improvements in noise reduction, frequency response and channel separation. These improvements were further confirmed by the listening test which showed improvements in resolution, texture, inner detail, control and transparency. The customer was extremely satisfied with the results.
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