Elekit TU-8550 preamp with phono stage
Elekit TU-8550 preamp with phono stage
Overview
This is a preamplifier kit with a built-in phono equalizer amplifier (MM cartridges), configured with tubes for all the signal stages. (In these two respects it differs from TU-8500).
Circuit description
The CR type RIAA equalizer circuit, which is considered to have excellent sound quality, is used. Furthermore, all time constant capacitors are DC bias superimposed, which is considered desirable for sound quality.
In the flat amplifier, a quadruple volume pot is used interlocking the volume control and gain control. If the input sensitivity of the power amplifier is low or the level of the sound source is low, a high gain is required for the preamplifier. However, the disadvantage of a high preamp gain is residual noise at low volumes. To overcome this, the TU-8550 uses a volume-gain linkage system in which the gain is lowered when the volume is lowered and increased when the volume is raised.
Volume and balance potentiometers are from the highly regarded Alps Alpine RK271 series.
Power Supply
The B power is rectified by a fast recovery diode and a slow-start stabilised power supply with MOSFETs provides better quality than tube type rectification. The A power supply (heater power supply) is also a full DC current system using LDO regulators to thoroughly eliminate hum noise.
Overview
This is a preamplifier kit with a built-in phono equalizer amplifier (MM cartridges), configured with tubes for all the signal stages. (In these two respects it differs from TU-8500).
Tube complement:
- 12AU7 x 2 (Electro Harmonix)
- 12AX7 x 4 (Electro Harmonix)
Circuit description
The CR type RIAA equalizer circuit, which is considered to have excellent sound quality, is used. Furthermore, all time constant capacitors are DC bias superimposed, which is considered desirable for sound quality.
In the flat amplifier, a quadruple volume pot is used interlocking the volume control and gain control. If the input sensitivity of the power amplifier is low or the level of the sound source is low, a high gain is required for the preamplifier. However, the disadvantage of a high preamp gain is residual noise at low volumes. To overcome this, the TU-8550 uses a volume-gain linkage system in which the gain is lowered when the volume is lowered and increased when the volume is raised.
Volume and balance potentiometers are from the highly regarded Alps Alpine RK271 series.
Power Supply
The B power is rectified by a fast recovery diode and a slow-start stabilised power supply with MOSFETs provides better quality than tube type rectification. The A power supply (heater power supply) is also a full DC current system using LDO regulators to thoroughly eliminate hum noise.
