Marantz 4270 Quadradial Receiver
The Marantz 4270 Marantz’s exclusive Vari-Matrix circuits used to emulate quadraphonic via stereo source and independent reproduction such as is rated to 70W/CH in stereo and 25W via Quad.
Features include front and rear tone controls, the variable martial dimension control (SQ/Vari/Discrete/2CH/MONO) including front/rear balance fader controls.
The Marantz 4270 has a unique power supply design in comparison to most of their 35V regulated designs with two full wave rectifiers and a single full-wave-bridge array.
All of the electrolytic capacitors here were replaced with a high temp (105C) low impedance Nichicon PWs with an increase in operating voltages. Bypass films were upgraded to high-grade WIMA PP type films. The full-wave diode arrays were replaced with a ultra-fast, soft recovery Vishay diodes. A new precision Bourns adjustment potentiometer installed. All small signal devices were replaced with a more robust TO-92L Fairchild devices and both regulators replaced with a heavy duty TO-220 TIP series devices with new full synthetic Wakefield thermal compound applied.
Upgraded, Heavy Duty TIP voltage Regulators w/ New Fully Synthetic Wakefield Thermal Compound
BEFORE
AFTER
35V Regulated SE
HARDWARE
The original 15,000MFD filter caps were replaces with a computer-grade Nippon Chem/Con and increased to 18,000MFD for better filtering and reserve capabilities and peak to peak output and subsonic responses.
+/- SE Supplies
Hardware LEDs
As the unit had warm-white, quality SMD LED’s already, new Meter and Display Vellum paper was installed as well as function indicators replaced with diffused LED type.
PE01 Pre-/Buffer
The 4270 has a different approach to the gain stage here, with a tiered input/output gain stages including additional tone control pickup. The PD01 and PE01 are mounted perpendicular tongue/grove fit which soldered versus wire leaded.
In the PE01 stage all the initial input .22MFD and other 1FMD< were replaced with a high grade WIMA polypropylene film capacitors, remaining electrolytics/tantalum were all replaced with a audio grade KT/KA Nichicon with an increase in operating voltages. The Decoupling was increased in MFD with a low impedance Nichicon PW. All small signal devices (16!) were replaced with low noise, modern TO-92 Fairchild devices.
BEFORE
AFTER
PD01 Tone
The PD01 tone buffer stage electrolytics and tantalums, like above were all replaced with audio grade KA/KT and low impedance PW, Bipolars were replaced with a audio-grade Nichicon MUSE type, all with an increase in operating voltages. All small signal devices were replaced with low noise, modern TO-92 Fairchild devices.
The PD01 tone buffer stage electrolytics and tantalums, like above were all replaced with audio grade KA/KT and low impedance PW, Bipolars were replaced with a audio-grade Nichicon MUSE type, all with an increase in operating voltages. All small signal devices were replaced with low noise, modern TO-92 Fairchild devices.
BEFORE
AFTER
PM01 Inverter
The distal stage phase inverter had all of the electrolytic capacitors replaced with audio grade KA/KT and low impedance Nichicon PWs with an increase in operating voltages. All new small signal devices were installed with TO-92/L modern low noise Fairchild devices.
BEFORE
AFTER
P700 Driver
Due to the Quadradial design the 4270 features two separated driver PCB’s both with two identical drivers per assembly, this is switchable via the X2 70W/ X4 25Watt selector on the rear of the unit.
All of the BJT devices in all four drivers were replaced (short of TO-66 type), new Fairchild, low noise TO-92 transistors were installed and matched 1% BETA for the differential stages, Vbias + stages as well. Pre-Drives and Drives were all updated to low noise Fairchild TO-92 and TO-126 devices for better dissipation. MV-13 diodes were replaced with modern 4148 type diodes in series. The Bias adjustments, as they are unlike the large plastic frame type Ive discussed before, were replaced with a precision potentiometer.
Differential Mapping
BEFORE
AFTER
The original electrolytic axial capacitors were replaced with low impedance high temp (105C) Nichicon PW’s including remaining electrolytic with an increase in operating voltages. High grade MKP polypropylenes for the coupling stage installed and high grade WIMA polypropylene films.
Bias Confirmation
P400 Phono
The gain stage NPN’s were all replaced with low noise modern Fairchild TO-92 devices matched to 1% BETA. The 100MFD electrolytic were replaced with a low impedance long life Nichicon PW and remaining electrolytic with audio grade KA/KT with an increase in operating voltages. The ceramics and 1MFD were all upgraded to WIMA polypropylene film capacitors.
BEFORE
AFTER
RF & P500 Vari-Matrix
Dolby and associated RF stage electrolytic and tantalum capacitors were replaced with a low impedance Nichicon PW with an increase in operating voltages.
The vars-matrix, which takes a stereo input and converted to quadraphonic output. All of the electrolytic here were replaced with a low impedance and audio grade KA/KT Nichicons with an increase in operating voltages. New high-grade WIMA PP films and all associated small signal devices were replaced with TO-92/L low noise Fairchild devices.
BEFORE
AFTER
Audio Notizen
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