D. Crosby & C. Schaub Marantz 2275 W/ BA312 Upgrade

Marantz 2275 Receiver W/ BA312 Upgrade

Today were showcasing two customers Marantz 2275 receivers we restored recently. One of the units as you will see below was a very very early production model prior to foil silk screening, with suitable variations in topography, the biggest being a different in bias feedback for the P700 amplifier stages. Both of these units had the new Analog Esoteric BA312 upgrade modules installed in the PE01 tone stages. One customer opted for a new production black faceplate as photo’d.

The 2275 is a particular favorite Marantz of mine, built exceptionally well, akin to the 2325 versus the 2270 which I despise from a technical point of view due to its amplifier design shortcomings. The 2275 has excessive RF shielding, robust filtering reserve, PE01 oriented pre-amp stage etc.

P800 Power Supply

The regulated 35/14V power supply is a tried and true Marantz design used in many series, composed of two full-wave rectifiers with a TO-220 regulator and full wave bridge rectifier for the B-/+ rails. The protection circuit is housed on the same PCB, acting as a DC deviation/thermal monitor.

All of the capacitors were replaced with a low impedance, high temp (105C) Nichicon PW capacitors with an increase in operating voltages. New high grade WIMA polypropylene films were also installed along with precision Bourns adjustments.

Common array diodes were replaced with more robust MUR TO-220 devices, as well as new TIP TO-220 robust voltage regulators, all remaining devices were replaced with modern Fairchilds TO-92L devices for better dissipation. 

BEFORE

(note one P800 had previously had capacitors replaced but was all redone)

AFTER

The original 15,000MFD filter capacitors for the B-/+ were replaced with a Nippon Chem-Con computer grade capacitors and increase to 18,000MFD for better subsonic response and handling. 

PE01 Tone Board W/ Analog Esoteric BA312 Upgrade

The PE01 used in the Marantz 2275 is identical to the 2250,2250B, 2265, 2285, 2325, 2330 models using two monolithic BA312 IC’s as a differential gain stage with a proceeding NPN/PNP coupled output stage. The New AE BA312 Upgrade modules are one of the biggest upgrades to these vintage units in decades, results from peer/customer reviews have been absolutely outstanding, with the modules adding a great degree of dimension and clarity to the Marantz presentation and associated decrease in distortion, increase in gain and damn near linear frequency response!

After the modules were installed replacing the old inferior IC’s all the capacitors including tantalums were replaced with a audio grade and low impedance KA/KT and PW with an increase in operating voyages, audio grade Muse BiPolar were used for the output R/C. High grade MKP polypropylene capacitors were installed for the input R/C network. The decoupling capacitor was increase in value for better filtering. New low noise TO-92 Fairchild devices were installed.

BEFORE

AFTER

P700 Drivers

The 2275 driver section employs a dual differential pair which drivers the output via H703 and predriver/driver H711/12/13 devices per channel with a global feedback circuit and dynamic bias control via H709/10 and a complimentary output stage.

As mapped below the differential pairs were matched within 1% and thermally coupled together, new constant current/ detect, pre drivers were installed using low noise, modern Fairchild TO-92 and TO-126 devices. New general axial Vishay diodes installed as well.

Differential Mapping 

New low impedance, high temp (105C) Nichicon PW’s installed with an increase in operating voltages, as well films to a MKP polypropylene input and PP .1MFD type including high grade WIMA polypropylene type. 

BEFORE

AFTER

P400 RIAA (Phono)

The phono stage is the same stage present in many of the 22/23 series Marantz receivers, most which feature the problematic 2Sc458 devices and VD diodes. The P400 is a coupled input/output stage which is quite linear compared to the RIAA standard when low noise, higher gain devices are used.

All of the capacitors here were replaced with low impedance PW Nichicon, including the axial to a more reliable radial, and increases in operating voltages. All the VD diodes were replaced with modern axial viceroy 4148 type and all NPN replaced with low noise Fairchild devices.

BEFORE

AFTER

RIAA Curve Response

Illumination

New vellum for both displays and meters were installed along with new custom SMD lamps and function indictors. 

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T. Monnich's Marantz 4270

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.

P800 Power Supply
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.

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

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