Tuesday, August 15, 2017

New Release Marantz & Sansui BA312 IC to Op-Amp Modification

New Release Marantz & Sansui BA312 IC to Hi-Fi Op-Amp Module

Applicable Models
Marantz 2250,2250B,2265,2275,2285,2325, 2330 PE01 X2
Sansui 8080DB/9090DB F2653 RIAA X2 — F-2544 Tone Control X2
Sansui 8080/9090 F2541 RIAA X2 — F2543 Tone Control(MST VOL.) X1 — F-2544 Tone Control X2
Sansui 7070 F2622 Tone Control X2 — F2620 RIAA
Sansui QRX-9001 Quad Tone Control X2 

Today I am very excited and proud to announce the release of my first modular product upgrade, and a first for the vintage audio community! The BA312-OPASIP7; an adaptive module for high performance, single ended operational amplifiers into existing BA312 designed pre-amplifier/phono stages!

Over about 8 months this last year I have been working on perfecting a concept I saw early on with talks on upgrading these original pre-amplifiers integrated circuits with modern operational amplifiers. After working with several companies I found Colorado based Sparkos Labs who specialize in designing and producing high-end discrete operational amplifier and voltage regulators. Through this partnership I was able to have my design cleaned and perfected and a production process for boards. The universal configuration was designed with their proprietary SS33601 high performance operational amplifier in mind in conjunction with my circuit adaptive module. 

A brief introduction on Pre-Amplifier IC’s and Operational Amplifiers
Our focus will be on the original BA312 and TA7136 integrated-circuits (IC) but first lets take a step back to the first Operational Amplifiers (OP-Amp). The earliest true version of the OP-Amp was a vacuum tube used during the 1940’s in RF equipment developed by Bell Labs as general purpose feed-back amplifier. With the advent of the transistor, IC and Jean Hoerni’s Planar Process of manufacturing came the release of what we know as monolithic IC OP-Amps. The early innovations came from supplies like GAP/R and Arizona based Burr-Brown which was finally absorbed by Texas Instrument in the year 2000 to combine their product series.

The BA312 we are focusing on is a SIP7 pin, high voltage (20-40Vdc) linear, monolithic device manufactured then by ROHM Semiconductor and Toshiba of Japan. Featuring at the time low distortion and high gain-loop qualities with relatively low noise, these early pre-amplifier IC’s. These were implemented as differential gain stages in many pre-amplifier and RIAA EQ (phono) circuit in audio equipment from the greater 1970’s and heavily in several specific Marantz, Sansui and Pioneer receivers, amplifiers, pre-amplifiers and integrated amplifiers. 

Benefits of the upgrade & Sparkos Labs SS3601 Operation Amplifier
The original BA312  have long been out of production...for decades. This means the only reliable replacement for your classic vintage units is to find a donor unit and salvage parts! With the release of the BA312-OPASIP7, we now have a extremely high quality, high performance  replacement option for failed BA312  components or owners looking for a significant sound improvement. 

Musical Notes
As we can see from the reports a significant improvement in the sub sonic response 20Hz to 750Hz was noted (see frequency response reports) with a linear response 50Hz to 5Khz with the upgrade which is a HUGE improvement over the original BA312 IC.  The BA312 does tend to lead to a somewhat lacking bass which is one of the reasons it was a prime candidate for the concept, the lower end definition is overall improve with transient peaks becoming more dynamic than fuzzy. The mid-range and high end response had a distinct clarity to upper crossover points while auditioning everything from Blues, Folk, Rock, Jazz even some Electronica so far I suspect from a cleaner,linear gain stage employed. Overall the upgrade brings the PE01 to the next level of performance with a distinct improvement in overall dynamic presentation and frequency response across the audible spectrum while retaining yet that smooth Marantz sound.

The choice of using Sparkos Labs SS3601 as an OP-Amp with my adaptive module was a no brainer..the acclaimed single-ended discrete, proprietary designed SS3601/3602 is fully discrete 8DIP family of OP-Amps. Touting features such as; high open loop gain 140dB, (2.9nV√HZ) Noise to 20KHZ, fully Class A biased with matched encapsulated transistors for the input stage and internal current mirrors. Comparatively outranking even the popular high-end OPA627 ( Gain @ 116dB & (4.5nV√HZ) Noise to 20KHZ)  Texas Instrument OP-Amp. Wide bandwidth operation (5Mhz) 75° of phase margin, and 10dB of gain margin.

Comparatively many enthusiasts have found an affinity over the sound presentation of discrete components versus monolithic IC’s such as run of mill TI/AD chips used in the bulk of consumer and high-end audio components today. 

Performance Report VS Original BA312 application 
(Marantz 2325 PE01 Tone Stage)
To get the best possible picture of whats going on, all tests were performed with the PE01 stage isolated from a full unit, with a constant source 35.09Vdc/1.5A SE rail source

Frequency Response
(Frequency Response measure the output level of a device at different frequencies. Showing changes in amplitude over frequency)


FFT Spectrum Analysis

Total Harmonic Distortion + Noise 
(THD+N, think of THD+N as the output produced other than the signal injected.)
Intermodulation Distortion
(IMD, the measurement of amplitude modulation of the injected signal compress in two or more frequencies caused by non-linear responses in a system design (7Khz/60Hz 4:1))

Signal/Noise Ratio
(S/N Ratio or SNR is a measurement the describes how much noise is in the output of a device, in relation to the injected signal amplitude.)
Construction of the BA312-OPASIP7 Adaptive Module
The BA312-OPASIP7 is fully discrete adaptive circuit module fitted with a high-end DIP8 discrete OPA device. Each module is hand built at my shop here and tested for use in each application and unit. Starting with high quality 65mil thick  FR4 (glass-reinforced epoxy ) dual copper layer PCB for a solid, clean and reliable substrate.

 Discrete components include; Panasonic ERA series thin-film  chip resistors which feature a very high reliability, high accuracy-low TCR with .1-.25% tolerances, and leading edge Samsung Electro-Mechanics multiplayer NPO ceramic smd capacitors with a very low ESR. Hardware includes all gold plated SIP-7 headers and gold plated 8DIP socket adapters.

Remaining PCB assemblies that house the module are rebuilt using low noise, modern TO-92 NPN/PNP discrete Fairchild transistors, Audio Grade Nichicon KT and low impedance PW Nichicon capacitors. The DC Filtering capacitors are increased (470MFD for PE01’s from 220MFD) and all input/output/bypass and ceramic pathway capacitors are replaced using high grade WIMA polypropylene film capacitors.

High-End Vintage Audio Restorations (N. Schumacher)
Sparkos Labs SS3601 High Performance Op-Amp

Monday, August 14, 2017

Paul's Sansui G-7700 Receiver

Sansui G-7700 Receiver

Today were showcasing a customers Sansui G-7700 Receiver. The G-Series had several variants released during the period with the G-X700 being the mid-way point. Touting a pure DC amplifier section, Peak LED and digital tuning display with their quartz-locking feature.

F-2980 Power Supply/Protection
The Sansui G-7700 and other G-series feature this similar layout, with a MAIN-PCB in the centre of the unit populated as the power supply and driver section F-2980.  Many of these G-series present the same faults here from an over heating power supply and caustic glue. The glue used to mount the large vertical capacitors in the power supply becomes oxidized over time and causes the exposed leads of components such as resistors to oxidize and break as well as excessive radiant heat from the nearby regulator devices (x3.)

One of the first issues to address as mentioned above was removing all the glue and replacing about half dozen or so resistors with new 1/2 carbon film KOA resistors and several diodes with axial modern Vishay/Fairchild diodes.   All three regulators were replaced with a robust ST, TO-220 modern regulators manufactured using their new construction standards along with new performance Wakefield thermal compound.

All of the electrolytic capacitors were replaced with a high temp (105C), low impedance Nichicon PW and VP Bipolar capacitors with an increase in operating voltage. New axial Vishay Ultra-Fast, Soft recovery diodes were installed as well.



The protection network integrated into the F-2980 is similar to the recent SX-780 I did with a HA12002 monolithic IC used to monitor dc deviation, current consumption in conjunction with varistors for thermal run-away.  This also controls the front “Safe” operation mode indicator. A NOS relay was installed from a reputable retailed in the UK and new filter capacitors. 

F-2980 Driver Stage
Shared on the same MAIN-PCB as the PS the G-7700 has an interesting design. Using an initial Dual FET 2SK150 devices the differential stage, current mirror/differential, and a two-stage OCL Darlington design.

All of the electrolytic here were replaced with high temp (105C), low impedance Nichicon PW capacitors with an increase in operating voltages. 1MFD< capacitors and mylar were replaced with high grade WIMA polypropylene ilm capacitors. New precision Bourns potentiometers installed, new modern, low noise TO-92 Fairchild (see underside adaption for smoother action while biasing protocol) for a matched constant current stage (see BETA mapping below), new modern low noise, low distortion audio applicable On-Semi TO-126 type NPN/PNP pre-drivers/current devices were installed.  Original drivers were removed and tested with new performance Wakefield thermal compound applied. (high volt. broad spectrum drivers should be cross references VERY carefully if replaced to prevent oscillation issues..note the often reference MJE15032/33 are NOT good references @ 30Mz)



BIAS Confirmation
(SM error, Correction at .66x5mA @ 3.3mV)

NPN BETA Matching
F-2855 Tone 
The tone control features a defeat option with dual Bass and Treble attenuations, a 41-stepped precision volume attenuator is used for gain control which is always nice to see, though not potted..
The tone is designed around an initial NPN differential gain stage.

All of the electrolytic capacitors here were replaced with audio KT and MUSE (Bipolar’s) along with VP Nichicons with an increase in operating voltages. All the small signal devices were replaced with modern TO-92 low noise Fairchild devices. 



F-2857 MIC AMP
The G-7700 features a separate driver for microphone line level and dual dubbing options.

The small signal devices here were replaced with modern TO-92 low noise Fairchild devices. Electrolytic’s were replaced with audio grade KT and low impedance PW Nichicons with an increase in operating voltages, a new high grade WIMA polypropylene .47MFD film was installed as well.



F-2865 EQ RIAA
The RIAA is placed under the main chassis carriage using a metal standoff as shielding. Built using an array of precision resistors for low noise (SN @ 78dB) comprised again of a PNP gain stage…..also the G-7700 has two phono inputs!

All of the small signal devices were replaced with low noise, modern TO-92 Fairchild devices. Electrolytic’s were replaced with low impedance and audio grade Nichicon KT capacitors and 470MFD VP Nichicon Bipolar with an increase in operating voltages.



F-3060 Digital Display Power Supply
The digital display requires its own power supply source, with a 5/13V output for the display.  Their are several variations of the supply, all suffering the same issues from the large wire-wound resistors radiating enough heat to scour the PCB. Each resistor should be increase in watt rating as well as foil foot prints exposed and expanded for a good anchor over time.

New robust ST, TO-220 modern regulators manufactured using their new construction standards along with new performance Wakefield thermal compound were installed. All electrolytic capacitors were replaced as well with high temp (105C), low impedance PW Nichicon capacitors with an increase in operating voltages as well as emitter values and several carbon film 3.9K 1/2W resistors.



F-3000 Digital Display
Using a FL type Tube display, it broadcast the FM/AM RF tuning indication and locking  features, it utilizes the MSM5540 monolithic IC with a advanced circuit NJM4558 OPs and BA658 monolithic devices.

All of the electrolytic capacitors here were replaced with a high temp (105C), low impedance PW and VP Bipolar Nichicon capacitors with an increase in operating voltages. The FL assembly was carefully dissembled and cleaned. 



F-2988 RF Stages
The G-7700 features a very fine tuned RF stage, with a emphasis around their “Digital Quartz Locked Tuning System”.  The FM uses a 4-gang tuning capacitor with a dual MOS-FET front end. The AM features a “Frequency linear, double-ganged tuning capacitor, along with a high performance monolithic IC in the IF circuit”.

In both stage all of the electrolytic capacitors here were replaced with a high temp (105C), low impedance PW Nichicon capacitors with an increase in operating voltages.

New Custom 8V SMD Warm White LED’s installed for the highlight