Vintage Audio Upgrades - BA312 IC Replacement.

sparkos labs vintage upgrade modules
vintage marantz

Resurrecting Legends:

Few things in the audio world are more iconic than the 1970's era Vintage Manrantz and Sansui Receivers.  We now have the first and only discrete op amp upgrade for the BA312 IC that is commonly found in these units.

The BA312 IC was a simple 3 transistor gain stage- and was not an op amp at all.  It is long out of production, had a high noise floor, and proved itself to be a massive sound quality bottleneck in these otherwise exemplary receivers.

Now, our BA312 Replacement Modules will take your vintage Marantz or Sansui to a higher level of performance, and allow you to relegate the stock BA312 IC's to the dust bin of history.  Which is where the original manufacturers of these IC's put them decades ago.

BA312-M Install video:

Youtuber Ah-Fix-it created this video showing an install of the BA312-M into a Marantz 2250B.  Things were soldered upon.  Measurements were taken.  Things were documented.  

Have a watch, and enjoy ~

vintage sansui

BA312 IC Replacement Modules:

Our BA312 replacement modules can be easily installed into these units and do not require any wires to run, traces to cut, kludging, or off-board components to install them.   Just remove some parts from the board, change out a few others with the parts provided in the kit, remove the old BA312 IC, and install our discrete op amp upgrade modules in their place.  Doing so will give these units about a 10dB  lower noise floor, a reduction in harmonic distortion, and a flatter frequency response all while retaining their classic signature sound.

Check below to see all of the vintage Marantz and Sansui Receiver Models that this upgrade can be used for.  The modules are sold in pairs as there are two BA312 ICs in each of these units (one for the right and left channels) and will come with all of the components that you will need along with step by step instructions on how to install them. You will need to order the BA312-M for upgrading vintage Marantz Receivers, and the BA312-S to upgrade a vintage Sansui unit.

For use in Marantz Models:


ba312 replacment IC in marantz

BA312-M upgrade modules installed in the Marantz
PE-01 tone control assembly.

For use in Sansui Models


ba312 IC replacement in sansui
BA312-M modules installed in the Sansui F2544 tone control assembly.

The BA312 Upgrade Module:

Each kit contains (X2) BA312 replacement modules fitted with our SS3601 Discrete Op Amps as well as (X4) Nichicon UKA/UKT capacitors and low noise Vishay carbon film resistors. Installation instructions are provided in the kit and can also be downloaded in PDF format using the links above.

For vintage Marantz Receivers, the BA312 IC  resides on the PE-01 tone control assembly, and are always in the signal path regardless of the tone control settings.  For Sansui units, the BA312 are used on the F2544 tone control assembly and behave in a similar manner to the one used in the Marantz units.  Be sure to order the appropriate upgrade module depending on whether it is needed for Marantz (BA312-M) or Sansui (BA312-S) as they have different gains and require slightly different components to be swapped out during installation.

With this upgrade, one can expect a flatter frequency response, a reduction in Total Harmonic Distortion (THD) and a lower noise floor.  The measurement plots below illustrate the before and after.  The exact measured results will vary slightly depending on which specific model of receiver the modules are installed in, but in every case they gave both a subjective and measured improvement in all units.

Bass and lower end definition will be improved by the transients becoming more dynamic. Mid-range and high end response will have a distinct clarity that they never had before when auditioning everything from Blues, Folk, Rock, and Jazz. Overall, this upgrade will bring the PE01 assembly in the Marantz, or the F2544 assembly in the Sansui to the next level of performance.  Expect a distinct improvement in overall dynamic presentation, sound stage, and frequency response across the audible spectrum while retaining these receiver's smooth characteristic sound. 

BA312 IC measurements
BA312 replacement IC vintage marantz parts
BA312 replacement IC vintage marantz parts
BA312 replacement IC vintage marantz parts
BA312 IC datasheet

About the BA312 IC:

The BA312 preamp IC is a now obsolete component that consisted of little more than 3 transistors and some resistors.  It was used extensively in many vintage receivers and amplifiers in the line stages and tone control stages.  It was not an op amp at all, but rather a single ended 3 transistor gain stage. The original BA312 IC suffered from high output impedance, noise, poor linearity and a less-than-flat frequency response. Installing our BA312 replacement modules will remedy all of these deficiencies in one fell swoop. 

Be sure to check out the reviews of these modules on Audio Karma, (see the link above) which is an audio forum predominantly dedicated to vintage audio upgrades and restoration.

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