MK-1 Preamp Anatomy (OVERALL DESCRIPTION)

After a very long  & boring  decoding session I finally managed to reverse engineer the whole circuitry .............................................................!!!!
;-)

 We can then see in the pic below the overall  organization of the MK-1 ensemble.
A kind of Google Maps Satellite vision of it...

Even if this implementation is maybe specific for a Cort A4 , I will bet my Hamster balls You will find more or less  the SAME setup on several other basses with very few variations.


If You are interested I have the fullsize 4000x4000 pixel image I  can share.

OVERALL DESCRIPTION

The preamp itself is based on three dual OpAmp TL062 . A total of 5 Operational Amplifiers are effectively used. In fact only half of the rightmost TL062 (IC3) is employed.  

This suggests me that sooner or later I will get rid of the half used Ic3,  obtaining a better organization of the things..... Less distortion , less noise,  less power consumption... :-)

We'll see...

As a sort of patch I found a diode added in parallel to the power supply. In my case this diode is meaningless as I have another  (schottky) diode in the battery compartment  in series to the +9v line. I phisically and digitally removed the diode (a common 1N4001).

In the whole circuit a virtual reference mid tension ground is used for driving correctly the  Operational Amplifiers in rail to rail mode.  A 4 components (2x 22uF + 2x22k)  resistive-capacitive divider is employed for creating the half tension Vref:

Be aware that externally all the potentiometers, input jack and pickups are grounded to the REAL GROUND , not to the vref virtual one!.


In the next post We'll see the organization of the preamp INPUT STAGE

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:-)