MK-1 Preamp (SSP-MOD)

Even performing all the optimizations done in the 1C-MOD & 3C-MOD.... We still have a problem to address...
The Treble control range is still affected in a significant way by the level of bass control applied.

This is unbearable HIGH with standard MK-1.... but  partially addressed in my 1C-MOD and 3C-MOD.
We can see a -6dB loss in the 3C-MOD.  In the standard MK-1 We would have  more than  8 Db loss !!!

the Red line is representing the equalization applied when both Bass& Treble controls are at their max level.

The SSD-MOD  arrange the Baxandall Treble & Loss filter in a way  to minimize the Treble loss INCREASING at a maximized  level  the independency between  Bass & Treble controls.

For example.....sometime is nice to get a "scooped"  sound from the bass and this is done  by:

• CRANK UP THE BASS CONTROL NEAR TO THE MAX
• CRANK DOWN THE MID
• CRANK UP THE TREBLE NEAR TO THE MAX

But this requires an high level of separation between the Controls..and remember .....in  the MK-1 Bass & Treble are implemented in the same active Operational Amplifier cell.

The SSD mod does the job in a optimized manner reducing at  less than 3 Db the average Treble loss when  BASS&TREBLE controls ARE CRANKED AT 100%:

Of course even in non cranked positions the B&T controls separation works well..

In the following picture We can see  the 6 components that need to be replaced for the SSP-MOD:

Another view of  the modification on the schematic chart:

TO SUM UP:

1. Replace both R4 & R5  (360 Ohm)  with 2  3.3k matched  resistors
2. Replace R8 (5.1k) with one of the two  360 Ohm resistors  removed in step 1  
3. Replace R3 (5.1k) with a 8.2k resistor.
4. Replace C2 (22n) with a 8.2n capacitor
5. Replace C5 with a with a 8.2n capacitor

ALL  SMD COMPONENTS TO BE USED ARE 0805 SIZE

AND FINALLY ...here the final summary equalization charts:

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KKPRINCE
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