That previous work partially presented in previous post prove to be good mod. That modified ART DJ Pre - II works stable and objectively measured much better then in original configuration. But now I have something even better, observing the position of Gain for my Pioneer Pro-DJ PC-X5 cartridge, which is no other then branded(OEM) AT-3600L i get puzzled why it needs the same ~+4 Gain trim which is like +39-40dB on printed scale, and on the other hand on my made Lab-Preamp (that metal box at my wok bench pics.) measurements shows that it can be put on +34-35dB to get same -1..-3dB signal levels. So I took of little 5k gain pot and find out source of problem is non linear etc. its logarithmic nature of strange applied amplification design.

It look like this:

In short by "fixing" inverse log position of DJ Pre II by switching to new 2,5k Lin pot. we can get almost linear selection of gain:

To get beyond +45dB up to that +53.8 gain, you need to disconnect Pot pin 1 and 4 or to bypass then with 100k-1M Ohm.
If you omit those resistors for Pot bypass (left open pin 1-2, 4-5) you will get no more then +53,9dB at the best.
So until my 2k Lin Burns (2 gang - stereo) Potentiometer arrives box stays open.

Best regards,
dr Jovan I.