Notes with regard to the circuits and boards in this directory:
Compressor designs:
	PCB:
	PCB_AA119_compressor.gif (200%) (23.03.2019)
	Circuit:
	AA119-line_level_compressor.gif
	Original design is from the seventies.
        Requires +15/-15V supply 
	Newest boards made and finished 30.03.2019 (two copies)
        Purpose: application in 'Plus-Minus' project.

        To be changed: last opamp would be better in the
        non-inverting configuration.
        The improved circuit is:
        SCH_AA119-line_level_compressor_2.gif
        The PCB for the improved circuit is:
        PCB_Compressor_2.gif  (200%), dated 31.03.2019

        A PCB for a dual compressor with power supply is this:
        PCB_Powered_Compressor.gif   (200%, 31.03.2019)

RIAA preamp design:
        PCB:
        PCB_RIAA_Amp.gif (this film has also 2 compressor boards as above.) 200%
        Circuit:  
        SCH_RIAA-preamp.gif
        Picture:
        RIAA_IMG_6942_600.JPG
        Original design is from the late seventies.
        Has 230V power supply on the board.
        Low impedance outputs, can even drive headphones.
        This version produced 30-31.03.2019.
        Built into our Lenco turntable, 02.04.2019. The sound is very good.
        Remarks: there is a ca.40mV DC offset on the output. Either we should use
                 a tracking power supply (LM325) or place blocking caps (4.7uF)
                 on the outputs.
                 A slight hum on the output is audible: groundloop, weak screening
                 or power supply weakness? To be researched.