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Purple Audio Action FET Compressor

Discussion in '500 series' started by audiokid, Oct 22, 2011.

  1. audiokid

    audiokid Chris Staff Resource Member

    Mar 20, 2000
    Prince George, BC
    Home Page:
    TDA FET compressor reminiscent of the MC77. Designed to work in standard "500" racks.

    The Action features a constant impedance 600 ohm input attenuator feeding the input transformer, just like our MC77 units. This makes the input more resistant to overload by hot signals. After the input transformer, the signal is attenuated by the same gain reduction FET as in the MC77. The attenuated signal is buffered by our class A KDJ3 opamp, which feeds the output fader. Lastly, our class AB KDJ4 output opamp drives our custom hexafilar nickel and steel output transformer. The total gain (with no attenuation) is 45dB, just like the MC77.TD

    The attack and release times cover a broader range than the MC77, which can cause distortion... which may or may not be what you are looking for. Use at extremes with caution. The ratios are the same as the MC77, and the threshhold moves up as the ratio goes up, just like the MC77.

    In the center of the unit is an SMT sidechain and stereo link amplifier, below that is our SMT compression LED ladder meter driver. Behind that is the SMT input and output tricolor LED meter driver.

    Stereo linking is accomplished by cross connecting pins 3 & 6 on the edge connector. On the Purple Sweet Ten, there is a second output XLR that can be used to link two Actions. The link is accomplished using a XLR-F to XLR-F cable with pin 2 on one XLR-F connecting to pin 3 on the other XLR-F and vice versa. Plug in the cable, flip the front panel switch and you are linked. Non-Purple racks do not have an easy way to connect pins 3 and 6, and will need modification to link two Action units.


    *Input attenuator feeding input transformer
    *Output level control
    *Input and output tricolor LED metering
    *Eight LED GR metering
    *Five ratios including "All buttons in" mode
    *Attack and Release controls
    *True Relay Bypass
    *Stereo Linking
    *Compression onoff switch
    *Discrete signal path
    *Over Current Resettable Fused (prevents any module problem from affecting your rack)
    *ROHS - Lead Free
    For easy serviceability and tweaking, the Purple discrete opamps can be replaced with any standard discrete opamp or a DIP-8 IC.

    *Total Gain: 45dBu
    *Ratios: 4:1, 8:1, 12:1, 20:1, ?:1 ("All buttons in")
    *Attack time: Continuously Variable from over 800 microseconds to 20 microseconds
    *Release time: Continuously Variable from over 1.1 seconds to 50 milliseconds
    *Input impedance: 600 ohms
    *Output impedance: 600 ohms
    *Current consumption: 90ma
    B Action pinoutB

    *Pin 1: Chassis Ground
    *Pin 2: Output A +
    *Pin 3: Link In - (Purple Audio Rack Only - XLR OUT 2)
    *Pin 4: Output A -
    *Pin 5: Audio Ground
    *Pin 6: Link Out - (Purple Audio Rack Only - XLR OUT 2)
    *Pin 7: Input -
    *Pin 8: Input -
    *Pin 9: Input +
    *Pin 10: Input +
    *Pin 11: NC
    *Pin 12: +15 or 16VDC 90ma
    *Pin 13: Audio Ground
    *Pin 14: -15 or 16VDC 90ma
    *Pin 15: NC (+48VDC)


    Attached Files:

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