Wednesday, May 30, 2012

Coffman Labs G-1A Preamplifier


      5 position selector switch with a mute position
      Three Line: S1, S2, S3 selected at front panel
            50k input impedance (S1 & S2); 10K (S3)
      Two phono: Phono selected at front panel:
            MM1 / MM2 or MM / MC:  Rear Panel Switch
            MM1 selectable impedance 47K / 70K / 95K

      5 position selector switch with ‘Off’ position
      Two Line level: (Inverted) Rear Panel:  “On” Selected
             Output impedance: 600 Ω “Out1” and 1000 Ω “Out2”
      Record out: (non-inverted)  Rear Panel: Always present
      Headphone Out (non-Inverted): Front Panel Selectable
              ‘Hi’ (100-300 Ω) or ‘Lo’ impedance (32-75 Ω)
      Front Panel Line Out: (Inverted) ‘Out’ via headphone jack

      Phono to REC OUT Jack:  MM=36 dB : MC = 52 dB
      Max Phono Gain (Line out):  MM=60.5 dB :  MC = 76 dB
      Line level output maximum undistorted: +14 dB
      Max Headphone power: ½ watt at 32 Ω, ¼ watt at 300 Ω

Tube Complement:
      2 X  12AX7 / ECC83 (RIAA Section)
      2 X  12AU7 / ECC82 (Phono Boost)
      2 X  5687 (Line Output)
      1 X 5AR4 (Power Supply)

Equalization: [measured in to 5 ohm load on MC input]
      Passive RIAA, Paper in Oil (PIO) capacitors used for filters.
       +0.5/- 0.2 dB 20Hz-20KHz (typical) 1Khz standard.
      7 Hz rumble filter inherent in Phono Section

Frequency Response:
      Line: 20Hz–100KHZ +0.2/-0.5dB;  15Hz–150KHz + /-1.0dB
      Headphone: -1dB at 15Hz, -2dB at 20KHz [Sennheiser 650]

Signal to Noise:  (partially dependant on specific tubes used)
      Phono:  approximately 85+ dB
      Line:  approximately 100+ dB

Chassis Configuration:
      Separate power supply on 5 foot cable.
       110/120 or 220/240:  Factory set per order

Purchase Options:
        Moving Coil: Replaces one MM input with MC input
            [Note: MC step-up is 15.5 dB: .3mV output or higher  
      120/240 Voltage:  Specify at the time of purchase.

Coffman Labs