Pro Co DB1 Uses the Pro Co DBT-1 transformer. Converts the signal level from line (or speaker) to microphone (-22 dB). There are ground connection buttons to the device chassis, a step reduction level of -20 dB (for connection to the power amplifier output), and a high-pass filter switch (4 kHz, 6 dB/oct) for guitar applications.
Technical specifications of Pro Co DB1:
Input – impedance 100 kOhm - unbalanced parallel two jacks.