Circuit topology Four dual triode vacuum tubes (Sovtek 6922), high-voltage discrete Class A Gain Range Microphone: Transformer balanced 850/2500 ohm, 0dB to +58dB Instrument: Unbalanced 1 meg ohm, 0dB to+30dB Line: Balanced Class A 20k ohms, -27dB to 28dB Maximum input level and connector types Microphone26dB@25Hz, +30dB@1kHz balanced XLR Instrument+30dB unbalanced front panel jack socket Line +36dB balanced XLR Maximum output level +30dB balanced 600 ohms, DC coupled, discrete Class A Output type and gain XLR connector, output trim gain -45dB to20dB Noise 20kHz unweighted -92dB Noise microphone EIN -116dB, 22Hz to 22kHz unweighted