The wonderfully simple 300B directly heated triode is virtually Lee De Forest's very first evolutionary 3-element piece, comprising only filament, input grid and anode output. Brought to reliable perfection by Western Electric USA and later by Standard Telephones UK as the 4300B, the 300B was very much intended and widely used for telephony amplification.
Vacuum Tubes: 2 x 300B (Output), 1 x 6SN7 (Driver), 1 x 6SL7 (Input),
2 x 5AR4 (Rectifier). (Units prior to 2011 used 5U4 rectifier tubes.)
Output Power 1kHz with 5 dB FeedBack in SINGLE-ENDED: 11 Watts 3% THD
Output Power 1kHz with 5 dB FeedBack in PUSH-PULL: 24 Watts 1.5% THD
Frequency Response with 5 dB FB in SINGLE-ENDED: 15 Hz - 15 kHz ±0.5 dB (measured at 5 watts)
Frequency Response with 5 dB FB in PUSH-PULL: 10 Hz - 20 kHz ±0.5 dB
GAIN SE Mode 0dB Feedback Setting: 30 dB
GAIN SE Mode 10dB Feedback Setting: 20 dB
Input Sensitivity with 5db FB SINGLE ENDED: 700mV for Maximum Power
Input Sensitivity with 5db FB PUSH-PULL: 450mV for Maximum Power
Input Sensitivity with 5db FB SINGLE ENDED: 165mV for 1V output into 8 Ohms
Input Sensitivity with 5db FB PUSH-PULL: 160mV for 1V output into 8 Ohms
S/N Ratio: SINGLE ENDED: 83.5dB Ref. 1W; 2.83v//8 Ohms,20KHz BW; 5dB FB.
S/N Ratio: PUSH-PULL: 85.4dB Ref. 1W; 2.83v//8 Ohms; 20KHz BW; 5dB FB.
Dynamic Range: SINGLE ENDED: 94dB Ref. 3% THD; 20KHz BW; 5dB FB.
Dynamic Range: PUSH-PULL: 99.5dB Ref. 1.5% THD; 20KHz BW; 5dB FB.
Input Impedance: 100 kOhm, direct coupled.
Optimum Speaker Load (switchable): 4 to 12 Ohm range appropriate for 4 & 8 Ohm speakers - 12 to 20 Ohm range appropriate for 16 Ohm speakers
Actual Output Impedance SINGLE ENDED: 2.25 Ohms
Actual Output Impedance PUSH-PULL: 1.86 Ohms
Damping Factor SINGLE ENDED: 3.5
Damping Factor PUSH-PULL: 4.3
Maximum Power Consumption: 240 Watts
Mains Voltage Frequency: 50~ 60Hz
Power transformer factory set for 100V, 120V or 220-240VAC operation for original destination country's mains voltage.
Operating Mains Voltage changeable with power transformer re-wiring and fuse value change.
Fuse type and ratings 117 VAC operation:
MAINS fuse: 3 Amp 3AG slow-blow use glass body Littlefuse Series 239
Fuse type and ratings 230 VAC operation:
MAINS fuse: 1.6 Amp 3AG slow-blow use glass body Littlefuse Series 239
B+ Fuse: MDA 400 mA SLO-BLO Ceramic Time-Delay fuse
Badge Illumination: Units produced before 7/2003 use 8V, 0.3A "Fuse-Lamp" 1/4" X 1 1/4" - Serial numbers after NSEPP314 use LED illumination which probably won't burn out
Dimensions: W= 8.5, D= 23, H= 9 inches, Including projecting controls and parts
Minimum Mounting Surface Dimensions: Feet Footprint = W= 7.5" D= 18"
Shipping Weight: 41 lbs. Each.