Hammond 124 Series Tube drivers 

Interstage Transformers 

124 Series Tube Driver - Interstage Transformers

Part	Watts	Primary Impedance ohms	DC Resistance ohms	Secondary Impedance Ohms	Secondary  DC Resistance ohms	Winding
124A	5 watts	10k	403	90k C.T	1524	C.T
124B	5 watts	10k	403	90k C.T	1500	C.T
124C	5 watts	10k	403	90 C.T	1524	C.T
124D	5 watts	7k C.T	454	15.8k C.T	681	C.T
124E	5 watts	15k C.T	728	33.8k/135k	3880	Dual
124F	5 watts	15k C.T	900	3.75k/15k	899.5	Dual

• Designed for general purpose or replacement use in push-pull or phase inverter tube driver circuits.
• Should not be used for single-ended applications. They have no gap for DC bias current present in SE mode.
• Open style with minimum 5" long primary leads.
• Minimum frequency response 150 Hz. - 15 Khz (+/- 1db max. ref. 1 Khz.) at full rated power.
• Part number 124B is the same as our 124A except for 49% Nickel laminations for greater fidelity.
• Part number 124C is the COIL ONLY (for those experimenters who want to use their own "iron").

Hook Up Data

• For Parallel connected operation (33.8K Ohm Secondary):
  • Connect the GRN/YEL wire to the GRN wire AND the BLK/YEL wire to the BLK wire.
• For Series connected operation (135K Ohm Secondary):
  • Connect the BLK/YEL wire to the GRN (this becomes the centre tap) - GRN/YEL and BLK wires are the output.