Got here a tube amp with 2 tubes of type 2P1P (russian, datasheet attached).
There's a heater supply line which connects to pin 7 of both tubes. Pin 5 of both tubes goes to ground via an inductor. Pin 1, the other heater pin is left not-connected. If understood correctly, this means that half of the heater is left unused. Is this correct ? Like powering a 12ax7 only using pin 9 and 5.
If so, what voltage and heater current should I use for proper heating of these tubes?
Normally in series (according to the attached datasheet) U = 2.4V and I = 60mA, or U = 1.2V and I = 120mA.
However, when turning up the power supply until a current of 120mA total (for both tubes) is measured, 60mA per tube, I measure 1.50V over the heater voltage per tube, thats before the inductor to ground. Due to the inductors to ground, total voltage is 5,75V but that's of no concern.
This is no circuit of my own, this is an existing circuit, which has been used.
There's a heater supply line which connects to pin 7 of both tubes. Pin 5 of both tubes goes to ground via an inductor. Pin 1, the other heater pin is left not-connected. If understood correctly, this means that half of the heater is left unused. Is this correct ? Like powering a 12ax7 only using pin 9 and 5.
If so, what voltage and heater current should I use for proper heating of these tubes?
Normally in series (according to the attached datasheet) U = 2.4V and I = 60mA, or U = 1.2V and I = 120mA.
However, when turning up the power supply until a current of 120mA total (for both tubes) is measured, 60mA per tube, I measure 1.50V over the heater voltage per tube, thats before the inductor to ground. Due to the inductors to ground, total voltage is 5,75V but that's of no concern.
This is no circuit of my own, this is an existing circuit, which has been used.