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We supply heater chokes, in case you want to order them. However you need to be very careful, designing with those. If the heater current is relatively high, the chokes will become relatively hot. Copper however has quite some temperature coefficient, of 0.4% per degree Celsius. Assuming the choke becomes 45°, raising to this temperature, beginning at 22° room temperature, is a difference of 9.2% in resistance. This is actually quite a lot, and you would need to make the power supply such that the tube in hot condition of the choke, gets exactly the right heater voltage. So for each choke, look at the copper resistance in cold condition, and compare this with the resistance in hot condition, which is higher.

This has to be done very correct, because tubes have only 5% tolerance on the heater voltage, where this 5% deviation by itself is even something to avoid if you can. However that means, during the warm up time of the choke, which can be 15 or 30 minutes, the tube is overheated. For this reason, we do NOT recommend heater chokes for Directly Heated Barium oxide tubes. Which includes all Emission Labs tubes. So no matter how you design this, the tube filaments are either under heated during normal use, or over heated during the warm up phase. Both of which compromise the life time.

Tungsten heater tubes ( so called "bright emitter" tubes) are less sensitive against this, and can be used with heater chokes, provided you make the design such that the heater voltage is correct for the warmed up choke.