Well, more inductance will be a better filter, but a 7H choke will have a smaller saturation current than a 2H choke of similar size, so the answer is, OK if the choke current spec is adequate. It's also remotely possible the 7H choke might have too much resistance. I have no other info about this preamp so I'm assuming its a tube circuit since that's the only place a 2H choke belongs.
> 4S preamp schematic
Be nice to give a link. 4S Universal Preamplifier for 12A*7 Tubes
This is essentially ONE 12A_7 tube. Several options, but they all use 100K plate resistor. At 245V it can't suck even 2.45mA per triode, and that would not pass audio. More likely half the 245V drops in each 100K, 1.2mA per triode, 2.4mA for stereo, round-up to 3mA.
They mostly do not make chokes as *small* as 3mA. In classic tube-work, 2H 50mA is about as small as it went. Classic days are gone and I suppose that designer had a 100mA choke in hand. Your 7H 50mA will work just as good, a hair better. And a 5,300 Ohm resistor will filter 120Hz near as well with only a negligible 16V drop.
At that point R-C filtering is efficient enough and far cheaper.
Be nice to give a link. 4S Universal Preamplifier for 12A*7 Tubes
This is essentially ONE 12A_7 tube. Several options, but they all use 100K plate resistor. At 245V it can't suck even 2.45mA per triode, and that would not pass audio. More likely half the 245V drops in each 100K, 1.2mA per triode, 2.4mA for stereo, round-up to 3mA.
They mostly do not make chokes as *small* as 3mA. In classic tube-work, 2H 50mA is about as small as it went. Classic days are gone and I suppose that designer had a 100mA choke in hand. Your 7H 50mA will work just as good, a hair better. And a 5,300 Ohm resistor will filter 120Hz near as well with only a negligible 16V drop.
At that point R-C filtering is efficient enough and far cheaper.
Thank you, and next time I will give the link when asking this type of question.
I'm just trying to build one of these preamps and gathering all the parts from the pile of stuff I have. I've also read about what the choke does and understand why you say that the R-C filtering would be efficient and cheaper. Thank you for your response.
I'm just trying to build one of these preamps and gathering all the parts from the pile of stuff I have. I've also read about what the choke does and understand why you say that the R-C filtering would be efficient and cheaper. Thank you for your response.
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