EDIT: I changed the title cause this diverged to a general discussion
I know this has been discussed before, but I haven't found answer to my specific question/questions.
I've read that a value for a capsule bias resistor in a condenser mic should be 100M-1G. Or even 3 gigs. But still in some classic designs it's much lower. 60M in U67 and even 8M in a ELA M 250/251 schematic I found. That's quite of a range.
I built a circuit following the G7 circuit but using 5840 tube, different transformer and different cathode resistor value. Now I'm testing it with a chinese K67 type capsule. First I tried 50M for the capsule bias resistor which I had lying around. Sounded good, brittle though, but that's what I expected for that capsule. Then I swapped it to 1G, same as in G7. Much more low end, which is nice, but also more hiss. Now I'm considering swapping the 50M back, cause I can easily EQ it for more bass. And because I'm going to get a Thiersch M7 type capsule, which haven't got as much high's as K67 type, I'm probably gonna need to boost highs for my pop mixes. But can't do that with that 'hissy' 1G capsule bias resistor. And I'm going to use the mic for close miking vocals anyway, so I probably get enough low's with the proximity effect.
Am I over simplifying things? Is it just that different type of capsules need different values? Or did I mess up my circuit with flux or something? Tried not to, and cleaned everything with isopropyl alcohol. Is hiss a normal side effect of large capsule bias resistors?
I should of course test different values when I get the Thiersch in, but still, I'd like to learn more about effects of a capsule bias resistor.
I know this has been discussed before, but I haven't found answer to my specific question/questions.
I've read that a value for a capsule bias resistor in a condenser mic should be 100M-1G. Or even 3 gigs. But still in some classic designs it's much lower. 60M in U67 and even 8M in a ELA M 250/251 schematic I found. That's quite of a range.
I built a circuit following the G7 circuit but using 5840 tube, different transformer and different cathode resistor value. Now I'm testing it with a chinese K67 type capsule. First I tried 50M for the capsule bias resistor which I had lying around. Sounded good, brittle though, but that's what I expected for that capsule. Then I swapped it to 1G, same as in G7. Much more low end, which is nice, but also more hiss. Now I'm considering swapping the 50M back, cause I can easily EQ it for more bass. And because I'm going to get a Thiersch M7 type capsule, which haven't got as much high's as K67 type, I'm probably gonna need to boost highs for my pop mixes. But can't do that with that 'hissy' 1G capsule bias resistor. And I'm going to use the mic for close miking vocals anyway, so I probably get enough low's with the proximity effect.
Am I over simplifying things? Is it just that different type of capsules need different values? Or did I mess up my circuit with flux or something? Tried not to, and cleaned everything with isopropyl alcohol. Is hiss a normal side effect of large capsule bias resistors?
I should of course test different values when I get the Thiersch in, but still, I'd like to learn more about effects of a capsule bias resistor.