musix2000
Member
I`m building an ELA M250e clone with a CT12, JAN GE 6072a mic. grade and a 13114 transformer by cinemag. As in the original schematics I use a 1k8Ohms (1k82) cathode resistor, instead of the no more produced 8M resistor I use one with 7M96(7)Ohms For tests and some experiments I have the capsule of a Rhode K2 in it. Because Telefunken have a 2k7Ohms (2k67) resistor in their C12 and ELA M251e I`ve also tried this: with 1k82Ohms 1.065V and with 2k67Ohms 1.37V are coming from the cathode (B+ is 120,6V). It seems: higher resistor values > higher cathode bias voltage. I was told that the cathode bias should be 1.1V, otherwise, with more voltage, the tube could be damaged. But I think the guys at Telefunken know what they do. They also have changed from the 8M resistor to a 10M (what I still haven`t tried, maybe this brings the cathode bias down to 1.1V??). Whether in their C12 resistors were changed or not I didn`t find out, instead of fixed bias they also use a 2k67Ohms resistor.
I still haven`t tried the microphone under studio conditions, I`ve just finished it with the K2 capsule and it`s in my workshop for the next days.
Is it ok to have a higher or lower cathode bias? What is the influence to the sound?
Does anybody know about this?
I still haven`t tried the microphone under studio conditions, I`ve just finished it with the K2 capsule and it`s in my workshop for the next days.
Is it ok to have a higher or lower cathode bias? What is the influence to the sound?
Does anybody know about this?