Hi Everyone,
I'm currently trying to set the (internal) gain of a mic preamplifier for exactly 65db of total gain. I have a Fluke 187 DMM which has the db metering function. What I've been doing is feeding the input a 1kHz tone from ProTools at -60db (trying to approximate a mic signal), measuring the db with the Fluke attached as follows:
RED: On pin 2 of input to preamp
BLACK: Attached to chassis ground of preamp
After I read about -55db on the Fluke, I attached the RED probe to pin 2 of the output XLR (with black probe still attached to the chassis ground of pre) and read about -7db with the volume of the preamp full up.
This seems weird because when I plug a mic into the preamp and mic something up, the pre seems to have way too much gain, even at a very low setting on the input gain knob. When compared to my Sytek pre (which is also supposed to have 65db of total gain), the Sytek is much less sensitive using the same mic, source sound, and gain setting. What might be going wrong here?
According to the Fluke, I should have 48db gain on my pre. Yet, it's overloading on most sources. Does it have something to do with the way ProTools is sending the signal to the pre? Or am I reading it improperly? I would do a simple voltage test on the input and output, then convert to db but I feel like the same problem will be present in my readings...
Thanks for any help.
I'm currently trying to set the (internal) gain of a mic preamplifier for exactly 65db of total gain. I have a Fluke 187 DMM which has the db metering function. What I've been doing is feeding the input a 1kHz tone from ProTools at -60db (trying to approximate a mic signal), measuring the db with the Fluke attached as follows:
RED: On pin 2 of input to preamp
BLACK: Attached to chassis ground of preamp
After I read about -55db on the Fluke, I attached the RED probe to pin 2 of the output XLR (with black probe still attached to the chassis ground of pre) and read about -7db with the volume of the preamp full up.
This seems weird because when I plug a mic into the preamp and mic something up, the pre seems to have way too much gain, even at a very low setting on the input gain knob. When compared to my Sytek pre (which is also supposed to have 65db of total gain), the Sytek is much less sensitive using the same mic, source sound, and gain setting. What might be going wrong here?
According to the Fluke, I should have 48db gain on my pre. Yet, it's overloading on most sources. Does it have something to do with the way ProTools is sending the signal to the pre? Or am I reading it improperly? I would do a simple voltage test on the input and output, then convert to db but I feel like the same problem will be present in my readings...
Thanks for any help.