sonicmook56
Well-known member
Hey gang,
A while back I enquired the group about techniques used for measuring the frequency response of speakers in a room. Thanks for everyone's input. (original thread) http://www.groupdiy.com/index.php?topic=29112
I have been busy reading everything I can get my eyes on and playing around with an extra set of room EQ's, a few software based RTA's, measurement solutions and a pair of Earthworks M30 measurement microphones, making adjustments to the EQ's, taking measurements and listing to the end results. So far so good. :grin:
What I want to do next is build a pair of simple ultra low distortion/ flat frequency response mic pre's to mate the the M30 microphones. I did a bit of datasheet surfing/ engineering and came up with this.
http://conwayrecording.gotdns.com/~benmook/personal/diy/ref-pre.jpg
{over-large image changed to link --PRR}
All IC's are the new LME49870, http://www.national.com/ds/LM/LME49870.pdf
supply is +/- 16V (probably will be in a API rack)
I haven't figured out the right resistor values for the stepped gain, but it will be equivalent to a 5K.
Phantom is always on. Do I need diodes on the input? Is there an easy way to get rid of the coupling caps?
Power connections are not shown for simplicity. Will probably be 10R resistors to some .1 decoupling caps.
Hoping for someone with much more experience to tell me what's fundamentally wrong with this.
A while back I enquired the group about techniques used for measuring the frequency response of speakers in a room. Thanks for everyone's input. (original thread) http://www.groupdiy.com/index.php?topic=29112
I have been busy reading everything I can get my eyes on and playing around with an extra set of room EQ's, a few software based RTA's, measurement solutions and a pair of Earthworks M30 measurement microphones, making adjustments to the EQ's, taking measurements and listing to the end results. So far so good. :grin:
What I want to do next is build a pair of simple ultra low distortion/ flat frequency response mic pre's to mate the the M30 microphones. I did a bit of datasheet surfing/ engineering and came up with this.
http://conwayrecording.gotdns.com/~benmook/personal/diy/ref-pre.jpg
{over-large image changed to link --PRR}
All IC's are the new LME49870, http://www.national.com/ds/LM/LME49870.pdf
supply is +/- 16V (probably will be in a API rack)
I haven't figured out the right resistor values for the stepped gain, but it will be equivalent to a 5K.
Phantom is always on. Do I need diodes on the input? Is there an easy way to get rid of the coupling caps?
Power connections are not shown for simplicity. Will probably be 10R resistors to some .1 decoupling caps.
Hoping for someone with much more experience to tell me what's fundamentally wrong with this.