hyuna wrote:

I build and measure loudspeakers at home as a hobby. But I have never had a decent mic preamp for my unmodified Panasonic ECM capsules. I use a USB sound card to accept the mic audio and analyze it with ARTA software.

After thinking about it for awhile I decided to go to the mountain and use the Linkwitz circuit for my measurement mic preamp, but with a couple changes.

The LM833N OPA(http://www.kynix.com/uploadfiles/pdf9675/LM833N.pdf) is a dual chip. Is there anything smart that can be done with the second amp?

And last, how long a cable can an uncut capsule push signal down before the high frequencies begin to be cut? I have seen home theatre mics with cable lengths of 20 feet or more. How far can I go with mic cable? Linkwitz suggests less than 30 ft with a cut capsule. What about a stock capsule?

The cable length, using balanced mike cables, should be non-critical as far as noise goes.

Attenuation of signal will depend on the input impedance of the circuit where the cable is terminated.