I humbly submit my experience with the hope that someone else will benefit from it. I have just learned from experience that Radio Shack dB meters have a limited lifetime. Recently, I upgraded my pre/pro and began noticing test tone problems. It seemed the tones were too soft and I couldn't calibrate them at 75 dB with my trusty Radio Shack dB meter. After a couple days of experimentation, all possible problems relating to my pre/pro were ruled out. There was nothing left but to suspect my dB meter of more than 6 years as the culprit. I replaced the battery, adjusted placement and got the same poor results. Hmmmm! Today, I bought a new dB meter and -Presto!: Accurate readings at reference level! It would seem that my old dB meter just bit the dust on me - my equipment was fine (and had been all along)! LESSONS:  Check the simple stuff first!  Your Radio Shack dB meter won't live forever. Some day it will fail. Hope this helps someone else!