I bought a couple of used pedals. One is the Boss TU2 Chromatic tuner. I thought it worked ok until I used it to drop tune to d with. It actually read tuned at d#. In other words it read tuned at d, but actually the bass was at d#. My buddy plugged his guitar in to test it and it tested true at d. ***? Are these pedals worthless at the lower frequencies of bass or is it something else? It works normally at standard tuning. Also, is it advisable to take the batteries out of these types of pedal while not in use for short periods of time (say a week) as long as they are not connected to anything? Or can they still be drained if left in? Thanks.