Hi Pros …

Please help me optimize my digital field recorder – Sony PCM D50 for recording speeches (vocals).

Work I do:
I volunteer at a spiritual organization. Been doing it for long time. I record spiritual discourses. It’s always one speaker – male with a deep bass voice.

I need to capture and give finalized CD with least changes to original speech (voice). So I have shed off most of the effects that do processing on the captured sound.

This is because, these spiritual discourses are supposed to capture the emotion and tone of the speaker as it is and reproduce them just like the original.

Our setup:
We have a recording studio like room that is acoustically treated and semi-sound proof.

I record using Sony D50 digital portable recorder, directly into the built-in MIC.

I was using Digi 002 with a n HP’s DAW and an AKG 1000S condenser mic before, but downgraded to the Sony PCM D50 as I have only one audio input and the built in MICs are doing excellent job. Portability is also important.

Help I need:
Now I need all you folks help in optimizing few features on this Sony D50. As it may not be as widely used in professional world, I am cut/pasting some info from its manual, below.

Please throw some light on the usage of the following three features this unit has. I am particularly interested to know, how much of a damage (change) it does to the original voice of the speaker:
LIMITER
LCF (Low Cut Filter)
SBM (Super Bit Mapping)

LIMITER η (Preventing distortion)

The recorder always reserves audio for the digital limiter, which is 20dB lower than audio processed in the normal circuit. This compensates for clipping that happens during digital processing if audio is over-input. When the LIMITER switch is set to “ON,” the digital limiter circuit operates. The following are the times required for recovery:

Notes :
• The limiter circuit functions to keep the signal below the maximum input level. When sound is input suddenly, the excess part of the sound is automatically set within the range of the maximum input level in order to prevent distortion.
• The limiter circuit of the recorder does not compensate for clipping when audio over 12dB is input. In this case sound may be distorted.
• When the setting is “ON,” the peak value with the limiter circuit in operation appears if the maximum value exceeds 0 dB.

LCF η (Low Cut Filter function)

When the LOW CUT FILTER switch is set to “ON,” the low cut filter is activated so that audio under the following frequencies is filtered and is not recorded. This function reduces noise caused by the flow of air-conditioning equipment, outdoor air, etc.

75 Hz Audio under 75 Hz frequency is not recorded.
150Hz Audio under 150 Hz frequency is not recorded.

SBM η8 (Super Bit Mapping function)

Super Bit Mapping reduces noise when the quantifying bit number is set to 16 bit in “REC MODE.”

ON The Super Bit Mapping functions to reduce noise.
OFF The Super Bit Mapping does not function.

Note:
• Super Bit Mapping significantly increases the dynamic range acoustically by reducing noise that is particularly easy to hear within the human audible band. In order to improve the audio quality when converting 20-bit data into 16 bit, the top 4-bit amount of information within the lower data, which is usually thrown away, is integrated into the 16-bit data.

Thanks so much in advance.