Issues with Sony's low priced MD recorders explained

(Sony MZ-R35/37, -R70/71, -R90/91, -R700, -N707)

Sony omitted the microphone pre-amp's "low sensitivity" (-20 dB) setting on these recorders, so they are often prone to mic pre-amp overload distortion (sometimes referred to as "brickwalling") when recording even moderately loud sounds.

To resolve this issue, there are several solutions:

1. Use less sensitive microphones. This works, but unfortunately, many low sensitivity microphones are also lower in overall sound quality. Even when they are high quality, the built in Sony mic preamp will add a noticeable amount of noise to the recording. This is generally not a good solution for high fidelity recording.
2. Use an attenuator between the mics and the mic input. This also works in some cases, but will lower the bias voltage getting to the microphones (for those that require it), which also lowers the maximum SPL the mics themselves can then handle (sort of a catch 22). So, you solve one problem while potentially creating another. However, this is a workable solution in situations where the mic input is just beginning to overload....the attenuator knocks the signal down just enough to eliminate the overload, but because the sound isn't too loud, there is still enough bias power to run the mics properly. Here is an attenuator cable that will work in this situation. Usually, with this cable, setting the level control at it's highest setting lowers the signal just enough to eliminate the overload. Keep in mind that even when this works, you are still adding some noise from the Sony mic preamp.
3. Use a microphone power module with level control. This solution will allow you to make all types of recordings without distortion. Loud recording would be made using mics plugged into a power module and the power module plugged into the 'line' input of the recorder, thus bypassing the mic input of the recorder completely. Medium loudness recordings would be made by plugging the power module into the mic input, but with the level control of the power module turned down sufficiently so that the mic input does not overload. Quiet recordings would be made with the mics plugged directly into the mic input. This is a pretty good solution, with the only drawback being that you would still need to use the mic input for medium loud recordings, thereby still adding some noise from the mic preamp of the recorder. Here is the section of microphone power modules.
4. Use a separate high quality microphone preamplifier. This solution offers the highest quality recording, albeit at the highest cost. Using a separate preamp will allow you to make recordings of all kinds, with low noise and no distortion. Here is an example of this type of preamp.