[Richard Crowley]

Without even listening to the samples, clipping is ALWAYS to be avoided. Attenuating is only ONE method of avoiding clipping.

Of course, if you attenuate, then you must deal with the lower audio levels, which move you closer to the OTHER side of the road, where faint sounds can run into the “mud” (noise floor).

[Richard Crowley]

Yes, it does sound like it is clipping. Although the waveform does not show the typical flattened peaks, so something more complex is going on there.

The background noise is a different issue, and all the usual techniques apply to increasing the signal to noise ratio.

[Richard Crowley]

You plugged a monaural balanced microphone into a stereo mic input and it recorded +signal on the left track, and -signal on the right track. Either track by itself would work, but when you combine them, they virtually cancel. You need to use a proper adapter/cable when connecting that microphone to your camera or recorder or whatever you used (undisclosed?)

[Richard Crowley]

The most common cause of your symptom is that one of the “stereo” channels is reverse-phase from the other. You didn’t explain how you miked or mixed the audio for recording? It is almost NEVER EVER a good idea to use “stereo” for dialog, and you have provided the prime example WHY. Try using JUST ONE of the tracks, either Left or Right, but NEVER BOTH.

[Richard Crowley]

Use ordinary mic cable (shielded pair with XLR connectors).
Then use an XLR to 1/4 inch phone adapter at the amp inputs.
For example:
https://www.allelectronics.com/make-a-store/item/xlr-330/xlr-female-to-1/4-plug-adapter/1.html

You don’t know if you really need an isolation transformer for your application without trying it. I would certainly try it without a transformer first, before spending the extra $$$. If you really need a balancing transformer, you can use something like the Ebtech HE-2 stereo isolation transformer.

[Richard Crowley]

I am not a Mac user, but in PC-land, we could extract the audio from the video and use an audio application to boost the level, then lay the boosted audio track back into the video edit application (Final Cut).

Are you able to extract the audio file from Final Cut?
Do you have an audio application like Garage Band(?) or Audacity?

Or does Garage Band (or whatever audio application you have) capable of using the audio track directly in the video file? (For example I can open a video file using Adobe Audition and manipulate the audio file directly).

[Richard Crowley]

If you look at the circuit schematic diagram of the Rolls PM55 (ref below) you will see that the microphone line connection is a PASSIVE, PASS-THROUGH where the “mic output” connects directly to the “mic input”. That means that the PM55 does not alter the mic signal in any way.

That is the fundamental difference between using a device like the PM55 vs. an ordinary mic preamp, where the mic signal is amplified and can be changed. It also means that the actual mic preamp in the mixer (or recorder or camera) is supplying the phantom power for the microphone, and the PM55 simply does a “passive sample” of the mic signal without altering the audio signal OR whatever phantom power is being used.

Where you mount the box (whichever one you use) depends on many logistical conditions like how your boom pole is wired, whether you are using a hard cable vs. a wireless transmitter, etc. etc. And it also depends on the personal preference/ergonomics of the boom operator, and what kind of cable you have from the operator’s headphones, etc. etc.

The PM55 is designed to not affect the microphone signal at all which is how it is fundamentally different than any mic preamp product.

PM55 Schematic: https://www.rolls.com/pdf/IS2_PM55.pdf

[Richard Crowley]

Mixpre-D is rather “overkill” for boom operator monitoring. But if you have a big budget, then certainly go for it.
Mixpre-D is not really physically optimized for mounting on the boom where it is convenient for the operator to plug in mic and headphones and view it while booming.
Mixpre-D (or MM-1 Preamp) has the DIS-advantage of allowing the boom operator to control the mic signal. There may be some cases where that is desirable, but I suspect there are more cases where that is NOT desirable. Adjusting mic preamp sensitivity and output level should be the purview of the production sound person, not the boom operator (unless it is the same person doing both jobs).

All of the suggested devices would be placed INLINE between the microphone and either the cable to the mixer/recorder/camera, OR the transmitter.

[Richard Crowley]

https://www.rolls.com/product.php?pid=PM55

[Richard Crowley]

You say: “AT 4053 sounds better”, but you give no definition for what you mean by “better”. We would be shooting in the dark attempting any response because we don’t know what the presenting symptom is. You wouldn’t go to the doctor and simply say: “I’m not felling well.”

By “better” do you mean directionality? sensitivity? “reach”? self-noise? ambient rejection? frequency response? Help us out here.