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New to Minidisc world and need some help

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BeauJangles

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Hi,

I recently acquired a Sony MZ-NH900 HiMD player/recorder. I think it is a great device, although I am having a hard time understanding the operation of it. I play traditional Irish music and was using the device to record a rehearsal session. I play wooden flute and my partner was playing fiddle. I was recording using a Sony ECM_MS907 stereo microphone. I had the device on a coffee table beside me and had placed the mic between me and my fiddle player on another table. I recorded about 2 hours of our practice, pausing the device occasionally. Later, when I was listening to the recording I'd made, at first the audio quality was really very good. In fact, had it not been for some background noises (fiddler's dog barking, spouse coming home, me shuffling in my seat) the quality was on par with some home studio CD's I have heard. But then I began to notice that the audioquality would very suddenly drop out, and then just as quickly it would be back to normal. Every few seconds, and only for a split second each time, the playback would sound as if it was an LP record where the needle hits a scratch. The sound wouldn't quite skip. But the effect was really as though there was a rapid frequency drop off for a split second and then it would go back to normal. This phenomenon happens thoughout the recording I made. I thought that maybe we were hitting certain frequencies or decibels that the microphone couldn't cope with and so the sound would drop out. That seems very unlikely since A) We were only playing acoustic instruments, and they were unamplified at that, and B) It's a pretty nice microphone that ought to be able to cope with a pretty wide frequency spectrum. I wondered also if it might have been that the effect was caused by our foot-tapping. Maybe the table the device was resting on was picking up that vibration. But it couldn't have been that much vibration. And I thought minidisc recorders were good a coping with such things.

A couple of weeks prior to this I had made another attempt to record our playing (not realizing that the battery on my microphone was dead the whole time) and during that time I did manage to drop my minidisc player onto a carpeted floor. I was pretty freaked out that I might have hurt it, but the playback of a few CD tracks I had on that disc was not affected, so I assumed that everything was okay. Those CD tracks still play back fine, but that one recording session is worrying me. Have I broken my minidisc player before I have even learned how to use it properly?

Sorry if this issue has already been addressed elsewhere. There is a huge amount of info on this site and I have not been able to get thru all of it yet.

Beau

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Sounds to me like AGC trying to do its job.

AGC compresses/limits the signal being recorded. When levels go above about -10dBfs [the middle hashmark on the record level meters is -12dBfs] compression rapidly kicks in.

For very dynamic sources [i'd say wooden flute fits in that category] the AGC can cause audible problems. Flutes and whistles [for example] depend on the player using consistent breath/pressure and knowing which notes are the most resonant .. so some notes may be way louder than others, and blowing harder for emphasis of course means higher volume as well. When you hit those loud notes, the AGC kicks in with compression, which makes the volume on your recording "duck" to prevent clipping. The compression also holds for a brief period of time after the volume drops again; with sources that go loud very briefly, this makes the "ducking" really obvious as the other instruments and ambience pump up and down with the loudest part of the source.

Solution: enable manual recording levels, set a level based on the loudest you'll be getting, and make your recording. The overall levels may seem lower, but the thing to remember is that this isn't cassette tape with a high noise floor and a dynamic range of 35-40dB you're using; even with a relatively mediocre microphone like the MS907 and the built-in preamp of a HiMD, your recordable dynamic range is >80dB .. in other words, when you go to listen, simply TURN IT UP. Alternately, you can apply light compression in post that has the same overall effect as the AGC without being so destructive to the recording in general.

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I'm afraid this is where my newbie-ness is showing. I just plugged in the mic, hit Record, and away we went. I assume that I was recording in Linear PCM. Does this seem right to you?

I don't actually recall what the default is, but I do know that the current recording mode is actually shown on the display when recording.

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Sounds to me like AGC trying to do its job.

Thank you for that detailed response. I think that you may be right. I'll experiment with the sensitivity settings and see what happens. Of course, you are right about the wooden flute, now that I think about it. It has a very overtone-rich sound, moreso than silver flute. Furthermore, the very rhythmic, almost percussive, style of Irish playing actually uses those overtones. I may try setting the microphone further away as well.

Beau

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It's not just the sensitivity settings, though you should use Low.

For the reasons Dex explained, you should use Manual recording level. This is one of the peculiar annoyances of Sony's MD units. You have to switch from Automatic (AGC) to Manual each time you begin recording.

Here's the drill: Push REC and Pause (simultaneously, or Pause afterward) and you'll see the display blinking. Push MENU, click up two slots to REC SET, Enter(>)it, click down to Rec Volume, Enter (>), click down to Manual and Enter (>). You'll probably see 13/30, push Enter again. Push Pause again to un-Pause and start recording (the time display will start counting). Look at the level meter and see that your level is between the middle dash and the one on the right. You can change the input volume (from 0/30 to 30/30) with the jog wheel or pointing stick.

This prevents the recorder from using AGC and making the sudden volume changes you heard. The tradeoff is that you have to make sure it's not overloading, so keep an eye on the meter. Eventually it will become second nature about what volume setting to use.

It's simpler than the description. But after you push STOP to save your recording, you have to reset to Manual the next time you record.

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[the middle hashmark on the record level meters is -12dBfs]

I really thought it is -12 dB... Until I once got heavily clipped recording.

Then I went through a trouble of precisely analizing the dB values of all the segments of my MZ-RH910, and they turned out to be like this (segments counting right-to-left starting at #0, the rightmost):

0: OVER

<the right dot>

1: 0..-2 dB - Sometimes this is also slightly over, may be +1 dB

2: -2..-4 dB

3: -4..-6 dB

<the left dot (middle hashmark) >

4: -6..-12 dB

5: -12..-20 dB

6: -20..-30 dB

7: -30..-40 dB

8: -40..-44 dB

Bottom line: the middle hashmark on MZ-RH910 is -6 dBFS

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Bottom line: the middle hashmark on MZ-RH910 is -6 dBFS

The manuals for all units, as well as the labels over the display, indicate the middle hashmark to be -12dBfs. This would be its lower threshold [as your experiment actually proves to be correct].

Basically if it's on/lit, levels are at or above -12dBfs.

---

Having reread both my and your posts, I'll call myself incorrect now. Heh. Your experiment does indicate that the hashmark is -6dBfs. The manuals and the labels on most units still ID it as -12dBfs, though.

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