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Offline WiFiJeff

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Odd dropouts
« on: August 17, 2011, 01:09:58 PM »
I've had intermittant dropouts before, usually of right channel audio when making a poor connection or having a battery die, but last night I had something that's a new one on me.

Great recording DPA4060 > MMA6000 > Sony D50 until the final five minutes.  Looking at the frequency spread in iZotope I see an intermittant dropout of the bass signal in both channels for a second or two, return of signal, dropout again, everything above say 200 Hz looks fine.  The low-cut switch on the MMA6000 was pretty firmly off, and I was seated pretty quietly so I doubt I was accidentally toggling it.  Anyone ever see something like this???

Jeff

Offline F.O.Bean

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Re: Odd dropouts
« Reply #1 on: August 18, 2011, 04:51:08 PM »
Maybe it happened to the bass and thats what the PA spewed out ???
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Offline WiFiJeff

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Re: Odd dropouts
« Reply #2 on: August 18, 2011, 09:47:53 PM »
Symphony orchestra, no PA. Live it sounded fine, and the waveform didn't look obviously bad in the basic view in Wavelab, but you could hear a problem on playback and the frequency spread in iZotope showed that for a few minutes the low end was winking out and on, sometimes there were "holes" other times stuff was missing but just weak not gone entirely.  A loud passage might bring it back for a moment, then it would go out again.

I cleaned all contacts, replaced the 9V cell in the MMA6000, then thought better of it and swapped out to a backup MMA6000, same mics and recorder last night and no problems.  But of course that could be luck, it ran fine for over three hours with just four-five bad minutes the night before. 

I just hate these random fails.

Jeff

Offline Scooter123

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Re: Odd dropouts
« Reply #3 on: August 19, 2011, 06:22:50 PM »
I find these are due to cord failures, or a bad battery connection that is giving power, just not tight enough for full power. 
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Offline Gutbucket

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Re: Odd dropouts
« Reply #4 on: August 19, 2011, 06:50:28 PM »
I'm with Scooter on this one. I've had similar problems, and its usually been from bad contact in a connnector, failing solder joint to a connector or preamp battery related.  It can be really frustrating sometimes chasing it down.

Random fails are always a bummer, but especially when the recording is otherwise great.
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Offline George2

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Re: Odd dropouts
« Reply #5 on: August 20, 2011, 08:23:21 AM »
replaced the 9V cell in the MMA6000,

How old was the battery?
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Offline WiFiJeff

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Re: Odd dropouts
« Reply #6 on: August 22, 2011, 06:17:23 PM »
The 9V cell in the MMA6000 was a Duracell good to March 2014, it showed 3 green lights out of 5 on my Universal Battery Tester after the incident.  This means about half down.  The MMA light was still blinking green, and I've gotten up to three and a half hours after it starts blinking red.  So it might have been defective in an annoyingly random way (had that happen once, but it turned off the MMA6000 entirely until a loud noise woke it up).  The D50 batteries are Imedion 2400 mAh rechargeables, about a year old and no problem with them before or since, they were only about 1/3 down at that point, I've run them to about 3/4 down.

Jeff

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Re: Odd dropouts
« Reply #7 on: August 23, 2011, 11:26:22 AM »
The 9V cell in the MMA6000 was a Duracell good to March 2014, it showed 3 green lights out of 5 on my Universal Battery Tester after the incident.

That's 3 lights out of 5 with no load, and I think it's not exactly clear what "3 out of 5" lights mean.  It would be more interesting to know what a voltmeter reads under load.
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Re: Odd dropouts
« Reply #8 on: August 23, 2011, 01:47:55 PM »
If you have this issue again, once you get home check voltage across the battery without disconnecting it from the preamp, with the preamp on.  Then compare that voltage against a new battery in the preamp (or a known good and freshly charged if using NiMH), again connected and preamp on.
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Offline WiFiJeff

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Re: Odd dropouts
« Reply #9 on: August 23, 2011, 03:41:05 PM »
Thanks for the suggestions.  I ran 5 1/2 hours straight Friday with no issues, so I hope contact cleaning and a fresh 9V cell cleaned it up, I just wish it were a reproduceable thing I could test out as fixed.  I'll run again tonight, if we are spared further earthquakes.

Jeff

 

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