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Audio Problems - Part 2
Welcome to our second newsletter. If
you are getting this for the first time, please read Audio Part 1 first. This is a
continuing subject.
Now for maintenance tips
If you notice low level or distorted audio when playing
back recorded audio or while monitoring your recording in the PB mode,
there is a way to help determine where the problems is. Because the
playback and record circuits are generally independent of each other,
just play back a known good tape. If that audio sounds just as bad as
the audio you just recorded, you can assume that the recording may be
OK. It might be worth the risk, to continue recording. If audio sounds
good then chances are the recording is bad.
Usually (about 95% of the time) this problem is due to
an audio head clogged with tape debris. A proper wet cleaning of the
heads will most likely fix your problem. If you don't have time, move
your most important audio source to the working channel. It is unlikely
that you’ll get two head clogs at the same time. It's also important to
remember that heads don't clog themselves. It is debris coming off the
tape that causes the problems. Some videographers have had years with no
record problems, because they were lucky to have had used good tape
stock. You just never know when some bad stock will show up. Under
conditions of high humidity and temperatures, marginal tape stock can
get even worse.
Another option to think about is the use of the back up
recordings made on the AFM tracks 3 and 4. This double recording can
save your butt if you happen to get a clog on one of your linear tracks
1 and 2. The Ch 3 & 4 AFM tracks recorded in the video signal are
independent of the linear recording circuits. With the broadcast BVW and
HL-V series camcorders, Ch1 & 2 simultaneously get recorded on Ch 3 & 4
when using metal tape. On the BVV-5, make sure the AFM input is switched
to CH 1& 2. The down side of this technique is that if the editing
playback decks do not have capabilities of AFM playback, a dub will have
to be made from one that has. This can however, save your shoot!
When recording non-recoverable events and you need only
one channel, use an XLR "Y" audio splitter and record on all 4 channels.
Some even use a DAT recorder or a back up Betacam deck in such
circumstances. Problems will and do occur, so be prepared.
Another trap is the 48-volt power that is included on
all camcorders and dockable audio XLR inputs. The purpose of this switch
is to provide 48-volt DC to power shotgun mikes that require external
power. Often the power switch is accidentally bumped or left in the "on"
position. This can over power and kill a normal microphone. We have
received quite a few calls on this one. If your camera mounted shotgun
mike has a problem, unplug it and plug it into rear mike jacks on deck.
Turn on the 48-volt switch and switch the audio input selector switch to
the mike position. We have made many repairs to the internal mike
circuits and by bypassing the front connector you can at least buy some
time until you can get it repaired.
We occasionally get calls about level problems, usually
Ch 1. On broadcast camcorders and dockable decks, Ch 1 has a second
audio control mounted either on the side of camera or on the front of
the viewfinder that makes it easy to adjust the Ch1 audio level on the
fly. Almost every one is caught once with this control accidentally
turned down. This control is in series with the side mounted one, and if
left turned down will make the normal level control
inoperative.
There are many common audio problems that may not even
be related to the recording deck. This is especially true with crews
that use a sound tech with a mixer and radio mikes, and would show up in
EE mode without even rolling tape. Start using the process of
elimination by plugging a hard wired one directly into camcorder or
deck. If problem clears up, look into mixer, cables, batteries, mikes,
RF interference as source of problem.
Take care,
Roger |
