analysis of DAT audio problems
Mike Hall
the re-recording mixer commented that my production tapes were full of
unplayable portions. They were tried in several decks in the post suite
to no avail. These decks displayed error rate messages and
unrecognizable sound. Luckily, he said, no takes that were needed were
affected, so it did not harm the final product.
I heard no problems on location monitoring off tape or when I had
occasion to play back a take later. Telecine reported no bad patches,
nor did the picture editor. I will be given one or two of the
production DATs in a day or so.
How should I approach the task of checking out these tapes; where in
Los Angeles would you take them to be evaluated.
My HHB has been serviced at LSC since the show in question wrapped. It
checked out fine, was cleaned and tweaked.
Mike Hall
Raymond Cross
Got "Clones of the worst offenders back, put them up on a THX wall,
no problems!
A couple of conference calls later, the solution...
turned out that the transfer / post facility had their Sony DAT decks
setup as standard, i.e. no error correction.
Once they were reset to maximum error correction, end of garbage.
No note of apology though... sigh.
On a slightly different note,
I have recently experienced problems with false error warnings on
one of my PD4s, I have verified that the recordings are actually A1.
I remember reading a thread ages ago about this very phenomenon,.
I seem to remember the fix was related to a ribbon cable or a dry joint?
Can anyone help with this, please?
Ray
Charles Tomaras
PD4 and an HD camera on my recent Alaska trip. Since there was very little
sync sound and mostly B-roll for a cruise line company my job was also to
try to minimize the amount of equipment I was carrying. I had it down to a
PD-4, stereo mic, two Lectro 200 series 100mw transmitters (block 22) and a
pair of the new 201 receivers. I used the PD-4 as a video mixer/transmitter
to camera most of the time. I was also asked to provide some ambiences and
other audio efx on DAT without the camera. I found that I could not do both
simultaneously. The transmitters in block 22 caused my PD4 error light to go
red and mute my headphones and balanced outputs even though it was recording
perfectly. It turned out not to be a huge issue on this trip but I'm gonna
try some other RF blocks to see if the PD4 is less prone to this RF
interference problem.
Charlie - Seattle
"Raymond Cross" <cr...@indigo.ie> wrote in message
news:3B6DBF4E...@indigo.ie...
JnyVee
<cr...@indigo.ie> wrote:
> I've had this situation happen to me a few years back...
> Got "Clones of the worst offenders back, put them up on a THX wall,
> no problems!
> A couple of conference calls later, the solution...
> turned out that the transfer / post facility had their Sony DAT decks
> setup as standard, i.e. no error correction.
> Once they were reset to maximum error correction, end of garbage.
> No note of apology though... sigh.
I'm not familiar with this mode of operaztion, is it specific to a few
models or a universal option to know about?
--
<Help Keep The Net Emoticon-free!>
Raymond Cross
that allows one to preset the level of error detection / rejection.
I don't know if this applies to all the SONY decks.
Check out the relevant manual.
Ray
"If all else fails... read the instructions".
William Tzouris
often indicate playback head errors and not actual record errors.
Once the offending RF is removed, the PCM errors go away and
subsequent playback of the tape indicates no PCM errors at all.
Example #1:
I've noticed red PCM errors on my PD-4 when I cue a Motorola UHF
walkie within 6 inches of the heads while in record. When you
playback the recording, the errors aren't there.
Example #2:
I had a recent experience where my assistant slid an active
Lectrosonics "Shark Fin" ALP-600 antenna in between the PD-4 Porta
Brace and the strap-on accessory bag (putting the Shark Fin right over
the heads). I had solid red PCM errors as soon as I went into record.
Again, there was no evidence of PCM errors on playback of that
section of tape. (I removed the Shark Fin and the errors immediately
went away) The shark fin was plugged into an Audio Ltd. Quad Box at
the time.
Example #3:
A friend of mine recorded on the deck of a US Aircraft Carrier with a
PD-2. He said that he was getting a lot of red PCM errors while in
record but he recorded the SFX anyway. When he checked the tape
later, there were no playback errors at all.
Example #4:
I built a custom DC-DC converter for my Fostex PD-2: It takes 9-18
volts in and outputs a tightly regulated 13.2 volts out. (40 watt
rating). When I first built the box, I had input ground isolated from
output ground through the converter. The PD-2 when into massive
Green/Red playback errors when in record, and it got worse when my
hand waved over the heads (like a theramin!). I was able to pinpoint
the PCM errors to be entirely playback-head related by using the
various PCM error modes on the PD-2. Once again, the problems were
not on tape. I subsequently strapped input ground to output ground on
the DC-DC converter and all the problems disappeared.
So, be aware that green and red PCM errors are sometimes just playback
head problems. When in doubt, keep recording and remove any RF
devices near the heads. And if it sounds good, just keep recording
period and move your machine to a different area in the room.
Hope this helped....
John Gooch
appear to have completely false errors and the tapes playback fine. My
situation is as follows.
My setup: freshly tweaked PD-4 in a portabrace bag, Lectro 210s (block
22), Lectro T2 tx( block 28) being fed from both L/R outputs,, powering
PD-4 from two NPs-one in the machine and one in the bag feeding to the ext
power in.
in gross detail here was my situation:
PD-4 in a highly saturated RF environment, also very hot and extremely
humid. As soon as my PD-4 started to get a little warm i started to get a
solid green light when recording. Having seen this before, i checked the
tapes and everything is fine, no errors at all. Over the course of the day
the PD-4 temperature starts to get warmer and warmer this does not worry me
until i start seeing the red light and the LCD display starts showing PCM
ERROR. Checking confidence heads seems to indicate that the recording is
fine. Regardless I start to breakout the backup machine. In desparate fear
that machine is going to melt from the heat i decide to use the only source
of cooling that i can find, a nearby water cooler filled with water bottles.
after stuffing them in my portabrace bag and constantly replacing warm
bottles with cold ones for about a half hour the LCD PCM ERROR dislpay goes
away. Now i am back to solid green light. I notice that if i close the
master pot, the green light now flickers or blinks. Open the master pot and
solid green again. solid green for the rest of the day.
A/D or D/A errors affected by heat? I.E. no audio = no data to convert= no
errors? Also my backup was being fed from the AES digital output from the
PD-4 and it was happy as a clam.
It is a mystery to me.
john gooch
Raymond Cross
Playback head AOK.
Serious intermittent fault on the servo board.
_ Unfortunately it's a tight smt chipset on a daughter board,
so, I have to get a new one.
At least I have "laid the ghost".
_I Hope!
Thanks to all who shared their experiences / knowledge.
Ray
John Gooch
In my further quest to nail down my PD-4 error problems i did the following
test.
1) test record with in my nice and cool office with a brand new
tape(exercised)- NO Errors, no green lights.
2) next i put the machine outside in the blistering sun and let it heat up
while recording.
3) After recording for about 45 minutes and a nice a toasty machine NO
errors. Turn on the tone generator while recording-Consistent blinking
green light!
4) Turn the tone off- NO Green light.
5) Return the PD-4 to my nice and cool office and let it cool down, no
green lights at all with the tone generator on or off while recording.
It seems that if the audio signal is removed then problem goes away.
I am convinced that there is a heat component to this problem. Also no
stray RF at all was present while i did my tests. I have seen this problem
before on my old machine, non- version 2 pd-4. the errors are not there on
playback at all, they are phantom errors.
anybody have any thoughts? has anybody seen this on their machines?
john gooch
Glen Trew
test tapes have a tone recorded at either -12dbf or 0dbf. Error rate
adjustments are done while recording and playing back a tone at -12dbf.
I'm not sure why heat from sunlight would increase the errors to the point
of triggering your green light, except for the mechanical effects it could
have on moving parts.
Glen Trew
"John Gooch" <john...@home.com> wrote in message
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Ray Collins
crystals in DAT machines. Years ago to keep a xtal on frequency you had to
keep the temperature constant. My guess is they make crystals better and
more stable today, but is there any chance this might be the cause of some
DAT audio problem? Do crystals drift like they used to?
Ty Ford
In a mostly parallel, but not direct, anecdote; my Honda Accord wouldn't
start after sitting in the sun. Get in the car, turn the key, engine turns
over, but no start. Cuss a lot, walk around for ten minutes, try again, car
starts right up.
Turns out it was the circuit board of the fuel pump relay, which is mounted
on the interior side of the firewall. When heated, it warped so when the
relay was triggered, the secondary side of the relay failed didn't connect
to pass power to the fuel pump. Opening the car let the circuit board cool
off and unwarp so contact could be made.
Regards,
Ty (shade tree) Ford
Ty Ford's audio demos and equipment reviews are available at
http://www.jagunet.com/~tford
He is a member of the Maryland Production Alliance
http://www.MDproductionalliance.org
Glen Trew
stability is somewhat subject to temperature changes. However, I can't
think of a reason this would have an affect on the error rates during
recording.
Glen Trew
"Ray Collins" <rc...@intergate.ca> wrote in message
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Ray Collins
e.g. 2 xtals beating at not quite their set freq. Perhaps harmonics are
being induced that the machine decides are errors.
Glen Trew
adusted can have an extremely low error rate when no audio is being played
or recorded. Record and play a tone, and the errors increase, even with a
machine that is properly adjusted.
Glen Trew
"Ray Collins" <rc...@intergate.ca> wrote in message
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