Recently, I installed a system which included a color camera with audio capability, 24Hr time lapse recorder, and a color monitor. The picture turned out to be surprisingly great. However, there's a problem with the audio; it will intermittently come and go when I had the audio cable from the camera through the VCR to the monitor. On the other hand, the audio will work perfectly when the cable connected directly from the camera to the monitor. I personally think the problem has to do with the VCR because it's the only device between the camera and the monitor. Somehow, one experienced technician believes it's not the VCR but a need of an audio amplifier. I'm having a hard time accepting that! So, I would really appreciate if you could provide me with the correct answer to this problem.
Sign me Hard of Hearing Pete
Dear Hard Pete,
Actually, in this particular situation, both you and your technician could be
right. That is, most recorders do require an audio amp of some sort to play back
sound. This is because most recorders, although having the option to record
sound, do not have the capability to play back, un-aided sound. It is part of
the cost options of design. Since televisions have amplifiers built in, such
circuits are left out of the recorders to reduce size, weight, and cost.... yes,
unfortunately, even the security models. However....... you may have a couple of
other problems as well.
First, you want to verify that you are using a microphone of the proper
impedance. That is, if your recorder requires an eight (8) ohm microphone and
you are using a sixteen (16) ohm microphone (or visa versa) you will have
problems that could range from no sound to intermittent sound to overheat or
circuit burn-out. You can verify this information on your recorder and
microphone specification sheets.
Secondly, you want to be very careful not to exceed the maximum cable run
from the microphone to the recorder according to the type and style of wire that
you are using. This also can be verified on the microphone and wire
specification sheets.
Lastly, you want to verify the style and design of the recorder that you are
using for sound recording. Most recorders, or I should say the large majority of
recorders will not recorder coherent sound at speeds beyond the twelve or
eighteen hour mode. This is because they are designed with a fixed position
audio head in the tape path. This means that the tape must be moving past the
tape path at a smooth pace in order to record the entire word or phrase. Once
past the twelve or eighteen hour mode, most recorders "Increment" the
video tape. That is, the recorders moves the tape forward a sixteenth (or so) of
an inch, records and image and then pauses for a pre-determined amount of time
before moving forward for the next image. This will tend to cause a very jumpy
sound that could be related to the following sentence:
Big Boys Run Very Fast ---- Real Time
Bi Bo R V y st -------------- Time lapse of the same sentence.
Note that you missed several key points of the words for playback. Machines
that are able to record in speeds beyond twelve or eighteen hours have what is
referred to as "Flying Audio Heads"... What has been done to these
machines is that the Fixed audio head in the tape path is disconnected. It is
still there because it is less expensive to put it in (part of the automation),
than it is to leave it out. The next thing done is to add one or two audio heads
to the video head cylinder. This way, the audio head is moving past the video
tape, versus the video tape moving past the audio head. This also gives the unit
the ability to record any/all sound as part of the video sequence, so that it
can be played back at the same speed it was recorded, but with no missing
syllable or sounds. The audio track is actually laid down between the video
tracks versus at the top sixteenth (16th) inch of the video tape as in most
situations. In the end, you must verify the video recorder's specification sheet
to confirm that maximum or minimum speed that the recorder can record coherent
sound.
I hope that this helps you out Pete. I really wasn't trying to cause you
additional problems, but you know how the old saying goes, "Cover your
bases" (ha ha)... OK it was a bad pun, but what do you want from the
inter-net....At any rate, that is the best I can do without more specific
information about your equipment or application... I hope that it helps.... Let
me know if you need anything else, and I will do my best for you... I am in your
service... Good luck and stay in touch..
