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Canon XH Series HDV Camcorders
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Old October 21st, 2007, 01:58 PM   #1
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A-1 mic attenuator...compression or gain?

Does anyone know how the attenuator on the microphone of the A-1 works?

Does the attenuator work as gain when needed or does it work as a compressor when needed?

Tx

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Old October 21st, 2007, 04:44 PM   #2
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Neither, really; it just "attenuates" or reduces the power of the incoming signal (by 12dB with the internal mic or 20dB with an external mic).
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Old October 21st, 2007, 04:46 PM   #3
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Dear Roger,

The attenuator works as neither gain or compression.

It reduces the sensitivity of the microphone input stages so that you can record louder sounds without distortion.
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Old October 22nd, 2007, 04:44 AM   #4
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Ben, Dan,

Thanks for the reply.

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Old October 22nd, 2007, 07:53 AM   #5
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It reduces the sensitivity of the input stage, by effectively lowering the gain of the input stage of the mic preamplifiers.

If all MIC ATT setting did was reduce the input signal as an in-line attenuator does, the noise floor would remain the same in the Mic ATT setting, but because the noise floor improves by about 5 dB in the MIC ATT setting, we can conclude that it is reducing the gain of the input stage of the preamps.
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Old October 22nd, 2007, 10:30 AM   #6
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Quote:
Originally Posted by Don Palomaki View Post
It reduces the sensitivity of the input stage, by effectively lowering the gain of the input stage of the mic preamplifiers.

If all MIC ATT setting did was reduce the input signal as an in-line attenuator does, the noise floor would remain the same in the Mic ATT setting, but because the noise floor improves by about 5 dB in the MIC ATT setting, we can conclude that it is reducing the gain of the input stage of the preamps.
That's sort of splitting hairs. I was guessing Roger didn't know technical terms like input stage or noise floor. Long as he understands what the attenuator is for. Thanks
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Old October 22nd, 2007, 04:31 PM   #7
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Perhaps it's best not to make assumptions about other peoples' technical abilities.

I thought Don's answer was clear and to the point. Can't see where he gathered the info from but if it's correct, it's useful to know.
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Old October 22nd, 2007, 04:49 PM   #8
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Hello All,

Thanks again for the help.

I'm quite familiar with digital sound recording, microphone inputs, gain, compressors and the like via a digital recording board....I've done that for a while.

Apparently, recording to tape on the A-1 via the XLR inputs functions somewhat differently than it would on my digital recording deck...at least that's what I'm getting from this post.

In my world of digital recording, compressors squash or at least cap a signal and other functions will boost a signal.

If I understand it right, the attenuator simply reduces the input signal if the signal is so hot it clips....at least that's what I'm getting from this.

And, actually, I don't know what a noise floor is as I'm a real newbie to digital video recording. I'm not familiar with that term in the world of digital recording.

Any help and any advice I get here, I very much appreciate and digest as best I can to improve my skills.

Thanks again.

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Old October 22nd, 2007, 05:31 PM   #9
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Quote:
Originally Posted by Bill Watson View Post
Perhaps it's best not to make assumptions about other peoples' technical abilities.

I thought Don's answer was clear and to the point. Can't see where he gathered the info from but if it's correct, it's useful to know.
Perhaps it's best not to make assumptions about other people's assumptions;) If Roger gets his question answered that's all that matters.
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Old October 23rd, 2007, 07:52 AM   #10
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Noise floor: see http://en.wikipedia.org/wiki/Noise_floor

Noise is essentially any unwanted signal, it may be generated internally in the camcorder preamps, the microphone internal electronics, or it could be from the radio waves from a nearby transmitter, or just the unwanted sound of a stray dog barking near the set.

In the case of the XH-A1 the noise floor would be the basic noise level (typically heard as a hiss) found in the recorded audio when no signal whatsoever is present at the input jacks; e.g., with the input (pins 2 and 3) of the XLR jack shorted together through a low noise ~600 ohm or less resistor.

With some camcorders (with marginal electronics) you may also hear some noise from the switching power supply and perhaps some noise at the horizontal frequency rate, at the head spin rate, or at the rate of other signals in the camcorder.

An attenuator reduces levels - generally by an equal percentage regardless of the signal level. The ratio of loudest sound to softest sound remains the same. (But sounds softer than the noise floor would be "lost in the noise.")

A compressor reduces the dynamic range of a signal. Depending on how it is setup, it may leave soft sounds unchanged, and reduce the amplitude of loud sounds by a substantial amount. More sophisticated models can leave sounds unchanged over a range of amplitudes and only decrease the amplitude sounds above the certain level. They typically operate by adjusting the gain of an amplifier by an amount that is based on the short term "average" amplitude of the signal going into the amplifier. Audio editing software offers the ability to do very complex compression.

An expander is similar to a compressor, but make loud sounds louder.

AGC in camcorder is essentially a combination of amplification and compression.

It is worth noting that most recordings are subject to compression, You do not hear the same dynamic range as you would at a live concert. This was especially prevalent with records, to get the softer sounds above the noise floor of the record/turntable system.
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Old October 23rd, 2007, 05:50 PM   #11
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Quote:
Originally Posted by Don Palomaki View Post
Noise floor: see http://en.wikipedia.org/wiki/Noise_floor

Noise is essentially any unwanted signal,
Don,

First of all, thanks for taking your time to reply. Your reply was well thought out and appreciated.

It was nice to know that noise is considered an unwanted signal both in video and recording.

I thought you did a nice job of explaining the process/causes of noise. I copied your notes for further review and digestion.

For what it's worth.....

I have noticed that 'digitized sound' on every camcorder whose sound I have listened to.

The nice thing about the A-1 is that it gives me a fighting chance with the tape format and XLR formats to re-recreate that 'creamy' sound of tape that most of us who have experience recording sound are looking for.

Re: sound and A-1.

This is one of major reasons I went with the A-1 is that it had XLR inputs, tape and adjustability.

Thanks Don and all, I do appreciate the time you have taken to answer my questions.

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Old October 24th, 2007, 07:06 AM   #12
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Quote:
The nice thing about the A-1 is that it gives me a fighting chance with the tape format and XLR formats to re-recreate that 'creamy' sound of tape that most of us who have experience recording sound are looking for.
Not sure what you mean by "tape"? Do you mean analog tape of a largely bygone era (e.g., reel-to-reel, 15 ips, Ampex, etc.) with corresponding soft limiting and tape hiss to mask A/D-D/A quantization error ? A bit like some people preferring the sound of vinyl and tubes to that of CDs and transistors?
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Old October 24th, 2007, 08:30 AM   #13
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The tape format that I refer to is mini-DV tape. From what I understand of what I have read it has a better sound than DVD or hdd recording.

That said, in many instances, I'll probably go:

mic - sound board - A1 XLR for the sound I want.

Thanks again.

Rog Lee
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