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Old July 24th, 2005, 12:42 PM   #1
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problems with impedance, xl1

Hello everybody!
I´ve been using a canon xl1 for some years and, as a whole, I am happy with the results. My real problems started when I was given a Sony C74 shotgun mic,
with XLR connectors. I bought the MA 100 and a phantom supplier device to feed the mic.
To my surprise and frustration, the input sound level was very low. I made some questions here but nobody could give me a solution to the problem.
I have learnt that the xl1 has an input impedance of 600 ohms and, when working with a high impedance mic, the result is low sound level. The Sony C74 has an impedance of 1000 ohms.
There are some devices called impedance transformers. Could they solve the problem?

Sorry for my unscientific wording...
Thanks for your time

Josema Herráiz
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Old July 24th, 2005, 02:56 PM   #2
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Although I've never thad the opportunity to work with phantom powered mics, I have found that a really low sound level is usually due to one of two things: 1) too low an impedance for the input, which in this case suggests the MA-100 is not bumping the impedance up to 600 ohms for the RCA Audio 1 inputs on the camera, or 2) a poor connection in the cables used to cconnect the mic to the MA-100. I would thoroughly check the cables first. You could have a broken wire inside the XLR connector or some other connector is improperly wired.
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Old July 25th, 2005, 04:37 AM   #3
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How low is very low output? The impedance mismatch you mention 600 to 1000 ohms, would result in about 2.5 dB sound reduction, not likely to be noticed as significant.

The most common problem people run into when first using the MA100 is that the XL1 defaults to consumer line level input on the RCA jacks. They have to use the menu systemto set the RCA jack input sensitivity to MIC level (or MIC ATT if the mic output is high, which the C74 might be). Based on the C74 specifications, that could be your problem.
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Old July 28th, 2005, 12:53 PM   #4
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Problems using the Azden XGM1000 with XL-1s

I just purchased a new Shotgun Mic and after connecting it thru the MA-100 to my XL-1s, I hardly get a peep out of this Microphone. In my set up I use a Samson wireless on the left channel of MA-100 and I am hoping to use the Shotgun Mic on the right channel.

Unless if I make a loud noise right next to the Mic., I can't see even a bar on the audio monitor. I have tried using the Manual and Auto settings on Audio 1 input and nothing helps.

I just read in this Forum that someone else had a similar issue with another shotgun Mic. My XLR cable is brand new and from what I gather, this has to do with the Line 1 setting on the XL-1s Menu?!?!

My question is: Can the right and left channel of Audio 1 be set independently?

Regards,
Frank
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Old July 29th, 2005, 05:20 AM   #5
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My understanding is the Audio1 input sensitivity for the XL1s channels is linked. They cannot be set separately. The controls are level and balance - implying stereo source, and the menu level setting.

Based on the spec sheets I've seen, the output level of the Azden mic is on the order of 20 dB lower than a Smson UHF Series One system wireless if the wireless is set to line level output. Also the Azden has a rated output impedance of 1500 ohms per the specifications I've seen, which may give you an additional 5 dB level loss when used with a 600 ohm input.

Assuming the wireless level is OK, you could try set the wireless output to the -40 dB setting, the Audio1 inpout level to MIC or MIC ATT from the menu, and see if that gives usable results.
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Old July 29th, 2005, 12:21 PM   #6
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Thanks Don,

I will give that a try and keep you posted.

Regards,
Frank
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Old July 31st, 2005, 11:06 AM   #7
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I always get the same answer, "you made a mistake with the xl1 menu".
But that´s not the problem, I swear.
I read in some article that the impedance of the camera should be much higher than that of the mic ( I even read 10 times higher)
Here we have Canon XL1 600 ohms and Sony shotgun mic C74, 1000 ohms.
When I use the sony mic with Sony DVCam cameras, everything is ok. These cameras have an impedance of 4000...
I understand that it´s improbable that someone having a Canon XL1 is going to spend 1400 dollars in a shotgun mic...But I say that low impedance is an important shortcoming that puts my very much loved xl1 closer to the consumer category
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Josema Herráiz
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Old August 1st, 2005, 05:28 AM   #8
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Traditionally, it is important to have impedances matched, a 600 ohm source feelding a 600 ohm input. That is legacy from the days of tube amplifiers when transformars were common, and is to maximize power transfer. It also applies to radio frequencies to avoid "ghosts" in the signal. With modern solid state system the match is not as important for audio, other than that the input impedance should not be significantly lower than the source - it can reduce the maximum available output level from the mic (reducs the sould pressure level at which output clipping starts).

Many common professional mics tend to have actual output impedances on the order of 150 to 200 ohms, but are rated at a nominal 600-1000 ohms; e.g., sennheiser K6.ME66. Consumer mics tend to be higher as is common with consumer gear inputs.

Having a very low impedance source feeding a very high impedance input results in a max apparent gain of about 6 dB relatve to 600 ohms feeding 600 ohms. Alternatively 600 ohms feeding 4K ohms nets an apparent gain of 4.8 dB in terms of voltage over equal impedances..

FWIW, the MA100/200 provides 6 dB of voltage gain over the single ended (unbalanced) audio input.

Using a 1000 ohm mic with a 4000 ohm input will give an apparent 6.6 dB higher output than with a 600 ohm input. If this 6.6 dB difference is killing your system audio, something elsie is amiss. The Audio 1 sensitivity setting is the most common issue.

However, http://www.vidinc.net/c74.html indicates that the output impedance of the C74 is 250 ohms. If true, the differnce would be on the order of 2.5 dB.
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Old August 1st, 2005, 06:23 AM   #9
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Thank you Don, for your explanations

Whatever the reasons, the Sony C74, shotgun mic, is incompatible with Canon
XL1. Íf I am wrong (I would like to!!!), please has anybody worked successfully with these two elements?

I want to buy a lavalier mic, which one works well with Canon XL1?
I don´t want to make mistakes.
Thank you for your patience
Regards
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Old August 1st, 2005, 02:59 PM   #10
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Does your phantom power supply output full 48-volt phantom power? If not, you may be getting poor performance from this mic.
Also check the power connection between your MA-100 and the camera. Clean the connector and make sure it's firmly seated. Do the same with the other connections.
Make absolutely certain you're set for MIC or MIC ATT on the input.
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Old August 1st, 2005, 04:32 PM   #11
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On the MA-100, be sure that the 5 vdc power lead is connected.

Have you tried the MA100 with a different mic to be sure it is working OK.

When you power up the XL1 and prees the MENU button, what do you see in the EVF to the right of the AUDIO MODE, AUDIO 1 IN, and AUDIO 2 IN entries?

I believe that the Sony C74 allows powering from a mercury battery (probably hard to find) or 3CR-MIC lithium (expensive) battery as an alternative to phantom power. Have you looked into the battery power option as an alternative to phantom power?
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Old August 9th, 2005, 05:34 AM   #12
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I´have changed the phantom power supplier and I think things have improved. The sound level is not deafening but is on the brink of good working (the mic will have to be very close to the source of sound)
Don, in my menu, in audio mode I can read "audio mode 16 bit, audio 1 mic, audio 2 -"
Batteries are incredibly expensive and very very hard to find.
I thank you both, Don and Jay for your kindness and good advice
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Old August 9th, 2005, 07:37 PM   #13
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Those sound like the correct settings.

Sony selling batteries - The mic uses a lot of power hog (50 hours on a battery if I recall the spec), and Sony is making a lot of money on them I suspect!
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