Is there an XLR Doctor in the House?

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Alan Craven
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XLR plugs have a connection to the body of the plug in addition to the three signal terminals. When connecting a Sennheiser K6 to a Beachtek box should one connect the cable screen to the two plug bodies as well as to pin 1, so bonding the microphone body to the Beachtek case?

There is a switch on the Beachtek which offers the choice of bonding the Beachtek case to the camera body. The instructions say try the two positions and use the one where the noise level is lower.

Nigel Longman
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It may depend

I would normally connect the metal case of a plug to the screening to provide the maximum earth shielding to the signal and continuity of earthing.

However I suspect that in this case the earth-lift switch on the Beachtek (DXA-6?) may achieve this by breaking the connection between the input transformer centre-tap and the earth rail of the Beachtek. (Since the Beachtek is made from metal and is presumably fixed to the camera with a metal screw I don't see how a switch can disconnect the camera from the Beachtek). If this is so then the connection in the plug between pin 1 and the case will short out the switch and prevent it from having any effect, so should not be made.

Hope this provides some help.

Regards NL

Alan Craven
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Thanks Nigel,

It is a DXA-8 and the manual says that the ground lift switch is designed to "allow the input and output grounds to be isolated to prevent ground noise on certain sony camcorders".

I am using it with a Canon XM2, but not mounted directly under the camera. I have it between a Manfrotto sliding plate and the head, so that I can detatch the camera and use it hand held if I need to. What you say about the met/metal connection would still apply I should think. I will have a check with a meter!

At the moment I do not have the cable screen connected to the plug bodies.

Alan Craven
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My trusty AVO shows:

Beachtek inputs pin 1 is grounded to the body.

Beachtek output side:

Ground lift switch at G1 : Beachtek body, tripod head, 3.5 mm jack sleeve common ground.

Ground lift switch at G2 : Beachtek body, tripod head common. 3.5mm jack sleeve isolated.

So the switch does what it says on the tin.

The 3.5mm jack sleeve on the camera is grounded to the tripod attachment.

Pin 1 on the K6 is grounded to the metal body as one would expect.

So at the moment, I do not have the microphone body grounded to the input to the camera. If I connect pin 1 to the plug bodies it will be. This may reduce noise. The microphone to Beachtek lead is 30cm long.

Nigel Longman
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If it's of any interest to you Alan, out of 4 commercially made XLR leads I have here, 2 have pin 1 connected to the body and 2 don't. So there doesn't seem to be any firm practice in this respect.

From what you say, it appears that the switch breaks the connection to the 3.5mm jack sleeve, so presumably if the Beachtek box is not in physical contact with the camera body you don't get a signal, since it relies on contact through the case for the return signal path when the switch is open.

I think you will have to continue to experiment to find the earthing arrangement that gives the lowest noise in your working situation.

Good luck, NL

Alan Craven
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I guess so. Perhaps John Willett will chip in with the definitive verdict!

The implications for this ground lift switch are that certain Sony cameras suffer from a ground loop if both input lead screen and camera body are connected to the Beachtek box.

Thanks for your advice.

John Willett
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If you connect pin-1 to the body then you have the best RF shielding. I think the new Neutrik XLRs do this automatically.

So, generally it is good to do this, but snip it if you suffer from ground loops.

John
 
A picture tells a thousand words, but sound tells a thousand pictures.

Alan Craven
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Thank you John!

My Neutriks are a couple of years old - I am using the right angle type at both ends. I will connect pin one to the body tag at either end and see what happens.

This Beachtek must have some very expensive components inside given its price; but then the currency conversion is the usual $1=£1. Daft, but not as daft as Argentina before their currency collapse three years ago, when they liked tourists to pay for everything in $US - they used $1=1 peso! The true rate would have been about 30 cents. You always got pesos as change, of course.

Alan Craven
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The Beachtek is first rate in use with my K6/ME67 and Canon XM2. I can set levels around -20dB for the general background chatter of waders, ducks, etc on a marsh and when a Mallard or Coot lets rip close by the levels are limited to below the clipping threshold of the XM2 imputs.

Previously I had to set levels much lower and use the XM2 mic attenuator to prevent the close up bird going to 0dB with horrendous clipping. The background chatter was then lost in the noise.

I have the Beachtek gain set at 0, limiting adjusted so that the indicator LED flashes on loud calls. The Canon is set with the audio inputs on manual, no attenuator, and the gain at about 50%.

The only problem now is that I find that the mike picks up some noise from the transport with my current set up. This has the mike alongside the camera at the transport side. I am going to have to shift it to the other side, modifying the bracket to allow me to use the LCD screen and access the controls.

Dave R Smith
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Joined: May 10 2005

I am pleased your new toy is moving quality in the right direction.
Some mounts have rubber etc absorbing materials incorporated - may help?

I like your Hovis advertisment on TV:D .

Alan Craven
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The microphone is in a Rycote Multimount. I suspect the noise is electromagnetically induced. It occurs if the microphone is hand held close to the transport, declining rapidly with increased distance.

Hovis advert? Sorry, you have lost me, I rarely watch TV.

Dave R Smith
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Mike position(s) noted.

The Hovis Ad features a family of Mallards. Well, wooden animated/painted ducks.
Thought of you as soon as I saw it - very good audio.

DVdoctor
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John W Of course is a real expert on all this stuff, but a few observations

we have seen a number of instances where the connection to the body of the xlr is not used mainly do to a possible problem where the connector might come into contact with a source of ground noise... for instance on a conductive surface or outside in some damp or wet environment, so it really is up to you the pins provide continual connection of the circut, but the actual shielding is not there at the two connectors, for the approx 1-2 inches of space so it is debatable if the lack of shielding is really all that much a factor giving the possibility that if the connector is electircally linked, and you then can introduce an additional ground possibly causing ground loops

There is a fair amount of debate on the whole issue of grounding on camcorders, especially when they are hand held and not on mains. Since the microphone and the camcorder are are not really "earthed" since there is no connection to the actual "earth"
the effectiveness of this can be brought into question. If the camcorder is on mains supply and IF the power supply actually provides a ground connection to the electrical " earth" that is one thing, but if lilke on the US for instance the sony power supplies are only two wire to the mains connection and infact DO NOT provide any earthing

I'd be very interested to see John W comments.

Sharyn

Alan Craven
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So would I, Sharyn!

I have tried the XLRs both without, and then with, the screen connected to the tag on the plug body. There is no difference. The DXA 8 has a ground isolation switch at the output, this makes no difference either - the manual says that isolation is needed on certain, unspecified, models of Sony camcorder.

Any failure in screening appears to be in the body of the microphone as the noise induction is worst when the front end of the K6 is close to the tape transport.

I think that basically I was expecting too much. It is just not reasonable to have the microphone that close to the transport. The system would simply become too space consuming and unwieldly if I moved the microphone further away on the transport side.

I have rebuilt my bracket so that it is adjustable, and turned my Manfrotto sliding plate to which it is fixed through 180 degrees, so that the microphone is alongside the extended LCD and this is fine. The only problem is that it does mask access to the controls on that side of the camera somewhat, but I can live with that.

The upside is the vast improvement is the quality of the sound I am getting. The next problem is to shut down RAF and private aircraft activity when I am working! I would welcome any ideas.

I live on the flight path for the RAF training school at Linton on Ouse, and I have toyed with the idea of applying for planning permission for an anti-aircaft battery.

Dave R Smith
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Mike could be clamped to tripod, but this while avoiding transport noise this may be more susceptible to knocks and vibrations from floor - it's not something I've tried.

Alan Craven wrote:
The upside is the vast improvement is the quality of the sound I am getting. The next problem is to shut down RAF and private aircraft activity when I am working! I would welcome any ideas.

I'm guessing sound doesn't necessarilly have to be recorded at same time as visuals.
Set your mike up linked to a minidisc recorder - or portable hard disc recorder and leave it in the area being filmed. . Build up a library of different birds etc, for dropping in to video - either entirely or just where biggles makes an appearance.
Lip synch shouldn't be a problem - only species synch.;)

Could even link up a mike close in to birdlife and connect via wireless radio kit.

I remember 10 years or so ago, seeing how a documentary was made of migrating deer in snowy barren landscape. Movement/smell of cameraman would frighten them, so very long lenses used. For sound of hooves on snow, they re-created it using custard powder inside a stocking, which was twisted to compress it and make a crunching sound.

So cheating is allowed in quest for quality!

John Willett
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Remember - you also need to address the cable properly as mechanical noise can come down the cable.

The best is tinsel starquad (from Canford Audio) - leave a loose loop at the back and clamp the cable to the mount. This will help decouple the cable from the mic. and reduce handling noise.

John
 
A picture tells a thousand words, but sound tells a thousand pictures.

Alan Craven
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Thanks John,

That is just what I am doing, using Neutrik right angle XLRs!

Perhaps I should stress that the hum I found was very low level - only audible with very good headphones. I can only hear it because of the vast improvement in noise levels brought about by the Beachtek box, etc. Whatever, by shifting the ME67 to the other side of the camera, it is gone. Of course, what I am trying to do is reverse the great Gilbert Briggs dictum about the wider opening of windows!

Dave,

Yes much of the time I have to use sound from my library as the new video is accompanied by aircraft, people talking, etc. It is incredible how much of the time in rural England there is an audible aircraft; you only begin to notice this when working on video with headphones as much of it is a low level drone.

Surprisingly beak-synch is a problem. There is nothing worse than a bird's beak opening and closing with no matching sound. In the past I have painstakingly re-created a bird call to beak-synch with a particularly good bit of video where the sound was unusable due to a passing car or aircraft.

Anyhow, thank you all for the advice. I think my latest arrangement is as good as I am going to get. The work I have done on what I acquired on Wenesday suggests that most of wy accumulated audio library is due for pulping.

Incidentally Canford are selling off their stock of Tinsel Starquad at 75p a metre!

Alan Craven
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I have ordered one of these which should make my mounting somewhat neater:

http://www.canford.co.uk/commerce/productdetails.aspx?productid=53-289

For the price this looks a very handy little bracket.

Dave R Smith
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Alan Craven wrote:
The work I have done on what I acquired on Wenesday suggests that most of wy accumulated audio library is due for pulping.

I'm pleased your efforts have paid off.
Don't bin your library though:
i)audio takes relatively small space
ii)BBC have been ctiticised on this forum for similar actions
iii)If it's bad due to background hiss, software like adobe audtion (and stuff yet to be invented) could clean it up. Better to have a rough sound of a speckled wotsit then none at all.

What make/model are your whizzo headphones?

Alan Craven
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Unfortunately most of my library has already been processed to death. This is a major delight of my new set up. I simply used the noise recorded during my midnight session as a profile in Audition and applied it to Wednesday's audio, after deleting biggles, et al.

Next time around, it should be even easier.

My headphones? This will please John, though he will probably tell me I should have bought better ones - Sennheiser HD280 pro.

Dave R Smith
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Alan Craven wrote:
.... I simply used the noise recorded during my midnight session as a profile ...
My headphones? This will please John, though he will probably tell me I should have bought better ones - Sennheiser HD280 pro.

So church clocks with appealing chimes.;)

I saw John Willett give a talk recently where he recomended HD25's (care there is also a cheaper HD25 SP)
http://www.videokit.co.uk/cgi-bin/store1/commerce.cgi?cart_id=1137345066.23089&product=HEADPHONES&pid=1267
I have short-listed these as I like the ability to twist one earcup away from ear - for simultaneous monitoring and normal hearing.

mooblie
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They missed - "skull crushing ability" off the HD25 feature list. :) Sound good in the field though, and do minimise extraneous noise or direct pickup of the live sounds you're trying to monitor.

(Maybe I've just got a big head.)

Martin - DVdoctor in moderation. Everyone is entitled to my opinion.

Dave R Smith
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From buying cycle helmets I know my head is smaller than average - but thanks for warning mooblie.

Alan Craven
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Mooblie is right about the skull-crushers - I tried them and realised that I could not wear them for long periods. They do sound better than the 280s, though.

I think I read somewhere that the cheaper HD25 SP were made for Concorde?

John Willett
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mooblie wrote:
They missed - "skull crushing ability" off the HD25 feature list. :) Sound good in the field though, and do minimise extraneous noise or direct pickup of the live sounds you're trying to monitor.

(Maybe I've just got a big head.)

You have probably got a big head ;)

I have had my own HD 25s for 17 years and have never found them to be over tight.

If you find them in any way uncomfortable, try the optional velour earpads.

John
 
A picture tells a thousand words, but sound tells a thousand pictures.

John Willett
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Alan Craven wrote:
Mooblie is right about the skull-crushers - I tried them and realised that I could not wear them for long periods. They do sound better than the 280s, though.

So you have a big head as well ;)

I can wear mine for ages without any problems - try the optional velour earpads as they are more comfortable.

You could also try leaving them on a wig stand when not in use as that will tend to stretch the headband and make them less tight (not normally recommended, but as you find them tight ...)

Alan Craven wrote:
I think I read somewhere that the cheaper HD25 SP were made for Concorde?

Sort of - the design was originally done by Sennheiser UK for Concord. Sennheiser Germany liked the idea and put them into full production.

However - the BA Concord headphones are 300-Ohms and the SP are 100-Ohms. It makes a big difference when driving them from camcorders.

John
 
A picture tells a thousand words, but sound tells a thousand pictures.

Alan Craven
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But, where would I put my wig then, John?

John Willett
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Alan Craven wrote:
But, where would I put my wig then, John?

On your head :D

John
 
A picture tells a thousand words, but sound tells a thousand pictures.