Thread: External mic hum ...could phantom power solve ..or am I stuck using batteries ?

Bob,

I've never tried plugging a mic with an XLR connector via an adaptor into my NV GS400 so I can't answer that specifically. I've no idea how you are connecting via the mains but it sounds to me (from my days being involved in bands) that you're creating an earth loop somewhere along the line.

I use a Senheisser ME66/K6 which I power using a battery. I connect this to my GS400 using a JuicedLink CX211 preamp which is designed to be mounted between the camera/tripod. This isteslf is powered and whilst this model doesn't do so there are models which provide phantom power. But this is all done from batteries. The other XLR adapator is made by BeachTek - but I don't think these have a pre-amp circuit - or at least they only have a passive one (= more background noise)

If you do not use a box such as this, you are not running a balanced signal and thusyou are more susceptable to picking up interference (from lights/passing taxis/Cosmic Background Radiation etc)

Thanks for coming to the rescue Tim !

I am connecting the NVGS400 to the mains socket using the cables that came with it (ie) mains lead and battery charger.

The mic is self powered at present with 9 v Duracell battery and like I said the mic plugs straight into NVGS400 with custom made lead £10 XLR for mic to 3.5 mm stereo jack for camcorder.

I found in the past when using a little sony stereo tie clip mic that when I played recorded footage through pc stereo speakers the sound just came through one speaker so the guy (absolute music) I bought Rode mic from said as I am recording my voice I didn’t need stereo and mono was fine he advised I get a custom made lead XLR to 3.5 mm mini jack.

This lead works a treat and I get equal sound now through both stereo speakers on playback.

Powering the camcorder with batteries causes no problems???

But as soon as I power the camera using mains lead a hum appears damn!

It would be great to be able to use mains for camcorder so much easier.

Tim your “Juiced Link CX211 preamp mounted between camera and tripod

What do you mean by mounted Tim (sorry) on a specific rack or is on floor o.k ?

You say it doesn’t have phantom power is this no good for me then?

Bit lost here?

What would you do in my shoes Tim stick to batteries or buy a proper unit that fixes the problem? (ie) provides phantom power for mic and also removes hum when connecting camcorder to mains.

Bearing in mind my setup NVGS400 with £150 Rode external mic

What unit would do the job in your opinion and approx how much are we looking at ?

Thanks a million Tim

Bob

It looks like you have the cheapest solution already which is to run the camera from the battery. The charger/mains input must be causing the hum. So using something like a Juiced Link may not stop this problem. You go to all sorts of measure up to and including re-wiring your house to fix a problem like this. So if I was you I'd use the solution you already have.

You have a rather unfortunate problem really. The smoothing on your camera power supply is probably not that good, and to get this mic connected to your two unbalanced inputs means that the hum reduction benefits of balanced operation don't exist, but I suspect the real hum problem is because your camera sticks 5v or so onto the mic socket to power electret condensers - and your mention of the clip on mic working in one channel, with no mention of hum suggests the dc power is applied. The Rode might be objecting to DC on it's output - it's transformer less, so the DC may be getting into the pre-amp - and the hum could just be tiny ripple on the DC getting straight into the mics preamp.

The slight spanner in the works is that using the internal battery doesn't hum - and I can't figure why that would be, if the dc supply is the entry point for the hum?

An external phantom power supply could be a problem too. Many designs simply apply the phantom as it passes through, but if the output of the phantom box has one of the pins shorted to connect to an unbalanced camera input, the phantom voltage drops drastically, and might be incapable of driving the preamp.

The Stagg phantom box doesn't like having it's output unbalanced. Mics that can work between 5 and 50 volts usually still get enough, bit some phantom mics really do need the proper higher voltage, and these just produce little or no output.

So my advice is to blame the power supply first - it's probably not faulty, but the DC from the mic socket is taking it to the mic. The simplest solution? Carry on with batteries for the mic. They last ages so not a huge outlay.

Originally Posted by slimbob

Tim your “Juiced Link CX211 preamp mounted between camera and tripod

What do you mean by mounted Tim (sorry) on a specific rack or is on floor o.k ?

p=1000w

(where p = picture and w = word)

Except I cannot get an image to upload - do we have the problem back?

It screws on to the bottom of the camera, into the socket for the tripod plate, and probides its own socket so you can screw your tripod plate into that.

Originally Posted by slimbob

You say it doesn’t have phantom power is this no good for me then?

You can use a CX211 but you'd still need batterties in the mic. Alternatively they do a different model pre amp which spplied phantom power. Note, these units are not cheap like a simple XLR->3.5mm might be.

I'd use batteries as Midnight has suggested. You're in a controlled environment. If you discover you are getting interference, then you'll want a balanced mic signal anyway. At that time either but something like the BeachTek or Juiced link - or use a shorter cable, your XLR-3.5mm kack converter abd and plug it into a Zoom H1/H2 or similar or splash out on a Zoom H4n and use XLRs into that. So many choices.

Originally Posted by TimStannard

Except I cannot get an image to upload - do we have the problem back?

Apologies Tim. I missed one of the changes. Should be fixed now.

5097049596_e4220e41a0.jpg

Thanks so much guys

Midnight = wise advice stick to what works!! Ha ha
(ie) Batteries for powering camcorder.

This I can do Midnight the mains power was a luxury but not a necessity

Rewiring the house is not an option (lol)!!!!!!!!!!!

Paulears = thanks very much for your great input and yes it sounds like the power supply is causing the problems so if I don’t use the phantom supply = no problem.
Don’t need to know why there is no problem just there is no problem ..sorted.

Cheers

Tim

I quickly looked into the juiced link pre amps and I understand now how they connect between the camcorder and tripod (sorry) (i.e.) self powered by 9 v battery. Great bit of kit for someone shooting outside like you do !!!

Yes I have seen the model with built in phantom power = yes they are expensive I must admit.

“Quote”

I'd use batteries as Midnight has suggested. You're in a controlled environment. If you discover you are getting interference, then you'll want a balanced mic signal anyway. At that time either but something like the BeachTek or Juiced link - or use a shorter cable, your XLR-3.5mm kack converter abd and plug it into a Zoom H1/H2 or similar or splash out on a Zoom H4n and use XLRs into that. So many choices.

Yes Tim sound like sticking to batteries is the present sensible thing to do here to solve the problem of hum and also be a cheap option/fix.

Out of interest and this question is open to Midnight and Paulears too

Would I notice a huge worthwhile difference in quality by using a Beach tek or juiced link product compared to what I am doing now (ie) plugging a decent external mic £149 Rode NT3 straight into the camcorder stereo mic input jack (XLR to 3.5 mm mini jack lead)?????

Is what I am doing now a travesty … (ie) not allowing my mic to do what it can do or hindering its potential performance in some way?

Is considering a “Juiced Link” or “Beach Tek” product (preamp/phantom power) a wise investment to aim and save for in the future.

Would the cost outlay be worth it fro the noticed improvement in audio?

I am all ears (sorry).

Cheers guys

Originally Posted by slimbob

Would I notice a huge worthwhile difference in quality by using a Beach tek or juiced link product compared to what I am doing now (ie) plugging a decent external mic £149 Rode NT3 straight into the camcorder stereo mic input jack (XLR to 3.5 mm mini jack lead)?????

You will only notice a difference in quality if what you're getting now suffers from the problems that your setup might cause (if that makes sense) - ie you are picking up interference (due to using unbalanced cables) or noise from the cable itself (due to poor quality cable or connections). The longer the run, the worse the problem will be. A balanced system eliminates this.

A pre-amp may well also improve the signal to noise ratio. The promotional stuff (including demo videos) for the JuicedLink box shows how much better that is s/n wise than the BeachTek. I always treat syuch claims with a pinch of salt as they are clearly designed to sell you their product. I do have a friend with a BeachTek and the only time I've ever used it with him we had some serious noise issues, but this was down to poor connections not the unit itself. Perhaps I should borrow it and do a side by side comparison, but given that I already own the JuicedLink and am unlikely to buy another such unit it wuld be rather academic.

Originally Posted by Marc Peters

Apologies Tim. I missed one of the changes. Should be fixed now.

Wah-hey! And I see my Avatar has re-appeared. Marc, you are a god. There is never a requirement to apologise to me.

CX211.jpg