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Dodgy battery in mic causing issues

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Re: Dodgy battery in mic causing issues

Postby Bill S » Fri Sep 21, 2018 8:57 am

Very helpful, much appreciate your thoughts. Think I'll stick to phantom power from now on!
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Re: Dodgy battery in mic causing issues

Postby Hugh Robjohns » Fri Sep 21, 2018 11:38 am

Bill S wrote:I’m still surprised that the battery seemed to cause buzzing as it started to run out of juice, rather than just going from (a) working fine, to (b) the mic suddenly creasing to work completely when the battery died.

That's not the way of analogue electronics. The performance will degrade in myriad ways as the supply voltage decreases. Depending on the complexity of the circuitry and its design, some sections of the signal path might go unstable and start oscillating (which could explain your buzz). The bandwidth might change (which might explain your sibilance). The noise floor might change. Distortion will certainly change and might become asymmetric... All very complicated and largely unpredictable.

Could this also be due to a battery on its last legs do you think?

Entirely possible... but it's easy to find out: just stick a new battery in it and see if it all gets better! Moreover, the fact that all these problems went away when you switched to phantom power does indicate pretty conclusively that you had a low voltage issue on battery-power.

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Re: Dodgy battery in mic causing issues

Postby Bill S » Sat Sep 22, 2018 11:10 am

Hugh Robjohns wrote:
Bill S wrote:I’m still surprised that the battery seemed to cause buzzing as it started to run out of juice, rather than just going from (a) working fine, to (b) the mic suddenly creasing to work completely when the battery died.

That's not the way of analogue electronics. The performance will degrade in myriad ways as the supply voltage decreases. Depending on the complexity of the circuitry and its design, some sections of the signal path might go unstable and start oscillating (which could explain your buzz). The bandwidth might change (which might explain your sibilance). The noise floor might change. Distortion will certainly change and might become asymmetric... All very complicated and largely unpredictable.

Could this also be due to a battery on its last legs do you think?

Entirely possible... but it's easy to find out: just stick a new battery in it and see if it all gets better! Moreover, the fact that all these problems went away when you switched to phantom power does indicate pretty conclusively that you had a low voltage issue on battery-power.

H

Hugh
Thank you for taking the time to explain. Although the technicalities are beyond me, the answer seems to be to use phantom power all the time. I can’t see any reason whatsoever to use a battery in my studio. Unless you tell me otherwise!

Anyway, thanks again.
Bill
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Re: Dodgy battery in mic causing issues

Postby Martin Walker » Sat Sep 22, 2018 3:38 pm

Hugh Robjohns wrote:
Bill S wrote:I’m still surprised that the battery seemed to cause buzzing as it started to run out of juice, rather than just going from (a) working fine, to (b) the mic suddenly creasing to work completely when the battery died.

That's not the way of analogue electronics. The performance will degrade in myriad ways as the supply voltage decreases. Depending on the complexity of the circuitry and its design, some sections of the signal path might go unstable and start oscillating (which could explain your buzz). The bandwidth might change (which might explain your sibilance). The noise floor might change. Distortion will certainly change and might become asymmetric... All very complicated and largely unpredictable.

Some esoteric stopboxes actually employ voltage starve to change their sound, anything from a change in distortion to schmitt-trigger-like gating.

I'm currently working on an electro-rhythm box that uses voltage starve with digital circuitry, for seemingly random chaotic sounds that can be disrupted so they play rhythmically.

Wonderful when used in the right circumstances! 8-)


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Re: Dodgy battery in mic causing issues

Postby ConcertinaChap » Sat Sep 22, 2018 4:12 pm

Bill S wrote:I can’t see any reason whatsoever to use a battery in my studio. Unless you tell me otherwise!

Hugh may (and normally does) know better than me but I'd always use my NT4 on phantom power in the studio. It's out of the studio where battery power comes into its own, and I assume the same would be true for the NT3. Most commonly I'll plug it into my Olympus LS10 when I want to get a decent live stereo recording without going to the trouble of my full live setup. I can get best quality with the latter but quick and surprisingly good with the former can be ever so useful. Wouldn't be possible without the battery.

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Re: Dodgy battery in mic causing issues

Postby Hugh Robjohns » Sat Sep 22, 2018 5:03 pm

It's always going to be best to use phantom whenever possible -- and bet to take the battery out when it in use.

Phantom power often gives more headroom, lower noise and less distortion than the internal battery, and no risk of corrosive leaks or getting caught out with gradually worsening performance.

But of course, battery power has its uses now and again...

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Re: Dodgy battery in mic causing issues

Postby Bill S » Sat Sep 22, 2018 8:51 pm

Hugh Robjohns wrote:
Phantom power often gives more headroom, lower noise and less distortion than the internal battery

H

I really didn’t know that. So glad I started this post, I’ve really learnt something.

Must hang out here more often!
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Re: Dodgy battery in mic causing issues

Postby Hugh Robjohns » Sat Sep 22, 2018 9:46 pm

Depends on the sophistication of the mic's electronics, but usually the circuitry's operating voltage rail will be considerably higher when receiving phantom power, compared to a 9V battery. That translates directly to more headroom and potentially less noise and distortion too.
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Re: Dodgy battery in mic causing issues

Postby Bill S » Tue Sep 25, 2018 3:18 pm

Unfortunately, after a few days trouble free motoring, the “medium frequency buzzing” I described in my original post has returned, this time with no battery in the mic and with it operating on phantom power.

It is clearly an intermittent issue. It only occurs when input echo is engaged. I don’t have another mic, or even access to one I can borrow to try to establish if it’s the mic. Ditto another audio interface. I have changed the mic cable, so it’s not that. It’s not related to any heavy duty household appliances being used. I don’t think it is an earth hum (frequency too high). It doesn’t occur when I plug in an electric guitar.

I live in Spain and it is tempting to blame dodgy household electrics, yet my gut says this isn’t the case, as it hasn’t been a problem before in the two years we’ve been here. I am beginning to think it might be the mic itself.

Any pointers as to how I can isolate the issue and discover the cause?
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Re: Dodgy battery in mic causing issues

Postby Wonks » Tue Sep 25, 2018 3:35 pm

I'd suggest it might be a grounding problem, where perhaps oxidation or poor contact between sections of the mic are stopping the whole case from being grounded and acting as a shield.

I'd use a multimeter to check that there's continuity between pin 1 and all the metal parts of the housing. I believe the finish should be conductive, though if not, there should be exposed metal around the screw threads, which would be better than nothing.

If you can't get a good reading from parts of the mic, then you could try taping a bare wire across all the metal surfaces and see if that cures the noise problem.

There are conductive greases containing carbon that you could carefully wipe around the screw threads of the separate sections to improve the overall conductivity if any break seems to be between screwed sections.

Otherwise it sound more likely to be a failing internal component. If you registered the mic, then it has a 10 year warranty instead of the normal 1 year.
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Re: Dodgy battery in mic causing issues

Postby Bill S » Tue Sep 25, 2018 5:14 pm

I should throw in that the NT3 is 18 years old! Having said that, it has led a very sheltered life. I’m certainly not averse to buying a new mic, and I’ve had my money's worth with this one. But before I do, I’d obviously like to know if it’s the mic that’s at fault.
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