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Help a real novice with their Sennheiser MKH50 P48


JDub
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I know I'm a total novice and will probably look stupid in this group full of experts, but can anyone help with an audio related issue with my Sennheiser MKH50 P48...

I have recently purchased a Sennheiser MKH50 P48. I am doing talking head work and plugging my MKH50 into a Sony XLR K3M which is connected to my Sony A7Siii. I am finding with the MKH50 that I am getting this very high pitched noise on my recordings. When I use my other XLR Microphones (I have tried two different ones) on the K3M I do not get this noise. As you can imagine I am tearing my hair out! You can listen to a sample of the noise here which is a WAV file - https://www.dropbox.com/s/lguudvie3afjjue/MKH50.wav?dl=0. (You can hear my bathroom fan running in the background sorry) Interestingly, If I plug the MKH50 into my USB audio interface for my laptop (Audient EVO 4) I do not get this high pitched noise either.

Is anyone with with audio knowledge able to help diagnose what might be the problem? As it stands I feel that I can't use my new mic with my Sony XLR K3M. You will have to forgive me as I am not an audio expert but would really appreciate the kind help of those more knowledgeable than me.

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Plug in a Sennheiser MKH 50 straight to Sony A7 is not the best idea, because that camera has been designed to capture image. 

 

That's why you don't get that issue with audio interface which designed for sound.

 

Mix Pre 3 II is my answer. 

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Perhaps your MKH50 is picking up RF noise from the camera? I'd guess that's more likely if it's a fairly old model; IIRC Sennheiser addressed some of those issues 10ish years. Or perhaps a screw is loose by the XLR connector?

 

I just searched this site. Looks like some good info and suggestions in this thread from several years ago:

 

 

 

 

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Try getting a cable that has pin 1 and the shell tab grounded together at the mic end or both ends. I found that with my brand new (2019) MKH50s they needed to use cables wired this way to avoid some fluorescent light related interference on set. It didn't sound like your sample but certainly worth a try.

Another idea.. make sure the 10 dB pad isn’t on. If it is maybe that’s just what the Sony adapter noise floor sounds like. 

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9 hours ago, Jim Feeley said:

Perhaps your MKH50 is picking up RF noise from the camera? I'd guess that's more likely if it's a fairly old model; IIRC Sennheiser addressed some of those issues 10ish years. Or perhaps a screw is loose by the XLR connector?

 

I just searched this site. Looks like some good info and suggestions in this thread from several years ago:

 

 

 

 

This may well be the case. I have put it in Airplane mode and tested but it makes no difference. It may of course still be generating RF. The MKH50 is brand new and purchased 2 weeks ago so should be a latest updated model. I have checked the screws near the XLR connector and they are also tight. Thanks for the link to the post from 2013 - very interesting. I shall continue troubleshooting using this.

 

Interestingly, when testing, I accidentally placed the MKH50 near a magnet and it changed the tone and also completely stopped in one position, the whining noise. You can hear this here: https://www.dropbox.com/s/w0avs9yumkfvv4t/Varying whine.wav?dl=0 - not sure if this helps pinpoint the reason?!

 

Thanks so much for your input.

6 hours ago, Patrick Farrell said:

Make sure the allen screws on the body of the mic are all snug. They make contact with a grounding strip that helps keep noise out.

Thanks Patrick, I have double checked the two Allen screws and they are both tight.

 

Interestingly, when testing, I accidentally placed the MKH50 near a magnet and it changed the whining noise tone and also completely stopped in one position. You can hear this here: https://www.dropbox.com/s/w0avs9yumkfvv4t/Varying whine.wav?dl=0 - not sure if this helps pinpoint the reason?!

 

Really appreciate you chipping in. I have a lot to learn with regard to audio but am finding it really interesting.

7 hours ago, Derek H said:

Try getting a cable that has pin 1 and the shell tab grounded together at the mic end or both ends. I found that with my brand new (2019) MKH50s they needed to use cables wired this way to avoid some fluorescent light related interference on set. It didn't sound like your sample but certainly worth a try.

Another idea.. make sure the 10 dB pad isn’t on. If it is maybe that’s just what the Sony adapter noise floor sounds like. 

Thanks Derek, I will look into this. All very new to me at the moment.... does this cable fit the bill? https://www.designacable.com/catalog/product/view/_ignore_category/1/id/4527/s/neutrik-emc-xlr-to-xlr-lead-van-damme-starquad-cable-balanced-boom-mic/ 

 

-10db pad is turned off.

 

It definitely seems to be specific to using the MKH50 with the Sony K3M Adapter. If I put the MKH50 into my Audient Evo 4 USB interface I don't get the high pitched whining at all. Something about the two of them together seems to be the issue.

 

Interestingly, when testing, I accidentally placed the MKH50 near a magnet and it changed the whining noise tone and also completely stopped in one position. You can hear this here: https://www.dropbox.com/s/w0avs9yumkfvv4t/Varying whine.wav?dl=0 - not sure if this helps pinpoint the reason?!

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At this point, I'd consider that the problem isn't with the MKH50 but elsewhere in the signal chain. I've heard that kind of noise before when it was a poor quality phantom power supply. Do you have an external phantom power box you could add in line? Or another mic you could try and see if the noise is still on the recording? You could also try cleaning the hot shoe contacts between the camera and accessory.

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That cable you linked to is worth a try. It’sa more elaborate solution than what I proposed. If you have a buddy with a soldering iron just try modifying one of your existing XLR cables. 

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1 hour ago, Patrick Farrell said:

At this point, I'd consider that the problem isn't with the MKH50 but elsewhere in the signal chain. I've heard that kind of noise before when it was a poor quality phantom power supply. Do you have an external phantom power box you could add in line? Or another mic you could try and see if the noise is still on the recording? You could also try cleaning the hot shoe contacts between the camera and accessory.

I feel like this is the case too i.e. not the MKH50. There are no issues with the MKH50 my USB audio interface (Audient Evo 4 which delivers 48V Phantom Power). I have tried a couple of other XLR mics but they do not exhibit this noise on the Sony XLR K3M that I can tell. Unfortunately I do not have an external phantom power box. I will try and clean the hot shoe contacts like you suggest. What are your thoughts on it being a cable issue?

44 minutes ago, Derek H said:

That cable you linked to is worth a try. It’sa more elaborate solution than what I proposed. If you have a buddy with a soldering iron just try modifying one of your existing XLR cables. 

Thanks Derek. Unfortunately I don't think I know anyone with a soldering iron. I will try another cable at the office tomorrow and see what effect that has. If not I will hunt down a soldering iron or try that other cable. Thank you for your help!

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