Unsure of what to do about mic hiss - Apex 175

Steve House · January 6th, 2006, 09:09 AM

Quote:

Originally Posted by Leo Mandy

What is the 'proper matching transformer'?

According to what I was able to find on the web about it, the MT-50 that you said in a previous message that you had is to match a low impedance source to a high impedance input. I believe that it is intended to match to a much higher impedance than is the mic input on your camera. Its output is TS instead of TRS and it doesn't block the DC bias I expect is on your camera's mic jack. Something like the Shure a96f or a purpose built adapter from someone such as Trew Audio that Ty mentioned in his comments would probably give better results IMHO.

Leo Mandy · January 6th, 2006, 09:35 AM

Thank you, I am going to look into that today. The Impedence transformer I bought from a music shop, I thought they might know what they are doing, but again this is camera tech and not music, so maybe it could have been a mistake easily overlooked.

Steve House · January 6th, 2006, 10:56 AM

Quote:

Originally Posted by Leo Mandy

Thank you, I am going to look into that today. The Impedence transformer I bought from a music shop, I thought they might know what they are doing, but again this is camera tech and not music, so maybe it could have been a mistake easily overlooked.

That may not be the source of the hiss you're hearing but it couldn't hurt to try it. The hum I hear under your sample clips made with your Apex mic yet the fact that it's not there on the clip recorded with the in-camera mic tells me there's noise being picked up between the mic and the camera while the "thin" quality in both Apex clips could be due to an impedance mismatch distorting the frequency response, bolstering my theory about the transformer. It's certainly worth experimenting to see what happens.

Leo Mandy · January 6th, 2006, 12:53 PM

How can I find out the impedence that my camera is looking for so I can match it up to the mic? It is a pana 852...

Steve House · January 6th, 2006, 01:12 PM

Quote:

Originally Posted by Leo Mandy

How can I find out the impedence that my camera is looking for so I can match it up to the mic? It is a pana 852...

Should be in the manual - it probably wants to have a low to medium impedance mic connected to it.

Leo Mandy · January 6th, 2006, 02:28 PM

Unfortunately, I could not find it in the manual. I have email Pana and hope they get back to me about it. I wanted to phone, but I was on hold for about 20 minutes, paying the long distance charges...

Steve House · January 6th, 2006, 03:09 PM

Quote:

Originally Posted by Leo Mandy

Unfortunately, I could not find it in the manual. I have email Pana and hope they get back to me about it. I wanted to phone, but I was on hold for about 20 minutes, paying the long distance charges...

LOL - "Customer Service" is fast becoming an oxymoron like "Jumbo Shrimp"!

Leo Mandy · January 6th, 2006, 03:13 PM

lol! Aint that the tooth.
I am looking thru the manual again, I will see what comes up. Thanks for all your help and support Steve.,

Steve House · January 6th, 2006, 05:47 PM

Quote:

Originally Posted by Leo Mandy

lol! Aint that the tooth.
I am looking thru the manual again, I will see what comes up. Thanks for all your help and support Steve.,

I downloaded a copy from Panasonic's website and all I could find was the a rated sensitivity of -60db but nothing about expected input impedance. Still, the camera is certain to be expecting expecting an unbalanced mic to be plugged into it. They will typically have an impedance of 150-300 up to 600 or so ohms. The line matching transformer that you have, with the XLR to 1/4 mono, is usually low impednace on the XLR side at 47,000 to 50,000 ohms on the output side. (Look on the transfomer, it should be labeled.) I'm not an expert and I might just be wandering around in the woods here - but I'm confident enough to think it merits an experiment or two to see if changing the way you connect the mic to the camera cleans up the audio.

The xformer I'm talking about is <$40 from BH Photo ... http://www.bhphotovideo.com/bnh/cont...ughType=search

Leo Mandy · January 9th, 2006, 09:35 PM

Got this message back from Panasonic :

Thank you for your email.

In regards to the mic input on the camera all that is listed for it is
the sensitivity which is -50 DB. In the case of the camera a 4Ohm
impedance mic should be just fine in the device so long as it has the appropriate
adaptor to physically fit in the device.

Best Regards,
Panasonic Canada Inc
Customer Care Centre
SM

Steve House · January 10th, 2006, 06:30 AM

Quote:

Originally Posted by Leo Mandy

Got this message back from Panasonic :

Thank you for your email.

In regards to the mic input on the camera all that is listed for it is
the sensitivity which is -50 DB. In the case of the camera a 4Ohm
impedance mic should be just fine in the device so long as it has the appropriate
adaptor to physically fit in the device.

Best Regards,
Panasonic Canada Inc
Customer Care Centre
SM

4 ohm?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!

Leo Mandy · January 10th, 2006, 11:53 AM

I am guessing it is
40 Ohm,

Steve House · January 10th, 2006, 12:55 PM

Quote:

Originally Posted by Leo Mandy

I am guessing it is
40 Ohm,

Even that seems awfully low. The generally accepted definitions are low impedance 150-600 ohm, medium impedance 600-10k ohm, and high impedance >10k ohm. Most good mics seem to lay in the 150 to 600 ohm range while super-cheap consumer mics like the $15 Radio Shack varieties can sometimes run 1.5k or higher. I'm betting they're recommending either 400 ohm or 4 kilohm.

Leo Mandy · January 14th, 2006, 08:53 AM

I emailed them back about this, and your response - but I haven't heard anything yet Steve. Hoping by next week!

David Ennis · January 14th, 2006, 10:26 AM

RE: Panasonic, you have encountered the incompetence and willingess to pull facts and advice out of the air that is typical of well-meaning customer service people. Because of the nature of the circuits they feed, cam mic jack inputs are relatively high; typically around 15K. Personally, I've never seen one spec'd at below 5K.

Equivalence between mic output impedance and cam input impedance is not the ideal. That would deliver the most power, but not the most voltage. Cam mic input circuits are voltage driven. You want the impedance of the mic to be on the order of about 1/10 or less of the cam input. That way most of the voltage developed by the mic is dropped across the cam input, not the mic innards. So any mic in the range of 150 to 600 ohms should be fine. The matching transformer that Steve mentions can help a bit with signal level because as it steps up the impedance it also steps up the voltage.

I think of hiss as electron traffic noise occuring at the molecular level in conductors and electronic components. It's often high when oxidation occurs in connections that are made between surfaces in contact, or at high resistance points like connections that are almost broken. Well chosen materials and designs in minimize it. If the mic and the cam aren't inherently noisy, it could be cheap or faulty cables. If all else fails, SoundSoap is pretty good at removing such noise.

January 14th, 2006, 10:26 AM	#30
David Ennis Fred Retread Join Date: Jul 2004 Location: Hartford, CT Posts: 1,227	RE: Panasonic, you have encountered the incompetence and willingess to pull facts and advice out of the air that is typical of well-meaning customer service people. Because of the nature of the circuits they feed, cam mic jack inputs are relatively high; typically around 15K. Personally, I've never seen one spec'd at below 5K. Equivalence between mic output impedance and cam input impedance is not the ideal. That would deliver the most power, but not the most voltage. Cam mic input circuits are voltage driven. You want the impedance of the mic to be on the order of about 1/10 or less of the cam input. That way most of the voltage developed by the mic is dropped across the cam input, not the mic innards. So any mic in the range of 150 to 600 ohms should be fine. The matching transformer that Steve mentions can help a bit with signal level because as it steps up the impedance it also steps up the voltage. I think of hiss as electron traffic noise occuring at the molecular level in conductors and electronic components. It's often high when oxidation occurs in connections that are made between surfaces in contact, or at high resistance points like connections that are almost broken. Well chosen materials and designs in minimize it. If the mic and the cam aren't inherently noisy, it could be cheap or faulty cables. If all else fails, SoundSoap is pretty good at removing such noise. __________________ "Nothing in the world can take the place of persistence..." - Calvin Coolidge "My brain is wired to want to know how other things are wired." - Me Last edited by David Ennis; January 14th, 2006 at 11:57 AM.

January 6th, 2006, 09:35 AM	#17
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	Thank you, I am going to look into that today. The Impedence transformer I bought from a music shop, I thought they might know what they are doing, but again this is camera tech and not music, so maybe it could have been a mistake easily overlooked.

January 6th, 2006, 12:53 PM	#19
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	How can I find out the impedence that my camera is looking for so I can match it up to the mic? It is a pana 852...

January 6th, 2006, 02:28 PM	#21
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	Unfortunately, I could not find it in the manual. I have email Pana and hope they get back to me about it. I wanted to phone, but I was on hold for about 20 minutes, paying the long distance charges...

January 6th, 2006, 03:13 PM	#23
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	lol! Aint that the tooth. I am looking thru the manual again, I will see what comes up. Thanks for all your help and support Steve.,

January 9th, 2006, 09:35 PM	#25
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	Got this message back from Panasonic : Thank you for your email. In regards to the mic input on the camera all that is listed for it is the sensitivity which is -50 DB. In the case of the camera a 4Ohm impedance mic should be just fine in the device so long as it has the appropriate adaptor to physically fit in the device. Best Regards, Panasonic Canada Inc Customer Care Centre SM

January 10th, 2006, 11:53 AM	#27
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	I am guessing it is 40 Ohm,

January 14th, 2006, 08:53 AM	#29
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	I emailed them back about this, and your response - but I haven't heard anything yet Steve. Hoping by next week!