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Oscar Sound Tech 802 (and Tram TR50?): Poor Signal

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Harlan Rumjahn
Oscar Sound Tech 802 (and Tram TR50?): Poor Signal
on Oct 11, 2015 at 12:31:20 am

Hello Good Folks,

I have a few related questions that I have not been able to find answers to, despite multiple searches.

There are two lavalier mics that are always highly praised: Sanken COS-11D and the Tram TR50. I have the Sanken COS-11D, which works VERY WELL with the plug-in-power of the Sony PCM-M10.

I was curious about the Tram TR50 so decided to purchase one of these, but was hesitant because I noticed the output impedance of the Tram (3000 ohms) is way more than that of the COS (700 ohms). I'm not an audio person in the least, but I found out through much searching that the output impedance of mics should be ten times LESS than the input impedances of the recorders. This happens to be the case for the COS-11D, but not for the Tram TR50. So I thought I would try to find out more before buying the Tram TR50.

Then I learned the Oscar Sound Tech (OST) lavs are pretty close to the Tram TR50s. So, rather than spending a few hundred to test out the Tram TR50, I spent about a hundred to see if the OST lav would work as beautifully as the COS-11D with the Sony PCM-M10. My thinking was that if the OST worked well, then the Tram would work just as well, and I would be comfortable in buying it.

Unfortunately, the OST 802 lav has a poor signal--less than half of that of the COS's. I was hoping this would not be the case, but I was not surprised because of what I mentioned having read in my searches: the output impedance of the mic should be ten times less than the input of the recorder. The PCM-M10, by the way, has an input impedance of about 4,000 ohms.


So my questions are these:

1. Is my thinking on the impedance correct, or is this wrong information I've gathered?

2. Is the impedance difference between the COS and OST the reason for their difference in signals?

3. Because the OST and Tram mics are so similar (in impedances, etc.) would it be correct to assume that the Tram TR50 will give a low signal, similar to that of the OST?

4. Is there a solution to allow me to use the Tram TR50 with as strong a signal as the COS-11D, or should I just stick with the COS-11D (and all other mics with impedances ten times less than that of my Sony PCM-M10's input impedance)?

I understand I can't go wrong sticking with the COS. I'm just curious about the Tram because of the rave reviews about it and the possibility that its sound character would be more to my liking, or at least better fitting for certain circumstances. I do personally think the COS-11D makes me sound higher pitched and irritating at times. I would like a warmer sounding voice ;)

Thank you!

Harlan


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Eric Toline
Re: Oscar Sound Tech 802 (and Tram TR50?): Poor Signal
on Oct 11, 2015 at 2:11:11 am

Are you sure the OST and the Tram are wired correctly for your Sony recorder? The OST is a 3 wire lav and one of the 2 signal wires has to get connected to the sleeve along with the ground wire.

"I push the RECORD button and hope for the best"


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Ty Ford
Re: Oscar Sound Tech 802 (and Tram TR50?): Poor Signal
on Oct 11, 2015 at 2:19:11 am

Hello Harlan and welcome to the Cow Audio Forum.

You're only looking at one spec. Impedance.

You're ignoring sensitivity and selfnoise. The sensitivity of the mic is the figure that tells how much voltage a mic generates. You want a high selfnoise, but not so high that if you clip the transmitter during loud speaking.

Usually, the larger the diaphragm, the higher the sensitivity because when a larger diaphragm swings, it generates more voltage.

Selfnoise is the figure that determines how noisy a mic capsule is. You want a low selfnoise.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Harlan Rumjahn
Re: Oscar Sound Tech 802 (and Tram TR50?): Poor Signal
on Oct 11, 2015 at 10:01:05 pm

Thank you all for the welcome to the forum and your intelligent/helpful responses!

I have no technical background in audio, so forgive my basic terminology and ignorant questions. Ty, when you say sensitivity, I'm not sure how to interpret this from the specs written for each microphone, as different sites seem to have different terms to describe the same things (I think).

I may have found the answer, however, by re-reading those spec sheets. The COS-11D has a "Sensitivity" of -41dB, and the Tram TR50 has an "Output Level" of -57 dB. Am I correct in thinking the "Sensitivity" is the same thing as the "Output Level"? If so, it would appear that the COS-11D is about 16 dB more sensitive than the Tram TR50, which would explain the differences in signals.

The other spec I could find, but was not sure how to interpret, was the "Equivalent Nose Level" for the Sanken (28 dBA, A-weighted) and the "Noise Level" for the Tram TR50 (26dB equivalent SPL). If my assumption is correct, both of these specs are talking bout the same thing, in which case both mics have similar characteristics in this area, with the Sanken coming out a little worse than the Tram TR50.

With all of the above info combined, along with the difference in impedances, I think there is a reasonable explanation for the signal of the OST 802 being much less than that of the Sanken COS-11D.

Please let me know if my thinking is inaccurate.

Bruce, I am happy with the quality of the sound of the OST 802, only the signal is on the low side. I ended up adjusting the levels in post, which demonstrated the OST's pleasing character, but I didn't like having to raise the levels so much and possibly introduce more noise (although in my test the noise levels seemed not to be a problem).

Originally I did use the mics with my Sennheiser system, but then switched over to the PCM-M10 because of its convenience, great results, and ability to mic up more than one person without buying multiple body packs and receivers (and then having a mess on my hands attaching everything to my camera ;)). I was hoping the OST 802 worked as well as the Sanken COS-11D because I prefer the warmer sound of the OST. Hence this post--to see if I would have to live with the low levels, or if I were doing something wrong, or if the OST were somehow defective.

Thanks again guys! I get a lot of good information from you Creative Cow experts, not just about audio.

Harlan


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Ty Ford
Re: Oscar Sound Tech 802 (and Tram TR50?): Poor Signal
on Oct 11, 2015 at 11:48:26 pm

Hello Harlan,

There are a lot of good folks on the Cow Boards. :)

You ran into what many do, the figures don't always match up for different manufacturers.

20, 24, 26 dB-A sounds about right for lavs. Maybe higher.

To rephrase my thought. Low sensitivity is the "proper" sensitivity if you have a very loud sound source. Like if you wanted o clip a lav to a PA cabinet at a live event when you can't get a proper line feed. Or if you're recording a live band that plays really LOUD.

A low sensitivity lav is NOT what you want for a person with a quiet voice.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Harlan Rumjahn
Re: Oscar Sound Tech 802 (and Tram TR50?): Poor Signal
on Oct 12, 2015 at 6:57:46 pm

Thank you Ty,

Just to make sure I understand you, when you say low sensitivity, you're speaking about those numbers I mentioned (-41 dB and -57 dB), right? Not the self-noise numbers, which have positive values (24 dB, 26 dB, etc.). And when you say low sensitivity you mean -57 is lower sensitivity than -41? Or is it the other way around? Those negative numbers are sometimes confusing!

Thanks again,

Harlan


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Ty Ford
Re: Oscar Sound Tech 802 (and Tram TR50?): Poor Signal
on Oct 12, 2015 at 8:18:45 pm

Harlan,

Yes, you got it all correctly! Gold star for your report card! :)

Now, a High-pass filter (also known as a low cut filter) is one that passes high frequencies and rolls off low frequencies.

A low-pass filter (also known as a high cut filter) passes the lows, but rolls off the high frequencies.

Nutty, but there you have it.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Harlan Rumjahn
Re: Oscar Sound Tech 802 (and Tram TR50?): Poor Signal
on Oct 13, 2015 at 8:51:06 am

Thank you Ty!

By the way, I enjoyed your videos on understanding shotgun vs hypercardioid microphones and the one of you playing ;)

Take care!

Until my next noob questions ;)

Harlan


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Bruce Watson
Re: Oscar Sound Tech 802 (and Tram TR50?): Poor Signal
on Oct 11, 2015 at 7:57:17 pm

[Harlan Rumjahn] "...I spent about a hundred to see if the OST lav would work as beautifully as the COS-11D with the Sony PCM-M10. My thinking was that if the OST worked well, then the Tram would work just as well, and I would be comfortable in buying it.

Unfortunately, the OST 802 lav has a poor signal--less than half of that of the COS's..."


You're the first person I've heard of using lavalier mics directly into a Sony PCM-M10 recorder. And the first person I've heard who isn't happy with the Oscar SoundTech lavalier mics.

I'm not saying recording directly to a PCM-M10 isn't done. But in my work recording dialog, the "standard practice" is to power the lavs from either a mixer (like an SD MixPre-D) or a wireless transmitter (like a Sennheiser SK-100 G3). Under these conditions, the Oscar SoundTech mics work wonderfully. I've got a pair of the 802s as my front line mics, and use them in both of the above workflows. I could not be happier with a lav; the 802s are excellent.

Since so many people have such good results with the OST mics using conventional workflows, I'm thinking the fault lies more with the PCM-M10 than with the mics. But call OST's customer support and talk to them about what you are trying to do. They are supposed to be really good; maybe they've encountered this before. IDK.


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