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Different output level from two Tram TR50 lavaliers

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Fred Hampton
Different output level from two Tram TR50 lavaliers
on May 31, 2013 at 8:00:50 am

We just received two new Tram TR50 lavalier mics. When we phantom power them and test them simultaneously in identical conditions we are getting a difference of about 10dB in their output.

Is this within normal tolerance? ...or perhaps one may be defective or poorly adjusted?

Thank you in advance.


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Michael Paul
Re: Different output level from two Tram TR50 lavaliers
on May 31, 2013 at 9:48:01 pm

10db is a pretty big difference. Tram does not offer TR50's in different sensitivities like some other manufacturers, so a gap like that would seem to indicate that one of them is defective.

The only main difference between Trams is whether they are positive or negative bias. This difference will mainly present itself as a phase issue between the two, but should have no effect on mic sensitivity.

Try this:

Remove the batteries from both of the power supplies and plug them both into a preamp with +48V power. If one of them doesn't work, then that one is a negative bias (neg bias needs the battery inserted to operate, even with phantom power).

If you are testing the mics right next to one another, and one of them is out of phase (neg bias) from the other, then you will get artifacts in the sound, and the levels may differ.

If both mics work on +48V, and the levels are still 10db off, try switching the mic channels on your mixer to see if there is an issue with that particular preamp channel or +48V supply.

If the problem still follows a particular Tram, and the difference in signal is that great, then I would contact the dealer you got them from and see if they can swap out one or both of them so you have a pair that is closer in frequency response.

There will be slight variances in response in just about anything, but usually those differences are only noticeable when analyzed on a bench. If they're audibly that far off, I would ask for a new one.

Michael Paul
Location Sound Corp


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Ty Ford
Re: Different output level from two Tram TR50 lavaliers
on Jun 1, 2013 at 3:29:12 am

Hello Michael and Fred and welcome to the Cow Audio Forum.

Fred, I think Michael has given you the right approach to figure out what's going on. If after the tests you still get different sensitivities, I'd reach out to Tram or the place from which you bought the mics.

Their site doesn't show any different models with different sensitivities. I wonder if one of them was altered with to lower the sensitivity for really loud sources like opera singers. Can you take apart the plug on the less sensitive one to see if there's a resistor in there? Or maybe it was wired for another type of transmitter and has a different pin out.

Please get back to us when you get an answer and post it so others may benefit from your discovery.

Regards,

Ty Ford
Cow Audio Forum Leader

PS: Michael; thanks for trying to help.

An Authorized TRAMĀ® Distributor

Toll-Free Phone: (800) 447-1179
Phone: (312) 867-1400

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


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Fred Hampton
Re: Different output level from two Tram TR50 lavaliers
on Jun 1, 2013 at 8:08:33 pm

Thank you Michael. Thank you Ty.

The TR50 test I described above was without any internal battery so that suggests the problem was not a function of negative bias. I did not think to switch inputs on the mixer, but I did cycle the connectors a few times. The mixer was a new SD 664 that seems to work flawlessly otherwise.

I contacted Tram by phone and spoke to a friendly tech. They asked me for the serial numbers (about 200 units difference), and they stated that the 10dB disparity is probably a quality control issue. They offered to exchange the mics at no charge. I'll mail them out Monday and report back if the problem is not resolved when I receive the replacement(s).

These TR50s were purchased together from B&H, for what it's worth.

Additionally, the tonal response of the two mics seemed markedly different (to my untrained ear at least).

Thanks again fellas.


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Ty Ford
Re: Different output level from two Tram TR50 lavaliers
on Jun 2, 2013 at 3:28:39 am

Fred,

Thanks for the followup!

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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