Why does a mic. generate hiss?

[toddboyle]

I bought a pair of Samson QV5 lavalier mics. These are condenser mics, and they come with an adapter transformer to XLR connector. With my Behringer UB802 mixer, they are too insensitive to be usable-- and there's an ocean of hiss. WTF@! My other condenser mics sound fine.

In general, what conditions on a mic. will cause the mixer to hear a lot of hiss like that, and attenuate the audio so badly? I wonder if these "PM6" adapter transformer things are damaged.. maybe somebody tried to use them with the speaker output from a guitar amp!!!

[Ben B]

Those are probably electret condensers, which are generally noisier.

-Ben B

[tINY]

Sounds like the Xformer is wired backwards - High impedance and attenuated output...



-tINY

[aussie_techie]

theres no listing of a QV5, have you got the right model? is the PM5 the right adapter for that model?

all active electronics generate noise, if everything is wired correctly then my guess would be theres is an impedance mic matching making a noisy mic and noisy pre in the mixer perform even worse. try the mic with a professional pre/mixer to test it.

[toddboyle]

Originally Posted by aussie_techie

theres no listing of a QV5, have you got the right model? is the PM5 the right adapter for that model?

all active electronics generate noise, if everything is wired correctly then my guess would be theres is an impedance mic matching making a noisy mic and noisy pre in the mixer perform even worse. try the mic with a professional pre/mixer to test it.

Thanks Aussie. Yes you're right, the model no. is QL5 as in lavalier. In fact there's no marking on the mics but they're in a bag with Samson PM6 adapters... so, who knows what they are. I bought them from a college student who said he doesn't know what they are.

So there's now 3 possibilities: a) both capsules damaged or defective in the same way? or b) somehow in their history, owner associated the wrong transformers for this model mic., e.g. in a big studio or rental shop, or c) both of the PM6's wired wrong.

I've tried them on several preamps now. No joy. Same problem. :-( For my next test I guess I will try to connect one of them to my camcorder without the transformer (I don't have any mini-XLR jacks, so it will be a kluge),
-TOdd

[toddboyle]

Well, here's further testing. The QL5s work normally with my camcorder, when I cut off the mini-XLR plug, and solder to a 1/8th inch plug (Skipping the Samson PM6 XLR adapter.)

Also I would like to commend Samson for their tech support, I asked for advice or tips, but they didn't offer any. They did confirm the QL5 works ok with the PM6 even though it was sold with a PM5 model.

I asked for a circuit diagram of the PM6 and they sent it to me. It's all solid state-no transformers. I guess my PM6s must be damaged/ fried by some overvoltage in the past, maybe.