Shure PG81 low output - any ideas!

[TDS]

I've had a pair of PG81's as part of my Shure drum mic set for a few years now, which I use for overheads. While checking them on a small Behringer mixer before packing for a gig last week, I noticed that one of the PG81's output was down about 20 dB compared to the other one, although it still sounded fine. i.e. No distortion, noise etc - just much lower output.

 

I wondered if there might be something wrong with the 18 Volt phantom from the mixer. I've never noticed the difference between the two '81's on this mixer before. I tried it on an internal battery - no change. Still 20 dB down.

 

Tried both PG's on my main Soundcraft mixer on 48 Volt phantom. Output now up to the same level as the other mic and both working normally.

 

Used them at the gig on 48Volts, no problem, performance normal!

 

Any ideas?

[pisquee]

You did try them on different channels on the Behringer, to check that the problem wasn't with the mixer and not the mics?

[Bobbsy]

At the risk of stating the obvious, you didn't have the 20dB pad switched in on the mixer, did you? (And, if it makes you feel any better) I did exactly that yesterday.)

 

Bob

[TDS]

You did try them on different channels on the Behringer, to check that the problem wasn't with the mixer and not the mics?

I reversed the channels and swapped the cables and used a different pair of channels too, it made no difference. The PG81 is spec'd for 11-48 volts phantom supply, but it definitely needed the higher 48 volt supply to work at normal output.

 

A concurrent post has been automatically merged from this point on.

 

At the risk of stating the obvious, you didn't have the 20dB pad switched in on the mixer, did you? (And, if it makes you feel any better) I did exactly that yesterday.)

 

Bob

Pretty sure, the Behringer mixer doesn't have a 20 dB pad.

[lightsource]

Try looking at the coil resistances with a multimeter,

 

Compare the good mic with the bad one, see if there's a difference.

[paulears]

er, ... it doesn't have a coil - so all the meter would show is the output impedance of the electronics - and as there will be a couple of resistors across 2 and 3 to recover the phantom power, the probable result will be identical. Worth a shot, I guess.

 

One thing - when you say with 48V it works normally, are you running much lower than this to cause the problem?

[lightsource]

er, ... it doesn't have a coil - so all the meter would show is the output impedance of the electronics -

 

 

Sorry Paul, missed they were condensers, but one thing that comes to light is they are normal at 48v but not at lower Phantom voltages, so, thinking of Ohms Law, could one of the resistors be the problem?