JM27 Upgrade Advice?

  • Thread starter Thread starter Slowjett
  • Start date Start date
S

Slowjett

New member
Hey guys, Got a pair of JM27s with modded Capacitors, but they are both rumbling and popping and have the blowing noise going on. I traded for them so im a bit disappointed. However the PO made good and said he would fix them if I sent them back. I figure I might as well do a better upgrade this time. So what are your suggestions for upgrades and for components (budget but decent) for this microphone?

Thank you!
Josh
 
Sounds like condensation on the diaphragm. Put 'em under a 100W lamp for a few hours. I've also gotten weird behavior that sounded a bit like that (loud rushing noise, no output) on one mic I own when the phantom power was way below what the mic needed. Make sure your pre is putting out a full 48V.
 
dgatwood said:
Sounds like condensation on the diaphragm. Put 'em under a 100W lamp for a few hours. I've also gotten weird behavior that sounded a bit like that (loud rushing noise, no output) on one mic I own when the phantom power was way below what the mic needed. Make sure your pre is putting out a full 48V.
Click to expand...

Mics were in A/C room, but I will try putting the capsules under some lights like that. Lots of popping too though. Phantom on my firestudio seems to be fine. Cant verify though.
 
Slowjett said:
Mics were in A/C room, but I will try putting the capsules under some lights like that. Lots of popping too though. Phantom on my firestudio seems to be fine. Cant verify though.
Click to expand...

As I understand it, pops are very typical of what you'd expect from condensation. Condenser mics work by detecting capacitance changes in a diaphragm close to a plate with a fixed charge. Drops of moisture change the capacitance semi-randomly. At least I think that's the reason they behave that way.... Maybe some of the folks who build mics could clarify....
 
Welp, I put them under a 100wt lightbulb for about 5 hours. After being on for 15 minutes the sounds returned. I am fairly certain its the capacitors.
 
Slowjett said:
Welp, I put them under a 100wt lightbulb for about 5 hours. After being on for 15 minutes the sounds returned. I am fairly certain its the capacitors.
Click to expand...

My guess would be thermal expansion near a poor solder joint somewhere. Unless you see an obviously bulged electrolytic or a shattered ceramic disc, caps are a lot less likely than a cold solder joint, IMHO.

Whoa, wait a second. You have TWO mics doing this? I missed that the first time. That screams "the problem is somewhere else" to me, e.g. bad/insufficient phantom power supply. I don't think for a minute you're going to see a mod cause two mics to both work perfectly, then suddenly cut out after a few minutes.

If it's not a moisture problem, as I said before, this screams insufficient phantom power to me.
 
Hmm. They dont both start doing it at the same time. One will start doing it a few minutes after the other one. I'll run them through my other board and through my other interfaces to see if I get the same results.

-josh



dgatwood said:
My guess would be thermal expansion near a poor solder joint somewhere. Unless you see an obviously bulged electrolytic or a shattered ceramic disc, caps are a lot less likely than a cold solder joint, IMHO.

Whoa, wait a second. You have TWO mics doing this? I missed that the first time. That screams "the problem is somewhere else" to me, e.g. bad/insufficient phantom power supply. I don't think for a minute you're going to see a mod cause two mics to both work perfectly, then suddenly cut out after a few minutes.

If it's not a moisture problem, as I said before, this screams insufficient phantom power to me.
Click to expand...
 
You must log in or register to reply here.
Back
Top