Harmonica Lewinskey
128 posts
Mar 14, 2016
9:43 AM
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Ok, so I have been having a strange chain of things happen with my microphone. The reason I ask if it is haunted is because it all started when I got this Fender Super Champ X2, which I was raving about. However I noticed that my JT-41 (same shell as a JT-30 but says JT-41 for some reason.. Could be part of the reason it is haunted but i'm not sure, lol) which has a NOS vintage CM element. Well anyways, it started making these creepy whispering voices through my amp.. I assume it was probably picking up radio frequencies somehow? but I have never had another mic do this to me, and the JT-41 has not done this again since the first day I tried the amp.
Now that the whispering has stopped, I get a hum through my mic. It is not all of the time, and sometimes it is worse than others.. like MUCH worse almost to the point that I can't play through it. I can get the hum to stop depending on where I hold the mic or what position I put it in. Seems like it is probably some sort of grounding issue? Is there anything in particular I should check to troubleshoot this? I know that it is not the amp or the cable because I can hook other mics up the same way and they are silent. I should also add that I soldered the element in myself and the guy who I bought the mic from installed a volume pot so perhaps there is some faulty wiring or something? It is strange though because I never had an issue with this mic until now, so maybe something got knocked loose since I have taken it out to a couple gigs these last few weeks.. I dunno though, any help would be very much appreciated..
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-LeWin$key
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1847
3290 posts
Mar 14, 2016
10:19 AM
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bad ass harmonicas
that would never happen with a stock crystal
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Last Edited by 1847 on Mar 14, 2016 10:20 AM
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CarlA
837 posts
Mar 14, 2016
11:59 AM
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.........do you see dead people :)
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MindTheGap
1284 posts
Mar 14, 2016
1:41 PM
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I'd rather have the hum than the whispering. Sounds like EVP.
Last Edited by MindTheGap on Mar 14, 2016 1:42 PM
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Ian
308 posts
Mar 14, 2016
1:46 PM
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Definitely haunted, time to get the exorcist in I think.
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Harmonica Lewinskey
129 posts
Mar 14, 2016
1:50 PM
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yea I dunno, I thought for sure it was just radio waves coming through the amp for some reason.. Could be EVP though, stranger things have happened..
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-LeWin$key
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dougharps
1185 posts
Mar 14, 2016
2:08 PM
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Since you say the cable is fine with other mics, and the amp is good with other mics, it sounds like a grounding issue in the shell or at the mic cable connector.
Or there are problems with the pot...
(intentional ambiguity)
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Doug S.
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Barley Nectar
1170 posts
Mar 14, 2016
7:08 PM
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Send it to Greg. He is an ordained mic exorcist and can rid the mic of the humming demon!
MwaaHaHahahahahaaaa......
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Harmonica Lewinskey
130 posts
Mar 15, 2016
10:07 AM
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Yeah Doug, I think it is probably an issue within the mic.. Could be the pot too, but it hasn't steered me wrong yet, lol
Barley, that was pretty much my plan if there is not an easy fix I can do myself.. I am a little bit weary about shipping this thing back and forth across the country though.. Do you guys know of any good microphone techs in Chicago? It would probably be nice to meet them anyways since I really like playing with mics, lol
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-LeWin$key
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Greg Heumann
3199 posts
Mar 18, 2016
9:33 AM
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The mic, cable, your body, the amp - are all part of the “system”. Hum is caused by The System picking up A/C noise (EMI aka "electromagnetic interference”) from your environment (power line condition, grounding, amount of stray EMI) and amplifying it. The mic and cable act like an antenna. And the cable can make noise by being moved which actually dynamically effects this. The “resonant frequencies” of that system depend on the combination of resistance and capacitance. You'll probably notice if you turn the mic's volume all the way down (if you have a volume control) it goes away - that is basically shorting the ends of the cable together - which reduces the resistance so much that nothing can get in. But as you open the volume control, the impedance of the system changes, and at various points it is more or less susceptible - generally as the impedance increases but not always. (Disconnect the mic from the cable, but leave the cable plugged into the amp - hum/noise is probably still there?) Sometimes the hum is louder with the mic’s volume in the middle because at that specific impedance the system is more resonant. The higher the impedance becomes, the more the preamp tube is able to hunt for the weakest possible signal and amplify it. When you touch the ground you are adding your body to the mix - changing the capacitance of the system. Sometimes your body provides a stronger path to absorb the EMI than the amp does, so the hum decreases. Because crystal elements are even higher impedance, they tend to make things worse. In some environments/combinations ANY crystal mic will hum. Just like guitar players there isn't a lot you can do - but here are factors to experiment with:
Grounding: If your amp has only a 2 wire system it isn't grounded to a known potential. Sometimes reversing the plug can help. If it is grounded, make sure anything else in the system is grounded to the same circuit.
Pedal power supplies - these are a common culprit. Run the mic straight into your amp. Hum still there? It wasn’t one of your pedals. If it IS a pedal, try powering it with a battery. If that fixes the problem, get a better filtered power supply.
Environmental: Fluorescent lights, dimmers of any kind (whether on a light or a soldering iron - don't ask me how I know) are big sources of A/C EMI. Try moving to a new location to compared the hum level.
Take any pedals out of the loop to see if that makes a difference. If it does, try battery power in the pedals. If that corrects the problem, get a better-filtered pedal power supply.
Cables: In general better made cables work better. However every cable will have a different capacitance and this is a factor in susceptibility to EMI.
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/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
Bluestate on iTunes
Last Edited by Greg Heumann on Mar 18, 2016 9:34 AM
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Barley Nectar
1172 posts
Mar 19, 2016
10:25 AM
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VERY well done Greg. Don't forget the Latin chant...
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