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Old 15th Jan 2012, 5:00 am   #61
mrmagnetophon
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Default Re: AKG C60 valve mic

Still attempting to fix the problem, everything is spot on with the mic and the schematic.
The ground lift switched don't seem to change the problem, it still hums.
-Chris
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Old 21st Jan 2012, 7:48 am   #62
mrmagnetophon
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Default Re: AKG C60 valve mic

I went to a new mixing console to test, and wow, huge difference, most of the hum is being rejected, its kinda distorted hum now, like a WAH sound, if that makes sense?

-Chris
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Old 22nd Jan 2012, 7:39 am   #63
mrmagnetophon
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Default Re: AKG C60 valve mic

Another huge breakthrough and progress forward!
I removed the ground wire of the transformer, (one from the transformer running to ground for the input side) and wow still humming, so I doubt now that it's the body of the mic causing a problem.

-Chris
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Old 4th Feb 2012, 11:06 pm   #64
mrmagnetophon
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Default Re: AKG C60 valve mic

Now I'm back at it, removed the signal wire from the transformer and it's still humming. The problem somehow seems to be maybe a induced voltage into the transformer not sure here.

-Chris
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Old 5th Feb 2012, 12:50 am   #65
mrmagnetophon
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Default Re: AKG C60 valve mic

After moving the output transformer from the power supply to an external box, I noticed a reduction in hum,10 fold, although it's still there slightly but not by much.

-Chris
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Old 6th Feb 2012, 4:06 am   #66
mrmagnetophon
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Default Re: AKG C60 valve mic

Should the chassis be connected to ground, or is using negative (combined ground) from the power supply fine?

Somewhere its gotta be picking up noise from having the power supply hooked up.

-Chris
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Old 6th Feb 2012, 5:17 am   #67
mrmagnetophon
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Default Re: AKG C60 valve mic

Used batteries and supplied around 45 volts for HT, batteries became warm, but this time, it produced static for sound?!?! almost like a untuned radio?!?!
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Old 10th Feb 2012, 4:45 am   #68
mrmagnetophon
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Default Re: AKG C60 valve mic

Its a low amount of hum, very small amount only heard when turning the volume all the way up, no other sound passes though.
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