bluzmn
18 posts
May 13, 2011
9:08 AM
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I have an old Astatic JT-30 with an MC-127 element. I remember that when I used it in the past, I wasn't very impressed, so when I started having problems with the volume control pot, I didn't try to fix it. So, it has laid around for years unused, but this week I decided to replace the 5 meg pot with another. I tried it out through a VHT Special 6 and a Fat Dog 1A; it had a very low output. I was able turn the volume all the way up on both amps (with all my other mics I can't turn the volume past 3 o'clock without feedback), and it was nowhere near as loud as any of my other mics, whether CR, CM, crystal or dynamic. I had to turn the tone all the way up on the VHT and to 3 o'clock on the Fat Dog to get any "balls" out of the mic; anything more than 7 o'clock is feedback territory with my other mics (and they sound plenty ballsy). My question is: is this typical for an MC-127 element, or is there a lot of variation among them and I got a dud?
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5F6H
667 posts
May 13, 2011
9:28 AM
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Hard to say whether it is a dud, yes there is some variation, as with anything mechanical. What is typical however is that ceramic elements have much less output than crystal and healthy CM/CR, Hi-Z dynamics. The ceramic piezoelectric material is just not as efficient as Rochelle salt crystal. This can make them a good option for unknown amps & amps with a lot of gain though.
From memory, the old specs show ceramic JT30 elements as having an output of *something like* -61dB, compared to -52dB for the crystal (lower the number, higher the output).
Last Edited by on May 13, 2011 9:29 AM
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Joe_L
1242 posts
May 13, 2011
10:30 AM
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Take the volume pot out of the circuit and try it again. The element may be on it's way to the element boneyard.
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The Blues Photo Gallery
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bluzmn
23 posts
May 19, 2011
5:48 AM
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I was finally able to get a good tone out of the mic; I just had to crank the hell out of the controls (pulled out the "boost" knob on the VHT, the Fat Dog was all the way up on the volume, at 3 o'clock on the tone). Part of the problem was that the speakers of my amps were turned toward the wall, and I had hernia surgery 6 weeks ago and wasn't supposed to move anything heavy; consequently the tone was a little muffled. The doctor just gave me the OK for heavy lifting, and so the tone was a lot better with the amps turned around. Thanks to everyone for your input.
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Greg Heumann
1133 posts
May 19, 2011
7:21 AM
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Your element is dying. Unfortunately there is nothing you can do about it except replace the element.
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/Greg
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bluzmn
24 posts
May 20, 2011
7:10 AM
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@gheumann
I was hoping you would chime in... I probably f!*ked it up when, not thinking, I baggage checked my harp case for a transatlantic flight. But, come to think of it, it never did sound very good. Do you still have CM elements for sale?
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Elvis
1 post
May 20, 2011
10:54 AM
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The same troble with my JT-30 on MC-101 :(
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