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Dirty-South Blues Harp forum: wail on! >
how to test elements for output?
how to test elements for output?
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toddlgreene
2206 posts
Dec 13, 2010
12:27 PM
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I often see pics of mic elements next to a multimeter readout. What setting would I want to use, and what would I need to touch with the leads to get this? Also, what's an ideal range for cm/cr elements? I have a 520D wired to high-Z that I think I want to sell, but would like to give evidence of the output. Thanks in advance.
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Todd L. Greene, Codger-in-training
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5F6H
437 posts
Dec 13, 2010
12:37 PM
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You don't want to use any setting, it's pointless, they are using an ohmmeter in the pics you have seen to measure the DCR (dc resistance) of the element. But, the transformers that convert the elements to h-z don't know what dc is, they only "see" AC. Thin wire might give a higher reading than thick wire, but it's the number of turns that is critical.
The only real use is to determine whether an element might be low-Z, medium Z or High-Z. Lo might be anything up to 250ohms, med might be around 600ohms (really still classed as lo) hi-Z might be between 1000 to 2000ohms.
This applies to CR/CM & dynamic elements. Crystals & ceramics are usually higher than most meters will register (all are hi-z anyway), but don't even try to measure them as you may well damage the element!
The only way to "test" elements is to make up a mic lead terminating in insulated crocodile clips, clip this to the element (mounted in a spare grill if you like), plug them into an amp & play them.
Last Edited by on Dec 13, 2010 1:03 PM
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toddlgreene
2212 posts
Dec 13, 2010
12:44 PM
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Ah, so the 'reading' is pretty much eyewash? Oh, and this is a white label Shure I am referring to. Gotcha. Always meant nothing to me anyways. So, I could just sum it up by saying 'strong output', and perhaps backing it up with an audio/video clip? Thanks!
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Todd L. Greene, Codger-in-training
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Greg Heumann
941 posts
Dec 13, 2010
5:05 PM
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Yep, I concur with 5F6H - measuring the DC resistance of an element won't tell you much other than whether it is in the high, medium or low impedance range. It can also tell you if there is an internal short or open - although this is rare. Having tried such an element in the first place, you would already have discovered it didn't work at all.
Word to the wise: if your ohm meter is older, it will pass more current than a modern good quality ohm meter does through whatever is being measured - in this case, the element. This won't hurt a dynamic element - the current is pretty miniscule - but it CAN fry a crystal.
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/Greg
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MP
1128 posts
Dec 14, 2010
10:03 AM
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oh, so we fried those crystals MojoKane! damn!
-thanks for the info 5F6H and Gregg!---------
MP
hibachi cook for the yakuza
doctor of semiotics
superhero emeritus
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toddlgreene
2218 posts
Dec 14, 2010
11:51 AM
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Thanks for the info, guys. I won't bother doing this reading then, IF I do sell either my 520 or my JT....I have two very good-sounding strong elements, so as much as I want to sell something to put towards my 'bigger amp fund', I'm hesitant.
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Todd L. Greene, Codger-in-training
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Greg Heumann
943 posts
Dec 14, 2010
7:26 PM
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Yep. Best way to compare elements is to actually blow them side by side. You can make a cable with clip leads on the end, and you can hear well enough just cupping the element itself in your hand - you don't have to install each in a shell first.
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/Greg
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toddlgreene
2222 posts
Dec 15, 2010
5:18 AM
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I've played that Mexican element side-by-side with a late-40s(if I recall correctly)black label, as well as a few newer 60s and 70s elements, and there wasn't a huge difference, if any, discernable by a roomful of experienced players. I dislike the shell size/weight and its lack of a volume control of the 520D it is installed in mostly. Plus it has that built in cord that I despise.
Actually, Greg...my hesistation for holding on to the 520D, or at least the element, is to eventually send it to you to put in one of your purty wood mics with a shiny grille that says 'TLG'...yessir. None of us are getting any younger, and I think that would be a beautiful, personalized hand-me-down for my kids when I go to the great blues jam in the sky.
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Todd L. Greene, Codger-in-training
Last Edited by on Dec 15, 2010 1:38 PM
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barbequebob
1460 posts
Dec 15, 2010
7:45 AM
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Todd, if you have a JT30 shell lying around, any CM/CR cartridge will fit them without a problem. During the 70's, many harp players often did that because the shells of JT30's are much lighter weight and also because the cable isn't hard wired into the cartridge, plus (until Switchcraft discontinued them in 1978) use a Switchcraft 329 volume control adapter with them. If you have an older JT30/BB shell that has a 500K volume pot in it, the GB cartridges will also fit as well, and the 500K pot is the right one for those and the wrong one for crystals/ceramics.
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Sincerely,
Barbeque Bob Maglinte
Boston, MA
http://www.barbequebob.com
CD available at http://www.cdbaby.com/cd/bbmaglinte
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toddlgreene
2223 posts
Dec 15, 2010
8:18 AM
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Thanks for the info, Bob. Should I decide to keep the Shure, I may do just that, and stick the element in either a JT or other shell(EV or Turner, perhaps)for the time being. If I go that route, I'll look for a non-working one for cheap.
The JT I have, actually a CAD HM50VC has a nice and strong 151/127 ceramic in it. Given the price that those go for, I may keep it too and get the upgrades done by Greg, or do some myself-the proper volume pot and getting that XLR boss outta there...
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Todd L. Greene, Codger-in-training
Last Edited by on Dec 15, 2010 8:19 AM
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