jnorem
51 posts
Feb 25, 2014
2:23 PM
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I have an Astatic JT30 that I've been using for about 16 years. I ordered it from Kevin's Harps, I think.
I've been reading about the different elements used in microphones, for example my Green Bullet, which I bought in the mid-80s, a 520 D, is a controlled magnetic microphone, whereas the vintage 520 is controlled reluctance.
So I'm guessing there must be a difference between old and recent JT30s, and I wonder if the JT30 I have is considered a "real" JT30
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Call me J
Last Edited by jnorem on Feb 25, 2014 2:23 PM
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1847
1517 posts
Feb 25, 2014
2:35 PM
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kevin used to have the real deal
he basically just copied rod piazza's mic
you have a keeper....keep it!
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i get a lot of request when i play my harmonica
"but i play it anyway"
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jnorem
52 posts
Feb 25, 2014
3:09 PM
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Wonderful!
Thanks, 1847.
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Call me J
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NiteCrawler .
269 posts
Feb 25, 2014
3:52 PM
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The one I got from Kevin 20 yrs back was called a crystal balls mic,it has either a 151 or 127 crystal in it.(I havn,t opened in a while)Its a strong mic,thinner than a cm or a cr but has its own voice,the only drawback for me which is a small one is the volume knob on it is in the opposite direction than the rest of my mics.boo,hoo,eh.
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SuperBee
1707 posts
Feb 25, 2014
4:42 PM
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What's 'real' though? There is a lot of variation in those elements.
The designation CR and CM is just a different term for the same thing. Sure, there is a cosmetic difference and the bobbin material is different I think...like that's a huge difference. And the glue used is different...which some think may perhaps influence the sound...but maybe not...
And the variation between individual CR elements can be greater that the difference between CR and CM series elements as a class.
With crystals the differences can be huge because there is the additional variable of environment-caused deterioration.
You can generalise about model numbers and years but it's pretty meaningless IMHO. Pretty much comes down to the particular element.
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Greg Heumann
2614 posts
Feb 25, 2014
5:48 PM
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@SuperBee - There is more to the difference between CR's and CM's, though I'm not sure what it has to do with the OP.
What's at the center of the diaphragm DOES impact how the diaphragm vibrates and copes with reflections. I believe it IS what gives a CR element more character to its breakup than a CM. The original opaque epoxy glue on the first CM's tends to make those elements sound closer to CR's than the later translucent glue.
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***************************************************
/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
BlueState - my band
Bluestate on iTunes
Last Edited by Greg Heumann on Feb 25, 2014 6:01 PM
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SuperBee
1708 posts
Feb 25, 2014
6:07 PM
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Oh, well, I thought it was like the OP postulated that there must be a difference between JT30 elements from vintage to more recent as vintage 520 were CR and 520D were CM. I was just trying to say that the change of designation doesn't necessarily mean much. But yeas Greg, the construction you point to is what I was thinking of as regards the CM/CR. I have several of each type, just enough to be able to say that I can't tell from the sound whether someone is playing a CR or CM.
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jnorem
53 posts
Feb 25, 2014
6:53 PM
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While we're discussing this, I have a strange problem. Today at Ken Stanton I bought a cable for my JT30, XLR to 1/4". My old cable is, well, old.
Tonight I hook it up, plug it in, and nothing. It just doesn't work. To make sure I use the old one and that works.
Then something occurs to me, and I hook the cable to a Samson R21 microphone. It works!
By the way, that R21 sounds real good when I cup it to the harp.
So the Samson is a low impedance mic. The JT30 is high impedance, so I must need a high impedance cable, right? DUH.
Now, my old cable works with my JT30 AND the Samson. So, what could that mean? And for the life of me I can't find a high impedance XLR to 1/4" cable anywhere. What the !@#$%?
Edit: I found this site:
http://www.oaktreevintage.com/Vintage_Style_Microphone_Cables.htm
Looks like He's got what I need.
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Call me J
Last Edited by jnorem on Feb 25, 2014 7:10 PM
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slackwater
1 post
Feb 26, 2014
12:32 AM
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Hey jnorem, I just wrote out a detailed description of what I thought could possibly your problem with the new cable but I went to post it and it was disalowed and wiped so I'm gonna be more brief this time.
Basically, check out how the old mic and the new cable are wired at the XLR.
Old American studio standard:1-shield
2-cold
3-hot
Standard defined by the Audio Engineers Society:
1-shield
2-hot
3-cold
For unbalanced connection (impedance isn't the issue)
the cold and shield connectors are mostly bridged.
If Your mic's in the older standard, as a Blues Blaster I got in the early 1980's was,then the cable will work with a balanced mic wired to the newer standard but in reverse polarity. However a cable wired to the newer standard wont work with a mic wired to the old standard because it will just ground your hot wire.
This is something I've come across in the past but I'm only guessing in your case.
A multi meter should give you an idea of the way things are wired if you don't want to pull stuff apart.
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Greg Heumann
2617 posts
Feb 26, 2014
8:04 AM
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Slackwater has it right. There are actually MANY different cables made with XLR connectors. Some can physically connect your mic to your amp, but that doesn't make them right.
The most popular, by far, and thankfully standard world wide, is a low impedance, "balanced" cable. Signal is on pins 2 and 3, and the shield is not part of the signal path - it provides noise resistance only. The shield is connected to pin 1.
There are TWO standards for high impedance (XLR to 1/4" cables. These are wired UNBALANCED, meaning the shield IS part of the signal path, and is connected to XLR pin 1. One is called "Pin 2 Hot" and as the name implies the hot signal is connected to Pin 2 on the XLR connector. The other is Pin 3 hot,. There is no advantage to one vs the other - but the mic has to match the cable. Pin 3 Hot is more common in the U.S. but hardly ever used (exceptions are the Hohner Blues Blaster and the modern Shure 545SD when you reconfigure it for high impedance according to Shure's instructions.) Pin 2 Hot is much more common in Europe and Asia.
To make it even more confusing, nobody at Guitar Center has a clue about this stuff, and the cables often come in packages that don't even say how they're wired!
There are ALSO XLR to 1/4" cables where the 1/4" connector is the stereo (TRS or "Tip Ring Sleeve") type. These are balanced and are for low impedance applications.
A Hohner Blues Blaster is wired for a Pin 3 Hot unbalanced cable.
Note that you can use an XLR to 1/4" unbalanced cable with a low impedance mic into an amp or pedal and you will get sound. However you'll be getting only about 1/2 of the mic's output.
You can ALSO use an XLR to XLR balanced cable with a high impedance mic and get sound though the PA. But again the chances that the devices at each end are getting the full signal is low.
MATCH IMPEDANCE. USE THE RIGHT CABLES.
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***************************************************
/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
BlueState - my band
Bluestate on iTunes
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jnorem
55 posts
Feb 26, 2014
10:33 AM
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So…where does one get a 1/4" to XLR 3 pin hot unbalanced cable? I've looked all over the internet and I went to my local music store. Nothing.
Are these cable being made anymore?
EDIT: Kevin's Harps has one. Pricey, but what can you do?
Last Edited by jnorem on Feb 26, 2014 12:19 PM
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1847
1523 posts
Feb 26, 2014
2:10 PM
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rapco
is this the right one?
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i get a lot of request when i play my harmonica
"but i play it anyway"
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Bruce S
32 posts
Feb 26, 2014
2:54 PM
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I made my own cables set up "pin 3 hot" as I couldn't find any in the UK. I still have one for my Shure 545 in hi z. Before I modified the bluesblaster to a switchcraft screw on connector, I set my bluesblaster up to use a pin 2 hot cable: under the Astatic or Hohner label around the base of the XLR there's a small set screw. Turned counterclockwise it lets you drop out the 3 pin XLR, and you can swap the wire that goes to pin3 (they are numbered) to pin 2. Then you can use commonly available cables or an XLR to 1/4 inch adapter.
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jnorem
56 posts
Feb 26, 2014
3:10 PM
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1847 "is this the right one?"
It seems like it is. It doesn't say "hot pin 3", it says "wired pin 3 to tip." I'm going to go out on a limb and guess that it means the same thing.
Here's what sells me on the Kevin's Harps cable:
Costly, but right on the money.
Here, I found a better deal on the M20K:
$27.00 including shipping.
Just remember, the Rapco M20K.
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Call me J
Last Edited by jnorem on Feb 26, 2014 3:47 PM
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slackwater
3 posts
Feb 27, 2014
9:09 PM
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I've acquired two Blues blasters over the years, one back sometime around 1980, when they still had a good element(Astatic MC-127/Mc-151) and another one just a few years ago, before I found out that they don't have good elements anymore..that one now has a Shure CM in it. Anyway, they were both wired in the "old American studio standard" as it was called when I first came across it years ago.
What I've done with both of those mics was that I rewired them to the more common standard because, although I make up my own leads, I thought it would be a good idea to be in a position where I could walk into any music shop anywhere and bye a lead of the shelf if I needed one in a pinch. Turns out too that I've had to do just that in the days since.
That lead in the photo above, the Rapco one, MAY be right for you or it may not. You'd have to check with a multi meter to see which contact was connected to the tip (hot/+ve) and which was one(s) were connected to the to sleeve (cold/-ve). Or, just take your mic to the store and try it with the lead into one of their amps.
the "pin three to tip" one is the one you want-- IF your mic IS in fact wired that way.
Oh and P.S. Greg Heumann is, of course, right about matching the impedance. I might have given the wrong impression when I wrote "impedance isn't the issue". What I meant was that in regards to you not getting any signal at all it was a hot- cold pin reversal thing, not an impedance thing.
Impedance is, of course, a big deal too.
P.P.S. I just checked out the different prices of the two leads (of the same brand)you've put up! There's another good reason to rewire the mic to the more, um ,common standard.
Last Edited by slackwater on Feb 27, 2014 9:18 PM
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jnorem
61 posts
Feb 27, 2014
10:07 PM
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slack water: "That lead in the photo above, the Rapco one, MAY be right for you or it may not. You'd have to check with a multi meter to see which contact was connected to the tip (hot/+ve) and which was one(s) were connected to the to sleeve (cold/-ve). Or, just take your mic to the store and try it with the lead into one of their amps."
I'm pretty sure that Rapco makes only one M20K.
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Call me J
Last Edited by jnorem on Feb 27, 2014 10:09 PM
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slackwater
7 posts
Feb 28, 2014
4:00 PM
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Yeah OK, the fine print again. I suppose it just proves the need for caveat emptor. Sorry about that.
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