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Author Topic: Astatic 10-d  (Read 2992 times)
WA2JHS
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Posts: 96




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« on: June 23, 2013, 02:37:13 PM »

Hello to all....anyone have any idea about these mics??? I have on without the element in it and there is a transformer inside...is this to go from low to high impedance or high to low???
Thanks
Bill
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KE3WD
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Posts: 5694




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« Reply #1 on: June 23, 2013, 03:39:44 PM »

Probably from the low impedance of the mic coil to high imp. output. 

You could likely use your ohmmeter on the transformer, comparing DC resistance of primary to secondary to see how it is currently wired, though.  With old mics, I take nothing for granted due to the possibility of modifications somewhere back down the timeline. 


73
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WA8UEG
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« Reply #2 on: June 25, 2013, 06:11:33 AM »

My guess is someone added a matching transformer to take the 10-D from high impedance to low (600 ohms) for use in a modern rig. They did not come with a matching transformer as far as I know.
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KE3WD
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« Reply #3 on: June 25, 2013, 07:12:37 AM »

Well, since the OP states that the capsule is missing, the assumption that the mic was set up for the good old high imp. original cartridge may be erroneous. 

It is not a stretch to think that at one time the original cartridge may have failed and the owner replaced it with something more readily available in the way of dynamic cartridges, which, by the 60s, often meant lower impedance due to less coil.  So a transformer is inserted to take care of that. 

Hence the addition of the xformer...

Again, the only thing that needs be done is to scope out that transformer.  Ohmmeter can help, also perhaps any markings or identifiers. 

There is also a high probability that the transformer found is a Shure or a clone thereof.  The famous Shure mic transformers are good stuff. 

Last resort, drive unknown xformer lightly with an AF amp such as a headphone output, load the other end and look at what's happening with 'scope. 

It has been my experience that many of the older Mic transformers are excellent performers, well worth keeping that xformer even if not used in this particular mic again. 
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WA5VGO
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« Reply #4 on: June 25, 2013, 04:42:38 PM »

The original microphone had a low impedance dynamic element and an integral transformer to step the impedance up for the high impedance input found in most of the old vacuum tube equipment.

Darrell
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KE3WD
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« Reply #5 on: June 26, 2013, 07:46:55 AM »

The original microphone had a low impedance dynamic element and an integral transformer to step the impedance up for the high impedance input found in most of the old vacuum tube equipment.

Darrell

Thanks for the clarification Darrell, I couldn't recall and didn't go look it up. 

But it makes sense, as the cartridge is dynamic and a high impedance coil would be rather massive hanging on the back of a diaphragm...

I had a D once, came along with a used TenTec Omni C or D (forgot that, too, these days, I think it was the C, it was black face and was also a superb CW rig, that I'll never forget)  I picked up at a hamfest and that mic and rig got outstanding audio reports all the time. 


73
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W4KVW
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Posts: 472




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« Reply #6 on: June 26, 2013, 08:01:07 AM »

I have & use a 10-DA on an ASTATIC Silver Eagle with my ICOM 746 PRO.I don't think it has a transformer in it but it gets great audio reports on SSB,FM, & AM as it is.Looks great on the Silver Eagle also.They were designed for SSB use from what I've read. {:>)   Grin

Clayton
W4KVW
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KB4QAA
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« Reply #7 on: June 26, 2013, 08:04:33 AM »

http://www.preservationsound.com/wp-content/uploads/2012/07/Astatic_Catalog_197.pdf

Here is the Astatic catalog from the 1970's.  10DA specs are on page 10.  Sorry no schematics.
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WA2JHS
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« Reply #8 on: June 26, 2013, 05:47:31 PM »

Hey all...sorry for the delay in responding...but the transformer that's in there is sort of sealed into the back of the mic head...I believe it to be the original transformer so I think Darrell might be right...it looks like it went from dynamic element to high impedance...now to find an element to put in there...HI
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KE3WD
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« Reply #9 on: June 27, 2013, 09:10:07 AM »

There are plenty of low imp dynamic cartridges to choose from, likely the only real problem is to make sure you get one that will fit into the space provided without a lot of modification.  

And don't overlook dynamic elements taken out of imported late model PA and possibly even recording application mics.  


73
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W8AAZ
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« Reply #10 on: July 04, 2013, 04:55:00 PM »

Probably a replacement element for radio comms like a dynamic element for a CB or ham rig nowadays will be an element with probably a 5--600 Ohm impedance, made to directly connect to a solid state rig.  The old fashioned dynamic elements often had much lower impedances, like something around 30-50 Ohms, thus the need for a transformer for just about any normal input.  IF you get a modern dynamic element with a 250-600 Ohm impedance, you ought to just directly connect it to the output cable for a modern solid state rig use. The transformer in the mic is probably low impedance to high, and may not be a good match for either the modern element, or the rig, for that matter. Unless you are using it with a vintage(tube) ham rig.
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