Good Mic?

[Mac]

I have a DX-100.  I thought that the EV-664 I had was in good shape till I tried it.     Bad.   Can I get some info on what would be a good mic to put on this old rig to get a good clean sound.

Thanks 73
Mac

[W3NP]

Plain non-amplified crystal D-104 would probably be your best bet.

[Ed-VA3ES]

The EV 664 has two chooseable output impedances, depending on the cable wiring.  Make absolutely sure you've wired it for Hi-Z.    In the Hi-Z position it should sound OK, but slightly thin (no lo-end).  Make sure your grid resistor, on the first 12AX7 has been changed out to at least 5M ohm, and your coupling caps are at least .1 µF.   If you've done all this, then the best choice is indeed, a straight, unamplified D-104.

[w8khk]

Mac, 

Pin 1 is the shield/ground connection, and pin 2 is the high-impedance output from the mic.  Low impedance (150 ohm balanced line) uses pins 3 and 4, with 1 as the shield/ground.  I will try to attach a .djvu file that contains the spec sheet and some mods for wiring the switch in the mic for PTT.  If I cannot attach this file type to the thread, I will gladly mail it to you if you would like it.  The 664 should make a good mic for the DX-100 if it is in good condition and wired correctly.

73, Rick

PS As I expected, got an error:

664.djvu.
You cannot upload that type of file. The only allowed extensions are txt,doc,mp3,wav,pdf,jpg,gif,mpg,png.

[Mac]

The 664 is wired right ,,, but the insides and wires are completely corroded.  Basically the insides are shot.  I heard that a Calrad-400c is a real good mic. Any info?

Thanks
73  Mac

[W3NP]

I heard that a Calrad-400c is a real good mic. Any info?

Thanks
73  Mac

The Calrad 400C would be fine. I still have mine from around 1960. (used it with my DX-40 back then). That mic is a HI-Z crystal mic and as such would work well.  In fact any similar mic would do - such as a JT-30, etc, but those mics have gotten pricey while the D-104's are prolific and cheap.

As was said earlier, a larger grid resistor and some fatter coupling caps will make the DX-100 sound relatively good with a xtal mic.

I have never had good results using a dynamic mic straight into an old transmitter.

[WB2RJR]

I have never had good results using a dynamic mic straight into an old transmitter.

True, that's why you need to get one of these:

http://www.radioshack.com/product/index.jsp?productId=2062443

It's what I use. That way I can buy a $20 dynamic mike that is flat from 50-10khz and use it on my old rigs.

The D-104 is a comm mike with a big peak in the 1700-2100 hz area. That's why everyone needs big coupling caps with it to get any low end.

I use .0018 uf coupling caps in my rigs with that transformer and a dynamic mike. .002 sounds too bassy and .0015 sounds a little high.

73

Marty WB2RJR

[flintstone mop]

For a DX100 power class transmitter, I have heard really nice audio from the D-104. For real hi-fi audio, you will have to get into the mic audio and modify. The Electrovoice 664 was a nice smooth sounding mic in its day. You might need a mic pre amp or matching transformer before the DX100 circuits.

Fred

[flintstone mop]

Some folks have had good success with those $2 Radio Shack condenser mics.
Fred

[Mac]

Thanks for all the info.  I have been looking at some broadcast mic's too.  Just have to get some more info and do some more reading,,,

Again thanks
73  Ron