+++++++++++++++++++ See also K2 Microphones +++++++++++++++++++ Date: Wed, 27 Feb 2002 17:41:32 -0600 From: George Franklin To: qrp-l at lehigh.edu Subject: [120931] Ref. Computer Mikes Hi Gangue, Please enlighten me concerning the mike in "computer headsets" designed to plug into a sound card. I have assumed that they are electret mike elements. Correct? If so they evidently derive the necessary operating voltage (2V or so) from the sound card. I haywired one up to the mike input of a Kenwood rig but didn't have any success with the pin #5 8V source on the mike jack, using a 1K resistor to the mike line. Perhaps I have a defective mike element in my headset? Anyone else tried this? Results? 72 de George/W0AV Hamming since '35 Thanks ++++++++++++++++++++ Date: Wed, 27 Feb 2002 20:02:45 EST From: PDouglas12 at aol.com To: w0av at juno.com, qrp-l at lehigh.edu Subject: [120938] Re: Ref. Computer Mikes Hi George, These mikes work very very well with modern rigs. They need only a cap and a resistor to get them working--the cap carries the audio, and the resistor carries the DC. But with simple circuits these electrets (yes they are electrets) can be shaped into very respectable communications mikes. I have about a half dozen in various configurations, and they all work well. Do see the archives of this list for references. Also, there's a great article by Steve Pituch N2MNN in the April 1996 QRP Quarterly on implementing these mikes as communications mikes. 72, Preston WJ2V +++++++++++++++++++ Date: Wed, 27 Feb 2002 21:06:54 -0600 From: George Franklin To: PDouglas12 at aol.com Cc: qrp-l at lehigh.edu Subject: [120948] Re: Ref. Computer Mikes Hi Pres & All, Thanks for the information. Here is the situation. The regular RS PN 270-092C electret mike (3-wire) works great wired to #1 (Mike), #7 (ground) and #5 (8VDC) on the Kenwood. The computer mike has a gnd-sleeve-tip 1/8" plug, but the tip and sleeve are apparently connected together inside the plug. I connected tip/sleeve to #1, ground to #7 and #5 through a 1K resistor to #1. I didn't use a cap because the 3 wire worked OK without it. Well, now here is the solution. My initial problem was that the electret mike in the RS 33-1107 Headset was defective, and I suspect that I accidently let its smoke out. Replacing the electret element (yep, that's what it was) with another from my 2-way goody repair/junk box brought the mike to life. It is essential to use a cap (I used a 0.l tantalum, positive toward the mike element) in series with the mike line to Pin 1 on the plug to my Kenwood. Also, I used a 510 ohm from the 8V pin on the mike jack (Pin 5) to the mike. Sorry to be so verbose, however I started this thread and wish to brink it to a conclusion. Thanks to all who responded to my plea for help. 72 de George/W0AV Hamming since '35 Unless one uses a series cap, the internal circuitry in the Kenwood is such that it shunts the voltage from the series resistor, and the electret element does not receive the necessary operating voltage. 72 de George/W0AV ++++++++++++++++++++