Your comment is right on the money. Since virtually all CB radios had low Z inputs, and because CB'ers like to drive the you know what out of their radios, the preamp D-104 was a hot seller for that market. I have experimented for years with several different types of microphones and have reached the conclusion that the D-104 (no preamp) has the best audio characteristics for communications audio with the Shure 444/450 series second. Either type is excellent for the old tube-type Drakes. Years ago someone told me the TR-4 had been designed with the Shure 444 in mind. Don't know how accurate the story is because I've heard so many old wives tales over the years. The 444 is what I have on my TR-4CW/rit and I have a D-104 on my T-4XB. The biggest obstacle was to find the correct size diameter right angle plug for the TR-4.
Someone also made a comment to the effect that microphone wire code may be inconsistent. I agree. The only reliable way to check this out is to look at the cable and determine which wires are used to switch to ground by checking continuity with a DVM, VOM or what have you. > There is an interesting article in Electric Radio Magazine for > September 2001 addressing the effect of load impedance on the "bare" > D-104 element. > > "With a crystal microphone, the bass response is governed by the value > of the grid resistor in the first stage. And input resistor of 100k > ohms will limit or "rolloff" at about 500 cycles, 500k at about 250 > cycles, and a 1 megohm will extend the response to about 100 > ycles." - W F Soules, W8HCW, Electro-Voice, Inc., 1958. > > This variation in response can make a big, little, or no difference, > depending upon your individual voice characteristics. > > I assume the reference to the 470 ohm resistor below is actually to a > 470k resistor? > > The base mounted preamp was in fact a product of the CB market, but was > intended to extend the life of the D-104 into the solid state era of low > impedance microphones rather than to enable overdriving the audio! The > amp also eliminated the effect of load impedance on the mic, and allowed > it to be used with both high and low impedance > circuits. > > 73, Garey - K4OAH > Atlanta > > ----- Original Message ----- > From: "Tim Kass" <[EMAIL PROTECTED]> > >> >> I also agree with the group, dont need a transformer, been using one > for a >> long time, great audio...also..better off w/o the preamp...stick a > 470 ohm >> 1/2 watt resister in the hot lead in series with the mic, improves > audio >> response...got this from Jack Geihl WB8BFS ...73 Tim K8WBL >> >> >From: "William J. Bennett" <[EMAIL PROTECTED]> >> >Reply-To: "William J. Bennett" <[EMAIL PROTECTED]> >> >To: "Drake List Server" <[EMAIL PROTECTED]> >> >Subject: [Drakelist] Drake T4X Microphone Question >> >Date: Thu, 3 Apr 2003 07:54:55 -0500 >> > >> > >> >I would like to use a D104 with my T4XC. I purchased a HI impedance > xformer >> >from Hiel but I'm not sure of the pin out of the D104 (red, white, > shield) >> >and how to wire the transformer between the T4X and the D-104. Does > anyone >> >have any experience using a D-104 with a Drake transmitter? >> > >> >TIA >> > >> >Bill K3TNM > > ---------------------------------------------------------------------- > Submissions: [EMAIL PROTECTED] > Subscribe: [EMAIL PROTECTED] - subscribe drakelist in body > Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in > body Hopelessly Lost: [EMAIL PROTECTED] - help in body of > message Brought to you courtesy of TLCHost.net http://www.tlchost.net > ---------------------------------------------------------------------- ---------------------------------------------------------------------- Submissions: [EMAIL PROTECTED] Subscribe: [EMAIL PROTECTED] - subscribe drakelist in body Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Brought to you courtesy of TLCHost.net http://www.tlchost.net ----------------------------------------------------------------------
