On 12/25/2013 11:57 PM, Gary Smith wrote:
I have an Electrovoice RE-10 which would probably be nice & needs no power
Being a retired audio pro who has done a lot of recording, I have a lot of pro mics, including several RE16s. Before I discovered the CM500 (thanks to W6XU, another audio pro), I used an RE16 in my ham station on a boom stand. It worked quite well.
The hookup of a pro dynamic mic to ham gear is very simple. Pro mics are wired balanced via shielded twist pair cable to a three-pin connector called an XL. Pin 1 is the shield, Pin 2 is "high", Pin 3 is "return." To connect a dynamic mic like the RE10, wire Pin 2 to mic in on the rig, wire Pin 3 to mic return on the rig, and connect Pin 1 to the chassis. I made up some adapters for the various rigs that I used that mic with.
Nearly all ham mics have a peaked response in the range of 3 kHz to compensate for the rolloff of SSB filters, both on RX and TX. This was, I believe, first developed by Shure about 40 years ago, and you can see it in the response of their communications mics. Pro mics don't have this peak (or if they do, it's in the range of 8-10 kHz), so TXEQ must be adjusted to provide that peak. I used the same low frequency rolloff for the RE10 that I use now for the CM500 -- the three lowest frequency bands max cut, the fourth cut by about half, tweaked by ear based on the reports of a known good listener. For the high end, I boosted the top band by about 10 dB, the next highest band by a few dB, again tweaked on the basis of reports from a good listener.
With rigs other than a K3 that don't have TXEQ, I added a capacitor in series with the mic wiring to the rig input and a resistor between the rig mic input and mic signal return. The resistor was about 470 ohms, and the capacitor value was chosen so that the network produced a strong rolloff below 2 kHz -- in other words, a sloped response that peaked around 3 kHz. I got very good audio reports from this simple setup with a TS850, an Omni V, an FT1000MP, and a K2.
I modified the K2 to add a low frequency rolloff around 400 Hz also to increase the mic gain by about 6 dB. I did this simply by changing the values of a few resistors and capacitors early in the audio signal chain. The purpose of the mod was simple -- with most ham mics, the K2 is a bit low on gain, so I wanted to hit the limiter harder. I also wanted to minimize the wasted LF energy, and also prevent that LF energy from activating the limiter.
73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
