K3 and SM20
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In readiness to use my new K3 I have rewired my Icom SM20 mic to the K3
configuration. I was surprised to find that it works exactly the same with the bias on or off. To ensure that K3 FP mic bias is performing correctly I have also tried out my new Elecraft Heil Proset. That works fine with the bias on but not at all with the bias off which is what I would expect. I thought the SM20 required bias as it is an electret mic but that does not appear to be the case. Has anyone got any experience of the SM20 with the K3 ? Barry Simpson VK2BJ _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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If you connected the +8V DC line from the SM-20 to pin 6 when you rewired it, you are getting bias. The K3 pin 6 power is present independent of the mic bias (pin 1 power) setting. 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Barry Simpson > Sent: Tuesday, August 12, 2008 5:50 AM > To: 'Elecraft' > Subject: [Elecraft] K3 and SM20 > > > In readiness to use my new K3 I have rewired my Icom SM20 mic > to the K3 configuration. I was surprised to find that it > works exactly the same with the bias on or off. To ensure > that K3 FP mic bias is performing correctly I have also tried > out my new Elecraft Heil Proset. That works fine with the > bias on but not at all with the bias off which is what I would expect. > > > > I thought the SM20 required bias as it is an electret mic but > that does not appear to be the case. > > > > Has anyone got any experience of the SM20 with the K3 ? > > > > Barry Simpson VK2BJ > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Barry Simpson
Hello Barry,
If you connected the SM20's Pin 2 (+8V DC Input) to K3 front panel Mic Pin 6 (8V Output) then the SM20 internal preamp will provide mic bias to the SM20 electret element. That's how I wired my SM20 and it works great on the K3. No additional Mic Bias is required. 73, Frank - W6NEK ----- Original Message ----- From: "Barry Simpson" <[hidden email]> To: "'Elecraft'" <[hidden email]> Sent: Tuesday, August 12, 2008 2:49 AM Subject: [Elecraft] K3 and SM20 > In readiness to use my new K3 I have rewired my Icom SM20 mic to the K3 > configuration. I was surprised to find that it works exactly the same with > the bias on or off. To ensure that K3 FP mic bias is performing correctly > I > have also tried out my new Elecraft Heil Proset. That works fine with the > bias on but not at all with the bias off which is what I would expect. > I thought the SM20 required bias as it is an electret mic but that does > not > appear to be the case. > Has anyone got any experience of the SM20 with the K3 ? > Barry Simpson VK2BJ _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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W6NEK wrote:
> If you connected the SM20's Pin 2 (+8V DC Input) to K3 front panel Mic > Pin 6 (8V Output) then the SM20 internal preamp will provide mic bias to > the SM20 electret element. That's how I wired my SM20 and it works > great on the K3. No additional Mic Bias is required. Actually, the so called bias on electret microphones only ever powers the pre-amplifier. Electrets are permanent electrostatic dipoles, and provide the electrostatic field needed for the microphone transducer. Those transducers are very high impedance, which is why you need a pre-amp very close to them. Typical electret units phantom feed the power, so it looks, at first sight, like bias. Condenser microphones, that were historically used as broadcast microphones, do need a high voltage bias to generate their electrostatic field. Electret transducers work on the same basic principle, but get their field from the electret. Electret "bias" voltages are far too small to be used directly to provide the field in the microphone. -- David Woolley "The Elecraft list is a forum for the discussion of topics related to Elecraft products and more general topics related ham radio" List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm> _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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On Fri, 15 Aug 2008 08:04:31 +0100, David Woolley (E.L) wrote:
>Condenser microphones, that were historically used as broadcast >microphones, Condenser mics have historically been used for MUSIC, both recording and broadcast (and they still are). Most broadcasters use dynamic mics for speech. Most US broadcasters wouldn't know a condenser mic if it bit them you know where. >do need a high voltage bias to generate their electrostatic >field. Electret transducers work on the same basic principle, but > gettheir field from the electret. Electret condenser mics need a different form of bias. The capsule (the transducer) is permanantly biased when it is manufactured -- it doesn't need anything from the circuitry. The very small signal produced by the capsule is amplified, usually by a FET follower circuit. This amplifier circuit is what needs DC voltage and current from the radio. >Electret "bias" voltages are far too >small to be used directly to provide the field in the microphone. See above. 73, Jim K9YC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Jim Brown wrote:
> On Fri, 15 Aug 2008 08:04:31 +0100, David Woolley (E.L) wrote: > >> Condenser microphones, that were historically used as broadcast >> microphones, > > Condenser mics have historically been used for MUSIC, both > recording and broadcast (and they still are). Most broadcasters use Thanks for the clarification; my memory was a bit shaky on the exact scope of use. > Electret condenser mics need a different form of bias. The capsule > (the transducer) is permanantly biased when it is manufactured -- > it doesn't need anything from the circuitry. The very small signal > produced by the capsule is amplified, usually by a FET follower > circuit. This amplifier circuit is what needs DC voltage and > current from the radio. I'm not clear how this differs from what I said. The FET follower is the pre-amplifier that I was talking about. > -- David Woolley "The Elecraft list is a forum for the discussion of topics related to Elecraft products and more general topics related ham radio" List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm> _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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