[Elecraft] K3 AF line out to mic attenuation
Hello, I want to connect K3 audio line out to a Toshiba laptop which only has a 3.5 mic socket for audio in. Does anyone have recommendations for attenuation/impedance matching? I was thinking of a simple votage divider. Thanks, Chris VK2LCD __ 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
Re: [Elecraft] K3 AF line out to mic attenuation
Chris, A simple voltage divider *may* be required, but I would suggest trying it without any attenuation first. It all depends on where the soundcard controls the microphone gain - be on the lookout for overload in the soundcard, and if present, add an attenuator. A series resistor may work just fine, or as you suggest, a voltage divider. Impedance matching is not necessary nor desirable. Audio devices operate well by using a low impedance source (able to provide more driving current than is required) and a high impedance sink (which will limit the current drawn). The characteristics of the sink (in your case, the microphone input) will determine how much current is drawn from the source (the K3). An analogy is to consider utility power wiring - the outlet receptacle provides a very low impedance source, and the device that you plug into that wall socket will determine how much current is drawn, therefore the amount of power that is transferred from the power company to your device. Within limits, an audio source/sink combination works the same way, but the actual source impedance will not be as near zero as the power company source, it will have some finite value such that if the current drawn is too large, distortion products will be developed in the driver. When the available source power is near the power to be dissipated (as in a transceiver/antenna situation), then impedance matching becomes important for maximum power transfer - because the source power is limited (or more correctly, not vastly greater than the power required by the sink). 73, Don W3FPR Chris Meagher wrote: Hello, I want to connect K3 audio line out to a Toshiba laptop which only has a 3.5 mic socket for audio in. Does anyone have recommendations for attenuation/impedance matching? I was thinking of a simple votage divider. Thanks, Chris VK2LCD __ 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 No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.287 / Virus Database: 270.12.8/2086 - Release Date: 04/29/09 06:37:00 __ 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
Re: [Elecraft] K3 AF line out to mic attenuation
Chris Watch out for the DC phantom voltage on that laptop's mic jack. I doubt if you want to feed that back to the K3. Otherwise you should be ok to just do a direct feed. Hopefully you won't have any ground loop problems. An alternative would be to use a cheap external USB sound card. Steve Ellington n...@carolina.rr.com - Original Message - From: Chris Meagher cmeag...@activ8.net.au To: elecraft@mailman.qth.net Sent: Wednesday, April 29, 2009 8:53 PM Subject: [Elecraft] K3 AF line out to mic attenuation Hello, I want to connect K3 audio line out to a Toshiba laptop which only has a 3.5 mic socket for audio in. Does anyone have recommendations for attenuation/impedance matching? I was thinking of a simple votage divider. Thanks, Chris VK2LCD __ 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 __ 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
[Elecraft] K3 AF line out to mic attenuation
Hi Chris, I connect both LINE OUT and LINE IN directly to the microphone and headphone jacks of my HP laptop without anything between. The IN and OUT gain settings of the laptop handle the levels OK. 73! Ken Kopp - K0PP elecraftcov...@rfwave.net http://tinyurl.com/7lm3m5 __ 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
Re: [Elecraft] K3 AF line out to mic attenuation
Chris, I think this is one of those your mileage may vary things. With this older HP laptop, I have a bit of overdrive going the other way - from the computer to the Line In on the K3. Adding an attenuator allowed the me to get better control (more granularity) over the laptop's audio out and at the same time lowered the drive level at the K3. You can build a Pi or T attenuator for either in or out at the computer. A fairly good calculator for this can be found at http://www.daycounter.com/Calculators/PI-T-Pad-Attenuator-Calculator.phtml FWIW, I designed and built a 5 dB attenuator for 1k line impedance. It seems to work and allowed volume adjustment to occur in smaller steps, which in this case is what was necessary to combat too much drive at lower Line In settings at the K3 (setting 4 was as high as I could use it, and setting it at 3 was too low). You can also buy a better sound device like the EMU-0202 from Creative Labs. This approach has the additional benefit of keeping digital modes' sound separate from whatever your computer o/s and applications generate. 73, matt W6NIA K3 #24 On Thu, 30 Apr 2009 10:53:38 +1000, you wrote: Hello, I want to connect K3 audio line out to a Toshiba laptop which only has a 3.5 mic socket for audio in. Does anyone have recommendations for attenuation/impedance matching? I was thinking of a simple votage divider. Thanks, Chris VK2LCD __ 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 __ 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
