Hi, Don. I thought to swap the headphones around to see if it might be my hearing in one ear; the reduced output swapped to the other ear. Will check using other sound sources to see if it might be the phones themselves.
What's confusing me a bit is the distortion that's introduced by plugging in a monaural plug feeding speaker all the way. It's a scratchy sound that I can make go away by reducing the volume control on the radio providing the audio in to the AF1 - I'm driving the AF via my Icom R-75s external speaker port, the receiver's headphone jack or rec line out - but then the AF1s audio output is too low to be enjoyable. Suppose I could just do a mod to replace the AF1's stereo out jack with a monaural one, and then using an adapter plug between the output and my stereo phones, but would like to leave the AF1 unmodified if possible. R, Paul N6LQ -------------------------------------------- On Sat, 12/28/13, Don Wilhelm <[email protected]> wrote: Subject: Re: [Elecraft] AF1 Audio Filter Question To: "Paul Clay" <[email protected]>, [email protected] Date: Saturday, December 28, 2013, 5:46 AM Paul, If you look at the schematic, you should see that the output jack is a stereo type with both channels connected together. That means your stereo headphones should receive the same signal in both channels. Try turning the phones backwards and see if the louder channel reverses - if it does, then the headphones are not balanced (maybe one is faulty). OTOH, if the weaker channel stays with the same ear, your hearing in that ear is diminished. Your observation with the mono speaker plug is what is to be expected - when you push the plug in all the way, you are shorting the output due to the sleeve of the plug contacting the jack's normal ring connection. 73, Don W3FPR On 12/28/2013 5:01 AM, Paul Clay wrote: > Just completed building an (external) AF1 audio filter mini module (Rev A board that required the cutting of a solder trace on the AF input and the addition of a jumper on the AF output). Works great except, I've noticed two things I'm curious about: > > 1. With stereo headphones plugged in, one the audio in one channel is noticeably louder than the audio in the other channel. > > 2. If I plug a speaker in with a monoral 1/8" plug all the way, I get audio out but the volume is low and there's some significant distortion in the audio output; BUT, if I insert the plug in just part way, I get lots of volume and no distortion. > > Wonder what might be causing this? Wouldn't think much of item two (figure I should just be using a stereo plug to connect my speaker), but the presence of the distortion and the lack of balance when using my stereo headphones makes me wonder if maybe the LM386 chip might be damaged. > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
