> Looks like making C8 a little bigger (like 10uF) would help to reduce > some of the turn on pop that you see on the speakers when powering the > unit on. There is mention of this on page 17 under "Selecting External > Components" > "Bypass Capacitor Value".
A couple thoughts... First, that may, or may not be the only area contributing to the pop. Secondly, the LM4950's click/pop artifact is also a function of the Cin value in addition to the Cb value. National recommends a Cin value no larger than 0.39 uF whereas the K3's Cin is 0.47 uF through 20K of series R. With the exception of this slight Cin value difference, the K3 uses nearly the identical input structure as shown in Figure 2 of the datasheet. I doubt it makes much a difference but experimenting is the only real way to know. >From the datasheet, the only internal workings of the chip are shown with a block diagram where Cb controls a bias block. I would presume that making Cb in larger would have the effect of keeping the amp off longer until stabilized. Just a guess though... In a recent firmware release, I believe the K3's power-on pop was minimized although I still hear it on my K3. Another possibility is to use an outboard R/C time-delay relay (set for 1-2 sec), and powered by the rig's rear panel aux power connector. That would mimic the manner in which the classic '60s and '70s audiophile amplifiers and receivers accomplished the pop muting at power-up. Speaker audio from the K3 would then route to the relay contacts before heading off toward the speaker. Mission accomplished and no internal mods to the rig. Paul, W9AC ______________________________________________________________ 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
