> I've been informed Elecraft is already replacing those caps with 100uF > caps in the current production units.
100 uF is the maximum size compatible with the existing PCB pads for C9/C13 on the main DSP Board. Moving up beyond 100 uF presents a problem. Even at 100 uF, I believe the SMT caps are now rated at close to 10 WVDC. There's just no more scaling back on the SMT cap's voltage rating in order to accommodate a fit with a higher C value above 100 uF. Why would anyone want a higher value than 100 uF at C9/C13? Consider a set of modern, medium-Z headphones with a Z of 32 ohms at 100 Hz. The -3dB turnover point calculates to roughly 150 Hz. Anyone wanting to take full advantage of the lowest vocal fundamental (e.g., AM or ESSB modes) wants that point down to ~ 70 Hz. So, a cap value of 220 uF would be preferred. I went to 330 uF in a radial style to allow extra margin for a wide range of headphone vintages and types. To make most use of the 100 uF coupling caps, I would ensure that my headphones are of the newer, medium Z type and not the older style with 4-8 ohm drivers. My guess is that scaling the caps beyond 100 uF is only of interest to a small minority of ops. The majority will probably be happy with the current choice of 100 uF. Going from 10 uF in the prior design to 100 uF is already a significant step in the right direction. Paul, W9AC ______________________________________________________________ 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
