> From: Jim Barber [mailto:audio...@charter.net] > > Thread hijack: > Tim: VOX is a bit painful (on the 5K at least) with lower-output mics (like > the PR-781) connected to the rear panel balanced input. Any particular tips?
I ran into this at the very beginning with my F5K. For my testing I used a Shure SM58 with a cable that let me plug into the front-panel mic jack and a second cable for the rear-panel 1/4" TRS balanced-in on the back. I could switch input just by plugging the proper XLR connector into the mic. From a purely audio point-of-view, either worked just fine after mic gain adjustment. On-air tests indicated that the two inputs were aurally indistinguishable. But from the point-of-view of the VOX and noise gate the two inputs made a big difference. It seems that the software is unaware of the gain difference between the line-level balanced-in on the back and the mic-level balanced-in on the front. Therefore you need to run the noise-gate and VOX gain controls way up when running through the rear-panel balanced line-in. Since there was no audio advantage to either input I selected the one for which the default settings for VOX, noise gate, etc., were most compatible. That turned out to be the front-panel mic input. Clearly that is where PowerSDR coders expect one to to connect a mic. (I would have preferred the rear-panel 1/4" TRS connector since my mic has no PTT and the "rear" panel is actually my front panel.) Going on into the more technical realm, if all the audio channels were mixed in hardware at the analog before being delivered to the audio ADC there would be nothing one could do. But the interesting thing is, if you look at the schematic for the F5K you see that all of the audio sources are kept separate and appear at the ADC as separate channels. This would allow the software to maintain separate gain settings for all the inputs, thus allowing all the inputs to be normalized to a single reference level so that the gain-dependent settings, e.g. mic gain, VOX gain, compressor threshold, noise gate, etc., can be referenced to that one reference level too. >From a hardware-design point-of-view, this was (IMHO) very forward-thinking. The software doesn't seem to take advantage of this right now but it strikes me as a relatively straight-forward improvement. Perhaps in the new generation? > And another by-the-way: > For experimentation's sake I ordered a batch of cheap Chinese Shure SM-58A > knock-offs. If they turn out to sound decent on the 5K I'll report back. How cheap? The SM58 is not all that expensive. Street prices are around $100 and it is an excellent mic, probably as good a dynamic voice mic as you are going to get. Shure itself has the PG58 which is almost as good as the SM58 and has a street price of $60. 73 de Brian, WB6RQN/J79BPL _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
