Mar. 29th, 2017

solarbird: (made her from parts)

Remember a long time ago – like, a little over three years ago – I built a ribbon microphone? I had all kinds of problems chasing radio interference ghosts and stuff, it was strange and messy but came out with a neat sound in the end.

Except… even after fixing the RF problems, it was kind of noisy. Not unusably so, not for direct-miking, which is how I’ve used it, but still… kinda noisy. Noisier than it should’ve been.

I rediscovered this when trying to use it in a “mid-side” type mic setup with the new RK-47, which I was doing just to see how that would work. (Tony of Vixy & Tony has been after me to try that for a while.) And because it involves playing towards a figure-eight microphone from the side – the point of least sensitivity – it required enough extra gain that the noisiness became a problem.

Since the special preamp (also a kit) was the entry point for the RF noise, and since said amp works with dynamic microphones, I tested that for noise, using an SM-58 as input. Dead silent, cranked all the way up. Result: it wasn’t the microphone preamp’s fault.

Then I remembered how the RK-47/990B build manual talked so much about making damn sure you had no solder rosin or finger oils at the high-impedence connection points in the circuit, and to just scrub those connections with isopropyl alcohol. So I took apart the ribbon microphone, redid those solder connections while I was in there, and then scrubbed the hell out of them. A downright confusing amount of old solder rosin came up when I did so.

Result? Problem sorted. Huge drop in noise. There’s still a little at the high end at probably more gain than I even need here – this may be an “only elves can hear this” moment, at least in part – but a little -3db cut starting at 14-15kHz sorts it. It might not even be true noise, it could be something like air movement – ribbons will pick that up in ways nothing else will, and I didn’t turn off the HVAC, etc.

So, yeah! Turns out that finicky bit about solder rosin and flux is real important, kind of generically, at high impedance. Good to know. (And is why I’m posting this, and why I’ll link to it from the old microphone buildout writeups.)

I still have not the vaguest idea why so much rosin ended up on those connection points. Seriously, it’s weird. That was my old stock of Radio Shack silver solder, which I’d had since I Don’t Even Know When, and not the BenzOMatic solder that gave me so many problems. I never noticed it doing that before – but then again, I wasn’t really looking. ¯\(ツ)/¯

Anyway, have a test recording I made at 1:30 yesterday morning trying out that configuration, with the Micparts RK-47/990B kit mic being used as the “mid” and the above-mentioned Austin OTA-1 ribbon microphone as the “side.” It’s intermixed with a recording made simultaneously using a pair of M-Audio Novas in a spread X-Y configuration. Both versions are mixed directly to mono, rather than spread-stereo, which is not what you usually do, but does allow maximum left-right placement in a mix.

(This may be called “T” rather than “mid-side” since mid-side includes a kind of subtractive mixing not used here? I dunno. But this is, again, just a straight mix to mono.)

The recording starts with the RK47/990B plus OTA 1 pair, then switches back and forth between that and the Novas. Remember: all of this is mono.

Kinda neat, eh?

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solarbird: (korra-on-the-air)
A few days ago, KOMO was forced by corporate (they were bought by Sinclair of Maryland) to air a rightist story about "fake news." Local employees are rebelling; "KOMO employees will take on Trump-friendly bosses." Good on ya, KOMO employees.

In Russia issue news, we have a few stories. "First GOP lawmaker calls for Nunes to recuse himself" - we'll be lucky to get more than two or three, but one is better than none. In "I'm Not Crying You're Crying" news, "Trump wants a Russia investigation … directed at Clinton." No, really. But the real hope today is that the Senate might do something, in "Senate Intelligence Committee Leaders Vow Thorough Russian Investigation."

Also, reportedly, "FBI Director James Comey Tried To Reveal Russian Tampering Months Before Election." Erf.

Science, and How the Republicans Hate It: first, there was an action item earlier, but it didn't help; "House votes to restrict EPA’s use of science." This is a restriction so onerous and comprehensive that if taken at black text, the EPA won't ever be able to do much of anything new again. I consider that intentional, particularly given that Lamar Smith called the journal Science - you know, one of the most important and respected journals on the planet - basically fake news, during this hearing: "Climate Scientist Fires Back at House Science Committee During Hearing." And, of course, you can't have a good purge without language controls, so "Energy Department climate office bans use of phrase ‘climate change’." That's fun! And finally, "E.P.A. Chief, Rejecting Agency’s Science, Chooses Not to Ban Insecticide."

Oh, did I mention that "Trump Proposes Slashing Medical Research This Year, Too"? Well, now I have.

"Seattle will sue Trump over sanctuary city threats." Good! We're doing pretty well so far, what with repeated victories in court against the Muslim travel bans. Another one came down yesterday, late, in fact - this time, Hawai'i gets the win. "We have just won in #HawaiivsTrump. Trump Admin lost everything it sought." They're describing it as a real smackdown of a decision, too. Relatedly, "Rep Gutierrez Tells CNN Sanctuary Cities Are Actually ‘Fourth Amendment Cities,’" which is good language from a rhetoric standpoint.

Still, "UW professor: The information war is real, and we’re losing it." See above about the 1,000-ish Russian hackers setting up rightist fake news sites through the election. Maybe this should've been with the above.

Corruption update: "Ivanka Trump will have an official White House position." Are all the kids on the payroll now? Is this everybody?

"Puget Sound transit projects would lose big under Trump budget." This is older, but I don't think I posted it before.

And finally, WashingtonWontDiscriminate.org is reporting that the fundraising rate with the fundamentalist "bathroom bill" initiative is "neck-and-neck," and that's really bad - I-1552 is getting infusions of cash from somewhere (I don't know where offhand but I can make a fleet of guesses) and they're asking for more donations. I know it's easy to get caught up in the Federal issues, but as I've said many times: we have to keep the bulwark here. Now is a good time to donate.

It's March 30, 2017; this is the news )

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