> On something like the THAT unit, do you still need to have a
> mix-minus feed out of your console, feeding everything in
> the station audio except the incoming caller's audio back
> into the phone line?
> I've seen problems with feedback and howling otherwise, then
> I've seen a few hybrids that electronically create a
> mix-minus feed back into the phone.
>
> GK
>
Well ANY phone hybrid needs a mix-minus, not just the JK Audio THAT's. Even the best hybrids typically can only do about -30dB of null on your average POTS line. That's nowhere near enough to truly prevent feedback if you don't have a proper mix-minus.
The THAT's chief disadvantage is that they can't do any nulling at all, nor can they do any AGC or Overboarding (lowering the caller's output level whenever the studio host is speaking). Generally speaking, they also don't give as "clean" a sound because they're tapping off a telephone's handset and therefore dependent on the phone's circuitry to get a clean audio feed. That WAS a bigger problem on older office PBX's...but any system installed in the past 10 to 15 years or so actually has pretty good circuitry so a handset tap works pretty well. Those new JK Audio Innkeeper PBX are essentially hybrids that work over the handset tap and they're pretty decent boxes for $500. We have one at WZBC; it works pretty well on their Nortel Meridian phones.
Of course, even the best hybrid can't do much with bad phone lines; and bad lines are everywhere. Check out
www.comrex.com and noodle around for the tech notes in the support section. Lots of good info there. If you have a major VoIP system you can be in luck as most VoIP's interface directly with the CLEC's system, so all calls are digital all the way to your desk phone. That means you can stick an ATA (analog terminal adapter) at your desktop and your call is very likely to be nice clean digital all the way to your hybrid. I have a setup like that at my office to a Telos ONE-by-Six and it works nicely. Of course, the CALLER'S phone line might be crap...I have that problem all the time. Especially with callers using cellphones...UGH!
Speaking of VoIP, Eric...something I'd forgotten about: if you have a computer in the studio, you could use SkypeOUT to accept calls from regular incoming POTS phones (as well as Skype calls, of course) and your computer becomes a hybrid. It's free and works fairly well...this summer I recorded a solo performance/interview by an artist down in Sag Harbor. There's a music store/recording studio down there and the guy who runs it has no telco gear at all...no ISDN or hybrids...but he does have the means to record tape-sync style, and a Windows computer. He'd used Skype before and was willing to give it a shot...I set up a SkypeOUT account for him to use so it'd be on my dime, and we recorded our end out of WGBH. It was a little hair-raising because we had no idea if the performance was recording cleanly to DAT (turns out it did just fine) but the phone call quality was as good as anyone could expect from POTS.
The kids at Swarthmore College use Skype to call Iraqis and interview them for their nifty show "War News Radio". It's actually a pretty cool show...and I hear they just started syndicating it, too. Check it out:
www.warnewsradio.com
So how's Ellenville's greatest little radio station workin' out, by the way?
- Aaron Read
- FriedBagels Technical Consulting
