Telephone hybrid - which to get?
Andy Evans
I'm in the UK and I want a really good system for coaching people over
the telephone. Best sound possible so I can pick up emotions behind
words etc. Right now I have a binaural headset which is OK but I'm
wondering what would be better than that - maybe a telephone hybrid so
I could have a mini-studio setup. I can build amps etc. but my
knowledge is mostly with tubes and not solid state. I'm not suggesting
constructing one unless there was a good kit. More thinking of a cheap-
ish broadcast model and any guidance as to which ones would work for
me and how to set it all up for best sound.
andy
Mike Cleaver
There are lots of good commercial solutions to this varying from
inexpensive to "oh my God.!"
Check any of the broadcast supply houses on the web.
I think Studio Spares might be a place to start in the UK.
Soundhaspriority
"Andy Evans" <performan...@gmail.com> wrote in message
news:73c1d923-d482-4354...@n35g2000yqm.googlegroups.com...
Andy, note that Skype now provides audio bandwidth to 12kHz. The most you
can get out of conventional telephony is about 2kHz. You can talk to
conventional telephones on Skype. Although the expanded bandwidth is not
available in such an arrangement, it does provide the equivalent of a
"digtal hybrid", without the crappy D/A conversion provided by the telco.
Bob Morein
(310) 237-6511
Joe Kotroczo
73c1d923-d482-4354...@n35g2000yqm.googlegroups.com, "Andy
Evans" <performan...@gmail.com> wrote:
Ebay. There's always cheap Studer, Gentner or Comrex hybrids to be found
there.
--
Joe Kotroczo kotr...@mac.com
Scott Dorsey
Actually, it's not all that hard to construct one; there used to be
a pretty good design in the ARRL Hints and Kinks for the Radio Amateur
book.
The older ones will require one or more manual adjustments to the balance
to make sure there is complete separation from the incoming and outgoing
signals. In the old days when the local loop was mechanically switched
it would require readjustment with every call, but these days you won't
find that to be the case because the line conditions stay the same.
If you buy one off Ebay that is intended for US service, the ringer
system won't work up, so if you want it to automatically pick up when
called you'll be out of luck. Also it will probably not have the UK
certification for connection to a BT line, which honestly nobody has
cared about for years.
I am personally fond of the old Bell System DAA units, if you can find
them, but any of the Gentners or Comrexes will be just fine. Try a
used broadcast supply house like Mooretronix or whatever the UK equivalent
is.
There are a lot of them out there. Even Heathkit made one, although I
can't recommend the Heathkit one...
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Steve King
"Scott Dorsey" <klu...@panix.com> wrote in message
news:hemfsh$mbs$1...@panix2.panix.com...
| Andy Evans <performan...@gmail.com> wrote:
| >
| >I'm in the UK and I want a really good system for coaching people over
| Actually, it's not all that hard to construct one; there used to be
| a pretty good design in the ARRL Hints and Kinks for the Radio Amateur
| book.
|
| The older ones will require one or more manual adjustments to the balance
| to make sure there is complete separation from the incoming and outgoing
| signals.
SNIP
| "C'est un Nagra. C'est suisse, et tres, tres precis."
Scott, were you ever able to balance out to "complete separation from the
incoming and outgoing signals"? I've built several analogue 'phone-patches'
using various transformers including the UTC hybrids, the bigger ones. I
don't think I was ever able to get more than 20-25 db separation and often
less. Of course, that was plenty for most purposes, but....
Steve King
Don Pearce
Complete cancellation was never required, in fact certainly in the UK,
a set level of side-tone is required so you can hear your own voice in
the earpiece.
I have experimented though and with careful trimming of the loading
resistors, you can get over 40dB.
d
Scott Dorsey
>
>Scott, were you ever able to balance out to "complete separation from the
>incoming and outgoing signals"? I've built several analogue 'phone-patches'
>using various transformers including the UTC hybrids, the bigger ones. I
>don't think I was ever able to get more than 20-25 db separation and often
>less. Of course, that was plenty for most purposes, but....
You should be able to do better than that at 1KHz, although frankly it's
a miracle if you can get 25 dB at 10 Khz.
It can help if the balance control, rather than just being a pot to adjust
the gain, is two pots, one with a series capacitor. This allows you to
get an overall balance, then balance the high frequencies, then go back
and get an overall balance again.
Some of the digitally controlled units claim as much as 50 dB rejection
but I have never seen anything that good myself.
--scott
--
black...@aol.com
JK Audio (US) has a lot of phone/audio interface gear. Look them up
at
www.markertek.com
philper
We built several funky analog interfaces for a project many years
ago--
basically some surplus transformers and a few other parts--they worked
pretty
well. Later we got some Gentner and JK gear which as a bit more hifi.
I actually think regular POTS analog phone service sounds a lot worse
than it used
to now that they use some much digital technology on the lines, so if
I were to
do that old project today I would definitely go for Skype or something
like that.
Philip Perkins
Steve King
news:f7b9994c-3847-4abf...@b25g2000prb.googlegroups.com...
Philip Perkins>>>
I don't think I agree. Starting in 1994 and continuing through 2007 I
produced a corporate audio newsletter distributed to several hundred
salesmen and managers. Much of the content was collected through recorded
telephone conversations. My observation is that the audio quality of these
recordings actually improved over the run of the program, the best being
recordings done with the interviewee speaking on a modern instrument on a
digital corporate system. The worst, of course, were interviews conducted
with people on cell phones, although many of those interviews resulted in
remakably good recordings. On my end I used a GentnerAuto Coupler, an
analogue hybrid at the lower end of the Gentner product line up. I should
also point out that my quality judgement is based on the relative absence of
line noise, low distortion, and natural sounding frequency response in the
voice range. Often recordings over telephone line were intercut with other
recordings of different speakers made using portable DAT recorders and
quality microphones. That never seemed to be a problem based on feedback
from the distribution group, nor was it objectionable to my ear in the
studio as I put these programs together. By far the noisiest, most
distorted lines originated with older analogue telephone systems.... again,
excepting the occasional hideous cell phone connection.
Steve King
Charles Tomaras
<black...@aol.com> wrote in message
news:df6f4503-5ae2-4106...@f16g2000yqm.googlegroups.com...
>JK Audio (US) has a lot of phone/audio interface gear. Look them up
>at
>www.markertek.com
Lots of choices at JK for a variety of budgets.
www.jkaudio.com
I've had one of these for years and it's served me very well.
http://jkaudio.com/inline-patch.htm