Innkeeper Gives Guests the Best
Reprinted from Radio World - July 19, 2000
Product Evaluation
By Carl Lindemann
Despite the power of the high-speed digital connections to send audio from the field, stations
still need to bring callers on-air through standard phone lines.
The JK Audio Innkeeper 1 Digital Hybrid uses advances in digital signal processing to get
the most out of plain old telephone service, or POTS.
Combined with the "Guest Module," a handy dial pad accessory, this telephone
hybrid is a convenient way to gather sound over conventional dial-ups. The digital hybrid
is a step above older technologies and is likely to remain useful until POTS become a vestigial
remnant of the analog age.
The Innkeeper 1 is an auto-answer hybrid to serve the needs of broadcasters for talk shows
as well as newsgathering.
It operates on both standard phone lines as well as "dry" lines in a PBX. The
core function is to separate transmit and receive audio.
As with all digital technology, performance is tied to the quality and sophistication of
the algorithms used to process signals. Given the rapid progress in developing algorithms,
what was state of the art a few years back is now dated.
Typically, "classic" digital hybrids have algorithms that use a mix of half duplex
switching and automatic gain control to achieve acceptable separation.
Some new designs send a tone or noise-burst down the line at the beginning of the call
and observe the echo return to determine the characteristics of the network.
Using actual audio
According to Joe Klinger, president of JK Audio, the Innkeeper 1 was designed after accessing
the shortcomings of these approaches. The result is what he describes as an echo canceller
utilizing a dual-convergence algorithm and an adaptive digital filter.
The algorithm uses the actual transmit signal to identify network conditions. Within the
first second of speech it tunes and corrects to remove the transmit signal from the caller
outputs. Line conditions are continually monitored, the unit tweaking the signal as necessary.
A 16-bit Texas Instruments DSP, capable of 16 million instructions per second, powers the
signal processing.
The firmware that contains the algorithm is socketed, not soldered, to the circuit board.
This allows for upgrades to the system as advances in algorithm design continue.
The layout of the unit is intuitive. On the back, three XLR connectors cover the caller,
send, and mix out. Standard phone jacks and a RJ-45 jack for the dial pad is also found
there. A screw terminal allows for connecting an external speaker and controls.
From the front, two buttons control it all. One picks up a call, the other drops it. Trimmer
adjustments for Send, Caller and mixed signal levels are wisely placed behind a screw-on
door. Two additional switches add presence EQ to the signal and activate or defeat the auto-answer
capabilities are also found on the front.
Once these levels and settings are selected and adjusted, it is a good idea to close the
screw-on door to prevent unauthorized "improvements."
Color-coded LEDs monitor the connection and levels. A quarter-inch headphone jack and volume
control allows for monitoring directly from the unit.
The test
I tested the Innkeeper 1 for some segments I produced for the "Beyond Computers"
show for Public Radio International.
Connecting the Innkeeper to my Mackie 1202 in my home studio was fast and easy. Interviews
conducted over the phone came out level and consistent.
I found the presence option added a welcome depth and warmth to correct the typical character
of POTS audio (200 Hz to 3.6 kHz).
I tested separation between send/receive by recording only the incoming audio. The send
sections were not dead silent, but it was reduced to a negligible, low mumble.
The unit does not get the amazing 110 dB specs that I have seen quoted with some all-digital
audio cards. But, the 50+ dB separation pushes the envelope as far as dealing with the inevitable
limits of POTS.
In other tests, the Innkeeper 1 sounded great when isolating the Send feed. Having hassled
with a few phone and hybrid setups, I found that the Guest Module keypad is a welcome convenience
for an extra $185.
Since putting this model through its paces, JK Audio has released an additional deluxe
version — the Innkeeper 1x.
This adds enhancements including a receive AGC, caller ducking and a 1 kHz tone generator.
The new model is based on a different motherboard, so there is no upgrade path from the
standard version. The standard desktop version lists for $750, while the 1x desktop goes
for $875. Opting for the rackmount box on both the 1r and 1rx adds an additional $75.
The Innkeeper 1 is a major contender for establishing the next, and perhaps last, generation
of hybrids designed to work with POTS.
The relatively low price for such high performance makes this worth a listen and a pleasure
to listen to.
Thumbs Up:
- Simple hookup and operation
- Excellent audio quality
- Upgradeable Firmware
- Inexpensive
Thumbs down:
Carl Lindemann is a frequent contributor to Radio World
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