In
another note I said I would post my audio panel evaluation if I could get it
into coherent form. I cleaned up my
chicken-scratchings a bit and here’s the result. Paulr, this one’s for you:
Audio Panel Evaluation
We’re
going to replace the audio panel in our plane as part of the avionics
upgrade. I evaluated what I thought were
the best choices for replacement. There
are 5½ evaluations.
Disclaimers
I
did this primarily for my own benefit. The
features I noted are those I found interesting or desirable. If you find value in my posting that’s fine. If not, you got what you paid for.
I
have not been paid to evaluate these panels (or any other avionics). My involvement in aviation is limited to
my wife and I owning an airplane and a small percentage of a flight school which does not
sell avionics.
Opinions are my own.
I
have not flown behind these, of course.
I’ve seen a couple in friends’ airplanes. My evaluation is based on the pilot’s guides,
installation manuals, and reviews on the Internet. All of this information is publicly available. I suggest you search for and read the pilot’s
guide for the panels that interest you.
I strongly recommend you look at the photographs of the panels, as I
have not commented on cosmetics, sizes of buttons, or anything like that.
There
may be inaccuracies. Feel free to post
corrections. If you have used one or more of these panels please post your opinions - you know things I don't.
Sometimes
I overanalyze things. And sometimes I’m
pedantic.
Features and Comments
All of these panels have a marker beacon receiver, several
unswitched inputs, and a speaker output.
All have single button access to COM and NAV radios. All have a split COM mode where the pilot uses COM 1 and the
copilot uses COM 2.
Garmin GMA 340
This is the oldest audio panel described here. It set the standard for the size and
connectors. It supports three radios. It has switched ADF and DME inputs.
There are two volume control knobs. One sets the intercom level for the
pilot. The other sets the intercom level
for the copilot or, by pulling the knob out, the intercom level for the passengers.
The VOX gain settings are manually adjusted. There are individual VOX circuits for the
pilot, copilot, and passengers. The VOX
gain for the pilot and copilot are individually adjustable, and the passengers
share a common setting.
There are three isolate choices: pilot, crew, and all. There are two buttons which select the
isolation mode.
There are two music inputs.
Music input 1 is muted by audio from other devices such as the COM
radios. The music is provided to
passengers and to any crew who hear the same things as the passengers do.
Comments
This is the least expensive panel in this evaluation.
It does not have automatic VOX.
It does not have audio playback.
It does not have Bluetooth.
Reports on the Internet suggest that when one microphone
opens the VOX all microphones are opened and that audio quality is not as good
as some other panels.
Garmin GMA 350
This is Garmin’s advanced panel. It supports two radios. It has one switched AUX input.
There is one volume control.
It is concentric. The outer knob
selects which item is being controlled.
The inner knob sets the volume. The
volume of the intercom for the pilot, copilot, and crew, and also the volume of
the music inputs can be adjusted.
It has a choice of manual or automatic squelch. In manual mode the squelch level can be set
for the pilot, copilot, and crew using the volume control knob.
There are five isolate choices. In addition to pilot, crew, and all, the
pilot can be connected to the passengers with the copilot isolated. There are three buttons which select the
isolation mode. The copilot position can
be set as a passenger and will receive the same audio as the rest of the
passengers.
It can play back messages received on the COM radios. There is a dedicated button for this.
There are two music inputs.
One is available through a front panel audio jack. They can individually be routed to any
combination of pilot, copilot, and crew.
Music can be muted during COM receive.
There is a telephone connection. The telephone can be routed to the pilot,
copilot, or passengers independently of the intercom or music settings.
It has stereo positioning of the radios and passengers. When activated COM 1 sounds like it is at 11
o’clock and COM 2 sounds like it is at 1 o’clock. The location of the copilot and passengers is
also set to make it sound like it is coming from where they are sitting.
It accepts verbal commands.
Press the PTC (push to command) button and say a command and it will
respond either by changes in status lights or with verbal confirmation. Just about everything can be set or changed
this way – there are probably a hundred voice commands.
Comments
The audio routing is very versatile. Pretty much any combination of inputs can be
routed to any combination of outputs.
I don’t know how useful the voice recognition really
is. I could see it being convenient for
functions which require multiple button presses or turning the control knob. But I would find it easier to press the COMM
1 button than to press the PTC button and say “COMM 1”.
I cannot comment on the usefulness of the stereo effects. Some things cannot be determined by reading
manuals.
It does not have Bluetooth.
PS Engineering PMA8000BT
This is a very popular panel. It has switched ADF and AUX inputs.
It has two volume controls.
One adjusts the intercom level for the pilot and copilot. The other adjusts the level for the
passengers.
The VOX is automatic with no adjustments.
There are three isolation choices: pilot, crew, and
all. They are selected using a single
button.
It can play back messages received on the COM radios. The audio playback is triggered by pressing
the active COM button.
There are two music inputs.
Music can be muted for the radios, intercom, both, or neither. Input 1 can be routed to the crew only or to
all headsets. The pilot and copilot cannot
hear music input 2.
There is a telephone connection. The telephone routing follows the
isolation. For example if the pilot is
isolated he will be the only person who can use the telephone.
A telephone and music source can be connected using
Bluetooth instead of by wiring the devices.
The panel can control audio playback of some Bluetooth
devices. It can request play/pause, skip back, and
skip forward for a music device. It can
also control some telephone functions.
These control functions are not marked on the panel.
Comments
This panel has a lot of functions which are triggered by
pressing multiple buttons or pressing and holding a button. Most of these are not labeled, or in the case
of the “smart buttons” the label does not describe to me what the function
does.
Pressing the active COM button to replay a message means the
COM buttons have two functions – if the button is not illuminated it will
select the receiver and if it is illuminated it will play back the last audio
message.
Using this panel for things which are not labeled on the
buttons seems confusing to me. However
they are functions I would not often use.
Reviews on the Internet suggest that the VOX works well and
that the audio quality is very good.
Bendix/King KMA 30
The KMA 30 is a PMA8000BT with the Bendix/King name on the
panel. The Pilot’s Guide is the same as
the PS Engineering manual. I did not
look at the installation manual (hence the ½ evaluation).
Comments
This panel normally retails for more than the PS Engineering
version. But Bendix/King has a trade-in
program which might make this less expensive.
Avidyne AMX 240
This panel is built by PS Engineering. It appears to be based on the PMA8000 series.
There are two volume control knobs. One sets the intercom level for the
pilot. The other is concentric. The inner knob sets the intercom level for
the copilot and the outer knob sets the intercom level for the passengers.
The VOX is automatic with no adjustments.
There are three isolation choices: pilot, crew, and
all. They are selected using a single
button.
It has audio playback.
Pressing the REPLAY button plays back the last received message. Pressing it again will play the previous
message etc.
There are two music inputs.
A dedicated button selects whether music input 1 will be muted when the
radios or intercom are active or will not be muted. Input 1 can be routed to the crew only or to
all headsets. The pilot and copilot cannot
hear music input 2.
There is a telephone connection. The telephone routing follows the
isolation. For example if the pilot is
isolated he will be the only person who can use the telephone.
A telephone or music source can be connected using Bluetooth
instead of by wiring the devices. The
Bluetooth music source will be routed as music input 1.
There is a mute button which will tell some external audio
annunciators to stop talking.
Comments
Since this is based on the PS Engineering 8000 series
technology I expect the audio and VOX to have similar performance. I don't know which external devices will interface with the mute button.
PS Engineering PMA 450
This is PS Engineering’s advanced panel. It supports two radios. It has three soft keys and an LCD display.
It has three switched AUX inputs. They are turned on and off using the soft
keys and display. The displayed names of
the inputs can be changed as desired.
There is one volume control.
It is concentric. The inner knob
sets the intercom level for the pilot and copilot and the outer knob sets the
intercom level for the passengers.
The VOX is automatic with no adjustments.
There are three isolation choices: pilot, crew, and
all. They are selected using a single
button.
It can play back messages received on the COM radios. The audio playback is triggered by pressing
the active COM receive button. The
message number and the number of stored messages are displayed on the screen.
There are two music inputs.
One is available through a front panel audio jack. They can individually be routed to any
combination of pilot, copilot, and crew.
Music can be muted when during COM receive. Music can be muted for the radios, radios and
intercom, or it can be set to never mute the music.
There is a telephone connection. The telephone can be routed to the pilot,
copilot, or passengers. The telephone
routing follows the intercom isolation. The display shows caller ID and soft
keys can be used to answer and end the call.
A telephone and music source can be connected using
Bluetooth instead of by wiring the devices.
The panel will show battery status.
It has stereo positioning of the radios. When activated the COM radios will appear to
be located at different positions. The
positions can be set using the soft keys and menus.
It has a 5V 1.5A USB jack which can be used to charge phones
or tablets. It does not have a data
connection.
Comments
The soft keys and display allow lots of features with only a
few buttons.
There are menus but I could not find a “back” button or
function.
The audio routing is fairly
complete with most inputs being able to be routed to most outputs.
I cannot comment on the usefulness
of the stereo effects. PS Engineering
has a demo program available but I have not tried it.
Capabilities and Comparisons
The Garmin panels do not have Bluetooth. The panels made by PS Engineering do.
The GMA 340 has inputs for three radios. The others have inputs for two radios. If three radios is required, the PS Engineering PMA 8000C (not
evaluated here) supports three COM radios.
Different panels have different numbers of switched inputs
and they are labeled differently. The
GMA 350 has only one. The rest have two,
except for the PMA 450 which has three.
On the PMA 450 the switched inputs are accessed through the soft keys
and it requires three presses to turn one on or off. On the other panels the switched inputs have
dedicated buttons and require one press.
All panels except for the GMA 340 have automatic VOX.
The GMA 350 has the most complete audio routing
capability. The PMA 450 is second,
having full capability but the telephone and intercom routing is shared. The others have limitations. For example the PMA 8000BT and the AMX 240
cannot route the music 2 input to the crew.
All of the panels except for the GMA 340 have audio
playback. On the GMA 350 and AMX 240
there are dedicated buttons for this feature.
On the PMA 8000BT and PMA 450 it is activated by pressing the active COM
receive button.
The GMA 350 and PMA 450 have the ability to present different
inputs at different apparent spatial locations.
The GMA 350 has fixed locations (or they are adjustable by the
installer) and includes the positions of the copilot and passengers. The PMA 450 allows the user to change the
apparent location of the input but it only works for the radios.
Most of the panels have telephone inputs. The most capable is the PMA 450 which can
show the caller ID and can answer or terminate a phone call. The PMA 450 manual includes this warning:
United States FCC
Regulations contained in 47 CFR § 22.925 currently contain prohibition on
airborne operation of cellular telephones. “Cellular telephones installed in or
carried aboard airplanes, balloons or any other type of aircraft must not be
operated while such aircraft are airborne (not touching the ground). When any
aircraft leaves the ground, all cellular telephones on board that aircraft must
be turned off.”
The PMA 8000BT and AMX 240,
although built on the same technology, are quite different. The PMA 8000BT has capabilities that the AMX
240 does not such as Bluetooth device control, and more options such as four
mute modes rather than two. The
trade-off is that the PMA 8000BT has more functions that require pressing
multiple buttons and these are mostly not labeled.
My Preferences
There are two goals -
“lots of features” and “easy to use”.
These goals are in conflict.
Additional features add complexity to the user interface. And they increase the chances that something
will be set “wrong”.
My experiences designing hardware and software (and the
human factors classes I’ve attended) tell me that for an audio panel the ideal
is that commonly used functions will have a dedicated labeled button or knob.
The COM 1 and COM 2 transmit and receive buttons are the
most frequently used. For IFR pilots the
NAV 1 and maybe NAV 2 buttons are frequently used but this may not be so with
the IFD because it has a Morse code reader.
The IFD has the ability to receive on the standby frequency. (Note:
This is not enabled in the original firmware shipped with the IFD 540.) It also has advanced receiver management
which allows frequency selection from a list.
With this combination it will be easier to get ATIS or similar
information using the IFD than it would be to do it using a normal COM 2 radio. This means that for stacks with a single IFD
the button which activates the standby receive function will be frequently
used. With a dual IFD stack the pilot
has the option of using the second IFD to pick up the ATIS using the
frequency list. I don’t know which
method will be preferable in a dual IFD stack.
GMA 340
The GMA 340 is the only panel in this list that I would
consider replacing if I already had one.
It isn’t that it is a bad panel, but the others have significant
features such as auto VOX and message replay.
GMA 350
This panel has the most versatile audio routing of any. And it has the ability to switch the copilot
position to being a passenger. The
controls are a bit complex but they are consistent so it is probably easy to
learn and remember how to use it.
It has a single button for message replay which makes it
easy to use this feature.
It only has one switched audio input. This probably disqualifies it from a dual IFD
stack because there would be no way to connect the second IFD standby receiver.
I’d consider this panel for a single IFD installation where
the audio routing capabilities are really important, or if a unique feature
such as voice commands is especially desired.
Otherwise I think there are better choices. I
suspect most Avidyne buyers are not going to want to put their IFD under a
Garmin panel anyways.
PMA 8000BT
This panel has lots of capabilities but they are implemented
in a way that I would find difficult to memorize. The frequently used buttons are easily available.
I would prefer a dedicated message replay button. The scheme used in this panel requires more
thought, which translates to higher workload.
And missing a message is a stress generator for most pilots.
For a single IFD stack the standby receiver audio could be
connected to the AUX switched input. For
a dual IFD stack the second IFD standby receiver audio would have to be
connected to the ADF input. That would be undesirable for a two IFD stack because the standby receive
buttons would be mislabeled and are not adjacent to each other or to the other
COMM radio buttons.
The functions which require multiple buttons or which use
buttons which aren’t labeled are functions most pilots won’t access frequently
if at all. I would keep a copy of the
manual in the plane in case someone bumped something and changed a setting
accidentally.
This isn’t my favorite of the panels but if I owned one I’d
happily keep it.
AMX 240
The features of this panel are limited as compared to others
in this evaluation (except the GMA 340).
However the controls are mostly obvious and it is easy to see how to
operate it.
The standby receiver audio would be connected to buttons labeled
MON 1 and MON 2. They are grouped
together with the COMM buttons.
It has a single button for message replay, labeled REPLAY.
I think this panel would be the easiest to use and for
situations where the features are adequate I think this would be the best
panel.
PMA 450
This is the most full featured panel evaluated. There a few minor features other panels have
that this one doesn’t but overall this does more stuff.
The features make the interface more complex. To manage this PS Engineering added a display
and three soft keys. These are used to
provide a simple menu- based scheme to access functions which are less
frequently used.
This scheme makes it easy to find all of the functions. Everything is labeled.
The interface is a hybrid – frequently used functions have
their own dedicated buttons.
The standby receiver audio would be connected to two of the
switched inputs which are available through the menu. The names of the inputs can be set by the aircraft
owner. They can be called MON 1 and MON
2, or STBY 1 and STBY 2 or pretty much whatever the owner wants. The switched inputs on/off keys are on the
third menu level. So it takes three key
presses to turn the standby receiver audio on or off. In a stack with one IFD this could be
annoying, but if the panel is wired correctly the three presses would all be on
the same key.
The message replay is activated by pressing and holding the active
COMM receive button. I would prefer a
single dedicated button.
These are minor quibbles and if there’s a feature which is
highly desired, such as the audio routing, the three switched inputs, or the
stereo radio positioning, or if you just happen to like the soft key interface,
I think this would be the best panel.
My Choice
Our aircraft is a Cessna 172. Most flights are just my wife and I going for
a $100 hamburger, or my wife flying approaches and precision maneuvers with a
CFI friend. If we have a third person in the plane, either another pilot or a
friend, we put them in the copilot’s seat and I sit in the back.
The existing audio panel is a KMA 26. The audio quality is OK but the VOX is not
very good.
The new stack will contain an IFD 540 and a KX 155A. There will be no DME or ADF equipment.
Many features are not important in our plane: - As far as I know we have never used the isolate
functions. If we did, it would be because a passenger would not stop talking, in which case the pilot would
select isolate.
- We’ve never listened to music while flying. One person who occasionally uses the plane
does but he has a way of placing music in his headset only. The rest of us have absolutely no interest
in hearing the music he prefers.
- We have a few Bluetooth devices but don’t have
much interest in tying them to the plane’s audio system. Setting up playback control sounds like more
trouble than it is worth.
- Due to an asymmetric hearing loss the stereo
effects are not useful.
- Voice commands aren’t very interesting. The pilots are used to pressing buttons and it
would be faster to press the COM 1 button than to press the voice button and
say “COMM 1”.
There are a few features we are interested in: - We want a better automatic VOX for the intercom.
- We don’t have the ability to replay messages and
all of the pilots are very interested in it.
- I think the ability to listen to the standby
receive frequency is going to be a big deal in our plane because it will be
much faster than twisting the knobs on the KX 155a. Once this feature becomes available on the
IFD we’ll probably set the second radio to 121.5 and leave it there.
The GMA 340 is missing features we want. Any of the other panels will work.
My first choice for our airplane is the AMX 240. It does what we want without being more
complicated than necessary. All of the
functions we would normally use have their own dedicated buttons with correct
labels.
My second choice is the PMA 450. Although the standby receive requires
multiple button presses the interface is easy to use and all functions will be
properly labeled.
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