Today's Message Index:
----------------------
1. 03:02 AM - Re: Low Audio Output (KITFOXZ@aol.com)
2. 06:15 AM - Re: Low Audio Output (Brian Lloyd)
3. 07:24 AM - Re: [Fw: Re: Low Audio Output(now not so low)] (f1rocket@comcast.net)
4. 07:41 AM - Re: Low Audio Output(now not so low) (Robert L. Nuckolls, III)
5. 08:06 AM - Re: Low Audio Output(now not so low) (f1rocket@comcast.net)
6. 08:37 AM - Re: Low Audio Output(now not so low) (Robert L. Nuckolls, III)
7. 08:40 AM - Re: Low Audio Output(now not so low) (Robert L. Nuckolls, III)
8. 09:53 AM - Re: Low Audio Output(now not so low) (Brian Lloyd)
9. 04:24 PM - XP Power Supply noise (David Schaefer)
10. 07:13 PM - Re: [Fw: Re: Low Audio Output(now not so low)] (Charlie England)
Message 1
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| Subject: | Re: Low Audio Output |
--> AeroElectric-List message posted by: KITFOXZ@aol.com
In a message dated 7/1/2004 7:50:54 PM Eastern Standard Time,
brianl@lloyd.com writes:
Well ... not really. The output impedance of this little amp is actually
well under an ohm. Most of these little amps are voltage amps with very low
output impedances. Even a preamp using an op-amp is going to have a
sub-10-ohm output impedance. And even with that the output impedance is going
to be a
function of the amount of feedback.
Yes, I forgot about feedback. Brian, you have this well thought out. I
will await your ideal choice for a plug and play preamp that will be the best
compromise for all considerations.
John P. Marzluf
Columbus, Ohio
Kitfox Outback (out back in the garage)
Message 2
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| Subject: | Re: Low Audio Output |
--> AeroElectric-List message posted by: Brian Lloyd <brianl@lloyd.com>
KITFOXZ@aol.com wrote:
> Yes, I forgot about feedback. Brian, you have this well thought out. I
> will await your ideal choice for a plug and play preamp that will be the best
> compromise for all considerations.
>
> John P. Marzluf
> Columbus, Ohio
> Kitfox Outback (out back in the garage)
Oh, I am not going to get into pontificating about "the best". Most any little
amp that has an output relative to ground and a single supply should do just
fine. It can be a couple of small-signal op-amps or it can be an audio output
chip like the LM380 with cap-coupled input and output. Several people have pointed
out suitable amps.
--
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
http://www.lloyd.com St. Thomas, VI 00802
+1.340.998.9447 (voice) +1.360.838.9669 (fax)
There is a time to laud one's country and a time to protest.
A good citizen is prepared to do either as the need arises.
Message 3
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| Subject: | Re: Low Audio Output(now not so low)] |
--> AeroElectric-List message posted by: f1rocket@comcast.net
Just curious Charlie, what problem does this create that makes it unacceptable?
Randy
F1 Rocket
-------------- Original message --------------
> --> AeroElectric-List message posted by: Charlie England
>
>
> I just *hate* it when this happens.
>
> #2 ain't gonna work in an airplane. I just took a closer look at the
> circuit on the data sheet & you can't tie the power supply ground to
> the audio ground in this device. I'm afraid you'd have to use an
> isolated battery to power it.
>
> I'll keep looking.
>
> Charlie
Just curious Charlie, what problem does this create that makes it unacceptable?
Randy
F1 Rocket
-------------- Original message --------------
-- AeroElectric-List message posted by: Charlie England
<CEENGLAND@BELLSOUTH.NET>
I just *hate* it when this happens.
#2 ain't gonna work in an airplane. I just took a closer look at the
circuit on the data sheet you can't tie the power supply ground to
the audio ground in this device. I'm afraid you'd have to use an
isolated battery to power it.
I'll keep looking.
Charlie
Message 4
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| Subject: | Re: Low Audio Output(now not so low) |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
I seem to be seeing about half the conversation on this. Missed the
original message and for some reason I'm getting only bits and
pieces of the thread. Is this all coming through the list or is
there some direct e-mails involved?
In any case, I'd be pleased to know more about the original
problem and what's being discussed to mitigate it.
Thanks!
Bob . . .
Message 5
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| Subject: | Re: Low Audio Output(now not so low) |
--> AeroElectric-List message posted by: f1rocket@comcast.net
Bob,
I started this thread by asking the question of "Is there an off the shelf, plug-n-play
solution to the problem of low audio output when connecting a portable
MP3 player to a PM3000 intercom via the music input jacks.
The response has been very interesting in that despite to proponderance of people
using portable music devices in the cockpit, the answer to my question appears
to be "NO".
Various headphone amp solutions have been proposed with varying degrees of success.
Portable battery devices like the Boostaroo, are not the most desireable
due to short battery life. A device that can be hooked up to the bus is more
desirable.
I'd appreciate any input you might provide. While building a device like the one
outlined on your website is an option, I desire a plug-n-play solution if possible,
as time is more important than money at the moment.
Randy
F1 Rocket
-------------- Original message --------------
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
>
>
> I seem to be seeing about half the conversation on this. Missed the
> original message and for some reason I'm getting only bits and
> pieces of the thread. Is this all coming through the list or is
> there some direct e-mails involved?
>
> In any case, I'd be pleased to know more about the original
> problem and what's being discussed to mitigate it.
>
> Thanks!
>
> Bob . . .
>
>
>
>
>
>
Bob,
I started this thread by asking the question of "Is there an off the shelf, plug-n-play
solution to the problem of low audio output when connecting a portable
MP3 player to a PM3000 intercom via the music input jacks.
The response has been very interesting in that despite to proponderance of people
using portable music devices in the cockpit, the answer to my question appears
to be "NO".
Various headphone amp solutions have been proposed with varying degrees of success.
Portable battery devices like the Boostaroo, are not the most desireable
due to short battery life. A device that can be hooked up to the bus is more desirable.
I'd appreciate any input you might provide. While building a device like the one
outlined on your website is an option, I desire a plug-n-play solution if possible,
as time is more important than money at the moment.
Randy
F1 Rocket
-------------- Original message --------------
-- AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<BOB.NUCKOLLS@COX.NET>
I seem to be seeing about half the conversation on this. Missed the
original message and for some reason I'm getting only bits and
pieces of the thread. Is this all coming through the list or is
there some direct e-mails involved?
In any case, I'd be pleased to know more about the original
problem and what's being discussed to mitigate it.
Thanks!
Bob . . .
anner ads or any other
Specific: http://www.matronics.com/aeroelectric-list
Message 6
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| Subject: | Re: Low Audio Output(now not so low) |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 03:03 PM 7/2/2004 +0000, you wrote:
>--> AeroElectric-List message posted by: f1rocket@comcast.net
>
>Bob,
>I started this thread by asking the question of "Is there an off the
>shelf, plug-n-play solution to the problem of low audio output when
>connecting a portable MP3 player to a PM3000 intercom via the music input
>jacks.
>The response has been very interesting in that despite to proponderance of
>people using portable music devices in the cockpit, the answer to my
>question appears to be "NO".
>Various headphone amp solutions have been proposed with varying degrees of
>success. Portable battery devices like the Boostaroo, are not the most
>desireable due to short battery life. A device that can be hooked up to
>the bus is more desirable.
>I'd appreciate any input you might provide. While building a device like
>the one outlined on your website is an option, I desire a plug-n-play
>solution if possible, as time is more important than money at the moment.
>Randy
>F1 Rocket
Understand. The output from a portable player is designed to
drive the common entertainment headphones which can range from
8 to 50 ohms impedance. Aircraft headsets run from 100 to 600 ohms
and take more voltage to produce similar perceived volume.
Have you tried the Boostaroo? In other words, if the Boostaroo
were bus powered, would it provide adequate performance. I note
that it speaks to 12 db of gain which is a voltage gain of
4x . . . just about right to make up the difference between
aircraft and entertainment headsets.
I suspect you could develop a battery-clean power source
to allow powering the Boostaroo from ships power. The amplifier
construction project described on my website can be set up
for a variety of gain values and would be a good, wired-in
example of an amplifier that can be powered from ship's bus.
It seems that whatever you do, you'll have to do some hammer-n-saw'n
on the device either to modify a battery powered off-the-shelf
product or to build-from-scratch.
Bob . . .
Message 7
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| Subject: | Re: Low Audio Output(now not so low) |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
Quick follow-up:
Check out this link
http://www.hobbytron.net/vk2572.html
Here's an amplifier assembly you can purchase assembled for about
$20 that would probably do the trick. You'd need to box it up
and mount it but it's already rigged for external power.
Bob . . .
Message 8
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| Subject: | Re: Low Audio Output(now not so low) |
--> AeroElectric-List message posted by: Brian Lloyd <brianl@lloyd.com>
Robert L. Nuckolls, III wrote:
> In any case, I'd be pleased to know more about the original
> problem and what's being discussed to mitigate it.
Problem: the current crop of intercoms with stereo music input have insufficient
gain to provide proper audio levels for the typical crop of personal music systems,
e.g. MP3 players, MD players, "Walkman", etc.
Solution: a stereo amp that provides some 10db-20db of gain.
--
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
http://www.lloyd.com St. Thomas, VI 00802
+1.340.998.9447 (voice) +1.360.838.9669 (fax)
There is a time to laud one's country and a time to protest.
A good citizen is prepared to do either as the need arises.
Message 9
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| Subject: | XP Power Supply noise |
--> AeroElectric-List message posted by: "David Schaefer" <dschaefer1@kc.rr.com>
Bob ...I wired an XM Delphi SKYFi received into my RV6. When I fired up the
avionics for the 1st time last week there was a high pitched noise on the
circuit. After considerable time I chased it down to the XM 12volt auto
converter for the SKYFi!
All the audio wires going to the XM are shielded, as are the headphone/mic
lines, separate ground to the panel etc. How can I eliminate this noise?
I can't live with out my XM! The only 'common' is that the 12 volt
converter and my headphone power supplies are run on the same 12 volt
circuit since they terminate in the same area.
Regards,
David
Message 10
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| Subject: | Re: Low Audio Output(now not so low)] |
--> AeroElectric-List message posted by: Charlie England <ceengland@bellsouth.net>
First, make a mental note that ' - ' isn't always the same as 'ground'.
Sometimes it's 'below ground'.
If you look closely at the schematic shown on the data sheet, you will
see that the 'negative' or 'ground' of the power connector doesn't
connect to 'ground' in the electronics. It connects to 'V-' . The
particular model opamp (triangles in the drawing) used in this device
requires both a positive & negative supply voltage, referenced to
ground. The designer is 'tricking' the opamps into seeing + & - by
creating an artificial ground reference at 1/2 the supply voltage. This
works fine if everything 'floats' as it would using headphones, but if
you wire it into the plane, you will tie the aircraft's ground to the
'V-', or negative voltage power supply terminal seen by the opamps.
Compare the power input circuit to
http://www.rolls.com/data/mp13man.pdf
Notice the 'fat' terminal of the power connector on this one connected
to the ground symbol, while the unusable one has that terminal connected
to a terminal labeled '-'.
BTW, this one would probably work, but you'd need 2 for stereo. The
'probably' is inserted because there's a 7812 12 volt voltage regulator
in there & it wants to see an input voltage a couple of volts above its
output voltage. An aircraft power bus with the engine running will be
close to 14 V, so there you go. Note also that the mfgr has labeled the
power jack 'DC IN 12V'.
These guys seem to make a lot of stuff; why not just give them a call &
ask whether they have anything more suitable. Tell them you need to see
a single ended 12 V DC negative ground power supply, with the power
supply, input & output sharing a common ground, adjustable gain of at
least 20dB, max undistorted output of at least 3 Volts RMS into
headphones or a 600ohm load, and 2 channels (stereo operation). Oh yeah,
you need >10k ohms input impedance.
http://www.rolls.com/
Rolls Corporation
5968 South 350 W.
Salt Lake City, Utah, 84107
Phone: (801) 263-9053 Fax: (801) 263-9068
You can also try your local pro musicians' shop. You'll need to find
their resident technogeek to match the above wish list with the products
they sell. They will probably have a headphone amp in stock that uses a
single ended power supply. You can also ask for an 'active direct box
with gain' but most direct boxes attenuate the input rather than boost it.
Charlie
(could have built you one quicker, but half the fun is in the hunt)
f1rocket@comcast.net wrote:
>--> AeroElectric-List message posted by: f1rocket@comcast.net
>
>Just curious Charlie, what problem does this create that makes it unacceptable?
>Randy
>F1 Rocket
>
>-------------- Original message --------------
>
>
>
>>--> AeroElectric-List message posted by: Charlie England
>>
>>
>>I just *hate* it when this happens.
>>
>>#2 ain't gonna work in an airplane. I just took a closer look at the
>>circuit on the data sheet & you can't tie the power supply ground to
>>the audio ground in this device. I'm afraid you'd have to use an
>>isolated battery to power it.
>>
>>I'll keep looking.
>>
>>Charlie
>>
>>
>
>
>Just curious Charlie, what problem does this create that makes it unacceptable?
>
>
>Randy
>
>
>F1 Rocket
>
>
>-------------- Original message --------------
>
> -- AeroElectric-List message posted by: Charlie England
> <CEENGLAND@BELLSOUTH.NET>
>
> I just *hate* it when this happens.
>
> #2 ain't gonna work in an airplane. I just took a closer look at the
> circuit on the data sheet you can't tie the power supply ground to
> the audio ground in this device. I'm afraid you'd have to use an
> isolated battery to power it.
>
> I'll keep looking.
>
> Charlie
>
>
>
>
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