solved 403mc aux music input problem

I had the same problem many others did connecting a music input to my flightcom 403mc. The music was so soft at top volume I could barely hear it on the ground and not at all in flight. Turns out in order to save $ there is apparently no pre-amp in this intercom. So if you want to hook up an mp3 player or walkman or whatever you need to supply your own pre-amp. I looked at all the options and decided to try to build my own. I looked at a lot of ciruits and borrowed heavily from some like Bob N. After lots of testing however I had to make changes to any existing designs to get the volume to a reasonable level in the headset with the volume control turned to a medium level on my mp3 player. My set-up is simple the mp3 player headphone jack simply goes into the aux music input jack which goes thru this little amp and then to the intercom. Anyway, I'm not an electrical engineer (I'm mechanical) so I am really not all that great at designing circuits, but this one works for me. I thought I would post it in case anybody want to use it as a starting point for their own amp.

http://www.geocities.com/bryanflood2001/AudioAmpfor403MC.bmp

Bryan

Kit bits....

looks like a good idea...

Mix these two kits together and use the included perf. board, and you'll have enough parts for your project, and probably cheaper than Rat Shack prices...

http://shop.vendio.com/vakits/item/736901368/index.html

http://shop.vendio.com/vakits/item/738448374/index.html

... was looking at these kits for a DIY audio isolator... sort of like yours but with 3 inputs... Comm 1, Comm 2 + Alert tone ... I don't want a full audio panel... Since I retired, my source of electronics parts has dried up...

gil in Tucson

PS Haven't bought from these guys (yet..) - just found them in a search

This one might be my audio isolator....
http://store.qkits.com/moreinfo.cfm/FK652

MP3 low volume

This was discussed several time before. Heres what I found.

"I have had the same problem with my MP3 player (Cell Phone). After reading this link I went to Radio Shack and bought 2 audio transformers. They are about ? inch square in size. Needed two as the output is stereo and I needed to mix down to mono. Made the appropriate cable for the phone with the transformers in line and the problem was solved. Prior to installing the matching transformers I would have to turn the volume on the MP3 player all the way to max just to hear it, now more that 1/3 volume is almost too much. Total cost $5 - $6 bucks and it is passive so I don?t need batteries. Quality is good. No worse than the cassette adaptor I use in the car. Took about an hour to make."

Hers a link to a drawing.

http://img114.imageshack.us/my.php?image=matchingtransformerfz7.jpg

Electronic Kits

Cool guys: Here is my post before:

http://www.vansairforce.com/community/showpost.php?p=97222&postcount=30


These are some of the electronic pre-amp kits you can buy all ready to solder together of $8-$12. Nothing wrong with the above. I just find when I buy separate parts and make a circuit they work but are a bit ugly. The kits get you all the parts and a etched board, and probably cost less or not much more than buying all separate.

PS Kit Plane has a good Jim Weir article on audio and military headset (mic and earpiece) adapter.

[email protected] said:

This was discussed several time before. Heres what I found.

Click to expand...

John Collins, cool transformer wire up stereo to mono. How does it work? What is the Part #? It's passive and cheap, which I like. I had other ideas to handle this but like your idea. Could it work for stereo out/stereo in to boost volume. What I gather is you are correcting an impedance issue, thus getting more amplification?

You are fixing a mismatch

Thats right the output of most mp3 players is in the 16 ohm range but your intercom expects 300 - 600 ohms. An amp will work but what you are realy doing with an amp is over driving to get the higher voltage the intercom needs. The amp is realy designed to produce more current not voltage although the two do go hand in hand. The transformer is just an 8 ohm in - to 500/1000 (Center tapped) ohm out, same power.... less current but higher voltage. You might losse a little fidelity becuase these are cheap transformers, but I have not been able to detect it. These are sold at radio shack and cost about 2.95 each. I used two to mix the left and right channels. The transformers are only about 1/2 inch square. Part numbers are on the other thread, search "matching transformers" to find it. Good luck....

PS ?I also took the output of the intercom (through a resistor/ divider to attenuate the output) and wired it to the mike input on the cell phone and can now make phone calls in flight or on the ground using the headset. I need to add a PTT button as the caller on the other end gets an echo as they speak. From caller ? to aircraft headphone to cell phone mike back to caller.

John

If you don't want to mess around building one...

This is the one I bought to use an MP3 player with my 403: http://www.cirruslog.com/products/imp_adp/garmin_296.htm

Works just fine, $35

Mark - N234C

RV-7 Flying 140 hrs.

Quick question... do you guys use a mono or stereo socket in the panel for the aux input on the Flightcom 403MC?

David

"Headbanger" headphone amp.

I built a homemade version of the "Headbanger" headphone amp, from scratch, using parts from Radio Shack. Parts cost about $30 and I didn't make a printed circuit board, I just used simple perfboard and soldered my own wire connections.

http://www.minidisc.org/headbanger.html

Works fantastic with intercoms such as portables and the Flightcom panel mount, which don't have enough input gain on the music input. It's a full stereo preamp too. A 9-volt battery always lasted me about 30 hours of use. Provides a lot of extra gain, much more than the little impedence-matching passive transformers do.

I've since moved up to a PS Engineering PM-3000 stereo intercom in my plane, and it needs no preamp at all, and sounds very, very good and loud with music.

My advice to anyone who hasn't yet bought their panel mount intercom and intends to run stereo.... go ahead and spring the extra $$$ for the PS Engineering PM-3000 unit. It's definitely worth the extra cost.

The definitive solution.

Neal@F14 said:

I built a homemade version of the "Headbanger" headphone amp, from scratch, using parts from Radio Shack. Parts cost about $30 and I didn't make a printed circuit board, I just used simple perfboard and soldered my own wire connections.

Click to expand...

This is slick, thanks. I guess you could make it permanent and power from the aircraft with a little LM317 voltage regulator.

ClearOfCloud said:

Quick question... do you guys use a mono or stereo socket in the panel for the aux input on the Flightcom 403MC? David

Click to expand...

David I don't have a Flightcom, but I read the manual. Its a MONO intercom, so a mono jack would be fine.

From the Flightcom 403MC manual:

AUXILIARY INPUT AND OUTPUT:
(See Wiring Diagram) If a music source is not installed permanently in the aircraft (Auxiliary Input), a 3.5mm mini jack can be installed in a convenient location to provide an interface for a portable recorder or CD player. The system output will be monophonic. Pin number 18 on the wiring diagram is for auxiliary input, allowing you to listen to a tape player or other source. To record from the intercom system (Auxiliary Output), install a second 3.5mm jack and connect it via one (1) 47k resistor to the pilot’s headphone output, pin 9. DO NOT attempt to combine both input and output functions on a single 3.5mm jack.

If you have a mono source, with a mono phone jack, than than you are fine. The problem is with a stereo audio source and mono amp (intercom). You can plug in a stereo phone into a mono jack and just get one channel of the stereo, but per the discussion above, you might still not get good volume due to impedance miss match. If you can accept getting one channel of stereo source than you are set with a mono panel jack.

I would discourage you from combining left and right channels together to make a mono signal. I'm not sure, but I fear you could burn out or blow the amp in your iPod.

So how do you go (mono to stereo) -OR- (stereo to mono)?

Mono to stereo - is easy, just split the mono to the L & R channels. With a mono source, all you do is split the one hot into two hot, L and R channels. You could make a little adapter cable with a mono jack and stereo phone plug at the other end. I think they sell adapters over the counter. Your intercom is NOT stereo, so its kind of moot. You are using a MONO jack in your panel.

Stereo to mono - If you call Flightcom's tech people, I think they will tell you to handle stereo to mono by using a resistor/capacitor. With a simple resistor/capacitor in-line with each channel, isolating them, before you tie them together into one mono signal. This is not as good as matching isolation amps some one posted above or Neal's isolation amp device above (with a little re-wiring). Stereo to mono is a compromise anyway you cut it.

How ever you decide to handle stereo to mono, you could wire a Stereo Panel Jack with a stereo/mono switch, and put all the stereo to mono electronics behind the panel. If you want hi-fi or at least good quality audio, a preamp is a good idea, espcially with a low cost intercom. When you need to turn the source WAY UP to get the acceptable sound levels, you increase distortion.

Neal suggested the PM-3000 does not need any help. I'll second his suggestion and add, if you really are going to use stereo input (iPod) and want quality sound. Neal said he did not need any matching preamp with the stereo PM-3000. I had the PM-2000 (stereo) intercom, predecessor to the PM-3000. I can testify to the quality. Their mono intercoms, PM1000 & PM1200 have separate pilot & co-pilot volume and squelch. The PM501 is their budget model. I know the PM3000 is big bucks, but you get what you pay for. I'm a cheap-skate, but critical, basic items I use every flight, like an intercom, I don't cheap out on. If you can find a used one or a PM-2000 than get it.

I'm not putting down Flightcom, but from their manual it looks like (I could be wrong) they don't isolate the audio grounds? This simplifies wiring and cuts cost, but opens the door to electical noise in the audio. High end intercoms ISOLATE the jacks and run dedicated grounds to each mic and phone. If you want music than get the PS Eng. There where other high end intercom brands, like DRE, but they're out of business.