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RV Audio Panel Design

ijustwannafly

Well Known Member
First let me apologize if this is in the wrong section. Mods please move it somewhere if it needs to be moved. I wasn't sure where to put it.


Im an Electrical Engineer and one thing that has always baffled me at moment is how expensive some avionics are. Certified electronics ok, but experimental stuff should not cost what it does.

I have set out to develop (JUST FOR FUN NOT AS A BUSINESS) my own handmade avionics. I will not be tackling a full-blown EFIS at the moment given the expense for R and D but one thing that came to mind initially was Audio Panels. Could someone please tell me how on earth an audio panel costs $1800?
Even on the cheap side i have seen them around $1k

This is mind boggling. The internal electronics are simple.

So here is what I'm asking from all the RV lovers in the world.

Tell me what you want out of an audio panel. What are the KEY features you want.
I know me personally I'm always on the look out for a low cost item that is simple and reliable. Im building a budget airplane (if there is such a thing) so everything i look at is price minded without sacrificing safety and reliability of course.

Please do not reply with "your nuts". I just want to know what you guys would like to have in an audio panel that would make you smile if say the thing costs $399 or $499 at most! For the guys with plenty of ash to burn and $150k RV7,s this doesn't matter. However for the dreamers out there that want to build a $65k RV7 i want to develop some low cost options.

Thanks for the suggestions!
 
I think I paid $300 or less for my Dynon ICS. Not many bells and whistles but does what I need. I hope to be flying later this year for under 70k.
 
I'll bite - I've looked at this as well.

Must-haves:
- Stereo
- 2 comms
- 2 navs
- 1 additional switched audio source (MB receiver, etc.)
- 2 (or more) unswitched audio sources
- Bluetooth connectivity (phones/music)
- Built-in 2place intercom with soft muting like PS Engineering's intercoms
- Dim-able backlighting (or design that obviates such)

Nice-to-haves:
- Separate music for pilot & pax
- 4 place intercom
 
I'll bite - I've looked at this as well.

Must-haves:
- Stereo
- 2 comms
- 2 navs
- 1 additional switched audio source (MB receiver, etc.)
- 2 (or more) unswitched audio sources
- Bluetooth connectivity (phones/music)
- Built-in 2place intercom with soft muting like PS Engineering's intercoms
- Dim-able backlighting (or design that obviates such)

Nice-to-haves:
- Separate music for pilot & pax
- 4 place intercom

Thanks for the reply!
 
Add to the "nice to have" list... Separate MIC inputs for each MIC, and an auto-squelching circuit that opens ONLY the active MIC for intercom. Once you hear this working, you will curse any intercom that opens all the MICs whenever one breaks the squelch. MGL was the first intercom I heard that had mastered this technique - truly stunning in comparison to most other intercoms.
 
Add to the "nice to have" list... Separate MIC inputs for each MIC, and an auto-squelching circuit that opens ONLY the active MIC for intercom. Once you hear this working, you will curse any intercom that opens all the MICs whenever one breaks the squelch. MGL was the first intercom I heard that had mastered this technique - truly stunning in comparison to most other intercoms.

Very Interesting. All the certified planes i have flown do what your describing. Really should not be a hard concept. Ill make sure that is on the design list.
Thanks
 
Here's a link to a whole flock of audio cicuits that may be useful in your endeavor. http://makerplane.org/?page_id=1059

Also, Jim Weir at RST used to sell a $200 audio panel kit and the schematic may still be available.

Btw, it's not the electronics that are hard, it's the mechanicals.
 
I'm right there with you on getting my head wrapped around the cost. I can understand the fully featured ones that have stereo 3D sound separation, VOX and other "cool" features. But for $2000, that's just a lot of money for these features, especially for a 2 place experimental. I have to admit, my audio panel is made of 3 standard switches :
Switch 1- Two place switch to TX between Com 1 or Com 2
Switch 2 - Three place switch to RX between Com 1, Com 2 and Both
Switch 3 - Two place switch to RX Nav 1 or Nav 2

Now this isn't perfect but it allows me to listen to 2 frequencies at once and switch between the 2 Coms or Navs at a flick of a switch.

Cost? approximately $15. Does it work? You betcha.
Is it cool and have nice features? Not a chance :D
 
Jim Weir did a 3-part article in Kitplanes a few years ago about building your own audio panel/intercom for less than a carton of beer. As many inputs as you wanted, failsafe (loss of power connected pilot headset/PTT to radio 1), dead simple.

I can't remember which edition it was but I might still have it tucked away if anyone is interested in having a crack at it yourself.
 
I've been down this road

So, I built my own intercom/audio panel, because (1) I wanted specific features, and (2) I'm cheap. All integrated circuits, op amps.
Intercom has a very good squelch circuit. Manually adjustable, but it is set once and forget. Only the mic that's being spoken into goes hot (important). There is some filtering to remove low and high frequency noise. Pilot and passengers have separate intercom volume controls. Plays music, I have xm wired in but could be anything. Pilot/passengers have their own music volume controls. Passengers have their own radio volume control (pilot uses the control on the radio(s). One switch selects between com 1 and com 2 for transmit. Both receivers are 'on' all the time, I turn down the volume if I don't want to hear one (typically, I rarely transmit on #2. Just listen to atis, etc.) Nav audio is selected via a switch on the SL-30. EFIS alerts are on all the time. This all works for me. Cost about $50, because I have a lot of volume controls and I bought nice knobs. The knobs are the most expensive part!
Now, PS makes very good panels. For noise reduction they use sophisticated digital techniques, well beyond what I could do in, say, 100 hours of work. But modest improvements are pretty expensive. Also, real companies have overhead. Ads for audio panels cost the same as ads for gps navigators. So does office space, etc. That's why nothing costs less than $500.
 
For me, i'd say:

Must-haves:
- Stereo
- 2 comms
- 2 navs
- Bluetooth connectivity (phones/music)
- Built-in 2place intercom with soft muting like PS Engineering's intercoms
- Dim-able backlighting (or design that obviates such)

Nice-to-haves:
- 1 additional switched audio source (MB receiver, etc.)
- 2 (or more) unswitched audio sources

I'm not going to get to the IFR stage so dual nav would probably never be needed. Ditto with Marker Beacon input. Having essentially four "comm-like" inputs would allow using a Nav input for something else if desired. Bluetooth is a must, it should work like your car audio system... Start the car, the phone connects automatically.

Mechanicals aren't that hard. When you need a case, i'd be happy to give a hand finding something.
 
So, I built my own intercom/audio panel, because (1) I wanted specific features, and (2) I'm cheap. All integrated circuits, op amps.
Intercom has a very good squelch circuit. Manually adjustable, but it is set once and forget. Only the mic that's being spoken into goes hot (important). There is some filtering to remove low and high frequency noise. Pilot and passengers have separate intercom volume controls. Plays music, I have xm wired in but could be anything. Pilot/passengers have their own music volume controls. Passengers have their own radio volume control (pilot uses the control on the radio(s). One switch selects between com 1 and com 2 for transmit. Both receivers are 'on' all the time, I turn down the volume if I don't want to hear one (typically, I rarely transmit on #2. Just listen to atis, etc.) Nav audio is selected via a switch on the SL-30. EFIS alerts are on all the time. This all works for me. Cost about $50, because I have a lot of volume controls and I bought nice knobs. The knobs are the most expensive part!
Now, PS makes very good panels. For noise reduction they use sophisticated digital techniques, well beyond what I could do in, say, 100 hours of work. But modest improvements are pretty expensive. Also, real companies have overhead. Ads for audio panels cost the same as ads for gps navigators. So does office space, etc. That's why nothing costs less than $500.

I know why they cost what they do but i think its excessive.
You made my point for me.

"Well beyond what i could do in say 100 hours of work"

Given the fact that i have a specialty in Digital signal processing i believe i can make an equally good panel for 25% of what these guys want. With all the elusive things in it that big companies tell you cost big bucks!
The designs previously talked about in the (rst) do it yourself realm are just fine but they are extremely old designs and work well enough but far from high fidelity.

The one thing i should of added in the original thread is that i intend to make a MODERN panel including blue-tooth and cut the cost in half :)

Thanks to everyone contributing to the Wants / nice to have lists as that is what I'm really after with this thread.
 
I don't want an audio panel for my RV-3, but for the experimentals, it might be worth including a signal generator that makes a tone when a simple switch is activated. That way someone could set up something that they didn't want to use an EFIS for and still get a warning tone.

Maybe have two of them and have some sort of user-configurable tone frequency or warbling.

Perhaps it could have a remote warning light that it can turn on too if necessary.

Dave
 
Audio Panel

This all sounds good. I do like the list, as that would work for me, but please don't forget the most important and expensive thing on the list. Product liability!!!!!

Even though we live in the experimental world of aviation, which allows us to built it anyway we want, and put anything in our experimental aircraft, there is plenty of widows who will file that frivolous lawsuit to gain anything they can when their other half doesn't return home one day because of ____________( you fill in the blank.)

Where a part of the cost for that intercom is R&D, there is a big chunk that still goes towards liability insurance. Please talk to your lawyer to protect yourself before you jump into this.

Thanks for thinking about us who want a great product, at a great price.

Just my 2 cents worth, as I was thinking about a low cost interconnect module for the Dynon SkyView system since AFS won't sell theirs out right. I have put it on hold for now due to the high risks involved.

Brian
 
This all sounds good. I do like the list, as that would work for me, but please don't forget the most important and expensive thing on the list. Product liability!!!!!

Even though we live in the experimental world of aviation, which allows us to built it anyway we want, and put anything in our experimental aircraft, there is plenty of widows who will file that frivolous lawsuit to gain anything they can when their other half doesn't return home one day because of ____________( you fill in the blank.)

Where a part of the cost for that intercom is R&D, there is a big chunk that still goes towards liability insurance. Please talk to your lawyer to protect yourself before you jump into this.

Thanks for thinking about us who want a great product, at a great price.

Just my 2 cents worth, as I was thinking about a low cost interconnect module for the Dynon SkyView system since AFS won't sell theirs out right. I have put it on hold for now due to the high risks involved.

Brian

Totally agree. This is one primary reason i have decided against making a full blown EFIS although i am totally capable of doing so.
The chance of an audio panel causing a flight critical accident is extremely thought but also something to consider for sure!
 
Totally agree. This is one primary reason i have decided against making a full blown EFIS although i am totally capable of doing so.
The chance of an audio panel causing a flight critical accident is extremely thought but also something to consider for sure!

The hard part in an EFIS is the software ... A modern EFIS is just a computer ... you could *almost* build one out of off-the-shelf components ...
 
Actually getting "high fidelity" for the music is quite easy (at least up to the level aviation headsets are capable of). The tricky part is getting clear and crisp audio on the intercom circuit while still reducing background noise - "high fidelity" is not what you want.
BTW, include "fail safe", e.g., power off leaves #1 com directly connected to your headset.
 
I am going to drift a little beyond the intercom. Have you thought about what it would take to design a 2.25" electronic directional indicator with an LCD screen? Obviously it wouldn't be gyro driven, but using the sensors that all of our phones use for their compass.

There are no other companies that make something like that and I think it would be really slick, and rather simple.
 
I am going to drift a little beyond the intercom. Have you thought about what it would take to design a 2.25" electronic directional indicator with an LCD screen? Obviously it wouldn't be gyro driven, but using the sensors that all of our phones use for their compass.

There are no other companies that make something like that and I think it would be really slick, and rather simple.

Here is a link I have had bookmarked for a while, lots of cool ideas, though maybe a bit old school. He has a digital compass, just not 2.25"
DIY Avionics: http://lea.hamradio.si/~s53mv/avionics/avionics.html
 
All of the mixer amps and stereo music adapters that I developed for aviation use had the capability of high fidelity (20 Hz-20 KHz +/- 1db, low THD). Simply by using the right Opamp, great improvements can be made while reducing cost. For example, the TLC082 opamp and related devices are almost ideal for this application. The only exception is that they are intolerant of overvoltage on the power supply, so good regulation is essential.

One could redesign the RST audio panel using these devices and achieve excellent results.

However, there is a rule of thumb that I learned 35 years ago while I was a designer at Mitel. Take your parts cost and multiply by four. That's an estimate of what your average selling price has to be. Anything less and you can't make money. The things I designed sold in the millions of units (telephone line circuits).

At lower volumes, you have to make more. At PMC-Sierra, we would not look at building a device that only had 75% gross margins. 75% gross margins are what furniture manufacturers make, with no R&D budget.

So it's fun to do and great for the community, but don't give up your day job!
 
I purchased a homebuilt with a great suite of king avionics but soon found out that all the audios were simply wire twisted together. What a mess. I too couldn't believe the prices on factory audio panels. So, I whipped up a simple, but proper panel using one of the available 8 channel audio mixers. Alltogether, about $150. Basic and works ok.

As a new feature, it would be nice to have voice synthesized capability that can be triggered by something like a canopy open microswitch, etc.

BTW, I encourage this grassroots development effort. Screw the legal bull. This is amateur, diy stuff, use at your own risk, and you aren't looking to be truly commercial.
 
Any progress?

Just curious if you have made any progress on this project? Sounds really interesting.
 
I'm right there with you on getting my head wrapped around the cost. I can understand the fully featured ones that have stereo 3D sound separation, VOX and other "cool" features. But for $2000, that's just a lot of money for these features, especially for a 2 place experimental. I have to admit, my audio panel is made of 3 standard switches :
Switch 1- Two place switch to TX between Com 1 or Com 2
Switch 2 - Three place switch to RX between Com 1, Com 2 and Both
Switch 3 - Two place switch to RX Nav 1 or Nav 2

Now this isn't perfect but it allows me to listen to 2 frequencies at once and switch between the 2 Coms or Navs at a flick of a switch.

Cost? approximately $15. Does it work? You betcha.
Is it cool and have nice features? Not a chance :D

I did something similar. I got a PM3000 on ebay for $100. I then used switches. I have a Com 1 / Com 2 switch and a 3 throw switch that connects one of the unswitched (and un-muted) inputs between my offline Com (Com switch routes the un-selected comm on this feed), Nav audio and GPS audio. The EFIS gets the other unswitched. Paid an additional $15 in switches (require a 4PDT and 2P3T / On-On-On). This seems to cover my needs well.

Larry
 
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All of the mixer amps and stereo music adapters that I developed for aviation use had the capability of high fidelity (20 Hz-20 KHz +/- 1db, low THD). Simply by using the right Opamp, great improvements can be made while reducing cost. For example, the TLC082 opamp and related devices are almost ideal for this application. The only exception is that they are intolerant of overvoltage on the power supply, so good regulation is essential.

One could redesign the RST audio panel using these devices and achieve excellent results.

However, there is a rule of thumb that I learned 35 years ago while I was a designer at Mitel. Take your parts cost and multiply by four. That's an estimate of what your average selling price has to be. Anything less and you can't make money. The things I designed sold in the millions of units (telephone line circuits).

At lower volumes, you have to make more. At PMC-Sierra, we would not look at building a device that only had 75% gross margins. 75% gross margins are what furniture manufacturers make, with no R&D budget.

So it's fun to do and great for the community, but don't give up your day job!

A small world. I sold PBX's early in my career and once worked for a Mitel distributor.
 
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