Combining vario and radio output into one speaker

[Paul B[_2_]]

I am wondering if it is possible to combine the outputs of a vario and a radio and send it to one speaker. I did try to Google it, but I did not find a satisfactory answer.

Any ideas please?


Cheers

Paul

[Peter Purdie[_3_]]

Yes in a number of ways, all of them more expensive, failure prone
and space consuming than installing a second speaker !

At 07:20 26 February 2015, Paul B wrote:
>I am wondering if it is possible to combine the outputs of a vario and a
>radio and send it to one speaker. I did try to Google it, but I did not
>find a satisfactory answer.
>
>Any ideas please?
>
>
>Cheers
>
>Paul
>
>

[krasw]

You would need a mixer circuit. Do not combine signals together, you'll burn your audio amps inside radio and vario. Best bet would be to use mixer designed for aircraft (http://www.aircraftspruce.com/categories/pilot_supplies/ps/menus/av/audiopanel_zaudiomixer.html), but I'm afraid most of these are designed to drive headsets and do not have enough power to drive speaker. There might be some radios or varios that accept other audio source and have built-in mixer. I installed two indentical speakers for my glider, very simple solution.

[Paul Remde]

Hi Paul,

I highly recommend that you do not try to connect 2 devices to one speaker.
It could damage one or both of the instruments. I have done repairs to
several soaring instruments which had their audio output circuits fried by
doing just this.

Best Regards,

Paul Remde
Cumulus Soaring, Inc.
_________________________________________________

"Paul B" wrote in message
...

I am wondering if it is possible to combine the outputs of a vario and a
radio and send it to one speaker. I did try to Google it, but I did not find
a satisfactory answer.

Any ideas please?


Cheers

Paul

[Bill D]

On Thursday, February 26, 2015 at 6:55:00 AM UTC-7, Paul Remde wrote:
> Hi Paul,
>
> I highly recommend that you do not try to connect 2 devices to one speaker.
> It could damage one or both of the instruments. I have done repairs to
> several soaring instruments which had their audio output circuits fried by
> doing just this.
>
> Best Regards,
>
> Paul Remde
> Cumulus Soaring, Inc.
> _________________________________________________
>
> "Paul B" wrote in message
> ...
>
> I am wondering if it is possible to combine the outputs of a vario and a
> radio and send it to one speaker. I did try to Google it, but I did not find
> a satisfactory answer.
>
> Any ideas please?
>
>
> Cheers
>
> Paul

Yes, one does need a mixer or audio panel. Not a bad idea though. If all the electronic noisemakers ran their output through an audio panel, sound levels could be "equalized" and it could have a master volume. Using one, larger speaker with good sound is better than a bunch of little crappy ones.

We would need a special unit for gliders. Airplane units are too big and intended for headsets.

[jfitch]

On Wednesday, February 25, 2015 at 11:20:35 PM UTC-8, Paul B wrote:
> I am wondering if it is possible to combine the outputs of a vario and a radio and send it to one speaker. I did try to Google it, but I did not find a satisfactory answer.
>
> Any ideas please?
>
>
> Cheers
>
> Paul

Look into motorcycle intercoms. There are a number on the market, one common feature is combining audio sources such as the other passenger, the stereo, and cell phone. They typically do it in a priority scheme such that the stereo (vario) will be muted or attenuated while the passenger (radio) speaks, when done the stereo ramps back to normal volume. Small box, doesn't use much power, doesn't cost what anything stamped "for aircraft" cost.

[George Haeh]

Many radios offer an auxiliary input, but
Paul Remde's experience with damaged
units suggests less heartache potential if
you keep them separate.

Now all I have to do is make a more
secure mount for my Vario speaker.

[Paul B[_2_]]

Thanks for all the advice above. I have done some further searching and did come up with some answers.
As I feared it is indeed not advisable to simply connect the outputs together. Whilst it may work, the chance of poor quality sound and indeed damage to equipment is high.
However it seems possible to connect different outputs to a single speaker with some relatively simple passive circuits. If anyone is interested, here are some links:

http://www.rane.com/pdf/ranenotes/Why_Not_Wye.pdf
https://www.gearslutz.com/board/geekslutz-forum/32861-stereo-mono-summing.html

Perhaps the next question should be. If the mixing is possible from the technical perspective, is it a good idea from the practical perspective?


Cheers

Paul

[Bruce Hoult]

On Friday, February 27, 2015 at 2:43:35 PM UTC+13, Paul B wrote:
> Thanks for all the advice above. I have done some further searching and did come up with some answers.
> As I feared it is indeed not advisable to simply connect the outputs together. Whilst it may work, the chance of poor quality sound and indeed damage to equipment is high.
> However it seems possible to connect different outputs to a single speaker with some relatively simple passive circuits. If anyone is interested, here are some links:
>
> http://www.rane.com/pdf/ranenotes/Why_Not_Wye.pdf
> https://www.gearslutz.com/board/geekslutz-forum/32861-stereo-mono-summing.html
>
> Perhaps the next question should be. If the mixing is possible from the technical perspective, is it a good idea from the practical perspective?

Sure, of course it's easy to mix signals by adding resistors to prevent drawing excessive current from one output to another one.

The problem then is your loudspeaker won't be very loud.

It can be ok for headphones.

For a decently loud loudspeaker, the result of such mixing needs to be fed into an amplifier. (perhaps a speaker with a built in amplifier, such as those made for connecting to PCs or MP3 players)

For the best results, you also want to put an "op amp" in negative feedback "voltage follower" configuration between the resistor mixer and the amplifier.

The really paranoid will also connect each input via maybe a 1 or 2 uF capacitor, and the same from the output of the op-amp to the amplifier.

You could also put a variable resistor with a knob on each of the inputs as a volume control. And another as the feedback resister on the op-amp as an overall volume.

Now you're getting fancy :-)

[Paul B[_2_]]

On Friday, 27 February 2015 15:05:45 UTC+10, Bruce Hoult wrote:

>
> Now you're getting fancy :-)

Thanks Bruce

The fancy is what I want to avoid, as the initial idea was to simplify things - i.e. one speaker instead of four :).

Cheers

Paul

[Darryl Ramm]

Yes but the stuff you are linking to is *irrelevant*. These circuits are talking about driving line level inputs. Those line level inputs have ~tens of kohm input impedance -- that is not at all what you are trying to do. You are trying to blend a signal that is driving a very low impedance (nominally 4 ohm or 8 ohm) speaker. If you want to blend low output impedance signals to drive something like a speaker you need to buffer that low impedance, which gets you into an op amp or similar buffer on each channel and and/or drive a summing amplifier directly, then a power driver circuit. Basically you are building an active audio panel. All that complexity and need to power it and have yet another thing to fail.

The simple solution is use two speakers. Not hard at all.


On Thursday, February 26, 2015 at 9:40:28 PM UTC-8, Paul B wrote:
> On Friday, 27 February 2015 15:05:45 UTC+10, Bruce Hoult wrote:
>
> >
> > Now you're getting fancy :-)
>
> Thanks Bruce
>
> The fancy is what I want to avoid, as the initial idea was to simplify things - i.e. one speaker instead of four :).
>
> Cheers
>
> Paul

[Bruce Hoult]

On Friday, February 27, 2015 at 6:40:28 PM UTC+13, Paul B wrote:
> On Friday, 27 February 2015 15:05:45 UTC+10, Bruce Hoult wrote:
>
> >
> > Now you're getting fancy :-)
>
> Thanks Bruce
>
> The fancy is what I want to avoid, as the initial idea was to simplify things - i.e. one speaker instead of four :).

Well, the good news is all those bits (except volume controls with knobs) would cost less than $10 in total and fit on a board a maximum of a couple of square inches in size.

Heh. These days you could use a $2 ATtiny85 microcontroller in an 8 pin DIP package. 20 MHz CPU. 3 10 bit analog to digital inputs. Scale and add them digitally. Output a pulse-width modulated 1 bit signal at 50 KHz or so, low pass filter (i.e. a resistor and a capacitor), then to the amplifier.

https://learn.sparkfun.com/tutorials/tiny-avr-programmer-hookup-guide/attiny85-use-hints

OK, I'm being silly.

[Dan Marotta]

I feel absolutely old-fashioned what with my vario speaker velcroed to
the top of my glare shield and my radio speaker mounted to the bulkhead
behind my right ear. But, hey! It works.

On 2/27/2015 12:00 AM, Bruce Hoult wrote:
> On Friday, February 27, 2015 at 6:40:28 PM UTC+13, Paul B wrote:
>> On Friday, 27 February 2015 15:05:45 UTC+10, Bruce Hoult wrote:
>>
>>> Now you're getting fancy :-)
>> Thanks Bruce
>>
>> The fancy is what I want to avoid, as the initial idea was to simplify things - i.e. one speaker instead of four :).
> Well, the good news is all those bits (except volume controls with knobs) would cost less than $10 in total and fit on a board a maximum of a couple of square inches in size.
>
> Heh. These days you could use a $2 ATtiny85 microcontroller in an 8 pin DIP package. 20 MHz CPU. 3 10 bit analog to digital inputs. Scale and add them digitally. Output a pulse-width modulated 1 bit signal at 50 KHz or so, low pass filter (i.e. a resistor and a capacitor), then to the amplifier.
>
> https://learn.sparkfun.com/tutorials/tiny-avr-programmer-hookup-guide/attiny85-use-hints
>
> OK, I'm being silly.

--
Dan Marotta

[Darryl Ramm]

On Thursday, February 26, 2015 at 11:00:11 PM UTC-8, Bruce Hoult wrote:
> On Friday, February 27, 2015 at 6:40:28 PM UTC+13, Paul B wrote:
> > On Friday, 27 February 2015 15:05:45 UTC+10, Bruce Hoult wrote:
> >
> > >
> > > Now you're getting fancy :-)
> >
> > Thanks Bruce
> >
> > The fancy is what I want to avoid, as the initial idea was to simplify things - i.e. one speaker instead of four :).
>
> Well, the good news is all those bits (except volume controls with knobs) would cost less than $10 in total and fit on a board a maximum of a couple of square inches in size.
>
> Heh. These days you could use a $2 ATtiny85 microcontroller in an 8 pin DIP package. 20 MHz CPU. 3 10 bit analog to digital inputs. Scale and add them digitally. Output a pulse-width modulated 1 bit signal at 50 KHz or so, low pass filter (i.e. a resistor and a capacitor), then to the amplifier.
>
> https://learn.sparkfun.com/tutorials/tiny-avr-programmer-hookup-guide/attiny85-use-hints
>
> OK, I'm being silly.

Oh come on, where is your ambition? Once you go digital there are lots of great options. You could add a digital parametric EQ, MIDI programming to customize the vario output, etc.

What is wrong with this industry and lack of innovation? Why has no vario developer offered MIDI output until now?

:-)

[Bruce Hoult]

On Saturday, February 28, 2015 at 9:51:53 AM UTC+13, Darryl Ramm wrote:
> On Thursday, February 26, 2015 at 11:00:11 PM UTC-8, Bruce Hoult wrote:
> > On Friday, February 27, 2015 at 6:40:28 PM UTC+13, Paul B wrote:
> > > On Friday, 27 February 2015 15:05:45 UTC+10, Bruce Hoult wrote:
> > >
> > > >
> > > > Now you're getting fancy :-)
> > >
> > > Thanks Bruce
> > >
> > > The fancy is what I want to avoid, as the initial idea was to simplify things - i.e. one speaker instead of four :).
> >
> > Well, the good news is all those bits (except volume controls with knobs) would cost less than $10 in total and fit on a board a maximum of a couple of square inches in size.
> >
> > Heh. These days you could use a $2 ATtiny85 microcontroller in an 8 pin DIP package. 20 MHz CPU. 3 10 bit analog to digital inputs. Scale and add them digitally. Output a pulse-width modulated 1 bit signal at 50 KHz or so, low pass filter (i.e. a resistor and a capacitor), then to the amplifier.
> >
> > https://learn.sparkfun.com/tutorials/tiny-avr-programmer-hookup-guide/attiny85-use-hints
> >
> > OK, I'm being silly.
>
> Oh come on, where is your ambition? Once you go digital there are lots of great options. You could add a digital parametric EQ, MIDI programming to customize the vario output, etc.
>
> What is wrong with this industry and lack of innovation? Why has no vario developer offered MIDI output until now?
>
> :-)

If you're going to do all that, you might need a more powerful CPU -- how about a full 32 bit ARM in an 8 pin DIP package for about the same price?

https://learn.adafruit.com/getting-started-with-the-lpc810?view=all

[son_of_flubber]

On Friday, February 27, 2015 at 2:03:14 PM UTC-5, Dan Marotta wrote:
> my radio speaker mounted to the
> bulkhead behind my right ear.

Is it better to have the radio audio output balanced between both ears? I assume that this would result in higher comprehension of radio calls with lower sound pressure (DB) driving each ear. If the speaker drives both ears equally, can you turn down the volume and get the same or better comprehension?

Is it better for the radio speaker(s) to have line of sight to the ears rather than bouncing the sound energy off the hard surfaces in the glider?

My thought is that the best solution is TWO small speakers each with line of sight to one ear. If the audio output bounces off a variety of hard surfaces, the echos will combine and make the signal that reaches the ears 'fuzzy'. So higher sound pressure will be needed.

So why do I want to minimize sound pressure? Hearing loss from exposure to high sound pressure is incremental and cumulative. The first step is to reduce wind noise in the cockpit. But the squeals coming over the air from malfunctioning radios are still pretty loud. Loud enough to be annoying and maybe loud enough to cause a tiny accumulating bit of hearing loss. There is no reason to not turn the radio down as low as feasible.

The vario can have one speaker buried anywhere. Unless you have one of those talking varios... a beep is a beep.

[Paul B[_2_]]

Thanks to all who replied, but I think the project came to an end when I came across this post on an electronics forum


"My guess is that the speaker output - terminal is not ground, but is driven to some AC voltage out of phase with the + terminal. It's how most automotive amps (and other low $ items) work to maximize power out, given a single +DC voltage supply like you'd have with a battery (vs a + and - DC voltage supply that would be made from the mains AC line) . The speaker + and - outputs should not be connected to anything other than the speaker itself."

I suspect that the the radio I have has an amplifier as described in the quote, they say not to connect the speaker -ve to a common ground.

Dual voice coil speaker is still a possibility though :).

Cheers

Paul

[Mike the Strike]

The only solution I can come up with is to use transformer coupling with three windings - two input windings from the two sources and one output winding to the speaker. The windings could all be on one toroid. The only coupling would be magnetic. I haven't had the energy to calculate what values might work, but offer it as a conceptual solution.

Mike

[Paul B[_2_]]

On Monday, 2 March 2015 15:09:04 UTC+10, Mike the Strike wrote:
> The only solution I can come up with is to use transformer coupling with three windings - two input windings from the two sources and one output winding to the speaker. The windings could all be on one toroid. The only coupling would be magnetic. I haven't had the energy to calculate what values might work, but offer it as a conceptual solution.
>
> Mike

Interesting thought Mike, just wondering if the current in the windings of one output would not induce current in the other windings so you still would wind up:) with current backfeeding to the other amps.

I'll just go the conventional way for now :(.

Cheers

Paul

[Peter Purdie[_3_]]

Not if it's a hybrid transformer

http://en.wikipedia.org/wiki/Hybrid_coil

I still would bet on sufficient independant speakers being the optimal
solution.

Second best is amplitude and impedance matching the vario output
into the aux audio input of the radio (with the bonus, or drawback,
that the vario output would be muted when receiving or transmitting.
No Outputting an 8 knot climb audio signal to your struggling
competitors)

Peter

At 05:38 02 March 2015, Paul B wrote:
>On Monday, 2 March 2015 15:09:04 UTC+10, Mike the Strike wrote:
>> The only solution I can come up with is to use transformer coupling
with
>=
>three windings - two input windings from the two sources and one output
>win=
>ding to the speaker. The windings could all be on one toroid. The only
>co=
>upling would be magnetic. I haven't had the energy to calculate what
>value=
>s might work, but offer it as a conceptual solution.
>>=20
>> Mike
>
>Interesting thought Mike, just wondering if the current in the windings
of
>=
>one output would not induce current in the other windings so you still
>woul=
>d wind up:) with current backfeeding to the other amps.=20
>
>I'll just go the conventional way for now :(.
>
>Cheers
>
>Paul
>

[Paul B[_2_]]

On Monday, 2 March 2015 21:00:06 UTC+10, pete purdie wrote:
> Not if it's a hybrid transformer
>
> http://en.wikipedia.org/wiki/Hybrid_coil

Thanks Pete, will check it out

>
> I still would bet on sufficient independant speakers being the optimal
> solution.

So it would seem, but as I am up to four (radio,two electronic varios, one with two outputs), I thought that there must be a better way.


>
> Second best is amplitude and impedance matching the vario output
> into the aux audio input of the radio (with the bonus, or drawback,
> that the vario output would be muted when receiving or transmitting.
> No Outputting an 8 knot climb audio signal to your struggling
> competitors)

I carry a special instrument for that :)

Cheers

Paul