Combining vario and radio output into one speaker

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

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...ny85-use-hints

OK, I'm being silly.

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...ny85-use-hints

OK, I'm being silly.

--
Dan Marotta

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...ny85-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?

:-)

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

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

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

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

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