O.K. here I go, I'll keep this as simple as I can and be glad to answer
questions.
List owner, please bug me if you think this is too "OT" for the list.
first, it is likely that using an adapter between two audio outputs E.G.
sound cards etc. and powered speakers will work fine, however there is some
chance that capacitors usually used between amplifier chips and the hot
output terminals could be damaged if the two signals occur concurrently and
if the peak voltages end up reverse polarizing one of these capacitors.
They're "electrolytic" caps and thus are polarized, allow voltage on them in
only one direction.
it's an unlikely event, but should one of these "blocking caps" become
damaged, it could short and possibly damage the sound chip.
So the simplest solution is a resistive mixer that will let the two outputs
operate independently of each other with both signals feeding the powered
speakers.
You can build it with fixed volume or with pots so each Chanel of each
stereo signal can be independently adjusted.
You need three 1/8th inch (3.5MM stereo jacks 8 small resistors and some
kind of box. that's for the fixed volume design. If you want adjustable
volume you need four potentiometers and four resistors.
What, you ask, what value resistors and pots? It almost doesn't matter,
they can be between 10K ohms and 30K ohms, but should be all the same.
Each jack should have three terminals, tip, ring and sleeve. Try not to buy
jacks with internal switches, like those used to switch out a speaker when
headphones are plugged in It can be a real bear to trace out which terminals
do what on many of those switched jacks.
So you have two input jacks and one output jack. Of course you can build as
many inputs as you like.
The sleeve terminals on all jacks are wired together and are "ground.
On each input jack, the tip and ring contacts go to one end of each of two
resistors. The other ends of these resistors go to tip and ring contacts on
the output jack such that each input tip goes through a resistor to the
output tip contact. Same with the rings. Now there are two resistors on
each of tip and ring of the output jack.
Now on the output jack, a resistor is connected between tip and sleeve and
another between ring and sleeve.
This gives each Chanel of each input a 2/1 resistive divider with the
center of the divider being the output.
I'll stop there having I hope given you the idea. Those of you with some
electronics in your blood can probably figure out the adjustable version.,
but again if there is interest, I'll go through it and try to answer any
questions.
Tom Fowle
On each input jack,
On Sun, Aug 07, 2016 at 06:46:56AM -0400, Angelo Sonnesso wrote:
Sounds like a nice building project.===========================================================
I am interested.
73 N2DYN Angelo
-----Original Message-----
From: raspberry-vi-bounce@xxxxxxxxxxxxx
[mailto:raspberry-vi-bounce@xxxxxxxxxxxxx] On Behalf Of Tom Fowle
Sent: Saturday, August 06, 2016 10:25 PM
To: raspberry-vi@xxxxxxxxxxxxx
Subject: [raspberry-vi] Re: Pulse solid, opinions sought
Mike,
from my viewpoint this sounds good as for now I don't need desktop speech
and would preferr console speech using the on-board audio out jack.
As a small project for anybody who wants both sources of speech to use the
same speakers/headphones, it's pretty easy to bung together a mixer that
goes between low level audi o out from two or more sources and amplified
(powered) speakers. A really good soldering practice project as it requires
no "board" and uses just jacks and pots.
Anybodyinterested ask and I'll put together a text discription of how to do
it.
Thanks for all your great work Mike and all.
tom Fowle
On Sat, Aug 06, 2016 at 11:15:00PM +0100, Mike Ray wrote:
Hello again.Foundation.
I have now tried using pulseaudio in the Mate desktop on the Pi and it
is very solid. It does not cause the same crash as we were seeing
with speech-dispatcher set up to use ALSA.
What is more is you don't get that nasty effect of the voice talking
over itself when you scroll rapidly down the menus.
But...
As I have explained elsewhere, when speech-dispatcher uses pulseaudio,
once you have logged in to the desktop, console speech stops because
espeak "sees" that pulse is running and tries to use it, but because
espeakup is running as root and pulseaudio is not, the result is a
silent console.
However, we have already solved this partly with my OMX audio code,
which we know does not stutter and does not use the ALSA driver, or
pulseaudio.
So, I can configure the Raspbian Mate image to:
1. Use a USB dongle and pulseaudio with speech-dispatcher in the desktop.
2. My OMX audio code in the console.
However, this does mean that console speech will come out of whatever
you have plugged in to either the analogue jack or the HDMI port while
desktop speech comes out of the USB dongle.
I think this is a small price to pay for what will be a very solid
speech experience in both.
What do people think?
Mike
--
Michael A. Ray
Analyst/Programmer
Witley, Surrey, South-east UK
Eyes-free Linux:
http://eyesfreelinux.ninja/
Raspberry VI:
http://www.raspberryvi.org/
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Administrative contact: <mike.ray@xxxxxxxxxxxxxx>
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Raspberry Pi and the Raspberry Pi logo are trademarks of the Raspberry Pi
and attitudes expressed by the subscribers to this list do not reflect those
This list is not affiliated to the Raspberry Pi Foundation and the views
of the Foundation.
===========================================================
Mike Ray, list creator, January 2013
The raspberry-vi mailing list
Archives: //www.freelists.org/archives/raspberry-vi
Administrative contact: <mike.ray@xxxxxxxxxxxxxx>
-----------------------------------------------------------
Raspberry Pi and the Raspberry Pi logo are trademarks of the Raspberry Pi
Foundation.
This list is not affiliated to the Raspberry Pi Foundation and the views and
attitudes expressed by the subscribers to this list do not reflect those of
the Foundation.
Mike Ray, list creator, January 2013
===========================================================
The raspberry-vi mailing list
Archives: //www.freelists.org/archives/raspberry-vi
Administrative contact: <mike.ray@xxxxxxxxxxxxxx>
-----------------------------------------------------------
Raspberry Pi and the Raspberry Pi logo are trademarks of the Raspberry Pi
Foundation.
This list is not affiliated to the Raspberry Pi Foundation and the views and
attitudes expressed by the subscribers to this list do not reflect those of
the Foundation.
Mike Ray, list creator, January 2013
