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Sound card question

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  Sound card question Danny <mynixmail@gmail.com> - 2015-09-30 16:00 +0200
    Re: Sound card question rlharris@oplink.net - 2015-09-30 16:40 +0200
      Re: Sound card question Danny <mynixmail@gmail.com> - 2015-10-01 15:50 +0200
    Re: Sound card question Doug <dmcgarrett@optonline.net> - 2015-09-30 19:50 +0200
      Re: Sound card question Seeker <seeker5528@comcast.net> - 2015-10-01 08:20 +0200
        Re: Sound card question Rob van der Putten <rob@sput.nl> - 2015-10-01 12:10 +0200
          Re: Sound card question Danny <mynixmail@gmail.com> - 2015-10-01 16:00 +0200
            Re: Sound card question Rob van der Putten <rob@sput.nl> - 2015-10-01 18:00 +0200
        Re: Sound card question Danny <mynixmail@gmail.com> - 2015-10-01 16:00 +0200
      Re: Sound card question Danny <mynixmail@gmail.com> - 2015-10-01 16:00 +0200
        Re: Sound card question rlharris@oplink.net - 2015-10-01 17:30 +0200
        Re: Sound card question Doug <dmcgarrett@optonline.net> - 2015-10-01 23:00 +0200
          Re: Sound card question rlharris@oplink.net - 2015-10-02 00:20 +0200
          Re: Sound card question rlharris@oplink.net - 2015-10-02 01:00 +0200
          Re: Sound card question Danny <mynixmail@gmail.com> - 2015-10-02 17:30 +0200
            Re: Sound card question Doug <dmcgarrett@optonline.net> - 2015-10-02 19:20 +0200
              Re: Sound card question rlharris@oplink.net - 2015-10-02 20:40 +0200
                Re: Sound card question Doug <dmcgarrett@optonline.net> - 2015-10-03 00:40 +0200
                  Re: Sound card question rlharris@oplink.net - 2015-10-03 04:20 +0200
                    Re: Sound card question Doug <dmcgarrett@optonline.net> - 2015-10-03 06:30 +0200
            RE: Sound card question "Larry Owens" <owens@netptc.net> - 2015-10-02 19:20 +0200
            Re: Sound card question David Wright <deblis@lionunicorn.co.uk> - 2015-10-02 19:30 +0200
            Re: Sound card question Stuart Longland <stuartl@longlandclan.id.au> - 2015-10-04 01:20 +0200
              Re: Sound card question rlharris@oplink.net - 2015-10-04 02:30 +0200
                Re: Sound card question Stuart Longland <stuartl@longlandclan.id.au> - 2015-10-05 23:00 +0200

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#158465 — Sound card question

Hi guys,

I have a Sigmatel STAC9227 on-board sound card. Everything works fine as it
should. It has the normal Mic , Ext.Speaker and Line-Out jacks.

Currently the Mic and Ext.Speaker plugs are permanently occupied via speaker/mic
headphones (Amateur Radio Stuff) ...

What I would like to know is if it would be possible to send audio that goes to
the headphones to the Line-Out jack at the same time?

Thank You

Danny

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#158468

On Wed, September 30, 2015 8:55 am, Danny wrote:
> What I would like to know is if it would be possible to send audio that
> goes to the headphones to the Line-Out jack at the same time?

I would be surprised that the case is otherwise.  I always install
"pavucontrol" (pulse audio volume control), which may be all you need.

But "jack" can provide any signal routing you need.

A few years back I began using a USB interface for sound on everything. 
This approach allows me to switch the entire sound apparatus from one
machine to another with only a single USB cable, so long as the machine
has a USB port and pavucontrol is installed.  And I no longer have to
worry about the idiosyncrasies of all various on-board sound systems.

One advantage of the USB interface approach to sound is the ability to use
professional (that is, balanced) apparatus, which, by design, eliminates
hum and buzz.  You might find balanced gear advantageous when
radio-frequency interference (RFI) is a consideration.

Entertainment and broadcast supply houses (bswusa.com, fullcompass.com,
markertek.com, bandh.com) stock a variety of economical USB interfaces.

For many in the audio business (podcasting, performance, and audio mixing
and editing), USB sound has obsoleted bus-based sound cards.

The Lexicon Alpha at less than fifty dollars is versatile and reliable,
and is powered from the USB bus.  The Lexicon design (Alpha and Omega)
uses the mixer paradigm, and can accommodate a mix of balanced and
unbalanced inputs and outputs.

RLH

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#158503

I actually ordered a Lexicon Omega for my son on e-Bay 2 weeks ago (still
waiting for delivery ... ;) ) ... however, it is a little overkill for my use
... but thank you anyway for your input ...

>n Sep 30 15, rlharris@oplink.net :
> To: debian-user@lists.debian.org
> Date: Wed, 30 Sep 2015 09:36:15 -0500
> From: rlharris@oplink.net
> Subject: Re: Sound card question
> User-Agent: SquirrelMail/1.5.2 [SVN]
> X-Loop: debian-user@lists.debian.org
> 
> On Wed, September 30, 2015 8:55 am, Danny wrote:
> > What I would like to know is if it would be possible to send audio that
> > goes to the headphones to the Line-Out jack at the same time?
> 
> I would be surprised that the case is otherwise.  I always install
> "pavucontrol" (pulse audio volume control), which may be all you need.
> 
> But "jack" can provide any signal routing you need.
> 
> A few years back I began using a USB interface for sound on everything. 
> This approach allows me to switch the entire sound apparatus from one
> machine to another with only a single USB cable, so long as the machine
> has a USB port and pavucontrol is installed.  And I no longer have to
> worry about the idiosyncrasies of all various on-board sound systems.
> 
> One advantage of the USB interface approach to sound is the ability to use
> professional (that is, balanced) apparatus, which, by design, eliminates
> hum and buzz.  You might find balanced gear advantageous when
> radio-frequency interference (RFI) is a consideration.
> 
> Entertainment and broadcast supply houses (bswusa.com, fullcompass.com,
> markertek.com, bandh.com) stock a variety of economical USB interfaces.
> 
> For many in the audio business (podcasting, performance, and audio mixing
> and editing), USB sound has obsoleted bus-based sound cards.
> 
> The Lexicon Alpha at less than fifty dollars is versatile and reliable,
> and is powered from the USB bus.  The Lexicon design (Alpha and Omega)
> uses the mixer paradigm, and can accommodate a mix of balanced and
> unbalanced inputs and outputs.
> 
> RLH
> 

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#158479

On 09/30/2015 09:55 AM, Danny wrote:
> Hi guys,
>
> I have a Sigmatel STAC9227 on-board sound card. Everything works fine as it
> should. It has the normal Mic , Ext.Speaker and Line-Out jacks.
>
> Currently the Mic and Ext.Speaker plugs are permanently occupied via speaker/mic
> headphones (Amateur Radio Stuff) ...
>
> What I would like to know is if it would be possible to send audio that goes to
> the headphones to the Line-Out jack at the same time?
>
> Thank You
>
> Danny
>
>
Why not just get a Y adapter?

--dm

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#158494

On 9/30/2015 10:39 AM, Doug wrote:
>
>
> On 09/30/2015 09:55 AM, Danny wrote:
>> Hi guys,
>>
>> I have a Sigmatel STAC9227 on-board sound card. Everything works fine 
>> as it
>> should. It has the normal Mic , Ext.Speaker and Line-Out jacks.
>>
>> Currently the Mic and Ext.Speaker plugs are permanently occupied via 
>> speaker/mic
>> headphones (Amateur Radio Stuff) ...
>>
>> What I would like to know is if it would be possible to send audio 
>> that goes to
>> the headphones to the Line-Out jack at the same time?
>>
>> Thank You
>>
>> Danny
>>
>>
> Why not just get a Y adapter?
>
> --dm
>
Ditto on the Y adapter, or some other external solution.

Normal 3 jack hardware would be Pink (Microphone), Green (Audio Out), 
Blue (Line In).

Some hardware implementations do allow some jack functions to be 
changed, but that
may or may not be the case for your specific hardware and if the 
hardware is capable
may or may not be a feature that is implemented in the linux 
driver/mixer software.

Normally if it is an option that is implemented I would expect it to 
show as a toggle in
one of the alsa mixers, possibly in the pulse audio stuff as well, 
similar to the way
'Mic Boost' might show in the mixers when the hardware supports that 
function.

If you do actually have an audio out and a line out and the line out 
doesn't produce
audio when something is plugged into the audio out, it may be an 
indication that it's
a hardwired mechanical function built into the audio out jack to break 
the circuit to the
line out jack when anything is plugged into audio out.

There are a few variables between the capabilities of the audio chip, 
the mixer it is paired
with at the hardware level, the way the jacks are routed to these and 
the way these show
up in the mixer at the software level.

Maybe someone with the same/similar audio hardware will chime in with 
what they see.

Later, Seeker

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#158499

Hi there


Seeker wrote:

<Cut>

> If you do actually have an audio out and a line out and the line out
> doesn't produce
> audio when something is plugged into the audio out, it may be an
> indication that it's
> a hardwired mechanical function built into the audio out jack to break
> the circuit to the
> line out jack when anything is plugged into audio out.

Systems with headphone jack at the front and a line out at the rear, 
will often switch of the the line out off when a headphone is plugged in.
This feature can usually be switched of by means of a jumper on the 
motherboard.
Consult your motherboard documentation.

<Cut>


Regards,
Rob

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#158505

No jumpers on the motherboard ... :( ...

On Oct 01 15, Rob van der Putten :
> To: debian-user@lists.debian.org
> Date: Thu, 01 Oct 2015 12:06:25 +0200
> From: Rob van der Putten <rob@sput.nl>
> Subject: Re: Sound card question
> User-Agent: Mozilla/5.0 (X11; Linux i686; rv:10.0.12) Gecko/20130119
>  Firefox/10.0.11esrpre Iceape/2.7.12
> X-Loop: debian-user@lists.debian.org
> 
> Hi there
> 
> 
> Seeker wrote:
> 
> <Cut>
> 
> >If you do actually have an audio out and a line out and the line out
> >doesn't produce
> >audio when something is plugged into the audio out, it may be an
> >indication that it's
> >a hardwired mechanical function built into the audio out jack to break
> >the circuit to the
> >line out jack when anything is plugged into audio out.
> 
> Systems with headphone jack at the front and a line out at the rear, will
> often switch of the the line out off when a headphone is plugged in.
> This feature can usually be switched of by means of a jumper on the
> motherboard.
> Consult your motherboard documentation.
> 
> <Cut>
> 
> 
> Regards,
> Rob

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#158508

Hi there


Danny wrote:

> No jumpers on the motherboard ... :( ...

Sometimes it's the way the connector is plugged into the motherboard or 
the front panel.
Sometimes it's a BIOS setting.
Look for AC 97.
See;
https://en.wikipedia.org/wiki/Intel_High_Definition_Audio

If all of this fails you need to hack the hardware a bit. See;


Regards,
Rob
-- 
ISDS is evil. Abolish ISDS.

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#158506

I checked alsamixer and have no means to enable/disable channels ... :( ...

On Sep 30 15, Seeker :
> To: debian-user@lists.debian.org
> Date: Wed, 30 Sep 2015 23:10:39 -0700
> From: Seeker <seeker5528@comcast.net>
> Subject: Re: Sound card question
> User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101
>  Thunderbird/38.2.0
> X-Loop: debian-user@lists.debian.org
> 
> 
> 
> On 9/30/2015 10:39 AM, Doug wrote:
> >
> >
> >On 09/30/2015 09:55 AM, Danny wrote:
> >>Hi guys,
> >>
> >>I have a Sigmatel STAC9227 on-board sound card. Everything works fine as
> >>it
> >>should. It has the normal Mic , Ext.Speaker and Line-Out jacks.
> >>
> >>Currently the Mic and Ext.Speaker plugs are permanently occupied via
> >>speaker/mic
> >>headphones (Amateur Radio Stuff) ...
> >>
> >>What I would like to know is if it would be possible to send audio that
> >>goes to
> >>the headphones to the Line-Out jack at the same time?
> >>
> >>Thank You
> >>
> >>Danny
> >>
> >>
> >Why not just get a Y adapter?
> >
> >--dm
> >
> Ditto on the Y adapter, or some other external solution.
> 
> Normal 3 jack hardware would be Pink (Microphone), Green (Audio Out), Blue
> (Line In).
> 
> Some hardware implementations do allow some jack functions to be changed,
> but that
> may or may not be the case for your specific hardware and if the hardware is
> capable
> may or may not be a feature that is implemented in the linux driver/mixer
> software.
> 
> Normally if it is an option that is implemented I would expect it to show as
> a toggle in
> one of the alsa mixers, possibly in the pulse audio stuff as well, similar
> to the way
> 'Mic Boost' might show in the mixers when the hardware supports that
> function.
> 
> If you do actually have an audio out and a line out and the line out doesn't
> produce
> audio when something is plugged into the audio out, it may be an indication
> that it's
> a hardwired mechanical function built into the audio out jack to break the
> circuit to the
> line out jack when anything is plugged into audio out.
> 
> There are a few variables between the capabilities of the audio chip, the
> mixer it is paired
> with at the hardware level, the way the jacks are routed to these and the
> way these show
> up in the mixer at the software level.
> 
> Maybe someone with the same/similar audio hardware will chime in with what
> they see.
> 
> Later, Seeker

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#158504

On Sep 30 15, Doug :
> To: debian-user@lists.debian.org
> Date: Wed, 30 Sep 2015 13:39:16 -0400
> From: Doug <dmcgarrett@optonline.net>
> Subject: Re: Sound card question
> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
>  Thunderbird/38.2.0
> X-Loop: debian-user@lists.debian.org
> 
> 
> 
> On 09/30/2015 09:55 AM, Danny wrote:
> >Hi guys,
> >
> >I have a Sigmatel STAC9227 on-board sound card. Everything works fine as it
> >should. It has the normal Mic , Ext.Speaker and Line-Out jacks.
> >
> >Currently the Mic and Ext.Speaker plugs are permanently occupied via speaker/mic
> >headphones (Amateur Radio Stuff) ...
> >
> >What I would like to know is if it would be possible to send audio that goes to
> >the headphones to the Line-Out jack at the same time?
> >
> >Thank You
> >
> >Danny
> >
> >
> Why not just get a Y adapter?
> 
> --dm

lol ... that never even crossed my mind ...

Using a Y-adapter naturally forces the following question:
Does it effectively split the power/gain into two and I end up with half on one
side and half on the other?

Danny

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#158507

On Thu, October 1, 2015 8:52 am, Danny wrote:
> Using a Y-adapter naturally forces the following question:
> Does it effectively split the power/gain into two and I end up with half
> on one side and half on the other?

A Y-adapter simply parallels two circuits.  There is no splitting as such.

The driving capability of the output circuitry normally is sufficient to
keep the output level nearly constant for any reasonable load.  Headphones
are the worst-case load; the input circuitry of an external amplifier
presents no appreciable load.  So the external amplifier sees whatever
output level results from plugging in the headphones.

RLH

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#158512

On 10/01/2015 09:52 AM, Danny wrote:
> On Sep 30 15, Doug :
>> To: debian-user@lists.debian.org
>> Date: Wed, 30 Sep 2015 13:39:16 -0400
>> From: Doug <dmcgarrett@optonline.net>
>> Subject: Re: Sound card question
>> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
>>   Thunderbird/38.2.0
>> X-Loop: debian-user@lists.debian.org
>>
>>
>>
>> On 09/30/2015 09:55 AM, Danny wrote:
>>> Hi guys,
>>>
>>> I have a Sigmatel STAC9227 on-board sound card. Everything works fine as it
>>> should. It has the normal Mic , Ext.Speaker and Line-Out jacks.
>>>
>>> Currently the Mic and Ext.Speaker plugs are permanently occupied via speaker/mic
>>> headphones (Amateur Radio Stuff) ...
>>>
>>> What I would like to know is if it would be possible to send audio that goes to
>>> the headphones to the Line-Out jack at the same time?
>>>
>>> Thank You
>>>
>>> Danny
>>>
>>>
>> Why not just get a Y adapter?
>>
>> --dm
>
> lol ... that never even crossed my mind ...
>
> Using a Y-adapter naturally forces the following question:
> Does it effectively split the power/gain into two and I end up with half on one
> side and half on the other?
>
> Danny
>
>
I believe that the output of the headphone jack is not impedance matched--I expect it's just
a voltage source. Wat's more, unless you are plugging the same low-impedance devices into
both Y outputs, _and_ the source is impedance matched, you would not split the power
equally. I don't know what you want to do with the second output, but it's more
than likely a relatively high impedance, so it would not load the circuit at all.
I could be wrong, but it seems logical to me.

--doug

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#158515

On Thu, October 1, 2015 3:57 pm, Doug wrote:
> I believe that the output of the headphone jack is not impedance
> matched--I expect it's just a voltage source. Wat's more, unless you are
> plugging the same low-impedance devices into both Y outputs, _and_ the
> source is impedance matched, you would not split the power equally. I
> don't know what you want to do with the second output, but it's more than
> likely a relatively high impedance, so it would not load the circuit at
> all. I could be wrong, but it seems logical to me.

With consumer electronics, the source (LINE OUTPUT) typically is of
low impedance, say ten to a hundred Ohms.  And the load (LINE INPUT)
typically is of high impedance, say a thousand to a hundred thousand
Ohms.  Consequently, loading is not a concern: the load cannot draw
sufficient current to affect the source.

Loads typically are connected in parallel one with the other, so no
"splitting" or voltage divider is involved, as would be the case if
loads were connected in series one with the other.

In consumer audio gear, (1) the HEADPHONE output may be driven by a
buffer amplifier stage which is driven from the LINE OUTPUT stage.
The buffer stage typically is able to provide a hundred milliAmperes
or so into any reasonable headphone load.  With this arrangement, even
a dead short across the output terminals of the buffer amplifier
should not affect the LINE OUTPUT.

But it may be that (2) the LINE OUTPUT and HEADPHONE jacks are
connected in parallel, one with the other, across a single output
stage.  Again, the output stage is going to be an amplifier which is able to
provide a hundred milliAmperes or so into any reasonable headphone
load.

So, whatever the case, connecting headphones to the HEADPHONE jacks
should not cause a lower level of the LINE OUTPUT.

RLH

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#158517

On Thu, October 1, 2015 3:57 pm, Doug wrote:
> What's more, unless you are
> plugging the same low-impedance devices into both Y outputs, _and_ the
> source is impedance matched, you would not split the power equally.

(This is an addendum to my previous reply)

There is no "splitting" of power.  Whatever device is connected to the
LINE OUTPUT jack looks only at the output voltage, and from that voltage
generates whatever power is required.  In other words, the function of a
LINE OUTPUT is to provide a voltage signal, and NOT to transfer power.

Almost always, the power-handling capability of a pair of headphones is
small in comparison with the power available from the output stage of a
computer sound card or a USB audio interface.

While a speaker in an enclosure may need a hundred Watts to provide
adequate loudness in a room, a pair of headphones typically requires only
a thousandth of that power, which is to say, only a few hundred milliWatts
per channel.  And a single garden-variety transistor stage (or today, an
integrated circuit) easily can provide that much power.

Here is the URL of a RANE corporation application note which provides and
excellent discussion of the matter: 
http://www.rane.com/pdf/old/note100.pdf

RLH

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#158520

> I believe that the output of the headphone jack is not impedance matched--I expect it's just
> a voltage source. Wat's more, unless you are plugging the same low-impedance devices into
> both Y outputs, _and_ the source is impedance matched, you would not split the power
> equally. I don't know what you want to do with the second output, but it's more
> than likely a relatively high impedance, so it would not load the circuit at all.
> I could be wrong, but it seems logical to me.
> 
> --doug

O.k ... let me explain why I asked the question for the sake of satisfying any
curiosity:

I have EchoLink (Ham Radio VOIP) connected to Jessie like this:

VHF Transceiver (with two interface cables going to the MIC and LINE-OUT jacks
on the back of an internal sound card. Incoming audio (radio frequency) 
goes through the antenna ... through the transciever ... to the sound
card (via the MIC interface cable) ... it gets processed by the sound card and
stuff happens on VOIP ... Because the VHF transceiver is effectively turned into a 
repeater NO transmit or recieve audio can be heard on the transciever itself 
(as it should be).

In order to hear comms coming in or out of the transciever (via an antenna) one
has to connect to the transciever with ANOTHER transciever in order to hear
people talk (if you are tuned to the same frequency off course)

Now ... my second transciever is fitted inside my car ... in order for me to
hear all comms on the frequency I need to go to my car and turn that transciever
on every now and then which becomes a pain in the donkey ... ;) ...

In order for me NOT to make a trip to the car every 10 minutes I though of
splitting the LINE-OUT and add a normal set of desktop speakers.

So ... I was just wondering if I will have any losses (in whatever form) when I
"split" the signal ... keep in mind that the audio signals processed by the sound
card should be strong and reliable ...

Thank You

Danny

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#158523

On 10/02/2015 11:27 AM, Danny wrote:
>> I believe that the output of the headphone jack is not impedance matched--I expect it's just
>> a voltage source. Wat's more, unless you are plugging the same low-impedance devices into
>> both Y outputs, _and_ the source is impedance matched, you would not split the power
>> equally. I don't know what you want to do with the second output, but it's more
>> than likely a relatively high impedance, so it would not load the circuit at all.
>> I could be wrong, but it seems logical to me.
>>
>> --doug
>
> O.k ... let me explain why I asked the question for the sake of satisfying any
> curiosity:
>
> I have EchoLink (Ham Radio VOIP) connected to Jessie like this:
>
> VHF Transceiver (with two interface cables going to the MIC and LINE-OUT jacks
> on the back of an internal sound card. Incoming audio (radio frequency)
> goes through the antenna ... through the transciever ... to the sound
> card (via the MIC interface cable) ... it gets processed by the sound card and
> stuff happens on VOIP ... Because the VHF transceiver is effectively turned into a
> repeater NO transmit or recieve audio can be heard on the transciever itself
> (as it should be).
>
> In order to hear comms coming in or out of the transciever (via an antenna) one
> has to connect to the transciever with ANOTHER transciever in order to hear
> people talk (if you are tuned to the same frequency off course)
>
> Now ... my second transciever is fitted inside my car ... in order for me to
> hear all comms on the frequency I need to go to my car and turn that transciever
> on every now and then which becomes a pain in the donkey ... ;) ...
>
> In order for me NOT to make a trip to the car every 10 minutes I though of
> splitting the LINE-OUT and add a normal set of desktop speakers.
>
> So ... I was just wondering if I will have any losses (in whatever form) when I
> "split" the signal ... keep in mind that the audio signals processed by the sound
> card should be strong and reliable ...
>
> Thank You
>
> Danny
>
>
You didn't mention that you want to add _speakers_. You might need a small amplifier
after the Y-adapter, since the speakers will be low impedance--4- or 8 ohms.
Visit  ramseykits.com  and find some small audio amplifiers in kit or assembled
form. They are probably overkill for your purpose, but cheap enough. A 14W stereo
kit, CK154, will run on 12 to 16 VDC at 1A. $26 for a kit, or $34 assembled. You
provide an enclosure and a wall-wart to drive it. (The "14W" rating is for 7W per
channel, and I would expect that it's a peak rating, since 16V at 1A is 16 Watts
_input_ power! I would guess that rms power is more like 2 or 3 Watts per channel.)

I just noticed a smaller one in ramsey: CK122 $20 for the kit, $26 assembled.
0.5W per channel into 4 ohms. Runs on 6VDC. Probably enough for your purposes.

There are other small amplifier sources--check on Google.

--doug  

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#158527

On Fri, October 2, 2015 12:10 pm, Doug wrote:
> You didn't mention that you want to add _speakers_. You might need a
> small amplifier after the Y-adapter, since the speakers will be low
> impedance--4- or 8 ohms. Visit  ramseykits.com  and find some small audio
> amplifiers in kit or assembled form. They are probably overkill for your
> purpose, but cheap enough. A 14W stereo kit, CK154, will run on 12 to 16
> VDC at 1A. $26 for a kit, or $34 assembled. You
> provide an enclosure and a wall-wart to drive it. (The "14W" rating is for
> 7W per
> channel, and I would expect that it's a peak rating, since 16V at 1A is 16
> Watts
> _input_ power! I would guess that rms power is more like 2 or 3 Watts per
> channel.)


In this context, mis-use of terms "impedance" and "power" is adding
nothing but confusion.

A pair of powered desktop speakers designed to plug into the output port
of a computer is a commodity item which can be purchased for about twenty
dollars at any computer store.  Everything is packaged nicely and there is
a volume control, a tone control, and a power supply which plugs into a
120V wall receptacle; the power output is several Watts.  The load which
these amplified speakers present to the audio source (computer,
transceiver, or whatever) is in the range of ten thousand Ohms to a
hundred thousand Ohms; in other words, the speakers present no significant
load on any audio line to which they are connected.

RLH

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#158529

On 10/02/2015 02:36 PM, rlharris@oplink.net wrote:
> On Fri, October 2, 2015 12:10 pm, Doug wrote:
>> You didn't mention that you want to add _speakers_. You might need a
>> small amplifier after the Y-adapter, since the speakers will be low
>> impedance--4- or 8 ohms. Visit  ramseykits.com  and find some small audio
>> amplifiers in kit or assembled form. They are probably overkill for your
>> purpose, but cheap enough. A 14W stereo kit, CK154, will run on 12 to 16
>> VDC at 1A. $26 for a kit, or $34 assembled. You
>> provide an enclosure and a wall-wart to drive it. (The "14W" rating is for
>> 7W per
>> channel, and I would expect that it's a peak rating, since 16V at 1A is 16
>> Watts
>> _input_ power! I would guess that rms power is more like 2 or 3 Watts per
>> channel.)
>
>
> In this context, mis-use of terms "impedance" and "power" is adding
> nothing but confusion.
>

I have no quarrel with the advice that follows, but I do not understand the
comment above.

Speakers are rated for the _imppedance_ they present to the amplifier
which drives them. Impedance is defined as R+jX, where R is resistance
and X is reactance, which can be either negative (capacitive) or positive (inductive),
and appears on the imaginary (y) axis of a rectangular graph, thus the j term.

Power is always expressed in Watts, and is defined as current times voltage, or
in engineering terms, P = IE. I is current in Amps, E is voltage in Volts.
The voltage is either DC, or the RMS value of an AC waveform. [j = sqrt (-1)]
The "120 volts" coming out of a wall outlet is an RMS value of voltage.
(RMS value of a sinusoidal waveform equals 0.7071 times the peak value.)

So, power can mean AC audio power sent to a loudspeaker, (or AC power from
a wall outlet sent to whatever device it powers),or DC power sent to
some load, such as a flash-light bulb, the supply for an amplifier, or whatever.
Nowadays, that DC power is frequently obtained from a module that plugs into
a wall outlet, commonly called a wall-wart. DC power can also be obtained
from batteries or from the lighter socket of your automobile.

--doug


> A pair of powered desktop speakers designed to plug into the output port
> of a computer is a commodity item which can be purchased for about twenty
> dollars at any computer store.  Everything is packaged nicely and there is
> a volume control, a tone control, and a power supply which plugs into a
> 120V wall receptacle; the power output is several Watts.  The load which
> these amplified speakers present to the audio source (computer,
> transceiver, or whatever) is in the range of ten thousand Ohms to a
> hundred thousand Ohms; in other words, the speakers present no significant
> load on any audio line to which they are connected.
>
> RLH
>
>
>

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#158531

On Fri, October 2, 2015 5:34 pm, Doug wrote:
>> In this context, mis-use of terms "impedance" and "power" is adding
>> nothing but confusion.
>
> I have no quarrel with the advice that follows, but I do not understand
> the comment above.

Doug,

As I recall, the thread began with the need to monitor the audio signal
being fed into a transceiver from the headphone-level audio output of a
computer.  Specifically, the question was whether a Y-adapter would
suffice.

In this application, the Y-adapter connects in parallel the input of the
transceiver and the input of the powered speaker system.  We immediately
get into trouble if we say "load" instead of "input", because the term
"load" implies a transfer of power, and in this application there is no
transfer of power from the computer output to either the transceiver or
the speaker system.

The most simple, natural, and common solution is to use an inexpensive
(about twenty-dollars) set of powered speakers.  The term "powered
speaker" commonly is used for an integrated unit which consists of
speakers (left and right), amplifier(two-channel), and power supply.  The
input (whether jack or cable with a 3.5mm stereo phone plug) of a powered
speaker has an impedance in the range of 10,000 Ohms to 100,000 Ohms; this
is for each channel.  Such a high impedance is all but invisible to the
output of the computer, because the output of the computer is designed to
pump 10 to 20 milliWatts into a pair of 8 Ohm earbuds.

So we take a functional system (the computer output feeding a signal into
a transceiver) and connect in parallel the powered speaker, which adds to
the computer output an almost-invisible load.  And, like the powered
speaker system, the transceiver input has a high impedance.  So,
essentially, the computer HEADPHONE output (which has a very low
impedance) is running unloaded.

The power consumed by the speaker mechanism (which consists of voice coil,
magnet, and paper cone) is of no concern to us, for that power is
furnished entirely by the power supply which plugs into the 120V
receptacle.

Inasmuch as powered computer speaker systems are a commodity item (twenty
dollars), there really is no incentive to purchase components and build
anything.

RLH

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#158532

On 10/02/2015 10:18 PM, rlharris@oplink.net wrote:
> On Fri, October 2, 2015 5:34 pm, Doug wrote:
>>> In this context, mis-use of terms "impedance" and "power" is adding
>>> nothing but confusion.
>>
>> I have no quarrel with the advice that follows, but I do not understand
>> the comment above.
>
> Doug,
>
> As I recall, the thread began with the need to monitor the audio signal
> being fed into a transceiver from the headphone-level audio output of a
> computer.  Specifically, the question was whether a Y-adapter would
> suffice.
>
> In this application, the Y-adapter connects in parallel the input of the
> transceiver and the input of the powered speaker system.  We immediately
> get into trouble if we say "load" instead of "input", because the term
> "load" implies a transfer of power, and in this application there is no
> transfer of power from the computer output to either the transceiver or
> the speaker system.
>
> The most simple, natural, and common solution is to use an inexpensive
> (about twenty-dollars) set of powered speakers.  The term "powered
> speaker" commonly is used for an integrated unit which consists of
> speakers (left and right), amplifier(two-channel), and power supply.  The
> input (whether jack or cable with a 3.5mm stereo phone plug) of a powered
> speaker has an impedance in the range of 10,000 Ohms to 100,000 Ohms; this
> is for each channel.  Such a high impedance is all but invisible to the
> output of the computer, because the output of the computer is designed to
> pump 10 to 20 milliWatts into a pair of 8 Ohm earbuds.
>
> So we take a functional system (the computer output feeding a signal into
> a transceiver) and connect in parallel the powered speaker, which adds to
> the computer output an almost-invisible load.  And, like the powered
> speaker system, the transceiver input has a high impedance.  So,
> essentially, the computer HEADPHONE output (which has a very low
> impedance) is running unloaded.
>
> The power consumed by the speaker mechanism (which consists of voice coil,
> magnet, and paper cone) is of no concern to us, for that power is
> furnished entirely by the power supply which plugs into the 120V
> receptacle.
>
> Inasmuch as powered computer speaker systems are a commodity item (twenty
> dollars), there really is no incentive to purchase components and build
> anything.
>
> RLH
>
>
>
Ok, I think we are not fighting over anything. I did not assume speakers
as the destination when I suggested a Y adapter. _Then_ the OP said he wanted
speakers. I did not assume, as you apparently did, that he was thinking of
powered computer speakers. With the exception of some Logitech powered
speaker systems, practically all others are junk, with no attempt at
fidelity. So I would not immediately think of "computer speakers."
And yes, the input impedance of any of such systems is at least a
couple of K-ohms, and will not load the Y adapter. Another responder,
as you no doubt know, suggested an old boom-box with an external audio
input jack. That might be the simplest answer of all, if there's one kicking
around somewhere.

Cheers--doug

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