TonyL wrote:

Eeyore wrote:
TonyL wrote:

Here's a problem that is causing me some grief. I'm rusty with
electronics these days, perhaps the experts in here can give me some
pointers ?

I want to combine the audio outputs of an unspecified number of
op-amps, say 2-20. A simple mixer would do the trick...except I need
the resulting summed audio level to be constant as outputs are
connected to and disconnected from the system.

Absolutely constant ? You need a thing called a hard limiter on the
mixer output.


Not absolutely...reasonably. Limiting has occurred to me but I wanted to
explore other options before I looked at active limiting. Hoping there was
some clever trick that would keep the levels constant such as an adaptation
of the virtual ground idea.

NO !


I know a virtual ground is the standard method to mix audio but
there's another wrinkle here. I also need to send the summed audio
signal to an unspecified number of outputs, between 2 and 20.

You need a distribution amplifier for that.

All readily available off the shelf for a price.


A DA would work if all of the outputs were to branch from a single location.
In the proposed setup, outputs were to be taken from various locations along
a single conductor.

That makes no sense.


The unexpected difficulties may force me to reconsider the "daisy chain"
configuration (which had lots of practical advantages) and go for a central
mixer/distribution amp instead.

I think you need an audio professional.

Graham

TonyL wrote:

A DA would work if all of the outputs were to branch from a single location.
In the proposed setup, outputs were to be taken from various locations along
a single conductor.

If it's a CONDUCTOR, it's doesn't bleeding matter where the outputs are
physically connected you twit.

Holy ****. Talking of which, is this for a Church ?

Graham

"EeySore"
TonyL wrote:

A DA would work if all of the outputs were to branch from a single
location.
In the proposed setup, outputs were to be taken from various locations
along
a single conductor.

If it's a CONDUCTOR, it's doesn't bleeding matter where the outputs are
physically connected you twit.

Holy ****. Talking of which, is this for a Church ?



** What the incredibly stupid OP is trying to make is almost the same as a
" talkback system " - as used by staging technicians et alia for decades.

Each user wears a headset with mic and carries a small box of electronics on
their person - the box plugs into a common XLR mic lead which daisy
chains to the next user and also a MASTER station that contains the PSU.

One of the two lines in the XLR cable is the "common audio buss" and the
other carries DC power - usually +30 volts.

All headsets are constantly active while a user has to push a button to talk
into the system. There is a control for headset volume.

The "common audio buss" is not a virtual earth - but APPROXIMATES one by
being at a low impedance ( maybe 100 ohms) compared to the mic-preamp output
feed resistor inside each user's box.

This avoids significant GAIN changes when boxes are added or removed from
the system, while leaving a usable few mVs of audio on the buss for all the
headset amplifiers.



..... Phil

"TonyL"
Here's a problem that is causing me some grief. I'm rusty with electronics
these days, perhaps the experts in here can give me some pointers ?

I want to combine the audio outputs of an unspecified number of op-amps,
say 2-20. A simple mixer would do the trick...except I need the resulting
summed audio level to be constant as outputs are connected to and
disconnected from the system.


** That is a MASSIVE FASLEHOOD.

You autistic, ****ing pommy idiot.





...... Phil

Phil Allison wrote:

** That is a MASSIVE FASLEHOOD.

You autistic, ****ing pommy idiot.


Got to take some pity on Phil. Sometime in his life someone professional
might have diagnosed him as autistic, and the twit though that *that*
was a useful sounding swear word - with obviously no idea what it meant ...

"widespread abnormalities of social interactions and communication, as
well as severely restricted interests and highly repetitive behavior"

--
Adrian C

"Adrian ****head "


** Another REVOLTING ASD ****ed pommy scumbag.

Peeeeeeeukkkkkkkeeeeee.....




..... Phil

In article , Phil Allison
scribeth thus

"Adrian ****head "


** Another REVOLTING ASD ****ed pommy scumbag.

Peeeeeeeukkkkkkkeeeeee.....




.... Phil








Hey Blue!, why don't you save a lot of bandwidth and bother in having a
go at the whole UK;?....

And the USofA and for that matter the whole world;?...
--
Tony Sayer

"tony sayer"


** Hey - you stupid, abominable pommy porker ****wit.

Oink, oink.......

Squeal, squeal .....





....... Phil

Adrian C wrote:

Phil Allison wrote:

** That is a MASSIVE FASLEHOOD.

You autistic, ****ing pommy idiot.


Got to take some pity on Phil. Sometime in his life
someone professional might have diagnosed him as autistic,
and the twit though that *that* was a useful sounding
swear word - with obviously no idea what it meant ...

"widespread abnormalities of social interactions and
communication, as well as severely restricted interests
and highly repetitive behavior"

Picking on him won't help anybody.

It is much more effective, and more instructive for
everyone, if you point out his technical errors. Just as you
might with anyone else.

Ian

Ian Iveson wrote:
Adrian C wrote:

"widespread abnormalities of social interactions and
communication, as well as severely restricted interests
and highly repetitive behavior"

Picking on him won't help anybody.

It is much more effective, and more instructive for
everyone, if you point out his technical errors. Just as you
might with anyone else.

Using the word "autistic" incorrectly is a technical error of Phil's,
which I'm merely pointing out.

I'm not having a go at him being autistic - heavens no, sorry if it
looked that way. But in the context knowlegabilty of the subject of
electronics, some of the symptoms of that may actually be a benefit once
his "I/O noise" misunderstandings have subsided.

And when they do, meds or whatever, Phils participation is welcome to me
- he is obviously a smart chap ...

And here's worthwhile campaign currently broadcasting around the UK.
http://www.time-to-change.org.uk

--
Adrian C