I have a pair of ATC SCA50 active speakers. They make a great sound but the
amplifiers run all the time, even when there's no signal to amplify. Since
they run in class A there is a significant current draw 24/7. As they are
at opposite sides of the room, turning them off involves two switches and
doesn't get done unless we're going away.

My previous Bowers Active 1s had an audio signal sensor in each speaker so
they went onto standby mode if there was no audio and "woke up" when audio
was present. Given the cost of running the ATCs all the time I'd like to do
the same with them.

There obviously needs to be a "switch off" delay so that the speakers don't
power down in quiet passages.

Do any of you experts know if something like the Velleman 4700 would do the
job? Or of any other circuit? I'm perfectly happy assembling something but
I'm no circuit designer.

Thanks in advance.

In article ,
Norman Billingham norman.at.tumulus.org.uk wrote:

Do any of you experts know if something like the Velleman 4700 would do
the job? Or of any other circuit? I'm perfectly happy assembling
something but I'm no circuit designer.

Not without considerable modification. It provides an initial delay at
switch on to prevent a 'thump' while the amp settles, and then checks for
excessive DC on the line which could destroy a speaker. You need an low
level AC sensing device which will switch mains. I'm not even sure the
relays in that kit would be suitable.

Haven't got time to look now as I'm about to go out, but Jaycar might well
do a kit which is just the job.

--
*Change is inevitable, except from a vending machine*

Dave Plowman London SW
To e-mail, change noise into sound.

In article , Norman
Billingham
norman.at.tumulus.org.uk wrote:
I have a pair of ATC SCA50 active speakers. They make a great sound but
the amplifiers run all the time, even when there's no signal to
amplify. Since they run in class A there is a significant current draw
24/7. As they are at opposite sides of the room, turning them off
involves two switches and doesn't get done unless we're going away.

Do any of you experts know if something like the Velleman 4700 would do
the job? Or of any other circuit? I'm perfectly happy assembling
something but I'm no circuit designer.

The simplest approach might be the best. In situations like these I just
use a switched mains disribution board, or a board with a 'torpedo' switch.
Choose a board with an indicator if the ATCs don't have any. This way you
can switch the preamp/source on and off at the same time if you want.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Norman Billingham wrote:

Thanks in advance.


Not quite automatic but a possible workaround and free:
http://www.freegreengadgets.co.uk/

On Sun, 12 Sep 2010 09:14:34 +0100, Norman Billingham wrote:

I have a pair of ATC SCA50 active speakers. They make a great sound but
the amplifiers run all the time, even when there's no signal to amplify.
Since they run in class A there is a significant current draw 24/7. As
they are at opposite sides of the room, turning them off involves two
switches and doesn't get done unless we're going away.

My previous Bowers Active 1s had an audio signal sensor in each speaker
so they went onto standby mode if there was no audio and "woke up" when
audio was present. Given the cost of running the ATCs all the time I'd
like to do the same with them.

There obviously needs to be a "switch off" delay so that the speakers
don't power down in quiet passages.

Do any of you experts know if something like the Velleman 4700 would do
the job? Or of any other circuit? I'm perfectly happy assembling
something but I'm no circuit designer.

I had a similar problem and solved it using cheap radio controlled
switches, Maplin part number N79FN. These are currently five pounds each.
If you have a pair and set both to the same channel, you could turn both
speakers off and on at the same time.

This is not an automatic solution, but it should be both cheap and
effective.

Norman Billingham wrote:

I have a pair of ATC SCA50 active speakers. They make a
great sound but the amplifiers run all the time, even when
there's no signal to amplify. Since they run in class A
there is a significant current draw 24/7. As they are at
opposite sides of the room, turning them off involves two
switches and doesn't get done unless we're going away.

My previous Bowers Active 1s had an audio signal sensor in
each speaker so they went onto standby mode if there was
no audio and "woke up" when audio was present. Given the
cost of running the ATCs all the time I'd like to do the
same with them.

There obviously needs to be a "switch off" delay so that
the speakers don't power down in quiet passages.

Do any of you experts know if something like the Velleman
4700 would do the job? Or of any other circuit? I'm
perfectly happy assembling something but I'm no circuit
designer.

Thanks in advance.

Do you turn the rest of your audio system off, or does it go
into standby? Jim or Chris have suggested clear solutions if
you habitually switch another part of the system off.

If the rest of your system is left on standby, and you are
into a bit of assembly, it should be possible to tie a mains
switch for the speakers to the standby function somehow.
Possibly easiest would be to use the standby indicator light
to trigger a simple logic circuit, and take a strong
low-voltage signal from there to a 5V mains relay or SCR in
each speaker. If this results in power-up or -down thumps or
whatever, things could end up a bit more complicated.

A switch that would sense an audio signal and make a
decision would require a "watchdog" timer. Every time it
senses a signal it would reset itself, otherwise it would
time out and shut down the system. Not particularly hard to
do, although preventing it from interacting with the audio
signal in a bad way may be a bit tricky, considering you
would need it to interact...

If it were dead easy, the speaker makers would have done it
I suppose.

Ian

not an expert

"Ian Iveson" wrote in message
...
Norman Billingham wrote:

I have a pair of ATC SCA50 active speakers. They make a great sound but
the amplifiers run all the time, even when there's no signal to amplify.
Since they run in class A there is a significant current draw 24/7. As
they are at opposite sides of the room, turning them off involves two
switches and doesn't get done unless we're going away.

My previous Bowers Active 1s had an audio signal sensor in each speaker
so they went onto standby mode if there was no audio and "woke up" when
audio was present. Given the cost of running the ATCs all the time I'd
like to do the same with them.

There obviously needs to be a "switch off" delay so that the speakers
don't power down in quiet passages.

Do any of you experts know if something like the Velleman 4700 would do
the job? Or of any other circuit? I'm perfectly happy assembling
something but I'm no circuit designer.

Thanks in advance.

Do you turn the rest of your audio system off, or does it go into standby?
Jim or Chris have suggested clear solutions if you habitually switch
another part of the system off.

If the rest of your system is left on standby, and you are into a bit of
assembly, it should be possible to tie a mains switch for the speakers to
the standby function somehow. Possibly easiest would be to use the standby
indicator light to trigger a simple logic circuit, and take a strong
low-voltage signal from there to a 5V mains relay or SCR in each speaker.
If this results in power-up or -down thumps or whatever, things could end
up a bit more complicated.

A switch that would sense an audio signal and make a decision would
require a "watchdog" timer. Every time it senses a signal it would reset
itself, otherwise it would time out and shut down the system. Not
particularly hard to do, although preventing it from interacting with the
audio signal in a bad way may be a bit tricky, considering you would need
it to interact...

If it were dead easy, the speaker makers would have done it I suppose.

Ian

not an expert



Thanks to everyone for some useful suggestions. I think I'll look into the
Maplins remote switching power units first though it will be yet another
remote on the coffee table!

I guess I coudl access the circuit diagrams for the old Bowers units and
copy those but that's a more complex path.

Anyway - thanks again to all