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Old 28th August 2010, 06:12 PM   #1
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Default power down

Dear all,

I dont want to have my power amplifiers and speakers powered when I am not playing music to save energy. The switch device should both power down

I have found this following circuit Audio Auto Shutoff. Which maybe what I want.

What I want is to have the preamplifier signal switch on the power to the amplifier and the amplifier remain powered for 20-30 mins after the audio signal has stopped, then switch off.

Do people know where I can find other circuits, PCB's, or suppliers of modules for this task?

Regards

Owen

Last edited by owenhamburg; 28th August 2010 at 06:15 PM. Reason: posted before finished
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Old 28th August 2010, 06:24 PM   #2
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Dear all

I also found this audio-signal-controlled-relay-switch-module but it seems that no specifications exist for how long the relay stays powered after the audio signal is removed, any experiences?

Regards

Owen
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Old 28th August 2010, 06:42 PM   #3
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Dear all,

I found Rod Elliott Signal Detecting Auto Power-On Unit but sadly no PCB.

Maybe the triac approach of the first circuit will switch higher powers than a relay. I'm just not sure the first circuit will auto switch on. but if it does it might be the most useful.

Regards

Owen
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Old 28th August 2010, 06:47 PM   #4
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Dear all,

I found another one, again just a circuit not a module.

Relay Switch Activated by Tone and Signal this seems quiet simplistic, and governed by just capacitor discharge.

No luck on finding modules though.

Regards

Owen
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Old 28th August 2010, 07:55 PM   #5
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Rod Elliott's circuit is a good design.
For a longer delay before the amplifier shuts down, increase the value of C4. For a shorter delay, decrease the value of C4.
I prefer to use relays when switching amplifier on and off. Triac's can introduce noise into the circuits.
Why not use Rod's design and build it yourself?
It should be pretty easy to construct.
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Old 28th August 2010, 08:23 PM   #6
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Dear Frank,

I like to use built modules for non sound critical issues if I can find them, as they just work and are simpler and take less time, failing that I like using a tested PCB's as they make a nice solutions.

Making PCB's is for me a little too much expense or effort, so I tend to construct on strip board.

I was hoping that what I would have thought is a standard module as I thought this would be a common requirement for users of power amps. I see this features is now common on active subwoofers.

Since I have some power amplifiers and am consider building a pair of class A amps for my quad ESL63 speakers I would definitely want to switch them off when not in use, and could switch the speakers off too.

Due to the high currents involved in powering amplifiers, particularly class A circuits, I felt for maintenance free, long life A triac would be preferable.

Thank you for the warning on Traic switching making noise, in what form are you thinking? I would imagine this is only when switching if not how is the issue minimized?

Also how can triac switching spikes be minimized?

I may just go with relays as they are suitably simple for me to understand completely.

I imagine that many things such as washing machines, dimmer switches etc will make nasty spikes on the electricity supply anyway. With speaker output protection, delay switch on relays and a regulated power supply could this issue be removed?

Regards

Owen
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Old 29th August 2010, 01:51 PM   #7
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A Triac doesn't pass an undistorted sinewave. There is a little glitch at the point where the current crosses the zero voltage axis. This can cause noise in some sensitive electronics. You can minimize the noise by bypassing the Triac with a suitable capacitor.
Many solid state relays are designed to minimize this crossover noise.
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Old 29th August 2010, 02:02 PM   #8
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Why not modify your source to switch the relay? That way, if the TT stops, or the CD player is powered down, all the rest will follow... The alternative is a big Frankenstein-esque switch on the wall that switches the mains on/off to your system.
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Old 30th August 2010, 11:43 PM   #9
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Default Power saving Hifi.

Dear All,

In the absence of signal, I would like my hifi to shut down, and to restart it with a single push button near the volume control would be all that is needed. From using less than Half a watt I might be able to justify using Class A amplification, which generates a lot of heat energy from electricity. If the amplifier is only powered when they are being used. This is most of the Energy saving needed. So a little more thinking and, I realize its not so simple. But lots of people would like it for example I imagine people doing soft start power for large toroids could do with ordered relay switching of power circuits.

The best way to power down my Hifi would be to detach the speakers, and power down the speakers, then cut the power to my power amplifiers (Endstufe), then the preamp (Vorverstärker), DAC etc. The best way to power up would be the reverse, the preamp, DAC first, then the power amplifiers, then the speakers, then the speakers plug reinserted into the amplifier. The power amplifiers are the other side of the room and the speakers need electricity too so it seems sense they should be closer together. The customizations seem quiet endless.

Has any one got such a device managing their amplifiers?

I think that two of these power off modules would be nice for my speakers and power amps, monitoring the signal input to the power amp level, signal left and right. And switching the power to amplifier and speakers.

Since I would like it to be nice, too switch off the amplifier after the speakers I guess I could extend
Signal Detecting Auto Power-On Unit by Rod Elliott (ESP)

By making combinations of Diode(D1) FET(Q1), capacitor(C4), and resistor charge(R9) discharge(R10) values. multiple relays could be driven with different switch on and off timings relatively cheaply for switching in order 4 relays on start and stop.

this is probably my preferred solution, but I am tempted by the modules being already built to cost but the manual is far from helpful. Ill let you know I have made a decision when I have one.

Regards

Owen
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