Remote Turn-On

Hi, Does anyone have a schematic, kit, or a complete product to sense a line level audio signal and turn a remote power amplifier on? I have done all the searches I can think of and have not found anything. These things can't be that rare!! Thanks...Mike DeAngelis

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Maybe you could use a VOX, a voice activated switch often used in CB and ham radio.

-- DF

Put VS-1 in the search box.

It's a vox kit for $9.95. It can drive a 100 mA load, such as a relay, which can turn the amplifier on/off.

Ed

100mA ! ???

You're kidding right ?

Graham

I doubt many ppl need to do it.

Why not design your own ? It isn't that difficult.

Graham

No. What it is about a 100 mA load that engenders your question?

Ed

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Do you want the amp to stay on until it\'s manually turned off later
or do you want it to turn off automatically some time after the

teach me how my name is sam email snipped-for-privacy@yahoo.com

Naaah! Your name is "Pest" ;-)

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |

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be

Yeah, like they said, a VOX. "Voice-operated transmission".

It seems to google up pretty good.

Have Fun! Rich

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OK. (view in Courier)

                                                     V+

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Oops... Discharging C1 through U1A\'s output transistor without some
sort of current limiting might hurt it.  200 ohms will limit the

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Thanks! :-)

DR1? ;)

C(harge)R(apidly)1 - clever! I would not have thought of it.

Ed

some

Mike DeAngelis wrote:

The audio line activated switch is not VOX as some have claimed- VOX is largely a radio term and describes detecting a few tens of mV or less of microphone output. Your circuit is working off of 100mV,RMS minimum, and up to 2V,RMS, into 10K loading. All you need to do is gain that up, rectify, smooth, and drive a relay. Actually, you don't need to do any of that using a single transistor and a CMOS 555. The circuit below uses a 2N3904 to gain up the line input to a 5Vpp swing at the 555 TRIG input. As long as the 555 receives triggers before the 15u can discharge, which takes about 2 mins, it will remain on keeping the relay activated. No adjustment should be necessary. View in a fixed-width font such as Courier.

. . . . NEUT ------------->

. GND -+----------->

. | . .-----------' . | . (-)---------+ HOT -----o---v . 5V | o--->

. (+)---------|---------. . |100u + | | . +--||-----+ . \\ | | | . \\|--+--||-----+ . \\| 0.1U | | . | -------- . .-----+----+------+---------+---|/ / / / |-. . AUDIO | | | | | -------- | . LINE 0.022u | | +| | +------|--+-||--. | | === [120K] | 1N4001 | . | | [100K] [10M] 15U | | | . | | | | | | TLC555------. | . | [10K] | | | | | VCC/RST | 2N4401 | . | | | | | | | | |/ . | +-[4.7M]-+-| . | | 22p | | | | | | . | +---||---+-----------------|---|TRIG DIS|--. | . | | | | | | | | | . | | | | | | | | | . | | |/ | +---|CONT | | | . | '------|2N3904 | | | | | | . | |> | | | GND | | | . | | | | '-----------' | | . [1M] | | | | | | . | | | [100K] | | | . | | | | | | | . | | | | | | | . | | | | | | | . '--------------+-----------------+-----------+------|-----' . | | | . --- | | . /// '-------------------------' .

6V RMS is not LINE level audio, but it makes no difference- just use a reverse diode in shunt with the input transistor base: View in a fixed-width font such as Courier.

. . . . NEUT ------------->

. GND -+----------->

. | . .-----------' . | . (-)---------+ HOT -----o---v . 5V | o--->

. (+)---------|---------. . |100u + | | . +--||-----+ . \\ | | | . \\|--+--||-----+ . \\| 0.1U | | . | -------- . .-----+----+------+---------+---|/ / / / |-. . AUDIO | | | | | -------- | . LINE 0.022u | | +| | +------|--+-||--. | | === [120K] | 1N4001 | . | | [100K] [10M] 15U | | | . | | | | | | TLC555------. | . | [10K] | | | | | VCC/RST | 2N4401 | . | | | | | | | | |/ . | +-[4.7M]-+-| . | | 22p | | | | | | . | +---||---+-----------------|---|TRIG DIS|--. | . | | | | | | | | | . | | | | | | | | | . | | |/ | +---|CONT | | | . | +------|2N3904 | | | | | | . | | |> | | | GND | | | . | | | | | '-----------' | | . [1M] | 1N4148 | | | | | | . | '--|

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2N7000 or any logic-level MOSFET capable of driving the coil of the
relay.