Turning on/off amplifier with 12v pulse

Thread Starter

jadded

Joined Nov 16, 2019
4
Hello,
i have an audio system with pre-amplifier and power amplifier.
Pre-amplifier have an option to send 12v signal constantly from "trigger out" while turned on.
Power amplifier waits the 12v pulse for no more than 50 milliamps and no longer than about 0.5 second.
One pulse for turn on and one pulse for turning off.
Could you please help me with scheme that generate 12v one pulse on getting 12v in and another pulse when there is no more 12v in?

I saw some older thread while searching, but the pictures are no more available.
 

crutschow

Joined Mar 14, 2008
24,057
Power amplifier waits the 12v pulse for no more than 50 milliamps
Do you mean it requires no more than 50mA?

Below is the LTspice simulation of a Schmitt-trigger XOR circuit that generates a pulse on both the start and end of the input signal.
Since the circuit requires only microamps of current, It's powered from the input signal through Diode D1.

1573951640588.png
 

crutschow

Joined Mar 14, 2008
24,057
thats what i've found in internet about trigger port of power amplifier.
Okay.
The CMOS gate can't provide that amount of current, so would need an added output buffer.

What is the output current/load rating of the preamp trigger out?

Do you have a link to the power amp that shows this input current, since that seems rather high?
 
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Thread Starter

jadded

Joined Nov 16, 2019
4
I didn't find a mention of the input current.

Can you apply 12V to the trigger input and measure the current?
That's to keep the circuit from being more complicated than it may need.
Oh, i think i get it. Will ask friend, to measure it.

About pre-amplifier trigger current - here is a quote from manual:
When connecting a device equipped with a TRIGGER IN jack such as a BD/DVD player to this unit, the device can be turned on or set to standby by interlocking the operation on this unit. When the desired input is selected on the unit, power link operation will be activated with a control signal of maximum 12 V/100 mA from the 12V TRIGGER OUT A jack or maximum 12 V/25 mA when using the 12V TRIGGER OUT B jack. You can select the zone to output the control signal by setting each of the inputs.
• For connection, use a monaural mini plug cable (ø1/8′′/3.5 mm) without resistance. Do not use a stereo mini plug cable.
 
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