Take two mono pre or power amplifiers, each with their own power on/off switch. For the simplicity it is assumed the two amplifiers are in the same case. They are wired as 2 x mono; only and directly connected by ground via the case.
A classic approach to add a volume control is to add a mono potmeter of appropriate value to each amplifier. Instead of a standard potmeter, also a relay controlled volume pot or a digital volume control can be installed. As with a standard potmeter, a relay controlled volume pot will always be connected at some resistive value.
Still a challenge emerges, as a separate power supply for the volume control is required: how to activate the power supply for the relay controlled volume unit? Options are:
a. add a separate mains on/off switch for the volume control, and always turn this on first before turning on the amplifiers. The mains switch may even be always ‘On’ so the volume control is continuously in ready state.
b. connect the power supply to the power on/off switch of one of the amplifiers.
c. create a current induced mains on/off sensor after both of the mains switches of the amplifier. This sensor then will activate the power supply of the volume control. This way whichever amplifier is turned on, the volume control will switch on automatically.
Question 1:
Do you have experience with one of the above options, or maybe with another option?
Question 2:
The option c. for a current sensor at the mains of both amplifiers is appealing. However, a search on this forum and on internet did not yield yet any suggestion.
Do you have a pointer for a design?
A classic approach to add a volume control is to add a mono potmeter of appropriate value to each amplifier. Instead of a standard potmeter, also a relay controlled volume pot or a digital volume control can be installed. As with a standard potmeter, a relay controlled volume pot will always be connected at some resistive value.
Still a challenge emerges, as a separate power supply for the volume control is required: how to activate the power supply for the relay controlled volume unit? Options are:
a. add a separate mains on/off switch for the volume control, and always turn this on first before turning on the amplifiers. The mains switch may even be always ‘On’ so the volume control is continuously in ready state.
b. connect the power supply to the power on/off switch of one of the amplifiers.
c. create a current induced mains on/off sensor after both of the mains switches of the amplifier. This sensor then will activate the power supply of the volume control. This way whichever amplifier is turned on, the volume control will switch on automatically.
Question 1:
Do you have experience with one of the above options, or maybe with another option?
Question 2:
The option c. for a current sensor at the mains of both amplifiers is appealing. However, a search on this forum and on internet did not yield yet any suggestion.
Do you have a pointer for a design?
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2 more relays with 230V coil are switched by the amp power switches.
the contacts in parallel can then switch on the transformer for the attenuator.
the contacts in parallel can then switch on the transformer for the attenuator.
Thanks, Bansuri,
The contacts of the two extra relays in parallel, so either way the amplifiers are switched on the power supply of the volume control is activated.
The contacts of the two extra relays in parallel, so either way the amplifiers are switched on the power supply of the volume control is activated.