Hello,
I'd like to add support for placing the Aleph-X into standby mode where the output mosfets would not conduct any current. Standby would be active during initial power-on of the amps to limit inrush currents but could also be entered afterwards instead of powering off the amps (for short periods of time).
I plan on using an RGB (red in standby, blue during normal operation) momentary anti-vandal switch with associated circuitry (not shown) to generate the standby signal. On power-up, the standby will be active until the switch is pressed. Later presses would enter/exit standby mode.
In the attached schematic, the relay output provides a DISABLE signal that is at V- when in standby, or V+ (via current limiting resistor) when not. This DISABLE signal feeds several PNP transistors that conduct when standby is enabled and, in turn, disable the aleph current source mosfet (Q10) and the output gain mosfet (Q11) via the transistors Qa and Qb, respectively.
The schematic provides 2 options for disabling the output gain mosfet (Q11). The first options just sinks the current from the input stage differential pair. The second option disables the input stage current source and, I think, is along the lines that Nelson has suggested in the past.
Does anyone see any problems with the proposed circuitry? Are there any improvements that can be made and which of the 2 options would be preferred for disabling the output current gain mosfet, Q11?
Much thanks in advance!
Brad
I'd like to add support for placing the Aleph-X into standby mode where the output mosfets would not conduct any current. Standby would be active during initial power-on of the amps to limit inrush currents but could also be entered afterwards instead of powering off the amps (for short periods of time).
I plan on using an RGB (red in standby, blue during normal operation) momentary anti-vandal switch with associated circuitry (not shown) to generate the standby signal. On power-up, the standby will be active until the switch is pressed. Later presses would enter/exit standby mode.
In the attached schematic, the relay output provides a DISABLE signal that is at V- when in standby, or V+ (via current limiting resistor) when not. This DISABLE signal feeds several PNP transistors that conduct when standby is enabled and, in turn, disable the aleph current source mosfet (Q10) and the output gain mosfet (Q11) via the transistors Qa and Qb, respectively.
The schematic provides 2 options for disabling the output gain mosfet (Q11). The first options just sinks the current from the input stage differential pair. The second option disables the input stage current source and, I think, is along the lines that Nelson has suggested in the past.
Does anyone see any problems with the proposed circuitry? Are there any improvements that can be made and which of the 2 options would be preferred for disabling the output current gain mosfet, Q11?
Much thanks in advance!
Brad
if you plan to kill current through input LTP, what is going to work as servo, regulating output DC Offset?
I think it is necessary to have it operative, to cover possible enable/disable transition changes
I think it is necessary to have it operative, to cover possible enable/disable transition changes
Thanks, ZM - i didn't consider that and just assumed that the 30 ohm output resistor would pull outputs to ground. But, how much control will the LTP / servo really have with the output mosfets disabled - i guess there could be a transitory period but most-likely the top and/or bottom mosfets will already have stopped conducting?
one never knows until actual test
you can LTSpice your bum off, and again, proof is in da pudding
in your boots, I'll actually try to shut off "just" Aleph CCS mosfets, trying that in vivo, and to see is input LTP capable to govern that change and shut off mosfets in negative rail
anyhow, have your fun; as long you're testing without load, then with dummy load, I'm pretty sure that everything is safe from gray smoke
you can LTSpice your bum off, and again, proof is in da pudding
in your boots, I'll actually try to shut off "just" Aleph CCS mosfets, trying that in vivo, and to see is input LTP capable to govern that change and shut off mosfets in negative rail
anyhow, have your fun; as long you're testing without load, then with dummy load, I'm pretty sure that everything is safe from gray smoke