12 VDC 4 Channel Adjustable Sequential Controller 37716 RL MPJA.com

Triggered 4 channel sequencer. When triggered, unit will turn on 1st relay (no Delay) followed by the 2nd (Count Up 1-2-3-4). relay after the delay you set (~3-60Sec.) continues as long as trigger is present untill all relays are energized. After all are energized, Releasing trigger reverses the relay sequence (Count Down 4-3-2-1). Removing the trigger at any point in the sequence reverses sequence, reapplying will cause the count to resume at that point in the sequence.
[Power:] 10-15VAC/DC 12V Nominal @ ~400mA
Delay Range: ~3-60Sec.
[Relay:] 4xSPST
Contacts: SPST 30A@250VAC/30VDC
Connections: Terminal Strips

[@feflofeflic]

... this device can be used e. g. in some diy amplifier between a chain of psu, amplifier and speakers... in some cases this device can replace a soft start and speaker protector (2 in 1)...u need to use not momentary, but a permanent switch of course...