That switch on THUMP

[LITTLEWING]

My combo has always done the loud ‘thump’ thing switching on and I can see the speaker visibly jump forwards and return. Can I disconnect the speaker (it has a jack on the rear) before and reconnect after switching on or wouldn’t the amp like it, making sure the master volume is down?

[Bill Fitzmaurice]

That thump is normal, more or less. Better quality amps don't do that. Pulling the plug would be a bad idea if it's 1/4 inch, as that could short the output when you plug it back in and cause serious damage.

[PaulWarning]

one of my Trace amps thumps the other doesn't, I always assumed it was some sort of capacitor fault, it's never damaged the speaker

[Dan Dare]

Take Bill's advice. Better amps don't do that, because they have protection circuitry and a relay which mutes them at switch on until the voltage in the output transistors has stabilised. That circuitry also helps guard against shorts, so if your amp bangs at switch-on, it doesn't have any protection.

[three]

 

On 06/11/2024 at 19:44, PaulWarning said:

one of my Trace amps thumps the other doesn't, I always assumed it was some sort of capacitor fault, it's never damaged the speaker

I've had this with some Trace amps too - especially older models (which were otherwise brilliant!). Thanks @Dan Dare for the explanation - that makes a lot of sense.  I have an Agi DB750 that's entirely quiet as it has diagnostic and protection circuits/relays that are activated at switch on (start up is delayed by around 20 seconds).  I also have powered monitors (ATC) that are perfectly silent at power-up but present a pronounced bump at power-down.  The manual alludes to this and indicates that it's entirely normal and non-problematic.  A bit of a surprise as most of the amps I've used either have almost no (or a relatively small) thump at power down