Amps that POP

[atomicAdam]

So - curious - I remember reading in one of Van Alstines old news letters that amps that *POP* when turning off and on have an out of wack bass and that they are pumping up the bass of the music.

Anyways - curious what you think about amps that POP when you turn them on/off.

I can say - for myself - I find it super irritating and probably wouldn't by one that did such a thing.

What do you all think?

-adam

[Ajani]

I have no idea whether the pop would affect the sound quality, but I'm sure it would annoy me every time I turned the amp on/off...

[Hyfi]

Not sure about the POP, but my sub Woofs when everything gets powered down. I'm not sure if its the amp or my pre causing it. I have a single cable coming from one side of my pre outs.

[Poultrygeist]

One thing I don't like about Tripath amps is they pop when turned on and again when turned off. HE speakers make it even worse.

[Feanor]

I have no idea whether the pop would affect the sound quality, but I'm sure it would annoy me every time I turned the amp on/off...

A lot of equipment "pops" on start-up, and a lot of amps "thump".

As I understand there are multiple causes all having to do with providing or withdrawing "juice" to the circuits.

On startup and/or shutdown I gather a lot of circuits, including preamps, create pops, crackles, etc. Timed relay circuits are sometimes used to mute these sounds.

On startup, transformers, especially large ones in power amps, experience "in-rush", i.e. a large spike in current before "the magnetic flux stablizes": I gather this can cause noise. Sometimes "soft start" circuits are used to mute these noices.

On shutdown, some amps cause a "thump", often after a delay of a few seconds. I'm told this has to do with the discharging of the main power filter capacitors. Larger capacitors tend to take longer to discharge, I believe.

[Ajani]

One thing I don't like about Tripath amps is they pop when turned on and again when turned off. HE speakers make it even worse.

Can't you just leave Tripaths on, considering they draw so little current in standby anyway?

[Poultrygeist]

I don't leave the Sure amp on for fear the fan will run. I've replaced enough fans in my PC to know they have a limited life span. Does Feanor leave his SDS on?

[Feanor]

I don't leave the Sure amp on for fear the fan will run. I've replaced enough fans in my PC to know they have a limited life span. Does Feanor leave his SDS on?

The SDS has a stand-by switch: this shuts off the amp module but doesn't cut the AC to the power supply i.e. the transformer, rectifier, and filter capacitors. I generally leave the amp on stand-by, though I suppose this still does draw a very slight trickle of power.

As you'll recall, my SDS has the linear power supply. As per earlier discussion, powering up the power supply will cause "in-rush" to the transformer (400 VA) -- however the SDS is silent on full power up and down in any case.

[Smokey]

On startup, transformers, especially large ones in power amps, experience "in-rush", i.e. a large spike in current before "the magnetic flux stablizes": I gather this can cause noise. Sometimes "soft start" circuits are used to mute these noices.

On shutdown, some amps cause a "thump", often after a delay of a few seconds. I'm told this has to do with the discharging of the main power filter capacitors. Larger capacitors tend to take longer to discharge, I believe.

Good discussion

It is worth mentioning that power supply's filter capacitor can cause thump on start up also due to rush of current as it is being charged and stabilized.

On most amps that have Standby switch (not Off), the power supply is kept "alive" as to avoide current rush at startup and shutdowns-thus eliminating the thump noise.