[K_19]

This is something I've been wondering for a while... please keep in mind that I'm really horrible as far as my knowledge of science goes 

 so this may be something obvious to the vets here, but y'know, better to ask and learn rather than be afraid to ask and never know.
 
So we all enjoy headphones and most of us have dedicated amps... and often we all plug in headphones after the amp is turned on. When you do, with most amps that I've tried, you get that soft "pop" or crackling sound. Often many amps get this as well when you have a headphone plugged in while it's off then you turn them on afterwards. As most amps do this I'm assuming this is not a harmful thing in general. However, I've noticed that there are some amps that don't have this feedback.... some amps in particular from memory that has literally gave zero noise from the jack at all at any time, are amps like M3, and the Violectric V200. Is this due to just difference in design, or are there some sort of muting device integrated into these amps so that it is noise free, and could these in theory possibly compromise the sound? I'm just wondering as I'd think ideally you'd want all amps to be noise free when plugging in, yet I see that some do and some don't. Maybe a cost/benefit issue?
 
Also another issue I was wondering about that I experienced recently... I got an ELE EL-D02 headamp/DAC and just to take a picture of it I had one of my cheapo earbuds laying around plugged into the headphone jack of the device, but without any sort of power connected to it (so there was no usb cable plugged in). However, I got a pop/crackling noise even if there was no power source at all! Thinking that it was weird, I kept plugging it back in and out (as this was a cheapo earbud I didn't really care about possibly damaging it) and I got the same soft popping sound the first 3-4 times, before it finally became silient from input... does this mean there is possibly some harmful residual leak from capacitors from previous use or something like that? It just seemed weird to me as the device was completely disconnected from its power source, yet it gave me this feedback from the headphone jack... this is a cheapo amp/DAC so I was just concerned if this was a design flaw.
 
So yeah... in all, if anyone can explain the whole general science behind this soft popping/crackling sound we usually get when we plug in headphones to our amps, it would be greatly appreciated... thanks in advance.

 

[stv014]

Originally Posted by K_19 /img/forum/go_quote.gif
 
So we all enjoy headphones and most of us have dedicated amps... and often we all plug in headphones after the amp is turned on. When you do, with most amps that I've tried, you get that soft "pop" or crackling sound. Often many amps get this as well when you have a headphone plugged in while it's off then you turn them on afterwards. As most amps do this I'm assuming this is not a harmful thing in general. However, I've noticed that there are some amps that don't have this feedback....

 
If you hear a popping sound when you connect headphones to an amplifier that is already turned on, then that is because it outputs some amount of DC offset. This can be a problem if the DC offset is excessively high (i.e. the pop is unusually loud), but a couple tens of mV or less is acceptable. The exact level depends on the amplifier design, and to some extent random sample variation.
 
Additionally, a low frequency transient may be output when the device is turned on and/or off. Some amplifiers mute this effect (which, similarly to DC, could be dangerous to the headphone drivers if it is at a very high level, and otherwise it is just annoying). There are a number of ways to implement temporarily muting the output, but it should not have an audible effect on the sound quality.

 

[threephi]

I am not an engineer, neither electrical nor audio, but I have always presumed that the pops you sometimes hear when inserting a headphone jack are due to the signal sections on the end of the plug shorting when they pass through the grounding collar on their way to full insertion, and if there were a bit of stray current on the ground (eg from static), it causes a tiny pop as it is discharged across the signal path of the phones.  Or did we just say the same thing?

 

[cdsa35000]

http://www.google.com/search?q=power+on+off+amp+popping

Most amps have active muting circuit when power on/off with muting transistors= stil could give minimum popping noise or with muting relays= only mechanical clicking noise.

When power on the large buffer elco's/capacitor are charging/shorting with max. loading current hence a powerful spike/pop at start!

Other mechanical plugging in/oout with/without power causes (static) voltage/current conducting/discharging of metal friction.

 

[K_19]

Thanks for thr responses all.

What are some examples of dedicated headamps that you've all use that mute this effect completely? Personally as I said in the first post the Violectric V200 and the M3 had absolutely zero noise when plugging in/out or turning on/off.

 

[cdsa35000]

Any generic (cheap) audio electronics/amps have muting transistors and/or relays:
Yes they affect sound badly, extra passive transistions influence SQ.
Muting transistors are the worst and also relays and interconnection inside are bad too, they muffled transients and ambiance of audio.
They're easy tweaks to improve SQ.

I tweak my hifi and remove muting tors and interconnection with direct wiring.
http://www.google.com/search?q=remove+muting+transistor

http://www.rock-grotto.co.uk/x-can-v3-tweaks.htm
Like those white connectors on the pcb are bad for SQ, I solder the wires directly to the print pads skipping multiple extra sound degrading transistions.
The downside of no muting is that I unplug/replug the hp on power on/off as once the popping blown 1 driver of my SA5000.

"Hi end" audio are all direct wired without pcb: http://www.high-endaudio.com/RC-Amplifiers.html

http://www.high-endaudio.com/RC-Amplifiers.html