[skeeb23]

I'm hoping to get some scientific insight to this, because I sadly had a bad experience today with this.

So I currently own a Schiit Jotunheim2 amp. I've always used my Jot2 the way the manual states in that you don't need to ever turn it off. I've plugged and unplugged headphones to it over the couple of years I've had it and no problems. Never any popping or anything. Now I do at least turn down the volume when doing so just for my own piece of mine.

Today I got to experience my first tube amp. I just finished building my BHC and had just passed all resistance/voltage checks. Not thinking at all I had the amp on, volume all the way down to 0 and the cable for the HP plugged in (but no HP plugged into the cable). So I then went ahead and plugged my headphone into the cable and immediately got a pop in the left channel I was starting with. Scared the crap out of me of course so I immediately shut off the power and unplugged the cable. I then went and plugged in my cheap Koss Porta Pro's into the amp and turned it back on. No pop and turned up the volume slightly as to not blow out the headphones and it worked great. I was shocked actually the 60ohm Koss could do it.

So, I went back to the other headphones of mine and sure enough the left channel is much lower in volume then the right. I switched cables and went back to my Jotunheim2, same thing. So, I have managed to blow or short out the left channel.

Long story short...I'm guessing plugging and unplugging a headphone directly from the amp is probably fine for most SS amps such as mine. Even on higher volume I would imagine. Do tube amps react differently? Or is this a case of being stupid and not thinking about the fact the cable was plugged in to the amp before it was plugged into the headphones.

My lesson is learned regardless, but I'm really trying to dissect whether its an actual problem that will happen, or if I just happened to have all bad possibilities line up and bork up my hp. I just really thought that even with the volume all the way down I would have been fine. I've had popping happen before in speakers and things and be fine...probably in a headset or two over the years too without actual damage.

 

[castleofargh]

Usually, plugging/unplugging headphones with the amp "playing" is bad for the amp itself because a ring on the plug could create a momentary short. The headphone doesn't care about that.
But for what you describe with the headphone, others will correct me if I'm wrong but I think it would be more of a DC matter.

 

[71 dB]

I'd say the output transformers of a tube amp is the issue here. As they are essentially massive coils, connecting something to them can generate massive voltage peaks.

 

[71 dB]

Usually, plugging/unplugging headphones with the amp "playing" is bad for the amp itself because a ring on the plug could create a momentary short.

It is up to the circuit design how much momentary shorts matter. In my passive cross-feeder/headphone adapter driven from my amp's B-speaker output my amp "sees" a change of a few percentages in the load impedance if I short the headphone output of my headphone adapter (for example from 40 Ω to 39 Ω). My amp itself of course has its own protection against shorts. So, for me plugging/unpluging headphones is very safe.

 

[hartphoto]

As mentioned, it can vary depending on circuit design.

I've made this same mistake over the years on my G&W tube/ss amp, no damage to amp or headphones so far (knock on wood). Recently, out of sheer convenience, I've had a 1/4" plug to mini XLR connector made for my G&W amp (SE use), and a XLR to mini xlr made for my Jotenheim 2 (used in balanced mode) to connect the LCD-X headphones to both amps. The LCD-X cable also has a mini XLR. When moving between amps, there's now no momentary shorts...it's just a mini xlr to mini xlr connection. The short 'converter cable' on each amp handles the correct pinout.

As a precaution over time though....particularly with the G&W amp, it's become habit to start a listening session with everything connected, volume down, then power it on. On my Jot 2....the habit has transferred, at least for always turning the volume to 0 before connecting. It remains on nearly constantly.

 

[bigshot]

If a headphone or amp can be damaged simply by plugging in and out, I would suggest getting a better designed amp or headphones. That should fall under the category of "normal use".