[The Dutch Guy]

I have always been a bit sceptical about the lack of proper protection circuits in modern headphone amplifiers: Putting a pair of loudspeakers right up to my ear that require a fraction of a milliwatt  , hooked up to an amplifier that puts out 100.000 times more power than needed to reach 90dB ,without any of the protection circuits that are common in pretty much any post-1980 integrated always seemed strange to me.
 
Yesterday my fear became reality, as my 6 month old headphone amplifier died while I was listening to it. An incredibly loud buzzing sound in the right channel caused me to literally throw off my headphones, but I fear the damage has allready been done: My ear has been ringing for the past 12 hours, which is a sure sign that permanent hearing damage has been done.
 
Now I am not making this thread to scare people into buying weaker amps,  but I am wondering if manufacturers of headphone amplifiers take this into consideration: Today's headphone amplifiers are so incredibly powerful, that it might be a good idea to start implementing some serious protection circuits, not just a "delay-relay". Now my Phonitor Mini was only 6 monts old, and it was probably a freak accident, but as these modern high powered amps age, solder joints and capacitors will go bad and other defects will eventually creep in, making accidents like mine much more common a few years from now.

 

[The Dutch Guy]

Not a single one with an opinion about this? I understand it's something that doesn't happen very often, but the consequences could be disastrous: A more sensitive set of cans on a more powerful amplifier could have literally deafened me permanently.
 
I am now looking into getting a new amplifier, if possible with protection built in.
So far the only headphone amplifiers i can find that have anything more than a basic "relay-delay" are the Oppo HA-1, the Gustard H10 and the Violectric HPA-V220/281.
I'd actually consider the HPA-V220, but it is quite expensive, and I don't really need all that power,(Main headphones are Oppo PM-1 and Senheiser HD600) It does have a lot of things going for it: Multiple inputs, pre-outs (My speaker set up is ancient, if it croakes I could just buy a set of actives and be done), balance knob et. etc.  But again: all that power makes me feel a bit uncomfortable with this week's accident still fresh in my mind. (And still some numbness in my ear)
Another option would be to get a portable amp: something that might not feature extensive protection circuits could probably still be considered 'safe" if it isn't very powerful. (the noise of a 80mW amp dying would not take out my eardrums is my reasoning).
Something like from Iqube or maybe even the oppo HA-2, but preferably with user-replaceable batteries.

 

[jcx]

headphone sensitivity differs orders of magnitude between models, even in a single category like dynamic drivers - making one headphone's "protection" another's continuous clipping distortion
 
and there's also the "if it can't get loud enough to make you deaf, it can't get loud enough for live music transients" - the difference being time of exposure - some instruments really do hit 120 dB SPL at the audience ears for fractions of a second and won't sound "real" on a amp+headphone combo that can't get there
 
https://web.archive.org/web/20150421234534/http://headwize.com/?page_id=266
 
read the headwise article twice - once for protection from too long, too loud and again for the short term, transient peak SPL produced by real acoustic musical instruments
 
 
many recordings do limit the dynamic range - so much that its a problem, but you can also see a few recordings with over 20 dB peak to average SPL: http://dr.loudness-war.info/
 
the low dynamic range "loudness war" compressed recordings can be more dangerous to your hearing because they stay close to the max all the time

 

[The Dutch Guy]

Thanks for your reply JCX,
 
I am well aware of the loudness war/dynamic range debate, as well as the requirements for realistic playback volumes.
I have however always been very careful with my hearing, my average listening volume is usually around the 70 dB mark, realistic listening levels are not something I aspire to as a daily listener who values his hearing. But even if 120dB peaks are the goal, modern amplifiers have far surpased it for 99% of all headphones, with output power of 4-6 watts getting more and more common. (Realisticly there are only 1 or 2 headphones that need that power to reach 120dB)
What worries  me is that even while being aware of these factors I got completely blindsided by the incredible loudness and accute pain caused by a (by today's standards) medium-powered amplifier failing into a high impedance set of cans (HD600).
 
With all the advancements made in amplifier technology, shouldn't a more adept set of protection routines be one of them?
Without wanting to repeat myself: what is going to happen when all of these super-powered headphone amps start to age, and components start to fail?  Maybe the protection circuits usually feature components that fail before the rest does? I've also read that many protection circuits used in older Japanese integrateds would not be sufficient for headphones, as the values they need to activate are allready way above what's needed to damage headphones.
There must be some reason why there are currently no adequqte protection measures for headphone amplifiers ,but with the continuing developments in "head-fi", now slowly making it's way to the massive engineering (and monetary) capabilities of the "big brands" , one would expect to see some improvements in this area.

 

[ppl]

The Dutch Guy made a valid point, in that the Headphone Amplifier should protect the Headphones in the event of malfunction of the Amplifier. Had the Amplifier the poster was using employed even rudimentary monitoring of the output for signs of excessive DC voltage and the clamped the output to ground thus protecting the Headphones from damage from a malfunction and since these same monitoring circuits can also shut down the Amp in the event of an error thus protecting the Amp from further damage.
 
Solid state Amplifiers for the past several decades have employed basically (2) two types of protection circuits (1) A DC monitoring circuit connected to a relay that disconnected the Loudspeakers from the Amplifier in the event of about 2 volts of more of DC. ( With headphone amps this is downsized to about 100mV). The (2) second is volt amp current Limiting to protect the Amplifier from load impedance that were lower than the Amps intended load and in the event the user shorted the speaker terminals while cranking up the volume wounder why no sound was created. These Amps I believe created the High End Audio Industry and volt amp current limiting was first and foremost on the not good sounding list of the day.
 
Years ago I compared a Technics SE-A5 MK II to a Threshold Stasis 2 the Threshold rated at 200 watts and the Technics at 150 watts. In theory according to leading experts of the day that all good Amplifiers sound the same Both the threshold and the Technics should have not had anything but a slight difference and that was only at loud listening levels. My how theory differed from reality the Technics Amp sounded totally anemic at all listening levels and worse had audible distortion at loudness levels that were far below the normal clipping of 150 watts into the B&W 801 loudspeakers. Further investigation revealed the volt amp current limiting on the Technics was seriously limiting the maximum real world power output to about 20 watts before the Current limiting kicked in and caused audible distortion of the worst kind. After disconnecting the volt amp limiting and installing thermal cutoff switches on the Heat sinks of the output transistors on the Technics Amp and then compared this modified Technics to the Threshold and WoW the gap shortened considerably and I could get 180 watts out of the Technics where previously was only able to get 20 watts before with that loudspeaker. the Next upgrade to the Technics involved reconnecting the DC output Relay from a series to shunt operation that would thus short the output of the Amp to ground rather than simply disconnecting the loudspeakers thus removing one set of switch contacts from the Amp to Speaker interface. the result of this was a blown fuse the intended result since the fuse was not in the signal path. the sonic improvement of this was greater sound stage by quite a lot and tighter bass and maybe I remember also lower distortion.
 
Headphone Amps operate at much lower power and so the shunt DC protection method could be used to protect the headphones and by simply over designing the output stage of the headphone Amp you could simply employ current limiting on the power supply for silent operation of the protection circuits with minimum intrusion on the dynamics however nothing is truly transparent.
 
As for the playing to loud situation again we have such a with range of headphone Impedance's and sensitivities that an all in one package that could be added to am amp is output voltage monitoring via old school VU type peak reading Meters or equiv. and then requiring the user to translate that into a in the head SLP with any given headphones, yes a daunting task indeed.
 
In conclusion having a sonically transparent protection circuit to protect the headphones from excessive DC is a blessing but added cost and could be potentially be degrading if not well implemented. The listener should take measures and seek out guidance on loudness levels both long and short term. this is one of the most useful virtues of this Forum the ability to take charge of all the complexities of system integration.