[PinkFloyd]

Dr. White was doing much the same thing 10 years ago......... check out his loudspeaker protection circuit http://www.wnaudio.com/ click on "products" and then click on "speaker protection"

He's been working on a bullet proof DC protection circuit for "headphones" for quite some time and it looks as if PCB's are imminent

http://www4.head-fi.org/forums/showp...&postcount=433

Nice one!

 

[ppl]

Over at diyaudio.com there is a thread that deals with this same issue and has plenty of different ideas http://www.diyaudio.com/forums/showt...threadid=57173
Including a circuit similar to AMB's. http://www.diyaudio.com/forums/attac...amp=1115921488
and also see http://www.diyaudio.com/forums/attac...amp=1115990451

http://www.diyaudio.com/forums/attac...amp=1116692994


Quote:

Originally Posted by kevin gilmore I do a very similar thing except i don't like anything in series with the audio signal if at all possible. So i use the normally closed contacts on the relay and then tie the contacts between the audio outputs thru the relay to a pair of back to back shottky diodes. That way the dc level limits to +/-.3 volt until the relay pulls in. Nice job AMB.

I Believe as Kevin dose that putting unneeded contacts in the signal path is not the Best for Sound quality regardless of how many op amps and switches the signal passed through prior to your equipment as this will just further degrade the signal even more. My recommendation is to turn your amp on first then connect your headphones Soft start circuits and DC protection can be done by turning on the output stage last and the Voltage gain stage is turned on First using AMB’s or similar circuit as the Root cause of turn on and turn off is the fact that the output stage in most Amps turns on prior to the Voltage gain stages so the Output stage is merely passing the turn on and turn off transient caused from the Voltage gain stage turning off first and turning on Last

Quote:

Originally Posted by pabbi1 Did someone move your cheese? So, now as an agent of change you are just determined to be a thread crapper - how sad. It has been clear from your 'Midnight Millet Attack' you have been aiming at m³ all along. I won't guess who has been stoking you about 'fair', but PPA does come to mind.

Oh and BTW anyone that thinks any member of the PPA Team is responsible for the action of Rick is seriously mistaken as Team PPA had to endure similar accusations from another member of this Forum http://www6.head-fi.org/forums/showt...ght=ballad+ppa

 

[rickcr42]

Quote:

Oh and BTW anyone that thinks any member of the PPA Team is responsible for the action of Rick is seriously mistaken as Team PPA had to endure similar accusations from another member of this Forum http://www6.head-fi.org/forums/show...ight=ballad+ppa

Wow ! never had i read that before because I make it a habit to take a pass on the "team" anything threads.I don't build the products and have no interest in the amps so i just cruise on past the threads and go to the more generic DIY posts.

As far as any action I decide to or not to take and anything said by me in any thread-all me all the time and no human has influence over my thoughts.I call 'em as I see 'em.
Always have,always will

personally ?

I think the DIY forum has gone to hell but since most would rather do DIY by the numbers and never figure out how anything works my attitude is FK it until or unless there is a rules change.I refuse to play but hey,I refuse to play in a lot of games I don't care for.........

and to say no one is making enough to make a living is all BS.ANY profit, even a tiny one is still a business and if not then try to use that argument with the IRS is they ever audit you and see how far you get.

nuff said and again I will bow out,just responding since my name was brought up by others even though i had left this thread permanantly........

 

[ppl]

 

[amb]

Guys, I would really appreciate it if you would please stop derailing this thread and take this mud-slinging elsewhere.

 

[xtreme4099]

*yawn* i gotta burritos in the microwave --- be right back ... *Zzzzzz*

 

[Pars]

Quote:

Originally Posted by rickcr42 I think the DIY forum has gone to hell but since most would rather do DIY by the numbers and never figure out how anything works my attitude is FK it until or unless there is a rules change.I refuse to play but hey,I refuse to play in a lot of games i don't care for......... and to say no one is making enough to make a living is all BS.ANY profit, even a tiny one is still business and if not use that argument with the IRS is they ever audit you. nuff said and agin I will bow out,just responding since my name was brought up........

Ya know Rick, anyone who has built a Gilmore or probably an M3 or PPA knows (or has found out) that it never is as easy as plugging some crap into a PCB and firing it up. Yeah, its on a PCB and might not meet your definition of DIY as being you design it, and build it Pt-Pt.

In doing my first Dynalo (on a commercial board from the prominent Gilmore vendor who it appears got chased off these boards before I got into phones at all), I had to learn Eagle, and design and etch my own rectifier boards to replace the GBU recifiers called for with Schottkys. And I had to learn how to match FETs and transistors (thanks for all the help Amb). And, once it was put together, I had to go thru the schematic and figure out what I should be seeing here and there to get the DC offset into a manageble (i.e. perfect, without the servo) state. So if someone tells me that this isn't DIY, I bristle a bit.

Personally, I think that some of the people around here that might be termed "manufacturers" under your definition are also some of the most helpful people in terms of knowledge and insight on these boards, and to hinder them and/or chase them away would be a serious mistake IMHO. I quite frankly do not understand the paranoia that seems to be prevalent on these boads WRT "manufacturers", unless all they are doing is pimping their products. I can assure you from what I see from people like Amb, ppl, etc. that they respond to specific questions with valid and responsive answers to the question asked, as they are in the basic sense, interested hobbyists just like you or me. I have not read one post yet which was a response to something where I felt anyone was trying to sell me anything or push their product. And I think that making some money off of their talents is defintely not blasphemy. When I see someone post something like "Sorry dude, gotta cut it short cuz my jet is waiting" then I might come to agreement with you. I don't think any of the manufacturers are making anywhere near that kind of money. If they are, could they please swing past Chicago next weekend and drop me off in the Carribean for a weekend of golf? Please be sure to have tee times and accomodations taken care of also

 

[Sovkiller]

Another point that I would like to add, is that most of those "manufacturers", became manufacturers years after they were here, in headwize, and in many other forums and sites, helping people and offering his free DIY support, the case of ppl, tangent, voodoochile, JMT, Meier, and so many others, of course after seeing that many of other "not so helpful people" are making money out of their knowledge (and even out of others knowledge) well why not them??? Inside the rules or not, with a commnercial point of view or not, what I feel at the end, is that they are helping many people to get out, of their problems....

 

[grasshpr]

Hey AMB,

Quick question. This circuit will immediately switch to the amp channel once the DC offset would reduce to less than 70mV. Also, one of the primary purposes of this component is to remove the popping effect when the amp gets turned on.

However, if you already have a signal being played on the amp, wouldn't switching from ground to some input signal immediately produce the same popping effect? I would assume you need some component that will reduce the transient response from ground to the amp signal smoothly.

Pretty neat circuit, BTW

grasshpr

 

[amb]

grasshpr, if the DC offset threshold is exceeded and the relay disconnects the headphones, and then the offset somehow drops back to normal, the relay will re-engage after a 3-second pause. If music was already playing then the audible effect of all this is a temporary mute. Granted it's not a smooth fade-out and fade-in, but there shouldn't be a "thump" like what might happen when you first turn on some amps.

 

[grasshpr]

Thanks for info. However, I've had bad experience (not with audio equipment, but with mechanical shaker tables) where switching from ground to some bounded quasi-periodic signal will produce a big thump. I assumed it would be very similar for headphones since the source signal is amplified to provide a good amount of current.

Now about fade-in/out, wouldn't it be simple enough to just put an additional stage which fades in/out the input signal (in about a millisecond or two with minimal phase shift) and switch to the actual input signal or ground after a millisecond or two?

Just a thought, since if your going to make a circuit that protects headphones, mind as well go all out and crazy

. That and its probably a nice touch to have a fade in/out circuit for an amp, just because it makes the amp sound a little more professionally built. (this is purely my opinion, BTW)

 

[amb]

This circuit doesn't "switch from ground". It simply disconnects and connects (see schematic) the headphones. This is no different than, say, unplugging and plugging your headphones while the music is playing (actually, it's better because the 1/4" phone jack briefly makes a couple of "wrong" connections as you insert/remove it, but this circuit doesn't do that).

As for fading, that would require quite a lot more circuitry, and tricky to do if we want it not to add additional noise/distortion or affect other performance criteria. To properly implement fading we would in effect need an electronically-controlled volume control, which should be at the input side of the amp rather than at the output.

This muting/delay protect circuit is intended to be cheap, simple, space-efficient, easy to integrate into a wide variety of existing amps, and not affect the sound quality. I don't think it's possible to achieve all these goals and add the sort of fading capability that you seek.

Not to mention that since it's supposed to protect the headphones in the event of a big DC offset; so when that happens we want the headphones to be disconnected now rather than playing any fading sound trick.

 

[grasshpr]

Quote:

Originally Posted by amb As for fading, that would require quite a lot more circuitry, and tricky to do if we want it not to add additional noise/distortion or affect other performance criteria. To properly implement fading we would in effect need an electronically-controlled volume control, which should be at the input side of the amp rather than at the output.

I don't think fading in/out would be very difficult to implement, simple solution is to put a low pass filter with a high enough corner frequency and switch out to the unfiltered amp input after a fixed period (using another relay). This would not effect the audio signal path that much (as much as your original dc offset protection circuit since it does include a capacitor in the audio path). This would not require any complicated volume control.

Also, isn't it dangerous to have one side connected with ground but the other as open (potentially connected with the body of the relay instead)? When the headphone is unplugged from a component, the ground and hot is at the same potential as air, which appears to be different compared with the circuit you provided.

 

[amb]

Quote:

Originally Posted by grasshpr I don't think fading in/out would be very difficult to implement, simple solution is to put a low pass filter with a high enough corner frequency and switch out to the unfiltered amp input after a fixed period (using another relay).

You lost me here. How does a low pass filter provide fading volume?

Quote:

This would not effect the audio signal path that much (as much as your original dc offset protection circuit since it does include a capacitor in the audio path).

Again you lost me. The muting/protect circuit I designed here does not add anything to the signal path except for relay contacts to switch the headphones in/out. What capacitor is it that you speak of?

Quote:

Also, isn't it dangerous to have one side connected with ground but the other as open (potentially connected with the body of the relay instead)? When the headphone is unplugged from a component, the ground and hot is at the same potential as air, which appears to be different compared with the circuit you provided.

No, I think you have a basic misunderstanding about circuits. When the positive side of the headphone leads are disconnected by the relay, the circuit is open and there will be no more current flow. There is no "danger" to speak of.

 

[grasshpr]

Quote:

Originally Posted by amb You lost me here. How does a low pass filter provide fading volume?

What I'm saying hear is using a low pass filter to provide smooth transitioning into the proper audio signal. A low pass filter is merely a stable state-space system that has an input and spits out an output. If the input is a quasi-periodic signal, then the output would simply be the same quasi-periodic signal with a phase shift. Only difference would be that this system would have to transition from some initial condition (which would be ground, or the way you have it which is in disconnection mode).


Quote:

Originally Posted by amb Again you lost me. The muting/protect circuit I designed here does not add anything to the signal path except for relay contacts to switch the headphones in/out. What capacitor is it that you speak of?

You are right in this case, however, the way you can design the fade in/out would not require you to affect the audio signal path as well. After several milliseconds of timing, use another relay to switch from the filtered signal to the non-filtered audio signal. Sorry for this confusion.

Quote:

Originally Posted by amb No, I think you have a basic misunderstanding about circuits. When the positive side of the headphone leads are disconnected by the relay, the circuit is open and there will be no more current flow. There is no "danger" to speak of.

Your relay switches between two signals, the way you have it, when the DC offset is high, you switch the hot signal to open. However, you still have your ground signal connected to ground (which can supply some current to the headphone right?). This is the same idea as having your open side fictiously at the potential of air and your ground signal supplying a current as a result. Same principle as static discharge, when you touch ground on a metal surface and your body is at another potential. Furthermore, this is not the same situation as having your headphones disconnected from your amp. If your really interested in switching the headphones to an open circuit, then use two DPST relays and open both ground and hot. I'm not saying that your circuit is incorrect (and also in no way am I criticizing your work), I'm saying under extrenuous situations, you could be providing an obtrusive signal to the headphones (e.g., colored noise) which may not be desired.

Lastly, I didn't mean to make such a fuss about this design. Maybe my comments are not warranted, however, I am just interested, thats all. Take it with a grain of salt