Mailliw

Passive LED-based headphone protection mod?
« Reply #20 on: November 24, 2006, 03:19:53 PM »
When the zeners are conducting, what power is dissipated by them? Is it the forward voltage X the current set by the resistor?

What value for the resistor would you choose? You don't want to increase the load too much and at the same time you don't want a large current being drawn once it is shunted?
All Things Must Pass


Passive LED-based headphone protection mod?
« Reply #21 on: November 24, 2006, 04:09:07 PM »
Right, I think I get it...

So... under the threshold voltage line set by the zener value, e.g. 5V (+0.6V for the other zener's negative V drop), there's no signal going through the mod circuit, but once the level goes over 5.6V the zeners start conducting.

Does this work by creating a parallel resistance between the headphone driver and the mod circuit's series resistor, thereby increasing the total impedance of the signal chain to reduce the perceived level?

If so does that mean the resistor needs to be a pretty high value so that the total impedance when active is greater than when not active?

Won't this just mean that the engineer can just keep turning up and turning up to overcome the effect of the mod?

Or am I missing the point?
Phil Plumpton, Olympic techy.
Compooter man, electronics noob.

Passive LED-based headphone protection mod?
« Reply #22 on: November 24, 2006, 04:11:36 PM »
Quote from: "SSLtech"

If they're in series with the load, the load will see nothing until the signal exceeds the voltage... a sort of humungous crossover distortion. If they're in parallel with the load, they'll "clip" the load by shunting excess voltage off as heat. (to the limit of their power handling capacity, and assisted by series resistance between them and the cource. The less series resistance, the more readily they'll pop.)

You must have a linear resistance in series. Only the shunt leg must be allowed to be nonlinear (semiconductor) in a passive setup. -And it really needs to be near symmetrical... At the very least it MUST act on both poles of the signal.

Keith


 :shock: Oh? So the zeners actually stop the total voltage from going above the threshold line at ALL?


...and presumably there's only so much heat the zeners can dissipate and over their capacity they "pop"?

So for this situation, how would you choose a resistor value?
Phil Plumpton, Olympic techy.
Compooter man, electronics noob.

Passive LED-based headphone protection mod?
« Reply #23 on: November 24, 2006, 04:31:14 PM »
...and this is what you mean, right?

Phil Plumpton, Olympic techy.
Compooter man, electronics noob.

bcarso

Passive LED-based headphone protection mod?
« Reply #24 on: November 24, 2006, 06:08:53 PM »
Input to resistor to headphone coil

Back-to-back zeners across headphone coil

SSLtech

Passive LED-based headphone protection mod?
« Reply #25 on: November 24, 2006, 07:01:15 PM »
Yep. -but -as Brad says- move the output to across the Zener pair. -drop the take-off line down to the other end of the resistor and you're there.

Yes, Zeners are rated in milliwatts (or watts for the big stud-mount type). -The series resistance should be big enough to protect the Zener, but not so big that it divides the voltage (headphone load included) to a wasteful degree... perhaps equal to teh load then you're throwing away 6dB or so...

Then a couple of 400mW Zeners should be fine. -If you're blowing too much power thorugh that then reconsider... but by then you'd have a watt or so into the cans, and by then I know from experience, DT100s are capable of lethal levels!

Funny that DT100's don't see much use over this side of the atlantic: They really are stunningly good headphones, and every single part is available for replacement. -They're a little light on LF, but that works great for backing track applications, where LF bleeds in from around the user, plus the "chest effect" of high-decibel envronments. -AKGs and the like seem to be preferred over here, but they are nowhere near as robust. -If you're blowing DT100's you'd have killed half a dozen sets of AKGs in the same time! :wink:

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

Kev

Passive LED-based headphone protection mod?
« Reply #26 on: November 25, 2006, 01:59:59 AM »
do the DT100 spare parts have choices on driver units ?
... different impedances ?

a higher impedance may save them from blowing up on the given distribution system.
Kev
DIY Factory

SSLtech

Passive LED-based headphone protection mod?
« Reply #27 on: November 25, 2006, 08:29:58 AM »
Yep. Anything from 32Ω to 600Ω is the range I've personally seen, and there may be more.

They also do mic booms, headside pads (for single-ear) and other modular options.

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

Passive LED-based headphone protection mod?
« Reply #28 on: November 30, 2006, 08:01:28 AM »
Thanks for all your help everyone, this is working a treat.

I'm using 6.8V zeners and 430R resistors, and it's knocking about 8dB from the volume level before distortion.

Cue the complaints that the cans don't go loud enough  :wink:
Phil Plumpton, Olympic techy.
Compooter man, electronics noob.

gyraf

Passive LED-based headphone protection mod?
« Reply #29 on: November 30, 2006, 08:49:07 AM »
:green:  :thumb:
..note to self: don't let Harman run your company..


Passive LED-based headphone protection mod?
« Reply #30 on: November 30, 2006, 09:39:35 AM »


My K800i hates these close-up shots  :mad:

pft 3.2MP.... tch.
Phil Plumpton, Olympic techy.
Compooter man, electronics noob.

Kev

Passive LED-based headphone protection mod?
« Reply #31 on: November 30, 2006, 03:13:44 PM »
I think that's more about optics and macro than it is about 3.2mp
Kev
DIY Factory

Passive LED-based headphone protection mod?
« Reply #32 on: December 01, 2006, 05:55:36 AM »
Quote from: "Kev"
I think that's more about optics and macro than it is about 3.2mp


Yes.








(there's always one  :roll: )




 :wink:
Phil Plumpton, Olympic techy.
Compooter man, electronics noob.

Passive LED-based headphone protection mod?
« Reply #33 on: December 04, 2006, 05:05:07 AM »
OK.... for anyone that's following this...

I finally got into one of our studios to test the newly modded cans.

Result:  Cans are way too quiet.  When pushed, fuses blow on cue lines.


I'm going to reduce the resistor value (to half) in the hope that the fuses will stop blowing, and increase the zener value to allow more volume in the cans.

More in a bit....
Phil Plumpton, Olympic techy.
Compooter man, electronics noob.

Passive LED-based headphone protection mod?
« Reply #34 on: December 04, 2006, 05:56:54 AM »
OK, with R= 220R and zener= 9V1 :

Result

Better.  Cans are louder, but still blew a fuse at max volume from desk.
Phil Plumpton, Olympic techy.
Compooter man, electronics noob.


 

Related Topics

  Subject / Started by Replies Last post
2 Replies
1685 Views
Last post August 25, 2004, 01:28:02 PM
by Mark Burnley
14 Replies
6707 Views
Last post December 06, 2006, 08:47:37 AM
by matthias
15 Replies
24065 Views
Last post November 24, 2006, 11:53:54 AM
by SSLtech
0 Replies
732 Views
Last post April 25, 2010, 06:14:58 PM
by myker