The IMPEDER = Less than 10 ohms output from any piece of gear

[j-curve]

I'm sure I'm not the first to think of this, but here's a way to combat the effects of any evil output resistors lurking behind the headphone sockets of your integrated amp, CD player etc.

If you haven't yet burnt your fingers with a soldering iron then you couldn't hope for an easier first project than this. All you need is a 3.5mm stereo plug and two 10 ohm resistors. [Oh, and a stereo miniplug double adaptor]. If you have a multimeter you might want to check that the resistors are a good match:-


Simply solder the resistors from the left and right connections to the common (earth) tab. A pair of pliers with a rubber band around the handles will reduce the swearing. I used 1/4 watt resistors with a metal shell plug. If your headphones are less efficient than HD580's then you might consider 1/2 watt resistors. Here's how a finished impeder should look with the back shell unscrewed:-


Plug your 'phones into the double adaptor as shown on the left:-

then you can plug in The IMPEDER! On the right is the impeder impeding! (Note and beware of the crankage...)

Here's the trick: If the volume doesn't drop significantly when you plug in the impeder, then you don't need the impeder for that particular piece of gear because the output impedance is already quite low. In most cases though, output resistors range in the tens to hundreds of ohms, so plugging in the impeder will require you to crank the volume.

Here's the catch: The volume drop with the impeder may be 20dB or more. It would be most uncool to unplug the impeder without turning the volume down first!! [and I take no responsibility for any consequences... disclaimer... exclusion... limited liability... poop...].

The impeder doesn't necessarily improve the sound - you be the judge. In particular, some gear will lack either the extra headroom (voltage) or the extra current capability that the impeder demands. In those cases, clipping distortion should be obvious.

How does it work? Basically you are wasting power in exchange for lower output impedance and the tighter driver control that goes along with that. With the HD580 the bass hump is reduced and lower midrange resolution is improved.

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[ServinginEcuador]

What a neat , prefessional, and sporty looking job J-Curve!! Let us know how it sounds with and without the Impeder in place!!! It would be interesting to see how this would affect impedance matching as many of us think that this is the culprit lurking in the shadows and explains why low impedance cans down't work with some amps, while high impedance cans do!! And vice verse.

Wouldn't you always get a volume drop using the Senn's 300 ohm impedance with the impeder?? It would seem that approximately 30 times the amount of current would travel thru it vice the cans since you connected it in parallel with the Senns. You would have equal amounts of voltage, but way less current in the Senns. This would tax the current output several times what it ws before adding it. Interesting......

[Joe Bloggs]

Listening impressions! Listening impressions!

Funny, I was thinking of the exact same thing a few hours ago You beat me to it though

That's a nice adapter to use quickly on any system, but if you need the impeder, the headphone jack is probably part of a speaker amp, and it would be better in the long run to connect more directly to the loudspeaker output:
(You've seen this right?)



This basically allows you to dictate the output impedance and voltage share (hence volume) freely. No more [low output impedance = low volume]!

[AndreYew]

Perhaps I'm missing something, but I don't think this lowers output impedance. It makes the headphone's input impedance appear lower to the amp.

--Andre

[Joe Bloggs]

Yeah, I feel strange about this too, but this has been touted before as a way to reduce output impedance, and even Kevin Gilmore says that the effective output impedance of the system with the resistor in parallel with the headphones is now the resistance of the output resistor in parallel with the resistor in parallel with the phones.

[ServinginEcuador]

Originally posted by AndreYew
Perhaps I'm missing something, but I don't think this lowers output impedance. It makes the headphone's input impedance appear lower to the amp.

--Andre

Basically it goes like this:
Suppose you have 120 ohm output impedance from the amp, plus 300 for the Senns. That adds up to 420 ohms since they're in series.

Now, add 10 ohms in parallel with the 300 ohm Senns and you've reduced the output impedance from 420 ohms down to 129.6 ohm!!! You've now reduced the output impedance down almost 290 ohms!!

It doesn't reduce the impedance output of the amp, just what the amp sees in total!!

[Joe Bloggs]

No...