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  #1  
Old 06-14-2008, 03:39 PM
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Default Impedence Adapter For The D2

The Etymotic ER4P To ER45 Resistor Adapter: http://cgi.ebay.com/ETYMOTIC-ER4P-TO...QQcmdZViewItem
and the Ultimate Ears Tool Kit: http://www.ultimateears.com/_ultimat...ccessories.php
Shure Volume level Attenuator:http://www.shure.com/PersonalAudio/P...vel_attenuator
All contain a sound level attenuator which adds to the resistance for listening on the D2. I'd been looking for a link to get a product like this for my D2 and so have many here. Just in case anyone had to do a little hoop-jumping I figured I'd make it a little easier.

I originally posted this on another site - be merciful!!!

Last edited by The DarkSide; 06-15-2008 at 07:39 PM.
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Old 06-14-2008, 05:18 PM
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It would be cheaper, though perhaps less professional looking, to get some plug/jacks and resistors @ http://www.fullcompass.com/ or http://www.partsexpress.com/ and just build one yourself.

FullCompass sells both Neutrik gold-plated jacks and plugs, but parts express also sells heatshrink if you plan on making very short connectors and want maximum sturdiness. :-)

[offtopic]FOUR FREAKIN HUNDRED POSTS!! WHOOT! I AM IMPORTANT NOW![/offtopic]
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  #3  
Old 06-14-2008, 08:01 PM
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It might be cheaper - but there are numerous people (like myself) who don't really feel comfortable doing this themselves. Besides, after purchasing all the parts and equipment, equipment I'll probably never use again anyway, it's not always cost-efficient for all.
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Old 06-14-2008, 09:20 PM
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Quote:
Originally Posted by Xenodius View Post
[offtopic]FOUR FREAKIN HUNDRED POSTS!! WHOOT! I AM IMPORTANT NOW![/offtopic]

GRATZORZ

Also thanks nywytboy68, I am thinking of getting one of these now ^^
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  #5  
Old 06-14-2008, 09:54 PM
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If you don't want to build it yourself, check out this option.
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  #6  
Old 06-15-2008, 07:05 AM
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Here's a cheaper ready made adapter: http://cgi.ebay.com/ETYMOTIC-ER4P-TO...QQcmdZViewItem
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  #7  
Old 06-15-2008, 07:39 AM
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http://captain-odegard.com/how-to-ma...r-adapter.html
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  #8  
Old 06-15-2008, 07:52 AM
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Quote:
Originally Posted by dr13zehn View Post
If you don't want to build it yourself, check out this option.
@dr13zehn: TOO EXPENSIVE !!!! Damn good though.

@dfkt: I saw those also BUT I have a serious distrust of eBay. Since it's being sent from Hong Kong makes me nervous. Heard about more and more rip-offs lately and most stem from China and HK.. Makes me a chicken.


@Cptn,....... I'm not as skilled as you. I've seen some of your creations and I can't hang. If I try to create an impedance adapter on my own I'll burn me house down!!! I still can't get over the R2-D2 iAudio D2 dock - even though it kinda' scared me the way it looked .
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  #9  
Old 06-15-2008, 08:40 AM
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Quote:
Originally Posted by nywytboy68 View Post
@dfkt: I saw those also BUT I have a serious distrust of eBay. Since it's being sent from Hong Kong makes me nervous. Heard about more and more rip-offs lately and most stem from China and HK.. Makes me a chicken.
Lots of people on Head-Fi and iAudiophile seem to use those Hong Kong made adapters. The seller seems legit (almost 100% positive since 2000), and even if it was a scam, it would be a relatively cheap one.

BTW, the Shure thing you linked in your first post is no "real" resistance adapter, it's a rather sub-par sounding inline volume control.
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  #10  
Old 06-15-2008, 02:29 PM
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Quote:
Originally Posted by dfkt View Post
... BTW, the Shure thing you linked in your first post is no "real" resistance adapter, it's a rather sub-par sounding inline volume control.
Interesting point! Can you elaborate more on this? I was going to suggest the Koss volume control (http://www.koss.com/koss/kossweb.nsf...&pc^ac^VC20#pd) which is only $9 in Amazon and has gold connectors.
When we talk about resistive impedance adapters (as opposed to active or inductive ones) I see no difference when using a "variable" resistor or a fixed one (well, except for wear after long use), and then you can also use it as a handy volume control for those players without dedicated buttons. In the end, the whole idea of the impedance adapters, I believe, is to be able to crank up the player's volume control in order to run its output amplifier at the optimum power level and signal to nosie ratio... and thus bury down the background hiss.
May be I am missing something here, so please correct me if I am wrong.
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  #11  
Old 06-15-2008, 02:40 PM
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Well, the idea is to add some more resistance/impedance to the output/phones, so the player's bass is less rolled-off, the background hiss disappears, and the stereo crosstalk gets minimized.

I'll have to do some RMAA tests with the Shure volume control, but I suspect it doesn't behave like a resistance adapter.
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  #12  
Old 06-15-2008, 03:03 PM
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Just as I suspected - the Shure volume control doesn't help a lot.The UE adapter does fix the usual issues (but craps out with harmonic distortions). It sure can't replace a decent amp.

Here's the results: http://rmaa.elektrokrishna.com/Vario...0Impedance.htm

Frequency response (linear is better):


Stereo crosstalk (lower is better):
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  #13  
Old 06-15-2008, 05:20 PM
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Wow!, those graphs are excellent!.

Now, it would be interesting to know what is the actual impedance presented by the Shure volume control to the player, and whether it changes when adjusting the volume knob. May be it is just a very low impedance potentiometer which would not help much. Also, can you tell what was the level you set on the Shure volume control and the player's one for those tests?

I would also be very interested in the particular setup you used with RMAA for this test.

I will probably buy the Koss vol. control (cheap) and do some investigation on their electrical design. It may be that I could use the volume control box to install a series resistor much like the ones used on the impedance adapters, and then keep the convenience of the external volume control as well. I hope to get the device in a couple weeks.
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  #14  
Old 06-15-2008, 05:47 PM
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Thanks dfkt!!! I removing the Shure from my initial post and adding the Etymotic to it instead. And, from your graph and quote on the findings, I'm gonna' need to get an amp, aren't I ?
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  #15  
Old 06-15-2008, 05:56 PM
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Petsin, you are absolutely right in your assumptions! I have to take back what I said before about the Shure volume control. Nywytboy68, sorry about the false information.

The first measurement was with the inline remote at full blast, now I measured it at half volume as well.

My setup for these tests is:
Code:
                           /-----> line-in to sound card (Echo Gina)
                          /
Cowon D2 -----> Y-splitter
                          \
                           \-----> impedance adapter ----> 16 Ohm headphone (V-Moda Vibe)
Here's the new measurements, and they tell quite a bit more. I *think* the volume control makes the sound a bit worse, but I can't really pinpoint what it is. At half volume it sure fixes some things, though. The measurements are actually better than the UE adapter now.

http://rmaa.elektrokrishna.com/Vario...%20Control.htm



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Old 06-15-2008, 06:53 PM
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Great dfkt! this clears up most of my doubts! I would dare to say that the inferior quality of the sound may be due to loss of channel separation that you measured. But this makes me think that the Koss unit deserves a try... though I will be using higher impedance IEMs (the FS Atrio as I am convinced now to buy).

One point that may be worth mentioning is that what you measure with the setup you use is the voltage applied to the phones, not the actual current going through, and what really drive the coils is mostly the current and not the voltage (since they are inductors, their impedance is lower at low freq. and viceversa). So, a fair test would really require to measure both (for instance measuring the voltage across the series resistor used as impedance adapter). Well, I am not sure if it is worth to try all this since in the end what counts is the listening experience, isn't it? An expert oppinion like yours is rather enough for me... Could you "feel" a better bass response using the Shure volume control on those low impedance phones?
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  #17  
Old 06-15-2008, 07:08 PM
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Thanks, Petsin. By no means am I a specialist when it comes to electronics, and this is the only way I know how to measure with RMAA showing the effect of various impedance headphones. If you have a different way of doing this, please tell me - I'm glad to learn new things.

Subjectively, I do perceive the more linear response with both the Shure volume control (at half) and the UE adapter. I'm quite sure it's no placebo, but it's hard to be absolutely sure what aspect of the audio was improved and what became worse, since I have to match the volume between listening.

The Shure remote sounds better than the UE adapter, that much is pretty obvious. Then again I have an old version of the UE adapter, I see a new model on their site - maybe it's an improved version? (My UE adapter seems to add a very high impedance - I can listen to my 16 Ohm, 92 dB/mW V-Moda Vibes at full volume 50 on the D2 without my head exploding.)

The difference is there, but it certainly is no "night and day" difference. I use a Corda Headsix amp usually with my D2, and the improvement is much more obvious with that one, compared to these impedance adapters.
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  #18  
Old 06-15-2008, 07:37 PM
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Shure back on the list then.

Last edited by The DarkSide; 06-15-2008 at 08:26 PM.
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  #19  
Old 06-15-2008, 09:11 PM
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Thanks for all the useful information and work invested dfkt, for sure I am learning a lot here (being rather new to this forum). Of course I will try to give my two cents from the electronics side, so right now, the only thing I can say is that a too high impedance load on a low voltage amplifier can easily drive it to the clipping zone, where you will certainly be annoyed by the high THD that will result. But to be sure this is the problem you are listening, the only way is to apply an oscilloscope (may be you want to get one of those inexpensive digital scope PCI cards and include it in your RMAA setup.) A quick glance on a scope signal using some reference sine wave will tell immediately if there is clipping going on.

As for measuring the current response on the output of the player you need a very similar setup using an impedance adapter:

. . . . . . . . . . . . . . . . . . . |------ line in sound card L
out L ------- phone L -----|
. . . . . . . . . . . . . . . . . . . |------ resistor --|
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
Common ------------------------------------|-------- line in common
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
. . . . . . . . . . . . . . . . . . . |------ resistor --|
out R ------- phone R -----|
. . . . . . . . . . . . . . . . . . . |------- line in sound card R

(please ignore the dots.. I don't how to keep the white space in between the lines and words as the web editor will remove all spaces but one between other chars.)

This setup requires that you separate the connection between the common lines of the earphones, like the ones used in airlines (guess you will try this on low cost ones ). The resistor should be of similar value as the phone's impedance.

In this way you should be able to measure the output current's frequency response. I have never tried this, but I think it should work with the RMAA.

I also checked the Corda Headsix (http://www.meier-audio.homepage.t-on...amplifiers.htm) and certainly looks interesting, but at $185 I guess I will stay without them for some time...

Last edited by petsin; 06-15-2008 at 09:28 PM. Reason: had to retouch the drawing.
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  #20  
Old 07-01-2008, 04:33 PM
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Quote:
Originally Posted by dfkt View Post
Well, the idea is to add some more resistance/impedance to the output/phones, so the player's bass is less rolled-off, the background hiss disappears, and the stereo crosstalk gets minimized.

.

Does this mean that the D2 would tend to reproduce stronger bass, have less background hiss, and less crosstalk with a higher impedance headphone like Koss KSC75's?

TIA
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