High Quality 3.5mm line attenuator/pad? My source is too loud! | Headphone Reviews and Discussion - Head-Fi.org

NeoteriX · May 12, 2009 at 4:03 AM

In a nutshell, I'm finding that the iPod (5th Gen) lineout to be pretty darn loud--especially when paired with sensitive earphones like the Shure SE530. I have the iPod linedout through a SiK Din into a Headphonia/Headstage Lyrix Total Pro USB.

When using the iPod and the amp on the lowest gain, I have to stick to the bottom range of the volume potentiometer, just above where the right/left channels sync. When using pretty much any other source (PC over USB, etc.) the input is manageable such that I can use my SE530s over the normal range of the potentiometer.

I think the lyrix amp offers 3x gain and 7x gain on its hi/lo settings which is still too much.

I think a solution is to use a small 3.5mm attenuator to bring things down a touch. However, I'm told that a majority of the available solutions diminish sound quality (as they alter the dynamic impedance of the headphones), and its a little disappointing to shell out money for an amp and decent earphones to stick something in the path that will diminish the quality.

I've seen people mention the Shure adjustable attenuator as well as the Ultimate Ears attenuator, but have read many comments that they negative affect sound quality.

I've also seen these, but not much information exists about them:

Apparently the solution is to use a "voltage divider" setup instead of the typical "resistors inline/in series." I do not possess the tools for a DIY effort, so that leaves premade options. Does anyone have any ideas where I can get a premade attenuator that utilizes a voltage divider method as to not effect the impedance of the headphones? I'm hoping to spend no more than $30, but we shall see.

Research Sources:

NeoteriX · May 13, 2009 at 12:32 AM

Update:

I emailed the folks at APureSound: APureSound - Where The Music Is Always Pure - APS Audio LLC.

This was their response:

Quote:

Building a voltage divider in this type of application is impossible. We use in line resistors. Resistors do not always degrade the sound quality. For instance in the KSC75 and 35 adding 75ohm actually tightens up the bass making it more controlled. By adding 75ohm to the ER4P makes the ER4S which is not a degrade in sound quality either.

Alex did try building a voltage divider in a small adapter, but decided against it due to much more work involved and more materials making the adapter way too high priced where we wouldn't be able to sell them anymore.

Thanks

I also emailed the folks at Core Sound: http://www.core-sound.com/attenuator-cables.html

And they responded:

Quote:

Quote:

You cite that this product is designed for microphones. I'm interested in using this for some headphones with a loud source. I'm wondering, is this product designed with resistors inline or are they arranged in a "voltage divider" setup?

Hi,

They use a voltage divider.

Quote:

Just to clarify, so with the voltage divider setup, you ultimately have 4 sets of resistors in the unit, correct? (2 per channel).

Yes.

NeoteriX · May 15, 2009 at 2:14 AM

Is this not the correct forum to be asking this kind of question? Is there a better one to direct this?

audiorapture · May 15, 2009 at 6:33 PM

I have the same problem but with a different source. I want to listen to my Senn headphones and fall asleep to the music. I have a DVD player on my nightstand and I play the cd's in that. I purchased a Radioshack L & R RCA to headphone jack. When I plug it in and use an old pair of Panasonics the sound is fine. However, when I use the Senn EH350's it's way to loud. I had a Labtec headphone extension cable with the line level so I could turn the sound up or down, but it broke. So I am looking for another cable or a better solution. Hopefully we can get an answer to the problems soon from our fellow members. I'll let you know if I hear anything and post it. Best of luck NeoteriX

avaddikt · May 27, 2009 at 8:10 PM

Well, I'll jump in on this. I am presently making a 'pad' if you will for my receiver and ATH-AD700 phones.
My Arcam receiver has an output impedance at the headphone jack of 330 ohms. The designer has responded and stated it is simply a resistor drop down off the stereo output circuit. Since my headphones have an impd. of 32 ohm, he suggest using resistors in the 22-47 ohm range. This should give a nice balance when adjusting the volume at the receiver, while keeping the signal sufficiently above noise.
This very topic was covered under an 'Arcam' topic a few years back.
One resistor goes to each signal wire (R&L) and ground return. (imagine a 'Y').
For 'phones' of other impedance do the same with other values.
The resistors are on the headphone side of the receiver, do not mod the network in the receiver. The result is basically a fixed pad.

Stretching that theory a bit, I think one could select other resistors for other phones, and use a selector switch (for multiple phones). For that matter, use a pad pot like they use for speakers (most are designed for 8 to 16 ohms, maybe ganged for 2 signals?). Add a resistor in series with the pots to keep it from dropping too low. But the switch would likely be easier and enable you to keep the entire package smaller.
Power rating is not critical. 1/4 watt should suffice.
After I try mine (waiting for parts) I will report back. I am getting precision Mills resistors to ensure stereo balance is not affected. Probably overkill.

NeoteriX · Jun 2, 2009 at 5:20 AM

[deleted]

NeoteriX · Jun 2, 2009 at 5:22 AM

avaddikt, do let us know how your experience goes.

So I received my Core Sound attenuator cables ( Core Sound Attenuator Cables ) just prior to the weekend; I had ordered two, one in 11dB and the other in 20dB to see which would fit my purposes better. I decided to try the Core Sound cables based on the information that they were of a voltage divider design that seemed to be well-recommended here on HeadFi.

Anyway, when I tried them paired with my Shure SE530s, I came away disappointed. There was a noticeable diminution of the sound quality -- as if a veil was placed over the sound. Everything was a bit muddier and less articulate. High Hats rung with a lot less crispness. I compared it with my Shure Adjustable Attenuator set to a comparable volume, and the Shure attenuator was much, much better. The sound was more detailed and crisper. When roughly compared with the Shure SE530 unattenuated, the sound quality was much much closer to that of the Shure Attenuated version.

To be sure, I did a rough single-blinded A-B test with my girlfriend, to first establish that there was an objective difference. I went through the rigamarole of assigning letters and numbers to the attenuators (A and B, and even and odd, respectively). I got her used to the sounds of A and B, and then generated random numbers for my test series and had her match the sound to either A or B. She was successful 93% of the time, and by the end of the test, she was 100% accurate, establishing an objective difference in sound quality. Then I asked her for her subjective opinions and they were similar to mine (without my describing to her my thoughts), she felt the Shure attenuated version was much clearer and detailed, and that the Core Sound version was more muffled. I'll be sending these guys back, thankfully there is a money back guarantee.

I am a little befuddled as to why the sound quality was noticeably diminished though. Was it possibly the quality of the resistors used? Was it the that the voltage divider is imperfect? Is it possibly the ratio of resistors used?

Additionally, I came away with a greater respect for Shure's attenuator. It's not perfect, but when I had the opportunity to compare some more, it's not all that bad. Ideally though, I'd like a fixed solution that didn't involve so many ways I can raise/lower the volume.

avaddikt · Jun 2, 2009 at 8:12 PM

I have to wonder myself what the difference would be. At $35 they have to be making a good profit even without the 'Shure' name. That is to say, there would be no reason to sacrifice on quality for the difference in price of a few resistors.

Granted, there are different ways to provide attenuation, some bridge circuits more complex than others. But we are not talking about difficult loads here.

I notice the text describing the Core does not indicate this is for the audio purist. Although, I would think even someone who does a fair amount of recording would know when something sounds better than something else. $35 might be on the high side on second thought.

NeoteriX · Jun 8, 2009 at 4:12 AM

Len, at Core Sounds replied to my email, so I just wanted to post it here for everyone's benefit. In summary, it seems like the low sound quality is a result of the impedance mismatch:

Quote:

The resistors are very high quality. What you're hearing is probably an impedance mismatch effect.

Those attenuators weren't designed for your application. They are designed to preserve roughly a 5K to 10KOhm input impedance for microphone pre-amps. Headphones want to driven by a low (typically less than 10 Ohm) impedance, and with these attenuators they're seeing at least a 2K impedance, and likely more. The headphone amp is similarly probably very unhappy.

avaddikt · Jun 8, 2009 at 7:57 PM

That would explain a lot! They might have mentioned the intended impedance match they are designed for in their ad copy.

Sam L · Oct 2, 2014 at 1:07 PM

neoterix said:
Len, at Core Sounds replied to my email, so I just wanted to post it here for everyone's benefit. In summary, it seems like the low sound quality is a result of the impedance mismatch:
Quote:

The resistors are very high quality. What you're hearing is probably an impedance mismatch effect.

Those attenuators weren't designed for your application. They are designed to preserve roughly a 5K to 10KOhm input impedance for microphone pre-amps. Headphones want to driven by a low (typically less than 10 Ohm) impedance, and with these attenuators they're seeing at least a 2K impedance, and likely more. The headphone amp is similarly probably very unhappy.

what solution did you end up using? The shure? I looked online and the only shure adjustable attenuator I could find is for xlr

NeoteriX · Oct 2, 2014 at 2:27 PM

Haha wow this is an old thread. I no longer use my iPod (it is dead) so it's no longer an issue. I either run my Shures directly out of my mobile device (Nexus 5) or more frequently these days, use a wireless Bluetooth setup.

Anyway, to answer your question, I used the Shure volume attenuator. It was the best I could do.

srREXed · Jun 7, 2018 at 11:27 PM

I’ve been using the ifi iematch 2.5 for balanced 2.5mm stuff and their iEbuddy for the 3.5mm stuff. I find that for the cost of the iEbuddy, it was a big improvement over just volume controllers that take down the nitrate of the source. On the other hand, once I found out the iematch2.5 works for both balanced and non, I had to pick it up. That one has two settings. High and ultra. In most cases I can use my devices without the attenuators, but when I’m using my iems it’s a mush. They work great and don’t take anything from the sound quality. Hope it helps someone.

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