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Monday, August 13, 2012

P2B adapter for Etymotic Research ER-4P



As encouraged by the manufacturer, ER-4P can be easily turned into ER-4S, by simply adding a resistor in series. However, it has been proven quite tricky to turn ER-4P into ER-4B, since ER-4B has a dedicated high-pass filter(100 ohm resistor & 220 nF capacitor in parallel) implemented in its barrel.


Once again, my friend vAsurada, let me borrow his DIY-adapter made for ER-4P, a 3-way switchable passive filter which converts ER-4P into a ER-4S and ER-4B, simply by clicking a switch. He told me (with some doubt) that the accuracy is 99%! And I am pretty sure my regular visitor, Carrot, is the designer of the high-pass filter, but please correct me if I am mistaken.

As seen on the right, the adapter is a dual-layered PCB circuit, with a 3-way rocker switch attached. The switch first bypasses(4P), adds a resistance(4S), and finally adds a high-pass filter(4B) to 4P. The built quality is of top-notch, and I don't think you can get this quality from conventional manufacturers.


And here's the actual measurement of unfiltered ER-4, P&S&B superimposed together at 94 dB SPL @ 1 kHz. The data are very accurate, even by comparing them to the data provided by Mr. Don Wilson, the designer of ER-4. (different insertion depth in consideration)

4P to 4B accuracy is the sole target of interest, since 4P to 4S adapter is simply a resistor in addition. Its accuracy is rather insignificant.



And here is vAsurada's adapter:

Wow, the difference is less than 1 dB within 20~20,000 Hz! If you have this adapter in your possession along with ER-4P, it is same as owning 3 different IEMs at once, only for much lower price. I don't know about the percentage of 99%, but the adapter is damn accurate. I should return the adapter soon, and if you have any interest of purchasing one, ask vAsurada, not me. (no commercialism, please) Last time I asked him, the price was whooping 250 in USD! Anyway, it was a very fun experience, tinkering with this adapter. Thnx, vAsurada!

20 comments:

  1. The schematic, and a comparison chart between P2B adapter and original ER-4B's circuit can be found in the link below(my article).

    http://www.seeko.co.kr/zboard4/zboard.php?id=forum_etymotic_1&no=7318

    I was suprised about the comparison result becuase of how I can easily construct this P2B adapter acurately!

    The work based on the impedance measurement resulf of iM-616 which seems to have identical impedance to ER-4P(See http://goldenears.net/board/1736517). Probably, using ER-4P's impedance data, it can be more precisely builded.

    I uploaded a spreadsheet file that was able to predicts the response of P2B adapter.

    https://dl.dropbox.com/u/91668521/im616_z_p2sb.xls

    It is very helpful if it is required some tweaks of P2B adapter.

    P.S. I didn't build own P2B adapter, but made a digital equalization filter preset using the spreadsheet. The filter is very simple and great! I'm loving it. :-)

    ReplyDelete
    Replies
    1. Digital equalization filter presets were uploaded on the website linked below.

      http://www.seeko.co.kr/zboard4/zboard.php?id=forum_etymotic_1&no=7474

      The First file is Electri-Q presets(Electri-Q is an awesome VST EQ made by Christian Budde! http://www.aixcoustic.com/index.php?id=13), and second one is presets of EasyQ which is great free VST EQ(http://www.rs-met.com/freebies.html).

      Delete
    2. Thnx for the reference, Carrot!

      Delete
    3. Ah! I had a mistake. The impedance data of iM616 wasn't used to design the filter's schematic. It was used only to simulate the change of amplitude response... For designing filter's schematic, I used a patent document of Etymotic, which described informations of ER-4. It includes the schematic of electronic filter used in ER-4B.

      So, there is no chance which make this filter more better. It's already perfect!

      Delete
    4. Thanks Carrot, I have the ER-4P (and the P-to-S cable), and trying the real ER-4S and the EQed ER-4S, I couldn't really tell the difference.

      Delete
    5. Carrot, what is the number of the patent that you used? Do you have a link? I've checked a few patent sites and can't seem to find anything. I'd like to be more clear on which models have what circuitry inside them before I make my purchase.

      Thanks!

      Delete
  2. Well over my head...

    Thanks, Jim

    PS Because I am so simple, I'll just buy all three.

    ReplyDelete
  3. Thanks to udauda & Carrot :)

    I have a suspiction about the measurement that seems slightly different insert condition. Nevertheless, it's ok because the difference of ±1dB at both edges of audio frequency can't be recognized by human's dull ears...

    If someone have a intrest to get my PSB adapter, please e-mail me - address is shown my profile. Well.. it's just few stocks because first time I have no idea for sale, so I have very limited meterials for adapter.

    ReplyDelete
  4. Hey Y'all,
    You guys know much more than I do.
    But, I thought that the B Model had a much different frequency response than the P or S.
    Here is a link to what I have seen and was expecting: Goldenears.net/board/21104
    Thanks, Jim

    ReplyDelete
    Replies
    1. My data are same as Etymotics', just uncompensated, That is all.

      To better understand the issue, here's my data compensated using Etymotic's reference target curve: http://goo.gl/7PmEd

      Delete
    2. Rin,
      I cannot get your link to work.
      I thank you for your work in this field.
      I need much more study.
      Thanks again, Jim

      Delete
    3. Always many thanks, Jim.

      How about this, copy and past below URL to your web browser.
      http://i.imgur.com/doT2f.png

      Delete
    4. Thanks Rin,
      I think I am beginning to understand.
      Thank you, Jim

      Delete
  5. Have you made a difference graph between ER4S and ER4B? If so does it correspond to something like the X-curve?

    ReplyDelete
  6. I went ahead and tried generating a difference graph with the tools I have at my disposal. (There's a small error above 15k): http://i.imgur.com/ow95gUY.png
    Somewhat resembles the Moeller curve: http://3.bp.blogspot.com/-q-rooFmLIpY/T_5Wlrv7LaI/AAAAAAAAAuk/lBVLj0pnQ2Y/s1600/toole.png

    ReplyDelete
    Replies
    1. That is exactly what the designer, Don Wilson of Etymotic Research, intended with 4S & 4P. Approximately, ER-4S is -5 @ 10 kHz, and ER-4P is -10 @ 10 kHz compared to ER-4B.

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    2. Found some related curves: http://www.cdpkorea.com/zboard4/zboard.php?id=forum_etymotic_1&page=1&sn1=&divpage=2&category=1&sn=off&ss=on&sc=off&select_arrange=hit&desc=desc&no=100

      Delete
    3. Another tidbit: http://www.erji.net/simple/index.php?t42675.html

      Delete
  7. I recently bought an headphone amp : C&C BH (model 2).
    This little ampy that could has 2 headphone out ports and port 2 is an "P to B" port, which is quite unique.

    It's only US$ 99,99 on eBay.
    So if you want a portable headphone amp and you have the "P to S" cable you can't go wrong.

    A review.
    http://www.head-fi.org/t/644363/c-c-bh-portable-headphone-amp-80-hours-from-a-single-charge-buyer-review

    ReplyDelete