EQ full recap (Poly Styrene, Film bypass caps and large El caps)

S12-eq-mod-with-silmic-ii-capsEQ capacitors have all been changed to poly styrene which are the best caps you can get for tone in the EQ circuit for the S12. They have the least inductive loss and are by far faster and more open sounding than the original budget caps used in the S12 channels. Less phase shift also. As you can see, some of the poly styrene caps are enormous compared with the original polyester film caps. The 20,000 pf value was especially hard to find ( ex soviet Military ones pictured here)  and is a noticeable upgrade of the channel . Many coupling caps had to be moved slightly by Teflon jacketing the leads to allow the installation of the large value poly styrene caps. This was not a fun task but the result was very positive.

Coupling caps  (33uf) are Elna SILMIC II which are the best sounding i could find that were reasonably priced ( i tried Panasonic FM, and Nichicon KZ MUZE series which are also very good)  all other caps here are Panasonic FM series because bang for the buck they are very good.


Back-side-of-card-with-bypass-capsI have some channels i’ve done with WIMA bypass caps on the electrolytics so the highs can pass through more easily through the smaller value film caps that are in parrellel with the much larger electrolytic caps ( 220 uf and 470 uf values) . The bypass caps are the little red ones on the back side of the board. There was just enough room on the back side of the PC board for the WIMA film caps. The sonic result is exactly what i wanted. Much punchier and faster transients. For overheads and vocals ( and horns) there is no comparison to the stock channels ( even after they are fully re-capped)

These are much more open sounding. But still has that analog air when compared to straight digital.

assignment-board-1My goal was simple in concept, i needed a higher fidelity EQ and channel, and was actually looking for an outboard EQ for this….but as we all know the recall ability of the S12  is of paramount importance to work flow, so i thought ”why not modify some S12 channels to a good outboard EQ’s specifications?”.

Easier said/thought  then done!

Now I have what i want. Killer fidelity, recall-ability with no compromise. It took a lot of research on which caps to bypass, a lot of trial and error of finding the caps that sound the best and took some time to pull off but in the end it is worth it. Also i have changed out many of the 5532 and mc33078 chips to the excellent LME49720 chips with great results, again by actually trying and testing them in different parts of the circuit to find were they are best used. I have tried many other IC’s in the channels as well ( AD8599, TI1612, TI1642 ), but found the IC’s are not the big problem in the S12 to get the best performance.

I am set up right now to make more of these channels ( i’ve done over 24 channels of them myself, not all with the WIMA film bypass caps though) so if anyone is interested i can Modify your channels for you.

io-board-close-1 io-board-close-2

If you would like to hear the difference between the original channels and my modified channels you can send me a file or two and i can pump your files ( maybe overheads or vocals ) and match your exact EQ settings and and send you back an original channel vs the mod channel files so you can hear it for yourself! I have lynx aurora 16 convertors BTW for reference. I also have some S12 channels for sale which i can sell in guaranteed working original condition, or : Fully recapped, Fully recapped with Eq mod or the , Fully recapped, EQ mod and Film Bypass caps on all main electrolytic caps. I have very reasonable prices. Contact me if you are interested.

Thanks all!

Shawn Sullivan


  1. May 23, 2012  3:04 pm by Paul Svenre

    Wow Shawn! Impressing! I'd love to try two channels of those sometime. I have a few spare channels I could use for that. Also I'm probably downgrading within a year or so and will get even more spare channels then, and room for a little experiment... Let me PM or email when it's time. Thanks for your work, generousity and the pics! (BTW, how do you attach pics in a post?... :-P)

  2. May 23, 2012  4:24 pm by michael s

    Very impressing Shawn !!! 8-0

    I'd love to hear how this changes the sound, but I'm afraid from the result, as I'm pretty sure it'll be great! ;-)

    I might also be interested some day in the future!

    All the best, and a million thanks for your work and generosity!


  3. May 24, 2012  6:07 pm by shawn sullivan

    Thanks guys! I'll post some sound files of a modded channel, vs original (recapped) vs modded with bypass caps, pretty soon. Heres how i'll do it. I'll use a close room mic ( lauten oceanus tube mic and then separate files with my fostex ribbon mic) then passively split the signal to all three channels mentioned above. so there is no conversion loss before hitting the channels, then they all go to a lynx aurora converter. that way i get the best fidelity. You absolutely will here a difference .

    for pictures, click on "blog", then (upper right) "post", then "blog" again, then underneath "title" there are a bunch of little pictures/symbols of things, look for the smiley face icon , once you find that move your mouse cursor over two symbols to the left and you are now on the "insert picture" button . Thats how i do it!

  4. June 25, 2013  3:59 pm by Studjo

    Holy Cow Shawn! RESPECT!
    I can't wait to hear the files! I fear you'll get a lot of work from me ;)


  5. June 25, 2013  4:03 pm by maikol

    Hi Jo! Nice to have you here (and trying the comment system! ;-) )
    Hope all's well,
    All the best!

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