SWR Aural Enhancer Bypass

Discussion in 'Amps and Cabs [BG]' started by duff2, Mar 29, 2010.

  1. damn, dmusic. "more bark". You definitely just made me want to investigate my workingMan... thanks alot... grumble grumble
  2. Yeah, if you want more 'bark,' and a bit less of everything else, it's a cool mod. :bassist:
  3. Hey Duff- thanks a LOT for starting this. Very, very cool.
    If you've been adding mids, in order to be heard rather than just felt, you will love the mod. It'll make your amp BANG, big time. It's a MUCH different sound. Hope you like it as much as I do so far(haven't gigged it yet.) Will report after a gig in a familiar room. Dj
  4. David1234


    Jun 1, 2004
    Sydney, Australia
    Endorsing Artist: SWR Amplifiers
    I'm still waiting for someone who's turned it into a switch, not just a bypass. That's what I'd like!
  5. hdracer


    Feb 15, 2009
    Elk River, MN.
    dmusic, Did you use the on-off pot like Duff was talking about using? If I understand this right, using the on-off pot you can go back & forth between stock & modified. Sorry, I am not a electronics whiz, and get lost in some of the technical stuff.
  6. No, but I'm considering it. I can see that there may be times I'd like to have the stock sound back- twiddling EQ knobs doesn't really get you there. It's totally do-able but I haven't figured out the switch wiring yet.
  7. will33


    May 22, 2006

    I have an SM400S. The board is laid out a little differently than yours but it's still pretty clear which 2 caps to switch. I'm going to have to get the picture posting thing down to show others who have this version of amp. The frontend guts in mine are all on one board instead of being a double-decker like yours. Also have 4 controls to the left of the eq and then 4 sliders with para adjustment knobs in the middle.

    The caps in question are still the group of 3 behind the aural enhancer knob. The bigger one is positioned "north and south" and the other 2 are "east and west" as opposed to all 3 being "east and west" like in your picture. You still pull the big red one and use it to replace the smaller blue one to do the mod. And yes, you have to remove the board to do it. That means removing 13 knobs/pots and 4 sliders and putting them all back again. Kinda sucks but it's still cool you can do the mod without buying any parts, just changing around a couple that are already in there.

    I've marked this thread and will get some pics whenever I can, God only know when that will be. Also have an old "pre-fender" Workingman's 4004 here to look into. If anything different on that one, can photo that one too. I'll know when I get it open, I'm betting even if it's a different layout, it'll still be obvious where and how to do the mod.
  8. hdracer


    Feb 15, 2009
    Elk River, MN.
    Hay Duff, Did you get your amp back yet? Still waiting for your report. How much did your tech charge?
  9. duff2

    duff2 Guest

    Dec 16, 2007
    OK, so I have had the amp back for a week now. The mod cost me $76 CDN (taxes included) and I have no regrets.

    Final verdict: I like this amp a LOT better now. It has way more lower midrange character and cuts through the mix like a knife through butter. It's also much louder than before.

    As I indicated in an earlier post, this capacitor swap mod was expected to completely flatten the frequency response curve for the preamp. Using fdeck's audio spectrum analyzer I have confirmed that this is indeed the case.

    The mod also converts the aural enhancer knob into a pure gain control, so that at it's maximum setting there's no longer any midrange scoop. Also, it's now a lot easier to overdrive the tube preamp using a passive bass.

    If I can convince my drummer to loan me his mp3 recorder, I'll try to upload some sound clips within the next couple of weeks.

  10. chicago_mike


    Oct 9, 2007
    Chicago - LA - Rome - Dallas
    Endorsing Artist : Genz Benz
    The bane of the Fender tonestack. Wich is what the swr aural enhancer is. You can change the other caps to .033 orange drops for a different curve that is not as dramatic and less scooped sounding. Did that to mine not to long ago.
  11. Illinimax


    Oct 11, 2008
    This seems like a great idea.
  12. Matt Dean

    Matt Dean Supporting Member

    Jan 2, 2007
    SF (North) Bay Area
    This is why I have never really gotten on with SWR... this mod makes tremendous sense!

    Nicely done.
  13. alltube


    Mar 5, 2005

    You guys have no idea how well timed this post is... I was about to sell my IOD next week on the bay because i did not like the direct sound... although i liked the OD tube side....

    So... I ran into this post which made me open up the IOD and see if its similar to the same circuit... low and behold it is and I did the mod.... less than 1hr...

    Now the pre is a keeper....

    Thanks guys..

    now about those orange drops... where exactly and which could be changed?
  14. IvanMike

    IvanMike TTRPG enthusiast, Happy, Joyous, & Free. Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    really odd question - can this mod be done with a switch on the unit to toggle between "classic" SWR voicing and the flatter response? I can see how the mod would be cool but i would miss the option of having the original voicing available.
  15. IvanMike

    IvanMike TTRPG enthusiast, Happy, Joyous, & Free. Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    ah didn't see this post but we are on the same page. i also need to get my electric blue head modified or checked to see if the XLR out mod is needed to make it safe to use with phantom power. max valentino clued me in a long time ago about that issue.

    Other than that - I haven't seen a marcus miller pre around but i'm wondering if the preamp sounds the same as the classic original SWR units? Barring that I'd settle for an original SM-900 to use as a preamp. my electric blue is the bomb but not having bass and treble shelving controls can be a bummer.
  16. IvanMike

    IvanMike TTRPG enthusiast, Happy, Joyous, & Free. Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    sorry for the billion questions. as a russ allee preamp i'm wondering if this modification ended up making your swr sound a lot more like an AMP or Eden or thunderfunk. Even without a graph or scope i've always known the swr units had a 200 Hz cut by ear.
  17. Illinimax


    Oct 11, 2008
    Seems like a great project for a capacitor box. What would raising or lowering the 2 cap values do to the tone? I think a half-way mod might sound pretty good. Anyone try this?
  18. David1234


    Jun 1, 2004
    Sydney, Australia
    Endorsing Artist: SWR Amplifiers
    I think MarkBass might have tried it! Isn't their "pre curve" set to dip at 380Hz?
  19. iammr2


    Jun 10, 2002
    I've checked my SM400 and BBII. They don't have the extra lead holes so I'm thinking I'll need to get new caps as the current ones leads may be to short. Looks like an interesting mod though.
  20. 12bass


    Jan 2, 2003
    Victoria, Canada
    Missed this thread until now.... always cool to read about hardware mods.

    When set flat, the Eden WT preamp is flatter than the (stock) SWR curves shown here. However, there's a considerable roll-off of high frequencies above 12 kHz, which might explain why you're wishing for more upper harmonics. I've modded mine so that it goes all the way up to 20 kHz, and it sounds considerably more open now.
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